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  • richardmitnick 3:23 pm on September 7, 2021 Permalink | Reply
    Tags: "One Lab’s Quest to Build Space-Time Out of Quantum Particles", AdS: anti-de Sitter space, , CFT: conformal field theory, Pairs of atoms could be entangled together and then each pair would itself be entangled with another pair and so on forming a kind of tree., Physicists have been suggesting for over a decade that gravity — and even space-time itself — may emerge from a strange quantum connection called entanglement., , , Quantum Gravity, , , Testing quantum gravity without black holes or galaxy-size particle accelerators., The Standard Model despite its success is clearly incomplete.   

    From Quanta Magazine (US) and Stanford University (US) : “One Lab’s Quest to Build Space-Time Out of Quantum Particles” 

    From Quanta Magazine (US)

    and

    Stanford University Name

    Stanford University (US)

    September 7, 2021
    Adam Becker

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    Quantum particles entangled in a “tree-like” structure correspond to various configurations of space-time.
    Credit: Olena Shmahalo & Samuel Velasco/Quanta Magazine; Photo: Felix Mittermeier.

    The prospects for directly testing a theory of quantum gravity are poor, to put it mildly. To probe the ultra-tiny Planck scale, where quantum gravitational effects appear, you would need a particle accelerator as big as the Milky Way galaxy. Likewise, black holes hold singularities that are governed by quantum gravity, but no black holes are particularly close by — and even if they were, we could never hope to see what’s inside. Quantum gravity was also at work in the first moments of the Big Bang, but direct signals from that era are long gone, leaving us to decipher subtle clues that first appeared hundreds of thousands of years later.

    But in a small lab just outside Palo Alto, the Stanford University professor Monika Schleier-Smith and her team are trying a different way to test quantum gravity without black holes or galaxy-size particle accelerators. Physicists have been suggesting for over a decade that gravity — and even space-time itself — may emerge from a strange quantum connection called entanglement. Schleier-Smith and her collaborators are reverse-engineering the process. By engineering highly entangled quantum systems in a tabletop experiment, Schleier-Smith hopes to produce something that looks and acts like the warped space-time predicted by Albert Einstein’s theory of general relativity.

    In a paper posted in June, her team announced their first experimental step along this route: a system of atoms trapped by light, with connections made to order, finely controlled with magnetic fields. When tuned in the right way, the long-distance correlations in this system describe a treelike geometry, similar to ones seen in simple models of emergent space-time. Schleier-Smith and her colleagues hope to build on this work to create analogues to more complex geometries, including those of black holes. In the absence of new data from particle physics or cosmology — a state of affairs that could continue indefinitely — this could be the most promising route for putting the latest ideas about quantum gravity to the test.

    The Perils of Perfect Predictions

    For five decades, the prevailing theory of particle physics, the Standard Model, has met with almost nothing but success — to the endless frustration of particle physicists.

    The problem lies in the fact that the Standard Model despite its success is clearly incomplete. It doesn’t include gravity, despite the long search for a theory of quantum gravity to replace general relativity. Nor can it explain dark matter or dark energy, which account for 95% of all the stuff in the universe. (The Standard Model also has trouble with the fact that neutrinos have mass — the sole particle physics phenomenon it has failed to predict.)

    Moreover, the Standard Model itself dictates that beyond a certain threshold of high energy — one closely related to the Planck scale — it almost certainly fails.

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    Monika Schleier-Smith’s lab at Stanford is a dense maze of cables and optical equipment. “But at the end of the day,” she said, “You can make a system that is clean and controlled.”
    Credit: Dawn Harmer/DOE’s SLAC National Accelerator Laboratory (US).

    Physicists are desperate for puzzling experimental data that might help to guide them as they build the Standard Model’s replacement. String theory, still the leading candidate to replace the Standard Model, has often been accused of being untestable. But one of the strangest features of string theory suggests a way to test some ideas about quantum gravity that don’t require impractical feats of galactic architecture.

    String theory is filled with dualities — relations between different physical systems that share the same mathematical structure. Perhaps the most surprising and consequential of these dualities is a connection between a type of quantum theory in four dimensions without gravity, known as a conformal field theory (CFT), and a particular kind of five-dimensional space-time with gravity, known as an anti-de Sitter (AdS) space. This AdS/CFT correspondence, as it’s known, was first discovered in 1997 by the physicist Juan Maldacena, now at the Institute for Advanced Study (US).

    Because the CFT has one fewer dimension than the AdS space, the former can be thought of as lying on the surface of the latter, like the two-dimensional skin of a three-dimensional apple. Yet the quantum theory on the surface still fully captures all the features of the volume inside — as if you could tell everything about the interior of an apple just by looking at its skin. This is an example of what physicists call holography: a lower-dimensional space giving rise to a higher-dimensional space, like a flat hologram producing a 3D image.

    In the AdS/CFT correspondence, the interior or “bulk” space emerges from relationships between the quantum components on the surface. Specifically, the geometry of the bulk space is built from entanglement, the “spooky” quantum connections that infamously troubled Einstein. Neighboring regions of the bulk correspond to highly entangled portions of the surface. Distant regions of the bulk correspond to less entangled parts of the surface. If the surface has a simple and orderly set of entanglement relations, the corresponding bulk space will be empty. If the surface is chaotic, with all its parts entangled with all the others, the bulk will form a black hole.

    The AdS/CFT correspondence is a deep and fruitful insight into the connections between quantum physics and general relativity. But it doesn’t actually describe the world we live in. Our universe isn’t a five-dimensional anti-de Sitter space — it’s an expanding four-dimensional space with a “flat” geometry.

    So over the past few years, researchers have proposed another approach. Rather than starting from the bulk — our own universe — and looking for the kind of quantum entanglement pattern that could produce it, we can go the other way. Perhaps experimenters could build systems with interesting entanglements — like the CFT on the surface — and search for any analogues to space-time geometry and gravity that emerge.

    That’s easier said than done. It’s not yet possible to build a system like any of the strongly interacting quantum systems known to have gravitational duals. But theorists have only mapped out a small fraction of possible systems — many others are too complex to study theoretically with existing mathematical tools. To see if any of those systems actually yield some kind of space-time geometry, the only option is to physically construct them in the lab and see if they also have a gravitational dual. “These experimental constructions might help us discover such systems,” said Maldacena. “There might be simpler systems than the ones we know about.” So quantum gravity theorists have turned to experts in building and controlling entanglement in quantum systems, like Schleier-Smith and her team.

    Quantum Gravity Meets Cold Atoms

    “There’s something really just elegant about the theory of quantum mechanics that I’ve always loved,” said Schleier-Smith. “If you go into the lab, you’ll see there’s cables all over the place and all kinds of electronics we had to build and vacuum systems and messy-looking hardware. But at the end of the day, you can make a system that is clean and controlled in such a way that it does nicely map onto this sort of elegant theory that you can write down on paper.”

    This messy elegance has been a hallmark of Schleier-Smith’s work since her graduate days at The Massachusetts Institute of Technology (US), where she used light to coax collections of atoms into particular entangled states and demonstrated how to use these quantum systems to build more precise atomic clocks. After MIT, she spent a few years at the MPG Institute for Quantum Optics [MPG Institut für Quantenoptik](DE) in Garching, Germany, before landing at Stanford in 2013. A couple of years later, Brian Swingle, a theoretical physicist then at Stanford working on string theory, quantum gravity and other related subjects, reached out to her with an unusual question. “I wrote her an email saying, basically, ‘Can you reverse time in your lab?’” said Swingle. “And she said yes. And so we started talking.”

    Swingle wanted to reverse time in order to study black holes and a quantum phenomenon known as scrambling. In quantum scrambling, information about a quantum system’s state is rapidly dispersed across a larger system, making it very hard to recover the original information. “Black holes are very good scramblers of information,” said Swingle. “They hide information very well.” When an object is dropped into a black hole, information about that object is rapidly hidden from the rest of the universe. Understanding how black holes obscure information about the objects that fall into them — and whether that information is merely hidden or actually destroyed — has been a major focus of theoretical physics since the 1970s.

    In the AdS/CFT correspondence, a black hole in the bulk corresponds to a dense web of entanglement at the surface that scrambles incoming information very quickly. Swingle wanted to know what a fast-scrambling quantum system would look like in the lab, and he realized that in order to confirm scrambling was taking place as rapidly as possible, researchers would need to tightly control the quantum system in question, with the ability to perfectly reverse all interactions. “The sort of obvious way to do it required the ability to effectively fast forward and rewind the system,” said Swingle. “And that’s not something you can do in an everyday kind of experiment.” But Swingle knew Schleier-Smith’s lab might be able to control the entanglement between atoms carefully enough to perfectly reverse all their interactions, as if time were running backward. “If you have this nice, isolated, well-controlled, highly engineered quantum many-body system, then maybe you have a chance,” he said.

    So Swingle reached out to Schleier-Smith and told her what he wanted to do. “He explained to me this conjecture that this process of scrambling — that there’s a fundamental speed limit to how fast that can happen,” said Schleier-Smith. “And that if you could build a quantum system in the lab that scrambles at this fundamental speed limit, then maybe that would be some kind of an analogue of a black hole.” Their conversations continued, and in 2016, Swingle and Schleier-Smith co-authored a paper, along with Patrick Hayden, another theorist at Stanford, and Gregory Bentsen, one of Schleier-Smith’s graduate students at the time, outlining a feasible method for creating and probing fast quantum scrambling in the lab.

    That work left Schleier-Smith contemplating other quantum gravitational questions that her lab could investigate. “That made me think … maybe these are actually good platforms for being able to realize some toy models of quantum gravity that are hard to realize by other means,” she said. She started to consider a setup where pairs of atoms could be entangled together and then each pair would itself be entangled with another pair and so on forming a kind of tree. “It seemed kind of far-fetched to actually do it, but at least I could sort of imagine on paper how you would design a system where you can do that,” she said. But she wasn’t sure if this actually corresponded to any known model of quantum gravity.

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    A view of the vacuum chamber at the center of the experiment. This view, taken several years ago, is now impossible, as there have been too many elements placed around the apparatus.
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    Inside the control room where researchers control the experiment and analyze the data. Credit: Khoi Huynh. Courtesy of Monika Schleier-Smith.

    Intense and affable, Schleier-Smith has an infectious enthusiasm for her work, as her student Bentsen discovered. He had started his doctoral work at Stanford in theoretical physics, but Schleier-Smith managed to pull him into her group anyhow. “I sort of convinced him to do experiments,” she recalled, “but he maintained an interest in theory as well, and liked to chat with theorists around the department.” She discussed her new idea with Bentsen, who discussed it with Sean Hartnoll, another theorist at Stanford. Hartnoll in turn played matchmaker, connecting Schleier-Smith and Bentsen with Steven Gubser, a theorist at Princeton University (US). (Gubser later died in a rock-climbing accident.)

    At the time, Gubser was working on a twist on the AdS/CFT correspondence. Rather than using the familiar kind of numbers that physicists generally use, he was using a set of alternative number systems known as the p-adic numbers. The key distinction between the p-adics and ordinary “real” numbers is the way the size of a number is defined. In the p-adics, a number’s size is determined by its prime factors. There’s a p-adic number system for each prime number: the 2-adics, the 3-adics, the 5-adics, and so on. In each p-adic number system, the more factors a number has that are multiples of p, the smaller that number is. So, for example, in the 2-adics, 44 is much closer to 0 than it is to 45, because 44 has two factors that are multiples of 2, while 45 doesn’t have any. But in the 3-adics, it’s the reverse; 45 is closer to 0 than to 44, because 45 has two factors that are multiples of 3. Each p-adic number system can also be represented as a kind of tree, with each branch containing numbers that all have the same number of factors that are multiples of p.

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    In p-adic geometry, different branches share the same number of factors that are multiples of p.
    Samuel Velasco/Quanta Magazine.

    Using the p-adics, Gubser and others had discovered a remarkable fact about the AdS/CFT correspondence. If you rewrite the surface theory using the p-adic numbers rather than the reals, the bulk is replaced with a kind of infinite tree. Specifically, it’s a tree with infinite branches packed into a finite space, resembling the structure of the p-adic numbers themselves. The p-adics, Gubser wrote, are “naturally holographic.”

    “The structure of p-adic numbers that [Gubser] told me about reminded me of the way Monika’s atoms interacted with each other,” said Hartnoll, “so I put them in touch.” Gubser co-authored a paper in 2019 with Schleier-Smith, Bentsen and others. In the paper, the team described how to get something resembling the p-adic tree to emerge from entangled atoms in an actual lab. With the plan in hand, Schleier-Smith and her team got to work.

    Building Space-Time in the Lab

    Schleier-Smith’s lab at Stanford is a dense forest of mirrors, lenses and fiber-optic cables that surround a vacuum chamber at the center of the room. In that vacuum chamber, 18 tiny collections of rubidium atoms — about 10,000 to a group — are arranged in a line and cooled to phenomenally low temperatures, a fraction of a degree above absolute zero. A specially tuned laser and a magnetic field that increases from one end of the chamber to the other allow the experimenters to choose which groups of atoms become correlated with each other.

    Using this lab setup, Schleier-Smith and her research group were able to get the two groups of atoms at the ends of the line just as correlated as neighboring groups were in the middle of the line, connecting the ends and turning the line into a circle of correlations. They then coaxed the collection of atoms into a treelike structure. All of this was accomplished without moving the atoms at all — the correlation “geometry” was wholly disconnected from the actual spatial geometry of the atoms.

    While the tree structure formed by the interacting atoms in Schleier-Smith’s lab isn’t a full-blown realization of p-adic AdS/CFT, it’s “a first step towards holography in the laboratory,” said Hayden. Maldacena, the originator of the AdS/CFT correspondence, agrees: “I’m very excited about this,” he said. “Our subject has been always very theoretical, and so this contact with experiment will probably raise more questions.”

    Hayden sees this as the way of the future. “Instead of trying to understand the emergence of space-time in our universe, let’s actually just make toy universes in the lab and study the emergence of space-time there,” he said. “And that sounds like a crazy thing to do, right? Like kind of mad-scientist kind of crazy, right? But I think it really is likely to be easier to do that than to directly test quantum gravity.”

    Schleier-Smith is also optimistic about the future. “We’re still at the stage of getting more and more control, characterizing the quantum states that we have. But … I would love to get to that point where we don’t know what will happen,” she said. “And maybe we measure the correlations in the system, and we learn that there’s a geometric description, some holographic description that we didn’t know was there. That would be cool.”

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Stanford University campus
    Stanford University (US)

    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members.

    Stanford University, officially Leland Stanford Junior University, is a private research university located in Stanford, California. Stanford was founded in 1885 by Leland and Jane Stanford in memory of their only child, Leland Stanford Jr., who had died of typhoid fever at age 15 the previous year. Stanford is consistently ranked as among the most prestigious and top universities in the world by major education publications. It is also one of the top fundraising institutions in the country, becoming the first school to raise more than a billion dollars in a year.

    Leland Stanford was a U.S. senator and former governor of California who made his fortune as a railroad tycoon. The school admitted its first students on October 1, 1891, as a coeducational and non-denominational institution. Stanford University struggled financially after the death of Leland Stanford in 1893 and again after much of the campus was damaged by the 1906 San Francisco earthquake. Following World War II, provost Frederick Terman supported faculty and graduates’ entrepreneurialism to build self-sufficient local industry in what would later be known as Silicon Valley.

    The university is organized around seven schools: three schools consisting of 40 academic departments at the undergraduate level as well as four professional schools that focus on graduate programs in law, medicine, education, and business. All schools are on the same campus. Students compete in 36 varsity sports, and the university is one of two private institutions in the Division I FBS Pac-12 Conference. It has gained 126 NCAA team championships, and Stanford has won the NACDA Directors’ Cup for 24 consecutive years, beginning in 1994–1995. In addition, Stanford students and alumni have won 270 Olympic medals including 139 gold medals.

    As of October 2020, 84 Nobel laureates, 28 Turing Award laureates, and eight Fields Medalists have been affiliated with Stanford as students, alumni, faculty, or staff. In addition, Stanford is particularly noted for its entrepreneurship and is one of the most successful universities in attracting funding for start-ups. Stanford alumni have founded numerous companies, which combined produce more than $2.7 trillion in annual revenue, roughly equivalent to the 7th largest economy in the world (as of 2020). Stanford is the alma mater of one president of the United States (Herbert Hoover), 74 living billionaires, and 17 astronauts. It is also one of the leading producers of Fulbright Scholars, Marshall Scholars, Rhodes Scholars, and members of the United States Congress.

    Stanford University was founded in 1885 by Leland and Jane Stanford, dedicated to Leland Stanford Jr, their only child. The institution opened in 1891 on Stanford’s previous Palo Alto farm.

    Jane and Leland Stanford modeled their university after the great eastern universities, most specifically Cornell University. Stanford opened being called the “Cornell of the West” in 1891 due to faculty being former Cornell affiliates (either professors, alumni, or both) including its first president, David Starr Jordan, and second president, John Casper Branner. Both Cornell and Stanford were among the first to have higher education be accessible, nonsectarian, and open to women as well as to men. Cornell is credited as one of the first American universities to adopt this radical departure from traditional education, and Stanford became an early adopter as well.

    Despite being impacted by earthquakes in both 1906 and 1989, the campus was rebuilt each time. In 1919, The Hoover Institution on War, Revolution and Peace was started by Herbert Hoover to preserve artifacts related to World War I. The Stanford Medical Center, completed in 1959, is a teaching hospital with over 800 beds. The DOE’s SLAC National Accelerator Laboratory(US)(originally named the Stanford Linear Accelerator Center), established in 1962, performs research in particle physics.

    Land

    Most of Stanford is on an 8,180-acre (12.8 sq mi; 33.1 km^2) campus, one of the largest in the United States. It is located on the San Francisco Peninsula, in the northwest part of the Santa Clara Valley (Silicon Valley) approximately 37 miles (60 km) southeast of San Francisco and approximately 20 miles (30 km) northwest of San Jose. In 2008, 60% of this land remained undeveloped.

    Stanford’s main campus includes a census-designated place within unincorporated Santa Clara County, although some of the university land (such as the Stanford Shopping Center and the Stanford Research Park) is within the city limits of Palo Alto. The campus also includes much land in unincorporated San Mateo County (including the SLAC National Accelerator Laboratory and the Jasper Ridge Biological Preserve), as well as in the city limits of Menlo Park (Stanford Hills neighborhood), Woodside, and Portola Valley.

    Non-central campus

    Stanford currently operates in various locations outside of its central campus.

    On the founding grant:

    Jasper Ridge Biological Preserve is a 1,200-acre (490 ha) natural reserve south of the central campus owned by the university and used by wildlife biologists for research.
    SLAC National Accelerator Laboratory is a facility west of the central campus operated by the university for the Department of Energy. It contains the longest linear particle accelerator in the world, 2 miles (3.2 km) on 426 acres (172 ha) of land.
    Golf course and a seasonal lake: The university also has its own golf course and a seasonal lake (Lake Lagunita, actually an irrigation reservoir), both home to the vulnerable California tiger salamander. As of 2012 Lake Lagunita was often dry and the university had no plans to artificially fill it.

    Off the founding grant:

    Hopkins Marine Station, in Pacific Grove, California, is a marine biology research center owned by the university since 1892.
    Study abroad locations: unlike typical study abroad programs, Stanford itself operates in several locations around the world; thus, each location has Stanford faculty-in-residence and staff in addition to students, creating a “mini-Stanford”.

    Redwood City campus for many of the university’s administrative offices located in Redwood City, California, a few miles north of the main campus. In 2005, the university purchased a small, 35-acre (14 ha) campus in Midpoint Technology Park intended for staff offices; development was delayed by The Great Recession. In 2015 the university announced a development plan and the Redwood City campus opened in March 2019.

    The Bass Center in Washington, DC provides a base, including housing, for the Stanford in Washington program for undergraduates. It includes a small art gallery open to the public.

    China: Stanford Center at Peking University, housed in the Lee Jung Sen Building, is a small center for researchers and students in collaboration with Beijing University [北京大学](CN) (Kavli Institute for Astronomy and Astrophysics at Peking University(CN) (KIAA-PKU).

    Administration and organization

    Stanford is a private, non-profit university that is administered as a corporate trust governed by a privately appointed board of trustees with a maximum membership of 38. Trustees serve five-year terms (not more than two consecutive terms) and meet five times annually.[83] A new trustee is chosen by the current trustees by ballot. The Stanford trustees also oversee the Stanford Research Park, the Stanford Shopping Center, the Cantor Center for Visual Arts, Stanford University Medical Center, and many associated medical facilities (including the Lucile Packard Children’s Hospital).

    The board appoints a president to serve as the chief executive officer of the university, to prescribe the duties of professors and course of study, to manage financial and business affairs, and to appoint nine vice presidents. The provost is the chief academic and budget officer, to whom the deans of each of the seven schools report. Persis Drell became the 13th provost in February 2017.

    As of 2018, the university was organized into seven academic schools. The schools of Humanities and Sciences (27 departments), Engineering (nine departments), and Earth, Energy & Environmental Sciences (four departments) have both graduate and undergraduate programs while the Schools of Law, Medicine, Education and Business have graduate programs only. The powers and authority of the faculty are vested in the Academic Council, which is made up of tenure and non-tenure line faculty, research faculty, senior fellows in some policy centers and institutes, the president of the university, and some other academic administrators, but most matters are handled by the Faculty Senate, made up of 55 elected representatives of the faculty.

    The Associated Students of Stanford University (ASSU) is the student government for Stanford and all registered students are members. Its elected leadership consists of the Undergraduate Senate elected by the undergraduate students, the Graduate Student Council elected by the graduate students, and the President and Vice President elected as a ticket by the entire student body.

    Stanford is the beneficiary of a special clause in the California Constitution, which explicitly exempts Stanford property from taxation so long as the property is used for educational purposes.

    Endowment and donations

    The university’s endowment, managed by the Stanford Management Company, was valued at $27.7 billion as of August 31, 2019. Payouts from the Stanford endowment covered approximately 21.8% of university expenses in the 2019 fiscal year. In the 2018 NACUBO-TIAA survey of colleges and universities in the United States and Canada, only Harvard University(US), the University of Texas System(US), and Yale University(US) had larger endowments than Stanford.

    In 2006, President John L. Hennessy launched a five-year campaign called the Stanford Challenge, which reached its $4.3 billion fundraising goal in 2009, two years ahead of time, but continued fundraising for the duration of the campaign. It concluded on December 31, 2011, having raised a total of $6.23 billion and breaking the previous campaign fundraising record of $3.88 billion held by Yale. Specifically, the campaign raised $253.7 million for undergraduate financial aid, as well as $2.33 billion for its initiative in “Seeking Solutions” to global problems, $1.61 billion for “Educating Leaders” by improving K-12 education, and $2.11 billion for “Foundation of Excellence” aimed at providing academic support for Stanford students and faculty. Funds supported 366 new fellowships for graduate students, 139 new endowed chairs for faculty, and 38 new or renovated buildings. The new funding also enabled the construction of a facility for stem cell research; a new campus for the business school; an expansion of the law school; a new Engineering Quad; a new art and art history building; an on-campus concert hall; a new art museum; and a planned expansion of the medical school, among other things. In 2012, the university raised $1.035 billion, becoming the first school to raise more than a billion dollars in a year.

    Research centers and institutes

    DOE’s SLAC National Accelerator Laboratory(US)
    Stanford Research Institute, a center of innovation to support economic development in the region.
    Hoover Institution, a conservative American public policy institution and research institution that promotes personal and economic liberty, free enterprise, and limited government.
    Hasso Plattner Institute of Design, a multidisciplinary design school in cooperation with the Hasso Plattner Institute of University of Potsdam [Universität Potsdam](DE) that integrates product design, engineering, and business management education).
    Martin Luther King Jr. Research and Education Institute, which grew out of and still contains the Martin Luther King Jr. Papers Project.
    John S. Knight Fellowship for Professional Journalists
    Center for Ocean Solutions
    Together with UC Berkeley(US) and UC San Francisco(US), Stanford is part of the Biohub, a new medical science research center founded in 2016 by a $600 million commitment from Facebook CEO and founder Mark Zuckerberg and pediatrician Priscilla Chan.

    Discoveries and innovation

    Natural sciences

    Biological synthesis of deoxyribonucleic acid (DNA) – Arthur Kornberg synthesized DNA material and won the Nobel Prize in Physiology or Medicine 1959 for his work at Stanford.
    First Transgenic organism – Stanley Cohen and Herbert Boyer were the first scientists to transplant genes from one living organism to another, a fundamental discovery for genetic engineering. Thousands of products have been developed on the basis of their work, including human growth hormone and hepatitis B vaccine.
    Laser – Arthur Leonard Schawlow shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for his work on lasers.
    Nuclear magnetic resonance – Felix Bloch developed new methods for nuclear magnetic precision measurements, which are the underlying principles of the MRI.

    Computer and applied sciences

    ARPANETStanford Research Institute, formerly part of Stanford but on a separate campus, was the site of one of the four original ARPANET nodes.

    Internet—Stanford was the site where the original design of the Internet was undertaken. Vint Cerf led a research group to elaborate the design of the Transmission Control Protocol (TCP/IP) that he originally co-created with Robert E. Kahn (Bob Kahn) in 1973 and which formed the basis for the architecture of the Internet.

    Frequency modulation synthesis – John Chowning of the Music department invented the FM music synthesis algorithm in 1967, and Stanford later licensed it to Yamaha Corporation.

    Google – Google began in January 1996 as a research project by Larry Page and Sergey Brin when they were both PhD students at Stanford. They were working on the Stanford Digital Library Project (SDLP). The SDLP’s goal was “to develop the enabling technologies for a single, integrated and universal digital library” and it was funded through the National Science Foundation, among other federal agencies.

    Klystron tube – invented by the brothers Russell and Sigurd Varian at Stanford. Their prototype was completed and demonstrated successfully on August 30, 1937. Upon publication in 1939, news of the klystron immediately influenced the work of U.S. and UK researchers working on radar equipment.

    RISCARPA funded VLSI project of microprocessor design. Stanford and UC Berkeley are most associated with the popularization of this concept. The Stanford MIPS would go on to be commercialized as the successful MIPS architecture, while Berkeley RISC gave its name to the entire concept, commercialized as the SPARC. Another success from this era were IBM’s efforts that eventually led to the IBM POWER instruction set architecture, PowerPC, and Power ISA. As these projects matured, a wide variety of similar designs flourished in the late 1980s and especially the early 1990s, representing a major force in the Unix workstation market as well as embedded processors in laser printers, routers and similar products.
    SUN workstation – Andy Bechtolsheim designed the SUN workstation for the Stanford University Network communications project as a personal CAD workstation, which led to Sun Microsystems.

    Businesses and entrepreneurship

    Stanford is one of the most successful universities in creating companies and licensing its inventions to existing companies; it is often held up as a model for technology transfer. Stanford’s Office of Technology Licensing is responsible for commercializing university research, intellectual property, and university-developed projects.

    The university is described as having a strong venture culture in which students are encouraged, and often funded, to launch their own companies.

    Companies founded by Stanford alumni generate more than $2.7 trillion in annual revenue, equivalent to the 10th-largest economy in the world.

    Some companies closely associated with Stanford and their connections include:

    Hewlett-Packard, 1939, co-founders William R. Hewlett (B.S, PhD) and David Packard (M.S).
    Silicon Graphics, 1981, co-founders James H. Clark (Associate Professor) and several of his grad students.
    Sun Microsystems, 1982, co-founders Vinod Khosla (M.B.A), Andy Bechtolsheim (PhD) and Scott McNealy (M.B.A).
    Cisco, 1984, founders Leonard Bosack (M.S) and Sandy Lerner (M.S) who were in charge of Stanford Computer Science and Graduate School of Business computer operations groups respectively when the hardware was developed.[163]
    Yahoo!, 1994, co-founders Jerry Yang (B.S, M.S) and David Filo (M.S).
    Google, 1998, co-founders Larry Page (M.S) and Sergey Brin (M.S).
    LinkedIn, 2002, co-founders Reid Hoffman (B.S), Konstantin Guericke (B.S, M.S), Eric Lee (B.S), and Alan Liu (B.S).
    Instagram, 2010, co-founders Kevin Systrom (B.S) and Mike Krieger (B.S).
    Snapchat, 2011, co-founders Evan Spiegel and Bobby Murphy (B.S).
    Coursera, 2012, co-founders Andrew Ng (Associate Professor) and Daphne Koller (Professor, PhD).

    Student body

    Stanford enrolled 6,996 undergraduate and 10,253 graduate students as of the 2019–2020 school year. Women comprised 50.4% of undergraduates and 41.5% of graduate students. In the same academic year, the freshman retention rate was 99%.

    Stanford awarded 1,819 undergraduate degrees, 2,393 master’s degrees, 770 doctoral degrees, and 3270 professional degrees in the 2018–2019 school year. The four-year graduation rate for the class of 2017 cohort was 72.9%, and the six-year rate was 94.4%. The relatively low four-year graduation rate is a function of the university’s coterminal degree (or “coterm”) program, which allows students to earn a master’s degree as a 1-to-2-year extension of their undergraduate program.

    As of 2010, fifteen percent of undergraduates were first-generation students.

    Athletics

    As of 2016 Stanford had 16 male varsity sports and 20 female varsity sports, 19 club sports and about 27 intramural sports. In 1930, following a unanimous vote by the Executive Committee for the Associated Students, the athletic department adopted the mascot “Indian.” The Indian symbol and name were dropped by President Richard Lyman in 1972, after objections from Native American students and a vote by the student senate. The sports teams are now officially referred to as the “Stanford Cardinal,” referring to the deep red color, not the cardinal bird. Stanford is a member of the Pac-12 Conference in most sports, the Mountain Pacific Sports Federation in several other sports, and the America East Conference in field hockey with the participation in the inter-collegiate NCAA’s Division I FBS.

    Its traditional sports rival is the University of California, Berkeley, the neighbor to the north in the East Bay. The winner of the annual “Big Game” between the Cal and Cardinal football teams gains custody of the Stanford Axe.

    Stanford has had at least one NCAA team champion every year since the 1976–77 school year and has earned 126 NCAA national team titles since its establishment, the most among universities, and Stanford has won 522 individual national championships, the most by any university. Stanford has won the award for the top-ranked Division 1 athletic program—the NACDA Directors’ Cup, formerly known as the Sears Cup—annually for the past twenty-four straight years. Stanford athletes have won medals in every Olympic Games since 1912, winning 270 Olympic medals total, 139 of them gold. In the 2008 Summer Olympics, and 2016 Summer Olympics, Stanford won more Olympic medals than any other university in the United States. Stanford athletes won 16 medals at the 2012 Summer Olympics (12 gold, two silver and two bronze), and 27 medals at the 2016 Summer Olympics.

    Traditions

    The unofficial motto of Stanford, selected by President Jordan, is Die Luft der Freiheit weht. Translated from the German language, this quotation from Ulrich von Hutten means, “The wind of freedom blows.” The motto was controversial during World War I, when anything in German was suspect; at that time the university disavowed that this motto was official.
    Hail, Stanford, Hail! is the Stanford Hymn sometimes sung at ceremonies or adapted by the various University singing groups. It was written in 1892 by mechanical engineering professor Albert W. Smith and his wife, Mary Roberts Smith (in 1896 she earned the first Stanford doctorate in Economics and later became associate professor of Sociology), but was not officially adopted until after a performance on campus in March 1902 by the Mormon Tabernacle Choir.
    “Uncommon Man/Uncommon Woman”: Stanford does not award honorary degrees, but in 1953 the degree of “Uncommon Man/Uncommon Woman” was created to recognize individuals who give rare and extraordinary service to the University. Technically, this degree is awarded by the Stanford Associates, a voluntary group that is part of the university’s alumni association. As Stanford’s highest honor, it is not conferred at prescribed intervals, but only when appropriate to recognize extraordinary service. Recipients include Herbert Hoover, Bill Hewlett, Dave Packard, Lucile Packard, and John Gardner.
    Big Game events: The events in the week leading up to the Big Game vs. UC Berkeley, including Gaieties (a musical written, composed, produced, and performed by the students of Ram’s Head Theatrical Society).
    “Viennese Ball”: a formal ball with waltzes that was initially started in the 1970s by students returning from the now-closed Stanford in Vienna overseas program. It is now open to all students.
    “Full Moon on the Quad”: An annual event at Main Quad, where students gather to kiss one another starting at midnight. Typically organized by the Junior class cabinet, the festivities include live entertainment, such as music and dance performances.
    “Band Run”: An annual festivity at the beginning of the school year, where the band picks up freshmen from dorms across campus while stopping to perform at each location, culminating in a finale performance at Main Quad.
    “Mausoleum Party”: An annual Halloween Party at the Stanford Mausoleum, the final resting place of Leland Stanford Jr. and his parents. A 20-year tradition, the “Mausoleum Party” was on hiatus from 2002 to 2005 due to a lack of funding, but was revived in 2006. In 2008, it was hosted in Old Union rather than at the actual Mausoleum, because rain prohibited generators from being rented. In 2009, after fundraising efforts by the Junior Class Presidents and the ASSU Executive, the event was able to return to the Mausoleum despite facing budget cuts earlier in the year.
    Former campus traditions include the “Big Game bonfire” on Lake Lagunita (a seasonal lake usually dry in the fall), which was formally ended in 1997 because of the presence of endangered salamanders in the lake bed.

    Award laureates and scholars

    Stanford’s current community of scholars includes:

    19 Nobel Prize laureates (as of October 2020, 85 affiliates in total)
    171 members of the National Academy of Sciences
    109 members of National Academy of Engineering
    76 members of National Academy of Medicine
    288 members of the American Academy of Arts and Sciences
    19 recipients of the National Medal of Science
    1 recipient of the National Medal of Technology
    4 recipients of the National Humanities Medal
    49 members of American Philosophical Society
    56 fellows of the American Physics Society (since 1995)
    4 Pulitzer Prize winners
    31 MacArthur Fellows
    4 Wolf Foundation Prize winners
    2 ACL Lifetime Achievement Award winners
    14 AAAI fellows
    2 Presidential Medal of Freedom winners

    Stanford University Seal

    Formerly known as Simons Science News, Quanta Magazine (US) is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 10:03 pm on August 24, 2021 Permalink | Reply
    Tags: "This Physicist Discovered an Escape From Hawking’s Black Hole Paradox", , In 1974 Stephen Hawking calculated that black holes’ secrets die with them., , Quantum Gravity,   

    From Quanta Magazine (US) : “This Physicist Discovered an Escape From Hawking’s Black Hole Paradox” 

    From Quanta Magazine (US)

    August 23, 2021
    Natalie Wolchover

    1
    Netta Engelhardt puzzles over the fates of black holes in her office at the Massachusetts Institute of Technology. Credit: Tira Khan for Quanta Magazine.

    In 1974 Stephen Hawking calculated that black holes’ secrets die with them. Random quantum jitter on the spherical outer boundary, or “event horizon,” of a black hole will cause the hole to radiate particles and slowly shrink to nothing. Any record of the star whose violent contraction formed the black hole — and whatever else got swallowed up after — then seemed to be permanently lost.

    Hawking’s calculation posed a paradox — the infamous “black hole information paradox” — that has motivated research in fundamental physics ever since. On the one hand, quantum mechanics, the rulebook for particles, says that information about particles’ past states gets carried forward as they evolve — a bedrock principle called “unitarity.” But black holes take their cues from general relativity, the theory that space and time form a bendy fabric and gravity is the fabric’s curves. Hawking had tried to apply quantum mechanics to particles near a black hole’s periphery, and saw unitarity break down.

    So do evaporating black holes really destroy information, meaning unitarity is not a true principle of nature? Or does information escape as a black hole evaporates? Solving the information paradox quickly came to be seen as a route to discovering the true, quantum theory of gravity, which general relativity approximates well everywhere except black holes.

    In the past two years, a network of quantum gravity theorists, mostly millennials, has made enormous progress on Hawking’s paradox. One of the leading researchers is Netta Engelhardt, a 32-year-old theoretical physicist at The Massachusetts Institute of Technology (US). She and her colleagues have completed a new calculation that corrects Hawking’s 1974 formula; theirs indicates that information does, in fact, escape black holes via their radiation. She and Aron Wall identified an invisible surface that lies inside a black hole’s event horizon, called the “quantum extremal surface.” In 2019, Engelhardt and others showed that this surface seems to encode the amount of information that has radiated away from the black hole, evolving over the hole’s lifetime exactly as expected if information escapes.

    Engelhardt received a 2021 New Horizons in Physics Prize “for calculating the quantum information content of a black hole and its radiation.” Ahmed Almheiri of The Institute for Advanced Study (US), a frequent collaborator, noted her “deeply rooted intuition for the intricate workings of gravity,” particularly in the discovery of quantum extremal surfaces.

    Engelhardt set her sights on quantum gravity when she was 9 years old. She moved to Boston from Israel that year with her family, and, not knowing any English, read every book in Hebrew she could find in her house. The last was Hawking’s A Brief History of Time. “What that book did for me was trigger a desire to understand the fundamental building blocks of the universe,” she said. “From then on, I was sort of finding my own way, watching different popular science videos and asking questions of anybody who might have the answers, and narrowing down what I wanted to work on.” She ultimately found her way to Hawking’s paradox.

    When Quanta Magazine caught up with Engelhardt in a recent video call, she emphasized that the full solution to the paradox — and the quantum theory of gravity — is a work in progress. We discussed that progress, which centrally involves the concept of entropy, and the search for a “reverse algorithm” that would allow someone to reconstruct a black hole’s past. The conversation has been condensed and edited for clarity.

    Would you say you and your colleagues have solved the black hole information paradox?

    Not yet. We’ve made a lot of progress toward a resolution. That’s part of what makes the field so exciting; we’re moving forward — and we’re not doing it so slowly, either — but there’s still a lot that we have to uncover and understand.

    Could you summarize what you’ve figured out so far?

    Certainly. Along the way there have been a number of very important developments. One I will mention is a 1993 paper by Don Page [Physical Review Letters]. Page said, suppose that information is conserved. Then the entropy of everything outside of a black hole starts out at some value, increases, then has to go back down to the original value once the black hole has evaporated altogether. Whereas Hawking’s calculation predicts that the entropy increases, and once the black hole is evaporated completely, it just plateaus at some value and that’s it.

    3
    Samuel Velasco/Quanta Magazine.

    So the question became, which entropy curve is right. Normally, entropy is the number of possible indistinguishable configurations of a system. What’s the best way to understand entropy in this black hole context?

    You could think of this entropy as ignorance of the state of affairs in the black hole interior. The more possibilities there are for what could be going on in the black hole interior, the more ignorant you will be about which configuration the system is in. So this entropy measures ignorance.

    Page’s discovery was that if you assume that the evolution of the universe doesn’t lose information, then, if you start out with zero ignorance about the universe before a black hole forms, eventually you’re going to end up with zero ignorance once the black hole is gone, since all the information that went in has come back out. That’s in conflict with what Hawking derived, which was that eventually you end up with ignorance.

    You characterize Page’s insight and all other work on the information paradox prior to 2019 as “understanding the problem better.” What happened in 2019?

    The activity that started in 2019 is the steps towards actually resolving the problem. The two papers that kicked this off were work by myself, Ahmed Almheiri, Don Marolf and Henry Maxfield3 and, in parallel, the second paper, which came out at the same time, by Geoff Penington. We submitted our papers on the same day and coordinated because we knew we were both onto the same thing.

    The idea was to calculate the entropy in a different way. This is where Don Page’s calculation was very important for us. If we use Hawking’s method and his assumptions, we get a formula for the entropy which is not consistent with unitarity. Now we want to understand how we could possibly do a calculation that would give us the curve of the entropy that Page proposed, which goes up then comes back down.

    And for this we relied on a proposal that Aron Wall and I gave in 2014: the quantum extremal surface proposal, which essentially states that the so-called quantum-corrected area of a certain surface inside the black hole is what computes the entropy. We said, maybe that’s a way to do the quantum gravity calculation that gives us a unitary result. And I will say: It was kind of a shot in the dark.

    When did you realize that it worked?

    This entire time is a bit of a daze in my mind, it was so exciting; I think I slept maybe two hours a night for weeks. The calculation came together over a period of three weeks, I want to say. I was at Princeton University (US) at the time. We just had a meeting on campus. I have a very distinct memory of driving home, and I was thinking to myself, wow, this could be it.

    The crux of the matter was, there’s more than one quantum extremal surface in the problem. There’s one quantum extremal surface that gives you the wrong answer — the Hawking answer. To correctly calculate the entropy, you have to pick the right one, and the right one is always the one with the smallest quantum-corrected area. And so what was really exciting — I think the moment we realized this might really actually work out — is when we found that exactly at the time when the entropy curve needs to “turn over” [go from increasing to decreasing], there’s a jump. At that time, the quantum extremal surface with the smallest quantum-corrected area goes from being the surface that would give you Hawking’s answer to a new and unexpected one. And that one reproduces the Page curve.

    What are these quantum extremal surfaces, exactly?

    Let me try to intuit a little bit what a classical, non-quantum extremal surface feels like. Let me begin with just a sphere. Imagine that you place a light bulb inside of it, and you follow the light rays as they move outward through the sphere. As the light rays get farther and farther away from the light bulb, the area of the spheres that they pass through will be getting larger and larger. We say that the cross-sectional area of the light rays is getting larger.

    That’s an intuition that works really well in approximately flat space where we live. But when you consider very curved space-time like you find inside a black hole, what can happen is that even though you’re firing your light rays outwards from the light bulb, and you’re looking at spheres that are progressively farther away from the bulb, the cross-sectional area is actually shrinking. And this is because space-time is very violently curved. It’s something that we call focusing of light rays, and it’s a very fundamental concept in gravity and general relativity.

    The extremal surface straddles this line between the very violent situation where the area is decreasing, and a normal situation where the area increases. The area of the surface is neither increasing nor decreasing, and so intuitively you can think of an extremal surface as kind of lying right at the cusp of where you’d expect strong curvature to start kicking in. A quantum extremal surface is the same idea, but instead of area, now you’re looking at quantum-corrected area. This is a sum of area and entropy, which is neither increasing nor decreasing.

    What does the quantum extremal surface mean? What’s the difference between things that are inside versus outside?

    Recall that when the Page curve turns over, we expect that our ignorance of what the black hole contains starts to decrease, as we have access to more and more of its radiation. So the radiation emitted by the hole must start to “learn” about the black hole interior.

    It’s the quantum extremal surface that divides the space-time in two: Everything inside the surface, the radiation can already decode. Everything outside of it is what remains hidden in the black hole system, what’s not contained in the information of the radiation. As the black hole emits more radiation, the quantum extremal surface moves outwards and encompasses an ever-larger volume of the black hole interior. By the time that black hole evaporates altogether, the radiation has to be able to decode everything that way.

    Now that we have an explicit calculation that gives us a unitary answer, that gives us so many tools to start asking questions that we could never ask before, like where does this formula come from, what does it mean about what type of theory quantum gravity is? Also, what is the mechanism in quantum gravity that restores unitarity? It has something to do with the quantum extremal surface formula.

    Most of the justification for the quantum extremal surface formula comes from studying black holes in “Anti-de Sitter” (AdS) space — saddle-shaped space with an outer boundary. Whereas our universe has approximately flat space, and no boundary. Why should we think that these calculations apply to our universe?

    First, we can’t really get around the fact that our universe contains both quantum mechanics and gravity. It contains black holes. So our understanding of the universe is going to be incomplete until we have a description of what happens inside a black hole. The information problem is such a difficult problem to solve that any progress — whether it’s in a toy model or not — is making progress towards understanding phenomena that happen in our universe.

    Now at a more technical level, quantum extremal surfaces can be computed in different kinds of space-times, including flat space like in our universe. And in fact there already have been papers written on the behavior of quantum extremal surfaces within different kinds of space-times and what types of entropy curves they would give rise to.

    We have a very firm interpretation of the quantum extremal surface in AdS space. We can extrapolate and say that in flat space there exists some interpretation of the quantum extremal surface which is analogous, and I think that’s probably true. It has many nice properties; it looks like it’s the right thing. We get really interesting behavior and we expect to get unitarity as well, and so, yes, we do expect that this phenomenon does translate, although the interpretation is going to be harder.

    You said at the beginning of our conversation that we don’t know the solution to the information paradox yet. Can you explain what a solution looks like?

    A full resolution of the information paradox would have to tell us exactly how the black hole information comes out. If I’m an observer that’s sitting outside of a black hole and I have extremely sophisticated technology and all the time in the world — a quantum computer taking incredibly sophisticated measurements, all the radiation of that black hole — what does it take for me to actually decode the radiation to reconstruct, for instance, the star that collapsed and formed the black hole? What process do I need to put my quantum computer through? We need to answer that question.

    So you want to find the reverse algorithm that unscrambles the information in the radiation. What’s the connection between that algorithm and quantum gravity?

    This algorithm that decodes the Hawking radiation is coming from the process in which quantum gravity encodes the radiation as it evaporates at the black hole horizon. The emergence of the black hole interior from quantum gravity and the dynamics of the black hole interior, the experience of an object that falls into the black hole — all of that is encoded in this reverse algorithm that quantum gravity has to spit out. All of those are tied up in the question of “how does the information get encoded in the Hawking radiation?”

    You’ve lately been writing papers about something called “a python’s lunch”. What’s that?

    It’s one thing to ask how can you decode the Hawking radiation; you also might ask, how complex is the task of decoding the Hawking radiation. And, as it turns out, extremely complex. So maybe the difference between Hawking’s calculation and the quantum extremal surface calculation that gives unitarity is that Hawking’s calculation is just dropping the high-complexity operations.

    It’s important to understand the complexity geometrically. And in 2019 there was a paper by some of my colleagues that proposed that whenever you have more than one quantum extremal surface, the one that would be wrong for the entropy can be used to calculate the complexity of decoding the black hole radiation. The two quantum extremal surfaces can be thought of as sort of constrictions in the space-time geometry, and those of us who have read Le Petit Prince see an elephant inside a python, and so it has become known as a python’s lunch.

    We proposed that multiple quantum extremal surfaces are the exclusive source of high complexity. And these two papers that you’re referring to are essentially an argument for this “strong python’s lunch” proposal. That is very insightful for us because it identifies the part of the geometry that Hawking’s calculation knows about and part of the geometry that Hawking’s calculation doesn’t know about. It’s working towards putting his and our calculations in the same language so that we know why one is right, and the other is wrong.

    Where would you say we currently stand in our effort to understand the quantum nature of gravity?

    I like to think of this as a puzzle, where we have all the edge pieces and we’re missing the center. We have many different insights about quantum gravity. There are many ways in which people are trying to understand it. Some by constraining it: What are things that it can’t do? Some by trying to construct aspects of it: things that it must do. My personal preferred approach is more to do with the information paradox, because it’s so pivotal; it’s such an acute problem. It’s clearly telling us: Here’s where you messed up. And to me that says, here’s a place where we can begin to fix our pillars, one of which must be wrong, of our understanding of quantum gravity.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Formerly known as Simons Science News, Quanta Magazine (US) is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 10:52 am on June 21, 2021 Permalink | Reply
    Tags: "Klarman postdoc seeks ‘theory of everything’ by approximation", Attempting to unify gravity with other fundamental forces of physics., , , , , Quantum Gravity, ,   

    From Cornell Chronicle (US) : “Klarman postdoc seeks ‘theory of everything’ by approximation” 

    From Cornell Chronicle (US)

    June 21, 2021
    Kate Blackwood
    cunews@cornell.edu

    1
    Francesco Sgarlata.

    Two pillar theories in physics – general relativity and quantum mechanics – stand up well on their own, but are incompatible with each other.

    “These two theories describe two different regimes of phenomena,” said Francesco Sgarlata, a Klarman Postdoctoral Fellow in physics in the College of Arts and Sciences (A&S).

    2

    Quantum mechanics, he said, describes physical phenomena at atomic or sub-atomic scales; general relativity describes very large phenomena.

    “The two theories are both correct in that they both predict very well, and we don’t have any violation of these theories. However, the two theories are inconsistent with each other,” Sgarlata said, adding that the inconsistencies show up in processes at extremely small scales.

    A member of the first cohort of six Klarman Fellows, Sgarlata is using his three-year fellowship to join theoretical physicists at Cornell and around the world in trying to solve this inconsistency.

    Physicists have long sought a “theory of everything,” or theory of quantum gravity, that would unify quantum mechanics and general relativity. In recent decades, researchers have tried a top-down approach, trying to come up with a unifying theory, such as string theory.

    Sgarlata, in contrast, is taking a bottom-up approach to finding a theory of quantum gravity, which attempts to unify gravity with other fundamental forces of physics.

    “We seek an approximation,” he said. “We don’t know what this theory of everything is. [Instead,] we are trying to write down some theory which can be seen as an approximation of quantum gravity, and we study what conditions this theory will have in order to be a good approximation of quantum gravity.”

    Sgarlata is working with Cornell’s theoretical physics community, including his faculty host, Csaba Csaki, professor of physics (A&S), and Thomas Hartman, associate professor of physics (A&S), to “identify some hidden properties of quantum gravity,” one at a time – and then build from there.

    “Francesco’s research is on the fundamental properties of particles and forces,” Hartman said. “His goal is to understand what particles are consistent with basic principles of relativity and quantum mechanics, and how these particles can interact.”

    Sgarlata’s background is in particle physics, Hartman said, while his own background is in black hole physics and string theory.

    “There is a lot of overlap, but these are two different perspectives,” Hartman said, “so this is a great opportunity for us to collaborate on new ideas. We are working on joining forces and combining our approaches.”

    To find conditions necessary to support a theory of quantum gravity, Sgarlata and collaborators focus on “first principles” – those we experience in everyday life but are difficult to prove mathematically. One example is causality – the link between cause and effect.

    “If I punch you, you will start feeling pain after I punch you, not before,” Sgarlata said. “We assume that this theory of everything respects causality.”

    Other first principles the researchers consider are unitarity (probabilities must add up to 1); and locality (particles only interact with neighboring particles.)

    From a “swampland” of possible theories arise islands of probable theories, Sgarlata said, narrowing the scope. “We get some constraints on the parameters of the theory,” he said.

    Hartman said that Sgarlata uses methods from particle physics to develop and interpret theories of physics at high energies.

    “In some cases, his methods can even be used to understand some corners of the more mysterious theory of quantum gravity at ultrashort distances,” Hartman said. “Over the next couple years, I think Francesco’s research at Cornell will lead to better insight into fundamental particles and new connections between particles, gravity and black holes.”

    The Klarman Fellowship, Sgarlata said, offers independence to pursue research collaborations toward solving the biggest problems in physics.

    “We have the tools to understand features of quantum gravity,” he said. “Today we are reinterpreting these concepts in a more modern way, and we are discovering new concepts of physics just by our interpretations.”

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

    Cornell University (US) is a private, statutory, Ivy League and land-grant research university in Ithaca, New York. Founded in 1865 by Ezra Cornell and Andrew Dickson White, the university was intended to teach and make contributions in all fields of knowledge—from the classics to the sciences, and from the theoretical to the applied. These ideals, unconventional for the time, are captured in Cornell’s founding principle, a popular 1868 quotation from founder Ezra Cornell: “I would found an institution where any person can find instruction in any study.”

    The university is broadly organized into seven undergraduate colleges and seven graduate divisions at its main Ithaca campus, with each college and division defining its specific admission standards and academic programs in near autonomy. The university also administers two satellite medical campuses, one in New York City and one in Education City, Qatar, and Jacobs Technion-Cornell Institute(US) in New York City, a graduate program that incorporates technology, business, and creative thinking. The program moved from Google’s Chelsea Building in New York City to its permanent campus on Roosevelt Island in September 2017.

    Cornell is one of the few private land grant universities in the United States. Of its seven undergraduate colleges, three are state-supported statutory or contract colleges through the SUNY – The State University of New York (US) system, including its Agricultural and Human Ecology colleges as well as its Industrial Labor Relations school. Of Cornell’s graduate schools, only the veterinary college is state-supported. As a land grant college, Cornell operates a cooperative extension outreach program in every county of New York and receives annual funding from the State of New York for certain educational missions. The Cornell University Ithaca Campus comprises 745 acres, but is much larger when the Cornell Botanic Gardens (more than 4,300 acres) and the numerous university-owned lands in New York City are considered.

    Alumni and affiliates of Cornell have reached many notable and influential positions in politics, media, and science. As of January 2021, 61 Nobel laureates, four Turing Award winners and one Fields Medalist have been affiliated with Cornell. Cornell counts more than 250,000 living alumni, and its former and present faculty and alumni include 34 Marshall Scholars, 33 Rhodes Scholars, 29 Truman Scholars, 7 Gates Scholars, 55 Olympic Medalists, 10 current Fortune 500 CEOs, and 35 billionaire alumni. Since its founding, Cornell has been a co-educational, non-sectarian institution where admission has not been restricted by religion or race. The student body consists of more than 15,000 undergraduate and 9,000 graduate students from all 50 American states and 119 countries.

    History

    Cornell University was founded on April 27, 1865; the New York State (NYS) Senate authorized the university as the state’s land grant institution. Senator Ezra Cornell offered his farm in Ithaca, New York, as a site and $500,000 of his personal fortune as an initial endowment. Fellow senator and educator Andrew Dickson White agreed to be the first president. During the next three years, White oversaw the construction of the first two buildings and traveled to attract students and faculty. The university was inaugurated on October 7, 1868, and 412 men were enrolled the next day.

    Cornell developed as a technologically innovative institution, applying its research to its own campus and to outreach efforts. For example, in 1883 it was one of the first university campuses to use electricity from a water-powered dynamo to light the grounds. Since 1894, Cornell has included colleges that are state funded and fulfill statutory requirements; it has also administered research and extension activities that have been jointly funded by state and federal matching programs.

    Cornell has had active alumni since its earliest classes. It was one of the first universities to include alumni-elected representatives on its Board of Trustees. Cornell was also among the Ivies that had heightened student activism during the 1960s related to cultural issues; civil rights; and opposition to the Vietnam War, with protests and occupations resulting in the resignation of Cornell’s president and the restructuring of university governance. Today the university has more than 4,000 courses. Cornell is also known for the Residential Club Fire of 1967, a fire in the Residential Club building that killed eight students and one professor.

    Since 2000, Cornell has been expanding its international programs. In 2004, the university opened the Weill Cornell Medical College in Qatar. It has partnerships with institutions in India, Singapore, and the People’s Republic of China. Former president Jeffrey S. Lehman described the university, with its high international profile, a “transnational university”. On March 9, 2004, Cornell and Stanford University(US) laid the cornerstone for a new ‘Bridging the Rift Center’ to be built and jointly operated for education on the Israel–Jordan border.

    Research

    Cornell, a research university, is ranked fourth in the world in producing the largest number of graduates who go on to pursue PhDs in engineering or the natural sciences at American institutions, and fifth in the world in producing graduates who pursue PhDs at American institutions in any field. Research is a central element of the university’s mission; in 2009 Cornell spent $671 million on science and engineering research and development, the 16th highest in the United States. Cornell is classified among “R1: Doctoral Universities – Very high research activity”.

    For the 2016–17 fiscal year, the university spent $984.5 million on research. Federal sources constitute the largest source of research funding, with total federal investment of $438.2 million. The agencies contributing the largest share of that investment are the Department of Health and Human Services and the National Science Foundation(US), accounting for 49.6% and 24.4% of all federal investment, respectively. Cornell was on the top-ten list of U.S. universities receiving the most patents in 2003, and was one of the nation’s top five institutions in forming start-up companies. In 2004–05, Cornell received 200 invention disclosures; filed 203 U.S. patent applications; completed 77 commercial license agreements; and distributed royalties of more than $4.1 million to Cornell units and inventors.

    Since 1962, Cornell has been involved in unmanned missions to Mars. In the 21st century, Cornell had a hand in the Mars Exploration Rover Mission. Cornell’s Steve Squyres, Principal Investigator for the Athena Science Payload, led the selection of the landing zones and requested data collection features for the Spirit and Opportunity rovers. NASA-JPL/Caltech(US) engineers took those requests and designed the rovers to meet them. The rovers, both of which have operated long past their original life expectancies, are responsible for the discoveries that were awarded 2004 Breakthrough of the Year honors by Science. Control of the Mars rovers has shifted between National Aeronautics and Space Administration(US)’s JPL-Caltech (US) and Cornell’s Space Sciences Building.

    Further, Cornell researchers discovered the rings around the planet Uranus, and Cornell built and operated the telescope at Arecibo Observatory located in Arecibo, Puerto Rico(US) until 2011, when they transferred the operations to SRI International, the Universities Space Research Association (US) and the Metropolitan University of Puerto Rico [Universidad Metropolitana de Puerto Rico](US).

    The Automotive Crash Injury Research Project was begun in 1952. It pioneered the use of crash testing, originally using corpses rather than dummies. The project discovered that improved door locks; energy-absorbing steering wheels; padded dashboards; and seat belts could prevent an extraordinary percentage of injuries.

    In the early 1980s, Cornell deployed the first IBM 3090-400VF and coupled two IBM 3090-600E systems to investigate coarse-grained parallel computing. In 1984, the National Science Foundation began work on establishing five new supercomputer centers, including the Cornell Center for Advanced Computing, to provide high-speed computing resources for research within the United States. As an National Science Foundation (US) center, Cornell deployed the first IBM Scalable Parallel supercomputer.

    In the 1990s, Cornell developed scheduling software and deployed the first supercomputer built by Dell. Most recently, Cornell deployed Red Cloud, one of the first cloud computing services designed specifically for research. Today, the center is a partner on the National Science Foundation XSEDE-Extreme Science Engineering Discovery Environment supercomputing program, providing coordination for XSEDE architecture and design, systems reliability testing, and online training using the Cornell Virtual Workshop learning platform.

    Cornell scientists have researched the fundamental particles of nature for more than 70 years. Cornell physicists, such as Hans Bethe, contributed not only to the foundations of nuclear physics but also participated in the Manhattan Project. In the 1930s, Cornell built the second cyclotron in the United States. In the 1950s, Cornell physicists became the first to study synchrotron radiation.

    During the 1990s, the Cornell Electron Storage Ring, located beneath Alumni Field, was the world’s highest-luminosity electron-positron collider. After building the synchrotron at Cornell, Robert R. Wilson took a leave of absence to become the founding director of DOE’s Fermi National Accelerator Laboratory(US), which involved designing and building the largest accelerator in the United States.

    Cornell’s accelerator and high-energy physics groups are involved in the design of the proposed ILC-International Linear Collider(JP) and plan to participate in its construction and operation. The International Linear Collider(JP), to be completed in the late 2010s, will complement the CERN Large Hadron Collider(CH) and shed light on questions such as the identity of dark matter and the existence of extra dimensions.

    As part of its research work, Cornell has established several research collaborations with universities around the globe. For example, a partnership with the University of Sussex(UK) (including the Institute of Development Studies at Sussex) allows research and teaching collaboration between the two institutions.

     
  • richardmitnick 9:20 am on June 18, 2021 Permalink | Reply
    Tags: "Physicists Nearly Reach Elusive Quantum Ground State on The Largest 'Object' Yet", Achieving the quantum ground state of a cloud of atoms isn't easy. You need to cool the atom by applying just the right amount of force to stop its vibrations., , , , , , , , Quantum Gravity, , , The work represents a new way to probe the quantum realm.   

    From Massachusetts Institute of Technology (US) via Science Alert (AU) : “Physicists Nearly Reach Elusive Quantum Ground State on The Largest ‘Object’ Yet” 

    MIT News

    From Massachusetts Institute of Technology (US)

    via

    http://www.sciencealert.com/”> Science Alert (AU)

    17 JUNE 2021
    MICHELLE STARR

    1
    One of LIGO’s mirrors. Credit: Caltech/ MIT Advanced aLIGO (US).

    Very rarely is anything completely still. All normal matter in the Universe is made of humming particles, minding their own business and vibrating at their own frequencies.

    If we can get them to slow down as much as possible, the material enters what is known as the motional ground state. In this state, physicists can perform tests of quantum mechanics and quantum gravity, probing the boundary with classical physics to search for a way to unify the two.

    Previously, this has been performed in the nanoscale; but now, for the first time, it’s been done on a massive ‘object’ – the collective motions of the four mirrors of the LIGO gravitational wave interferometer, known as an optomechanical oscillator, with an effective mass of 10 kilograms (22 pounds).

    Caltech /MIT Advanced aLigo .

    The work represents a new way to probe the quantum realm.

    “Nobody has ever observed how gravity acts on massive quantum states,” said mechanical engineer Vivishek Sudhir of MIT.

    “We’ve demonstrated how to prepare kilogram-scale objects in quantum states. This finally opens the door to an experimental study of how gravity might affect large quantum objects, something hitherto only dreamed of.”

    Achieving the quantum ground state of a cloud of atoms isn’t easy. You need to cool the atom by applying just the right amount of force to stop its vibrations. If you don’t cool it enough, it merely slows; so you need to know the exact energy level and direction of the atom’s vibrations in order to apply the appropriate force to stop it.

    This is called ‘feedback cooling’, and on the nanoscale it’s simpler to do, because it’s easier to isolate the smaller groups of atoms and minimize interference. The larger you go, though, the harder it becomes to handle that interference.

    LIGO is one of the most precise instruments for measuring fine motion. It’s designed to detect tiny ripples in space-time generated by collisions between massive objects up to billions of light-years away.

    It consists of an L-shaped vacuum chamber, with laser lights beamed along its two 4-kilometer (2.5-mile) tunnels, and sent to a beam splitter to four mirrors, one at each end of each tunnel. When space-time ripples, the mirrors distort the light, producing an interference pattern that scientists can decode to determine the cause. And it’s so sensitive that it can detect a change just one ten-thousandth the width of a proton, or 10-19 meters.

    Each of LIGO’s four 40-kilogram mirrors is suspended, and it’s their collective motion that makes up the oscillator. The balance of the mirrors effectively reduces 160 kilograms of total weight to a single object of just 10 kilograms.

    “LIGO is designed to measure the joint motion of the four 40-kilogram mirrors,” Sudhir said. “It turns out you can map the joint motion of these masses mathematically, and think of them as the motion of a single 10-kilogram object.”

    By precisely measuring the motion of this oscillator, the team hoped to work out exactly the rate of feedback cooling required to induce the motional ground state… and then, obviously, apply it.

    Unfortunately the very act of measuring throws a degree of randomness into the equation, making it difficult to predict the kinds of nudges needed to sap the energy out of the mirror’s atoms.

    To correct for this, the team cleverly studied each photon to estimate the activity of previous collisions, continuously building a more accurate map of how to apply the correct forces and achieve cooling.

    Then, they applied the calculated force using electromagnets attached to the backs of the mirrors.

    It worked. The oscillator stopped moving, almost completely. Its remaining energy was equivalent to a temperature of 77 nanokelvin (-273.15 degrees Celsius, or -459.67 degrees Fahrenheit).

    Its motional ground state, 10 nanokelvin, is extremely close, especially considering the room temperature starting point. And 77 nanokelvin is also very close to the temperatures used in motional ground state studies on the nanoscale.

    Moreover, it opens the door to some exciting possibilities. Macro-scale demonstrations and measurements of quantum phenomena – and maybe even applications for the same.

    But quantum gravity is the big kicker. Kilogram-mass objects are more susceptible to gravity; the team’s work raises hope to use this mass regime to study the quantum realm.

    “Preparing something in the ground state is often the first step to putting it into exciting or exotic quantum states,” said physicist Chris Whittle of MIT and the LIGO collaboration.

    “So this work is exciting because it might let us study some of these other states, on a mass scale that’s never been done before.”

    The research has been published in Science.

    See the full article here .


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    MIT Seal

    USPS “Forever” postage stamps celebrating Innovation at MIT.

    MIT Campus

    Massachusetts Institute of Technology (US) is a private land-grant research university in Cambridge, Massachusetts. The institute has an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory, the Bates Center, and the Haystack Observatory, as well as affiliated laboratories such as the Broad and Whitehead Institutes.

    Founded in 1861 in response to the increasing industrialization of the United States, Massachusetts Institute of Technology (US) adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength. It is frequently regarded as one of the most prestigious universities in the world.

    As of December 2020, 97 Nobel laureates, 26 Turing Award winners, and 8 Fields Medalists have been affiliated with MIT as alumni, faculty members, or researchers. In addition, 58 National Medal of Science recipients, 29 National Medals of Technology and Innovation recipients, 50 MacArthur Fellows, 80 Marshall Scholars, 3 Mitchell Scholars, 22 Schwarzman Scholars, 41 astronauts, and 16 Chief Scientists of the U.S. Air Force have been affiliated with Massachusetts Institute of Technology (US) . The university also has a strong entrepreneurial culture and MIT alumni have founded or co-founded many notable companies. Massachusetts Institute of Technology (US) is a member of the Association of American Universities (AAU).

    Foundation and vision

    In 1859, a proposal was submitted to the Massachusetts General Court to use newly filled lands in Back Bay, Boston for a “Conservatory of Art and Science”, but the proposal failed. A charter for the incorporation of the Massachusetts Institute of Technology, proposed by William Barton Rogers, was signed by John Albion Andrew, the governor of Massachusetts, on April 10, 1861.

    Rogers, a professor from the University of Virginia (US), wanted to establish an institution to address rapid scientific and technological advances. He did not wish to found a professional school, but a combination with elements of both professional and liberal education, proposing that:

    “The true and only practicable object of a polytechnic school is, as I conceive, the teaching, not of the minute details and manipulations of the arts, which can be done only in the workshop, but the inculcation of those scientific principles which form the basis and explanation of them, and along with this, a full and methodical review of all their leading processes and operations in connection with physical laws.”

    The Rogers Plan reflected the German research university model, emphasizing an independent faculty engaged in research, as well as instruction oriented around seminars and laboratories.

    Early developments

    Two days after Massachusetts Institute of Technology (US) was chartered, the first battle of the Civil War broke out. After a long delay through the war years, MIT’s first classes were held in the Mercantile Building in Boston in 1865. The new institute was founded as part of the Morrill Land-Grant Colleges Act to fund institutions “to promote the liberal and practical education of the industrial classes” and was a land-grant school. In 1863 under the same act, the Commonwealth of Massachusetts founded the Massachusetts Agricultural College, which developed as the University of Massachusetts Amherst (US)). In 1866, the proceeds from land sales went toward new buildings in the Back Bay.

    Massachusetts Institute of Technology (US) was informally called “Boston Tech”. The institute adopted the European polytechnic university model and emphasized laboratory instruction from an early date. Despite chronic financial problems, the institute saw growth in the last two decades of the 19th century under President Francis Amasa Walker. Programs in electrical, chemical, marine, and sanitary engineering were introduced, new buildings were built, and the size of the student body increased to more than one thousand.

    The curriculum drifted to a vocational emphasis, with less focus on theoretical science. The fledgling school still suffered from chronic financial shortages which diverted the attention of the MIT leadership. During these “Boston Tech” years, Massachusetts Institute of Technology (US) faculty and alumni rebuffed Harvard University (US) president (and former MIT faculty) Charles W. Eliot’s repeated attempts to merge MIT with Harvard College’s Lawrence Scientific School. There would be at least six attempts to absorb MIT into Harvard. In its cramped Back Bay location, MIT could not afford to expand its overcrowded facilities, driving a desperate search for a new campus and funding. Eventually, the MIT Corporation approved a formal agreement to merge with Harvard, over the vehement objections of MIT faculty, students, and alumni. However, a 1917 decision by the Massachusetts Supreme Judicial Court effectively put an end to the merger scheme.

    In 1916, the Massachusetts Institute of Technology (US) administration and the MIT charter crossed the Charles River on the ceremonial barge Bucentaur built for the occasion, to signify MIT’s move to a spacious new campus largely consisting of filled land on a one-mile-long (1.6 km) tract along the Cambridge side of the Charles River. The neoclassical “New Technology” campus was designed by William W. Bosworth and had been funded largely by anonymous donations from a mysterious “Mr. Smith”, starting in 1912. In January 1920, the donor was revealed to be the industrialist George Eastman of Rochester, New York, who had invented methods of film production and processing, and founded Eastman Kodak. Between 1912 and 1920, Eastman donated $20 million ($236.6 million in 2015 dollars) in cash and Kodak stock to MIT.

    Curricular reforms

    In the 1930s, President Karl Taylor Compton and Vice-President (effectively Provost) Vannevar Bush emphasized the importance of pure sciences like physics and chemistry and reduced the vocational practice required in shops and drafting studios. The Compton reforms “renewed confidence in the ability of the Institute to develop leadership in science as well as in engineering”. Unlike Ivy League schools, Massachusetts Institute of Technology (US) catered more to middle-class families, and depended more on tuition than on endowments or grants for its funding. The school was elected to the Association of American Universities (US)in 1934.

    Still, as late as 1949, the Lewis Committee lamented in its report on the state of education at Massachusetts Institute of Technology (US) that “the Institute is widely conceived as basically a vocational school”, a “partly unjustified” perception the committee sought to change. The report comprehensively reviewed the undergraduate curriculum, recommended offering a broader education, and warned against letting engineering and government-sponsored research detract from the sciences and humanities. The School of Humanities, Arts, and Social Sciences and the MIT Sloan School of Management were formed in 1950 to compete with the powerful Schools of Science and Engineering. Previously marginalized faculties in the areas of economics, management, political science, and linguistics emerged into cohesive and assertive departments by attracting respected professors and launching competitive graduate programs. The School of Humanities, Arts, and Social Sciences continued to develop under the successive terms of the more humanistically oriented presidents Howard W. Johnson and Jerome Wiesner between 1966 and 1980.

    Massachusetts Institute of Technology (US) ‘s involvement in military science surged during World War II. In 1941, Vannevar Bush was appointed head of the federal Office of Scientific Research and Development and directed funding to only a select group of universities, including MIT. Engineers and scientists from across the country gathered at Massachusetts Institute of Technology (US) ‘s Radiation Laboratory, established in 1940 to assist the British military in developing microwave radar. The work done there significantly affected both the war and subsequent research in the area. Other defense projects included gyroscope-based and other complex control systems for gunsight, bombsight, and inertial navigation under Charles Stark Draper’s Instrumentation Laboratory; the development of a digital computer for flight simulations under Project Whirlwind; and high-speed and high-altitude photography under Harold Edgerton. By the end of the war, Massachusetts Institute of Technology (US) became the nation’s largest wartime R&D contractor (attracting some criticism of Bush), employing nearly 4000 in the Radiation Laboratory alone and receiving in excess of $100 million ($1.2 billion in 2015 dollars) before 1946. Work on defense projects continued even after then. Post-war government-sponsored research at MIT included SAGE and guidance systems for ballistic missiles and Project Apollo.

    These activities affected Massachusetts Institute of Technology (US) profoundly. A 1949 report noted the lack of “any great slackening in the pace of life at the Institute” to match the return to peacetime, remembering the “academic tranquility of the prewar years”, though acknowledging the significant contributions of military research to the increased emphasis on graduate education and rapid growth of personnel and facilities. The faculty doubled and the graduate student body quintupled during the terms of Karl Taylor Compton, president of Massachusetts Institute of Technology (US) between 1930 and 1948; James Rhyne Killian, president from 1948 to 1957; and Julius Adams Stratton, chancellor from 1952 to 1957, whose institution-building strategies shaped the expanding university. By the 1950s, Massachusetts Institute of Technology (US) no longer simply benefited the industries with which it had worked for three decades, and it had developed closer working relationships with new patrons, philanthropic foundations and the federal government.

    In late 1960s and early 1970s, student and faculty activists protested against the Vietnam War and Massachusetts Institute of Technology (US) ‘s defense research. In this period Massachusetts Institute of Technology (US) ‘s various departments were researching helicopters, smart bombs and counterinsurgency techniques for the war in Vietnam as well as guidance systems for nuclear missiles. The Union of Concerned Scientists was founded on March 4, 1969 during a meeting of faculty members and students seeking to shift the emphasis on military research toward environmental and social problems. Massachusetts Institute of Technology (US) ultimately divested itself from the Instrumentation Laboratory and moved all classified research off-campus to the MIT (US) Lincoln Laboratoryfacility in 1973 in response to the protests. The student body, faculty, and administration remained comparatively unpolarized during what was a tumultuous time for many other universities. Johnson was seen to be highly successful in leading his institution to “greater strength and unity” after these times of turmoil. However six Massachusetts Institute of Technology (US) students were sentenced to prison terms at this time and some former student leaders, such as Michael Albert and George Katsiaficas, are still indignant about MIT’s role in military research and its suppression of these protests. (Richard Leacock’s film, November Actions, records some of these tumultuous events.)

    In the 1980s, there was more controversy at Massachusetts Institute of Technology (US) over its involvement in SDI (space weaponry) and CBW (chemical and biological warfare) research. More recently, Massachusetts Institute of Technology (US) ‘s research for the military has included work on robots, drones and ‘battle suits’.

    Recent history

    Massachusetts Institute of Technology (US) has kept pace with and helped to advance the digital age. In addition to developing the predecessors to modern computing and networking technologies, students, staff, and faculty members at Project MAC, the Artificial Intelligence Laboratory, and the Tech Model Railroad Club wrote some of the earliest interactive computer video games like Spacewar! and created much of modern hacker slang and culture. Several major computer-related organizations have originated at MIT since the 1980s: Richard Stallman’s GNU Project and the subsequent Free Software Foundation were founded in the mid-1980s at the AI Lab; the MIT Media Lab was founded in 1985 by Nicholas Negroponte and Jerome Wiesner to promote research into novel uses of computer technology; the World Wide Web Consortium standards organization was founded at the Laboratory for Computer Science in 1994 by Tim Berners-Lee; the MIT OpenCourseWare project has made course materials for over 2,000 Massachusetts Institute of Technology (US) classes available online free of charge since 2002; and the One Laptop per Child initiative to expand computer education and connectivity to children worldwide was launched in 2005.

    Massachusetts Institute of Technology (US) was named a sea-grant college in 1976 to support its programs in oceanography and marine sciences and was named a space-grant college in 1989 to support its aeronautics and astronautics programs. Despite diminishing government financial support over the past quarter century, MIT launched several successful development campaigns to significantly expand the campus: new dormitories and athletics buildings on west campus; the Tang Center for Management Education; several buildings in the northeast corner of campus supporting research into biology, brain and cognitive sciences, genomics, biotechnology, and cancer research; and a number of new “backlot” buildings on Vassar Street including the Stata Center. Construction on campus in the 2000s included expansions of the Media Lab, the Sloan School’s eastern campus, and graduate residences in the northwest. In 2006, President Hockfield launched the MIT Energy Research Council to investigate the interdisciplinary challenges posed by increasing global energy consumption.

    In 2001, inspired by the open source and open access movements, Massachusetts Institute of Technology (US) launched OpenCourseWare to make the lecture notes, problem sets, syllabi, exams, and lectures from the great majority of its courses available online for no charge, though without any formal accreditation for coursework completed. While the cost of supporting and hosting the project is high, OCW expanded in 2005 to include other universities as a part of the OpenCourseWare Consortium, which currently includes more than 250 academic institutions with content available in at least six languages. In 2011, Massachusetts Institute of Technology (US) announced it would offer formal certification (but not credits or degrees) to online participants completing coursework in its “MITx” program, for a modest fee. The “edX” online platform supporting MITx was initially developed in partnership with Harvard and its analogous “Harvardx” initiative. The courseware platform is open source, and other universities have already joined and added their own course content. In March 2009 the Massachusetts Institute of Technology (US) faculty adopted an open-access policy to make its scholarship publicly accessible online.

    Massachusetts Institute of Technology (US) has its own police force. Three days after the Boston Marathon bombing of April 2013, MIT Police patrol officer Sean Collier was fatally shot by the suspects Dzhokhar and Tamerlan Tsarnaev, setting off a violent manhunt that shut down the campus and much of the Boston metropolitan area for a day. One week later, Collier’s memorial service was attended by more than 10,000 people, in a ceremony hosted by the Massachusetts Institute of Technology (US) community with thousands of police officers from the New England region and Canada. On November 25, 2013, Massachusetts Institute of Technology (US) announced the creation of the Collier Medal, to be awarded annually to “an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of the Massachusetts Institute of Technology (US) community and in all aspects of his life”. The announcement further stated that “Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness”.

    In September 2017, the school announced the creation of an artificial intelligence research lab called the MIT-IBM Watson AI Lab. IBM will spend $240 million over the next decade, and the lab will be staffed by MIT and IBM scientists. In October 2018 MIT announced that it would open a new Schwarzman College of Computing dedicated to the study of artificial intelligence, named after lead donor and The Blackstone Group CEO Stephen Schwarzman. The focus of the new college is to study not just AI, but interdisciplinary AI education, and how AI can be used in fields as diverse as history and biology. The cost of buildings and new faculty for the new college is expected to be $1 billion upon completion.

    The Caltech/MIT Advanced aLIGO (US) was designed and constructed by a team of scientists from California Institute of Technology (US), Massachusetts Institute of Technology (US) , and industrial contractors, and funded by the National Science Foundation (US) .

    MIT/Caltech Advanced aLigo .

    It was designed to open the field of gravitational-wave astronomy through the detection of gravitational waves predicted by general relativity. Gravitational waves were detected for the first time by the LIGO detector in 2015. For contributions to the LIGO detector and the observation of gravitational waves, two Caltech physicists, Kip Thorne and Barry Barish, and Massachusetts Institute of Technology (US) physicist Rainer Weiss won the Nobel Prize in physics in 2017. Weiss, who is also an Massachusetts Institute of Technology (US) graduate, designed the laser interferometric technique, which served as the essential blueprint for the LIGO.

    The mission of Massachusetts Institute of Technology (US) is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the Massachusetts Institute of Technology (US) community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

     
  • richardmitnick 10:28 am on February 11, 2021 Permalink | Reply
    Tags: "Researchers gather numerical evidence of quantum chaos in the Sachdev-Ye-Kitaev model", , , , , Chaos in quantum systems composed of strongly interacting particles also known as “many-body chaos”, , , , Quantum Gravity,   

    From UC Berkeley via phys.org: “Researchers gather numerical evidence of quantum chaos in the Sachdev-Ye-Kitaev model” 

    From UC Berkeley

    via


    phys.org

    February 11, 2021
    Ingrid Fadelli , Phys.org

    1
    A schematic phase diagram showing the behavior of the Sachdev-Ye-Kitaev model for different regimes of temperature and system size. From high to low temperature, the model transitions from behaving like interacting particles, to a semiclassical black hole, to a highly quantum black hole. Credit: Kobrin et al.

    Over the past few years, many physicists worldwide have conducted research investigating chaos in quantum systems composed of strongly interacting particles, also known as “many-body chaos”. The study of many-body chaos has broadened the current understanding of quantum thermalization (i.e., the process through which quantum particles reach thermal equilibrium by interacting with one another) and revealed surprising connections between microscopic physics and the dynamics of black holes.

    Researchers at University of California, Berkeley have recently carried out a study [Physical Review Letters] examining many-body chaos in the context of a renowned physical construct called the Sachdev-Ye-Kitaev (SYK) model. The SYK model describes a cluster of randomly interacting particles and was the first microscopic quantum system predicted to exhibit many-body chaos.

    “Our work is motivated by the fundamental question of how quickly information can spread in strongly-interacting quantum systems,” Bryce Kobrin, one of the researchers who carried out the study, told Phys.org. “A few years ago, a beautiful theoretical prediction emerged which suggested that in certain high-dimensional systems, information spreads exponentially fast, analogous to the butterfly effect in classical chaos.”

    In addition to hypothesizing this rapid spread of information in certain high-dimensional systems, previous studies proved that there is a universal speed limit on the rate at which this ‘chaos’ can develop. Interestingly, the only known or hypothesized systems that reach this limit are closely related to black holes, or more specifically, quantum theories that describe black holes. A major surprise was when researchers predicted that the SYK model also saturates the universal bound on chaos. This insight led to further analyses indicating that the low-temperature properties of the SYK model are, in effect, equivalent to that of a charged black hole.

    Although these ideas have been supported by theoretical calculations, verifying their validity and observing quantum chaos in numerical simulations has so far proved to be an enduring challenge. Kobrin and his colleagues set out to investigate the chaotic nature of the SYK model. They did this by simulating the dynamics of exceptionally large systems using cutting-edge numerical techniques they developed. Subsequently, they analyzed the data they collected using a method based on calculations from quantum gravity.

    “As a function of temperature, we observed the system change from behaving like ordinary interacting particles to agreeing precisely with the predicted behavior of a quantum black hole,” Kobrin said. “By developing new procedures to analyze our results, we determined the rate of chaos and explicitly showed that, at low temperatures, it approached the theoretical upper bound.”

    Kobrin and his colleagues gathered direct numerical evidence of a new dynamical phenomenon, namely many-body chaos, which translates chaos from classical mechanics to strongly interacting quantum systems. Their findings also highlight the valuable interplay between quantum simulations and quantum gravity theories.

    While in their recent study the researchers used the numerical tools that they created to examine many-body chaos in the SYK model in the future the same techniques could be applied to other models that are difficult to examine using common analysis frameworks. Ultimately, this could aid the ongoing search for quantum systems that exhibit the same behavior as black holes. Finally, the methods employed by this team of researchers could also inspire the development of experimental techniques to simulate quantum dynamics on controllable quantum hardware, for instance using arrays of cold atoms or trapped ions.

    “I am excited to investigate other phenomena at the intersection between quantum information and quantum gravity,” Kobrin said. “For example, it is predicted that by coupling together two copies of the SYK model, one can form a so-called traversable wormhole through which information can be communicated. This is a highly counterintuitive result which demonstrates that quantum chaos can, in fact, help move information from one place to another.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

    UC Berkeley Seal

     
  • richardmitnick 4:25 pm on January 27, 2021 Permalink | Reply
    Tags: "How heavy is Dark Matter? Scientists radically narrow the potential mass range for the first time", , , Dark Matter cannot be either ‘ultra-light’ or ‘super-heavy’., Gravity acts on Dark Matter just as it acts on the visible universe., If it turns out that the mass of Dark Matter is outside of the range predicted by the Sussex team then it will also prove that an additional force acts on Dark Matter., , , Quantum Gravity, U Sussex (UK)   

    From U Sussex (UK): “How heavy is Dark Matter? Scientists radically narrow the potential mass range for the first time” 

    From U Sussex (UK)

    27 January 2021
    Anna Ford

    1
    Credit: Greg Rakozy on Unsplash.

    Scientists have calculated the mass range for Dark Matter – and it’s tighter than the science world thought.

    Their findings – due to be published in Physical Letters B in March – radically narrow the range of potential masses for Dark Matter particles, and help to focus the search for future Dark Matter-hunters. The University of Sussex researchers used the established fact that gravity acts on Dark Matter just as it acts on the visible universe to work out the lower and upper limits of Dark Matter’s mass.

    The results show that Dark Matter cannot be either ‘ultra-light’ or ‘super-heavy’, as some have theorised, unless an as-yet undiscovered force also acts upon it.

    The team used the assumption that the only force acting on Dark Matter is gravity, and calculated that Dark Matter particles must have a mass between 10-3 eV and 107 eV. That’s a much tighter range than the 10-24 eV – 1019 GeV spectrum which is generally theorised.

    What makes the discovery even more significant is that if it turns out that the mass of Dark Matter is outside of the range predicted by the Sussex team, then it will also prove that an additional force – as well as gravity – acts on Dark Matter.

    Professor Xavier Calmet from the School of Mathematical and Physical Sciences at the University of Sussex, said:

    “This is the first time that anyone has thought to use what we know about quantum gravity as a way to calculate the mass range for Dark Matter. We were surprised when we realised no-one had done it before – as were the fellow scientists reviewing our paper.

    “What we’ve done shows that Dark Matter cannot be either ‘ultra-light’ or ‘super-heavy’ as some theorise – unless there is an as-yet unknown additional force acting on it. This piece of research helps physicists in two ways: it focuses the search area for Dark Matter, and it will potentially also help reveal whether or not there is a mysterious unknown additional force in the universe.”

    Folkert Kuipers, a PhD student working with Professor Calmet, at the University of Sussex, said:

    “As a PhD student, it’s great to be able to work on research as exciting and impactful as this. Our findings are very good news for experimentalists as it will help them to get closer to discovering the true nature of Dark Matter.”

    The visible universe – such as ourselves, the planets and stars – accounts for 25 per cent of all mass in the universe. The remaining 75 per cent is comprised of Dark Matter.

    It is known that gravity acts on Dark Matter because that’s what accounts for the shape of galaxies.

    Dark Matter Background
    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, some 30 years later, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com.


    Coma cluster via NASA/ESA Hubble.


    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.
    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.
    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL).


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu.

    See the full article here.

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    The University of Sussex (UK) is a leading research-intensive university near Brighton. We have both an international and local outlook, with staff and students from more than 100 countries and frequent engagement in community activities and services.

     
  • richardmitnick 12:37 pm on December 8, 2020 Permalink | Reply
    Tags: , Entangled quantum systems, , , , Quantum Gravity, , , Three of the four fundamental forces in physics can be described in terms of quantum theory. This is not the case for the fourth force (gravity).,   

    From University of Gronigen [Rijksuniversiteit Groningen] (NL) via phys.org: “Experiment to test quantum gravity just got a bit less complicated” 

    From University of Gronigen [Rijksuniversiteit Groningen] (NL)

    via


    phys.org

    December 8, 2020

    1
    In the proposed experiment, two diamonds are each placed in superposition and studied in freefall. Apart from gravity, the Casimir effect also draws them together, causing noise in the experiment. A thin copper plate can shield this effect, reducing the noise and making the experiment more manageable. Credit: A. Mazumdar, University of Groningen.

    Is gravity a quantum phenomenon? That has been one of the big outstanding questions in physics for decades. Together with colleagues from the UK, Anupam Mazumdar, a physicist from the University of Groningen, proposed an experiment that could settle the issue. However, it requires studying two very large entangled quantum systems in freefall. In a new paper
    [Physical Review A], which has a third-year Bachelor’s student as the first author, Mazumdar presents a way to reduce background noise to make this experiment more manageable.

    Three of the four fundamental forces in physics can be described in terms of quantum theory. This is not the case for the fourth force (gravity), which is described by Einstein’s theory of general relativity. The experiment that Mazumdar and his colleagues previously designed could prove or disprove the quantum nature of gravity.

    Superposition

    A well-known consequence of the quantum theory is the phenomenon called quantum superposition: in certain situations, quantum states can have two different values at the same time. Take an electron that is irradiated with laser light. Quantum theory says that it can either absorb or not absorb the photon energy from the light. Absorbing the energy would alter the electron’s spin, a magnetic moment that can be either up or down. The result of quantum superposition is that the spin is both up and down.

    These quantum effects take place in tiny objects, such as electrons. By targeting an electron in a specially constructed miniature diamond, it is possible to create superposition in a much larger object. The diamond is small enough to sustain this superposition, but also large enough to feel the pull of gravity. This characteristic is what the experiment exploits: placing two of these diamonds next to each other in freefall and, therefore, canceling out external gravity. This means that they only interact through the gravity between them.

    Challenging

    And that is where another quantum phenomenon comes in. Quantum entanglement means that when two or more particles are generated in close proximity, their quantum states are linked. In the case of the diamonds, if one is spin up, the other, entangled diamond should be spin down. So, the experiment is designed to determine whether quantum entanglement occurs in the pair during freefall, when the force of the gravity between the diamonds is the only way that they interact.

    “However, this experiment is very challenging,” explains Mazumdar. When two objects are very close together, another possible mechanism for interaction is present, the Casimir effect. In a vacuum, two objects can attract each other through this effect. “The size of the effect is relatively large and to overcome the noise it creates, we would have to use relatively large diamonds.” It was clear from the outset that this noise should be reduced to make the experiment more manageable. Therefore, Mazumdar wanted to know if shielding for the Casimir effect was possible.

    Lockdown

    He handed the problem to Thomas van de Kamp, a third-year Bachelor’s student of Physics. “He came to me because he was interested in quantum gravity and wanted to do a research project for his Bachelor’s thesis,” says Mazumdar. During the spring lockdown, when most normal classes were suspended, Van de Kamp started working on the problem. “Within a remarkably short time, he presented his solution, which is described in our paper.”

    This solution is based on placing a conducting plate of copper, around one millimeter thick, between the two diamonds. The plate shields the Casimir potential between them. Without the plate, this potential would draw the diamonds closer to each other. But with the plate, the diamonds are no longer attracted to each other, but to the plate between them. Mazumdar: “This removes the interaction between the diamonds through the Casimir effect, and therefore removes a lot of noise from the experiment.”

    Remarkable

    The calculations performed by Van de Kamp show that the masses of the two diamonds can be reduced by two orders of magnitude. “It may seem like a small step, but it does make the experiment less demanding.” Furthermore, other parameters such as the level of vacuum needed during the experiment also become less demanding due to the shielding of the Casimir effect. Mazumdar says that a further update on the experiment, which also includes a contribution from Bachelor’s student Thomas van de Kamp, will probably appear in the near future. “So, his six-month project has brought him co-authorship on two papers, quite a remarkable feat.”

    See the full article here.

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    The University of Gronigen [Rijksuniversiteit Groningen] (NL) is a public research university in the city of Groningen in the Netherlands. The university was founded in 1614 and is the second-oldest university in the Netherlands. In 2014, the university celebrated its 400th anniversary. Currently, RUG is placed in the top 100 universities worldwide according to three international ranking tables.

    The university was ranked 65th in the world, according to Academic Ranking of World Universities (ARWU) in 2019. In April 2013, according to the results of the International Student Barometer, the University of Groningen, for the third time in a row, was voted the best university of the Netherlands.

    The University of Groningen has eleven faculties, nine graduate schools, 27 research centres and institutes, and more than 175-degree programmes. The university’s alumni and faculty include Johann Bernoulli, Aletta Jacobs, four Nobel Prize winners, nine Spinoza Prize winners, one Stevin Prize winner, royalty, multiple mayors, the first president of the European Central Bank, and a secretary general of NATO.

     
  • richardmitnick 2:47 pm on September 29, 2020 Permalink | Reply
    Tags: "How big can a fundamental particle be?", , , , Quantum Gravity, , ,   

    From Symmetry: “How big can a fundamental particle be?” 

    Symmetry Mag
    From Symmetry<

    09/29/20
    Sarah Charley

    Extremely massive fundamental particles could exist, but they would seriously mess with our understanding of quantum mechanics.

    1
    Illustration by Sandbox Studio, Chicago with Steve Shanabruch.

    Fundamental particles are objects that are so small, they have no deeper internal structure.

    There are about a dozen “matter” particles that scientists think are fundamental, and they come in a variety of sizes. For instance, the difference between the masses of the top quark and the electron is equivalent to the difference between the masses of an adult elephant and a mosquito.

    Still, all of these masses are extremely tiny compared to what’s physically possible. The known laws of physics allow for fundamental particles with masses approaching the “Planck mass”: a whopping 22 micrograms, or about the mass of a human eyelash. To go back to our comparisons with currently known particles, if the top quark had the same mass as an elephant, then a fundamental particle at the Planck mass would weigh as much as the moon.

    Could such a particle exist? According to CERN Theory Fellow Dorota Grabowska, scientists aren’t completely sure.

    “Particles with a mass below the Planck scale can be elementary,” Grabowska says. “Above that scale, maybe not. But we don’t know.”

    Scientists at particle accelerators such as the Large Hadron Collider at CERN are always on the look-out for undiscovered massive particles that could fill in the gaps of their models. Finding new particles is so important that the global physics community is discussing building larger colliders that could produce even more massive particles. US involvement in the LHC is supported by the US Department of Energy’s Office of Science and the National Science Foundation.

    CERN FCC Future Circular Collider map.

    ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan.

    China Circular Electron Positron Collider (CEPC) map. It would be housed in a hundred-kilometer- (62-mile-) round tunnel at one of three potential sites. The documents work under the assumption that the collider will be located near Qinhuangdao City around 200 miles east of Beijing.

    If scientists found a fundamental particle with a mass above the Planck scale, they would need to revisit how they think about particle sizes. For the kind of research performed at the LHC, fundamental particles are all considered to be the same size—no size at all.

    “When we think about the pure mathematics, elementary particles are, by definition, point-like,” Grabowska says. “They don’t have a size.”

    Treating fundamental particles as points works well in particle physics because their masses are so small that gravity, which would have an effect on more massive objects, is not really a factor. It’s kind of like how truck drivers planning a trip don’t need to consider the effects of special relativity and time dilation. These effects are there, at some level, but they don’t have a noticeable impact on drive time.

    But a fundamental particle above the Planck scale would sit at the threshold between two divergent mathematical models. Quantum mechanics describes objects that are very tiny, and general relativity describes objects that are very massive. But to describe a particle that is both very tiny and very massive, scientists need a new theory called quantum gravity.

    Mathematically, physicists could no longer consider such a massive particle as a volume-less point. Instead, they would need to think about it behaving more like a wave.

    The particle-wave duality concept was born about 100 years ago and states that subatomic particles have both particle-like and wave-like properties. When scientists think about an electron as a particle, they consider that it has no physical volume. But when they think about it as a wave, it extends throughout all the space it’s granted, such as the orbit around the nucleus of an atom. Both interpretations are correct, and scientists typically use the one that best suits their area of research.

    The mass-to-radius ratio of these waves is important because it determines how they feel the effects of gravity. A super massive particle with tons of room to roam would barely feel the force of gravity. But if that same particle were confined to an extremely small space, it could collapse into a miniature black hole. Scientists at the LHC have searched for such tiny black holes—which would evaporate almost immediately—but so far have come up empty-handed.

    According to Grabowska, quantum gravity is tricky because there is no way to experimentally test it with today’s existing technology. “We would need a collider 14 orders of magnitude more energetic than the LHC,” she says.

    But thinking about the implications of finding such a particle helps theorists push the known laws of physics.

    “Our model of particle physics breaks down when pushed to certain scales,” says Netta Engelhardt, a quantum gravity theorist at the Massachusetts Institute of Technology. “But that doesn’t mean that our universe doesn’t feature these regimes. If we want to understand massive objects at tiny scales, we need a model of quantum gravity.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 8:33 am on April 25, 2019 Permalink | Reply
    Tags: "Could An Incompleteness In Quantum Mechanics Lead To Our Next Scientific Revolution?", , , , Quantum Gravity   

    From Ethan Siegel: “Could An Incompleteness In Quantum Mechanics Lead To Our Next Scientific Revolution?” 

    From Ethan Siegel
    Apr 24, 2019

    1
    The proton’s structure, modeled along with its attendant fields, show how even though it’s made out of point-like quarks and gluons, it has a finite, substantial size which arises from the interplay of the quantum forces and fields inside it. The proton, itself, is a composite, not fundamental, quantum particle. (BROOKHAVEN NATIONAL LABORATORY)

    A single thought experiment reveals a paradox. Could quantum gravity be the solution?

    Sometimes, if you want to understand how nature truly works, you need to break things down to the simplest levels imaginable. The macroscopic world is composed of particles that are — if you divide them until they can be divided no more — fundamental. They experience forces that are determined by the exchange of additional particles (or the curvature of spacetime, for gravity), and react to the presence of objects around them.

    At least, that’s how it seems. The closer two objects are, the greater the forces they exert on one another. If they’re too far away, the forces drop off to zero, just like your intuition tells you they should. This is called the principle of locality, and it holds true in almost every instance. But in quantum mechanics, it’s violated all the time. Locality may be nothing but a persistent illusion, and seeing through that facade may be just what physics needs.

    2
    Quantum gravity tries to combine Einstein’s general theory of relativity with quantum mechanics. Quantum corrections to classical gravity are visualized as loop diagrams, as the one shown here in white. We typically view objects that are close to one another as capable of exerting forces on one another, but that might be an illusion, too. (SLAC NATIONAL ACCELERATOR LAB)

    Imagine that you had two objects located in close proximity to one another. They would attract or repel one another based on their charges and the distance between them. You might visualize this as one object generating a field that affects the other, or as two objects exchanging particles that impart either a push or a pull to one or both of them.

    You’d expect, of course, that there would be a speed limit to this interaction: the speed of light. Relativity gives you no other way out, since the speed at which the particles responsible for forces propagate is limited by the speed they can travel, which can never exceed the speed of light for any particle in the Universe. It seems so straightforward, and yet the Universe is full of surprises.

    3
    An example of a light cone, the three-dimensional surface of all possible light rays arriving at and departing from a point in spacetime. The more you move through space, the less you move through time, and vice versa. Only things contained within your past light-cone can affect you today; only things contained within your future light-cone can be perceived by you in the future. (WIKIMEDIA COMMONS USER MISSMJ)

    We have this notion of cause-and-effect that’s been hard-wired into us by our experience with reality. Physicists call this causality, and it’s one of the rare physics ideas that actually conforms to our intuition. Every observer in the Universe, from its own perspective, has a set of events that exist in its past and in its future.

    In relativity, these are events contained within either your past light-cone (for events that can causally affect you) or your future light-cone (for events that you can causally effect). Events that can be seen, perceived, or can otherwise have an effect on an observer are known as causally-connected. Signals and physical effects, both from the past and into the future, can propagate at the speed of light, but no faster. At least, that’s what your intuitive notions about reality tell you.

    4
    Schrödinger’s cat. Inside the box, the cat will be either alive or dead, depending on whether a radioactive particle decayed or not. If the cat were a true quantum system, the cat would be neither alive nor dead, but in a superposition of both states until observed. (WIKIMEDIA COMMONS USER DHATFIELD)

    But in the quantum Universe, this notion of relativistic causality isn’t as straightforward or universal as it would seem. There are many properties that a particle can have — such as its spin or polarization — that are fundamentally indeterminate until you make a measurement. Prior to observing the particle, or interacting with it in such a way that it’s forced to be in either one state or the other, it’s actually in a superposition of all possible outcomes.

    Well, you can also take two quantum particles and entangle them, so that these very same quantum properties are linked between the two entangled particles. Whenever you interact with one member of the entangled pair, you not only gain information about which particular state it’s in, but also information about its entangled partner.

    5
    By creating two entangled photons from a pre-existing system and separating them by great distances, we can ‘teleport’ information about the state of one by measuring the state of the other, even from extraordinarily different locations. (MELISSA MEISTER, OF LASER PHOTONS THROUGH A BEAM SPLITTER)

    This wouldn’t be so bad, except for the fact that you can set up an experiment as follows.

    You can create your pair of entangled particles at a particular location in space and time.
    You can transport them an arbitrarily large distance apart from one another, all while maintaining that quantum entanglement.
    Finally, you can make those measurements (or force those interactions) as close to simultaneously as possible.

    In every instance where you do this, you’ll find the member you measure in a particular state, and instantly “know” some information about the other entangled member.

    6
    A photon can have two types of circular polarizations, arbitrarily defined so that one is + and one is -. By devising an experiment to test correlations between the directional polarization of entangled particles, one can attempt to distinguish between certain formulations of quantum mechanics that lead to different experimental results.(DAVE3457 / WIKIMEDIA COMMONS)

    What’s puzzling is that you cannot check whether this information is true or not until much later, because it takes a finite amount of time for a light signal to arrive from the other member. When the signal does arrive, it always confirms what you’d known just by measuring your member of the entangled pair: your expectation for the state of the distant particle agreed 100% with what its measurement indicated.

    Only, there seems to be a problem. You “knew” information about a measurement that was taking place non-locally, which is to say that the measurement that occurred is outside of your light cone. Yet somehow, you weren’t entirely ignorant about what was going on over there. Even though no information was transmitted faster than the speed of light, this measurement describes a troubling truth about quantum physics: it is fundamentally a non-local theory.

    7
    Schematic of the third Aspect experiment testing quantum non-locality. Entangled photons from the source are sent to two fast switches that direct them to polarizing detectors. The switches change settings very rapidly, effectively changing the detector settings for the experiment while the photons are in flight. (CHAD ORZEL)

    There are limits to this, of course.

    It isn’t as clean as you want: measuring the state of your particle doesn’t tell us the exact state of its entangled pair, just probabilistic information about its partner.

    There is still no way to send a signal faster than light; you can only use this non-locality to predict a statistical average of entangled particle properties.

    And even though it has been the dream of many, from Einstein to Schrödinger to de Broglie, no one has ever come up with an improved version of quantum mechanics that tells you anything more than its original formulation.

    But there are many who still dream that dream.

    8
    If two particles are entangled, they have complementary wavefunction properties, and measuring one places meaningful constraints on the properties of the other. (WIKIMEDIA COMMONS USER DAVID KORYAGIN)

    One of them is Lee Smolin, who cowrote a paper [Physical Review D] way back in 2003 that showed an intriguing link between general ideas in quantum gravity and the fundamental non-locality of quantum physics. Although we don’t have a successful quantum theory of gravity, we have established a number of important properties concerning how a quantum theory of gravity will behave and still be consistent with the known Universe.

    9
    A variety of quantum interpretations and their differing assignments of a variety of properties. Despite their differences, there are no experiments known that can tell these various interpretations apart from one another, although certain interpretations, like those with local, real, deterministic hidden variables, can be ruled out. (ENGLISH WIKIPEDIA PAGE ON INTERPRETATIONS OF QUANTUM MECHANICS)

    There are many reasons to be skeptical that this conjecture will hold up to further scrutiny. For one, we don’t truly understand quantum gravity at all, and anything we can say about it is extraordinarily provisional. For another, replacing the non-local behavior of quantum mechanics with the non-local behavior of quantum gravity is arguably making the problem worse, not better. And, as a third reason, there is nothing thought to be observable or testable about these non-local variables that Markopoulou and Smolin claim could explain this bizarre property of the quantum Universe.

    Fortunately, we’ll have the opportunity to hear the story direct from Smolin himself and evaluate it on our own. You see, at 7 PM ET (4 PM PT) on April 17, Lee Smolin is giving a public lecture on exactly this topic at Perimeter Institute, and you can watch it right here.


    1:18:47

    I’ll be watching along with you, curious about what Smolin is calling Einstein’s Unfinished Revolution, which is the ultimate quest to supersede our two current (but mutually incompatible) descriptions of reality: General Relativity and quantum mechanics.

    10

    Best of all, I’ll be giving you my thoughts and commentary below in the form of a live-blog, beginning 10 minutes before the start of the talk. [See the full article.]

    Find out where we are in the quest for quantum gravity, and what promises it may (or may not) have for revolutionizing one of the greatest counterintuitive mysteries about the quantum nature of reality!

    Thanks for joining me for an interesting lecture and discussions on science, and just maybe, someday, we’ll have some interesting progress to report on this topic. Until then, you don’t have to shut up, but you still do have to calculate!

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 1:10 pm on July 27, 2018 Permalink | Reply
    Tags: , , , , , Quantum Gravity, This Simple Thought Experiment Shows Why We Need Quantum Gravity   

    From Ethan Siegel: “This Simple Thought Experiment Shows Why We Need Quantum Gravity” 

    From Ethan Siegel
    Jul 27, 2018

    1
    Quantum gravity tries to combine Einstein’s general theory of relativity with quantum mechanics. Quantum corrections to classical gravity are visualized as loop diagrams, as the one shown here in white. Whether space (or time) itself is discrete or continuous is not yet decided, as is the question of whether gravity is quantized at all. (SLAC NATIONAL ACCELERATOR LAB)

    If our current laws of physics can’t predict what will happen, even probabilistically, we need something new.

    There are two theories we have that explain all the particles and their interactions in the known Universe: General Relativity and the Standard Model of particle physics. General Relativity describes gravity perfectly everywhere we’ve ever looked. From the smallest-scale attractions we’ve ever measured in a laboratory to the expansion and curvature of space due to Earth, the Sun, black holes, galaxies, or the entire Universe, our observations and measurements have never deviated from what we’ve observed. The Standard Model is equally successful for the other three forces: electromagnetism and the strong and weak nuclear forces. Every experiment, measurement, and observation has agreed perfectly with these two theories.

    It sounds great, until you try to combine the two. If we do that, it all falls apart. The solution? We need a quantum theory of gravity. Here’s why.

    2
    The spacetime curvature around any massive object is determined by the combination of mass and distance from the center-of-mass. Other concerns, like velocity, acceleration, and other sources of energy, must be factored in. (T. PYLE/CALTECH/MIT/LIGO LAB)

    From Einstein’s theory of gravity, we can compute what the curvature of space is at any location in the Universe, from here on planet Earth to the largest scales in the cosmos. We’ve performed experiments that have tested the gravitational force law down to micron-sized scales, and on astrophysical scales in extreme environments, such as the galactic center, merging neutron stars, and at the edges of black holes. Even esoteric predictions, such as the production of gravitational waves, the effect of frame-dragging, or the precession of planetary orbits, are completely in line with every measurement we’ve ever taken. In every case, Einstein’s theory perfectly describes reality.

    3
    The Standard Model of particle physics accounts for three of the four forces (excepting gravity), the full suite of discovered particles, and all of their interactions. Quarks and leptons are fermions, which have a host of unique properties that the other (bosons) particles do not possess. (CONTEMPORARY PHYSICS EDUCATION PROJECT / DOE / NSF / LBNL)

    From the Standard Model, we know how electricity, magnetism, radioactive decays and nuclear forces work. Take any particle and let it interact (or not) with anything else in the Universe, and we’ll know the probability distribution of all possible outcomes. Even though the quantum world isn’t entirely deterministic, we can still successfully describe the expected set of outcomes in a mathematically precise fashion. If we perform the same experiment thousands upon thousands of times, we’ll see the results match our best quantum predictions, even for bizarre and unintuitive setups.

    But if we take a look at one such setup in particular — the famed double-slit experiment — we can see immediately why a quantum theory of gravity is absolutely necessary.

    4
    The wave-like properties of light became even better understood thanks to Thomas Young’s two-slit experiments, where constructive and destructive interference showed themselves dramatically. These experiments were known for classical waves since the 17th century; around 1800, Young showed they applied to light as well. (THOMAS YOUNG, 1801)

    Imagine you’ve got a set of quantum particles: they could be photons, neutrinos, electrons, or anything else. Imagine that you’ve set them up so they’ll bombard a tiny area of a barrier, with two slits cut into the barrier extremely close together, to allow these quantum particles to pass through. Behind the barrier, you’ll set up a screen, so you can detect where the particles wind up. This is the classic setup of the double slit experiment.

    If you send through a bunch of particles at once, they act just like a wave. The particles might go through one slit or the other, but they interfere. At the end of the day, you wind up with a clearly identifiable interference pattern on the screen, the same way you would for a water wave passing through a similar set of slits.

    5
    Double slit experiments performed with light produce interference patterns, as they do for any wave. The properties of different light colors is due to their differing wavelengths. (TECHNICAL SERVICES GROUP (TSG) AT MIT’S DEPARTMENT OF PHYSICS)

    Well, you can’t have your particles interfering with one another, so you decide to send them through one-at-a-time. You measure where it hits the screen and record it, and then you fire the next particle. It doesn’t matter which particle you choose; if we can detect it on the screen, we see the same behavior. The interference pattern builds up one-particle-at-a-time, but clearly emerges. Somehow, these quantum particles are passing through both slits simultaneously, and are interfering with themselves.

    6
    The wave pattern for electrons passing through a double slit, one-at-a-time. If you measure “which slit” the electron goes through, you destroy the quantum interference pattern shown here. Note that more than one electron is required to reveal the interference pattern. (DR. TONOMURA AND BELSAZAR OF WIKIMEDIA COMMONS)

    Perhaps you decide you’re not a fan of this quantum weirdness, so you decide to measure which slit each particle goes through. You set up a photodetector around each slit, and measure when a particle passes through it. The first particle goes through, and you detect its passage through slit #2. The second one arrives, and also goes through slit #2. The third one goes through slit #1, then the fourth through #2, and then the fifth through #1 again. You repeat this, over and over, for thousands of particles. And when you look at the resulting pattern on the screen, you find something extremely troublesome: the interference pattern is gone. Instead, all you see is a pile of particles that passed through slit #1, along with another pile that passed through slit #2. They did not interfere.

    7
    If you measure which slit an electron goes through, you don’t get an interference pattern on the screen behind it. Instead, the electrons behave not as waves, but as classical particles. (WIKIMEDIA COMMONS USER INDUCTIVELOAD)

    This is weird! This unintuitive weirdness is at the heart of what makes quantum physics, and the Standard Model in general, such a powerful tool. At a fundamental, quantum level, we can accurately predict when you have this quantum behavior and when you won’t, and what that behavior will look like when it appears.

    For the electromagnetic, strong nuclear, and weak nuclear forces, this works exquisitely well. It works so well that, as bizarre as they may be, no repeatable experiment has ever disagreed with any significance from the Standard Model’s predictions. And yet, if we were to ask the following simple question, we don’t have any way to arrive at an answer:

    What happens to the gravitational field of an electron when it passes through a double slit?

    8
    The gravitational field of the electron, as it passes through a double slit, would behave differently if gravity is fundamentally quantum (bottom) or non-quantum (top). (Sabine Hossenfelder)

    The reason we can’t answer it is we don’t know a huge number of properties about gravity on the quantum scale. We don’t know whether gravity is quantized or not. The particles must be quantized, but gravity might not be, and if it isn’t, the double slit experiment would give different results than if it is.

    We don’t know whether space is fundamentally discrete (with a minimum length scale) or continuous. If there were a minimum length, there would be a fundamental resolution limit to our experiments, one we might someday encounter at high enough energies. There are questions we cannot answer about how gravity behaves under certain experimental conditions.

    9
    Even two merging black holes, one of the strongest sources of a gravitational signal in the Universe, doesn’t leave an observable signature that could probe quantum gravity. For that, we’ll have to create experiments that probe either the strong-field regime of relativity, i.e., near the singularity, or that take advantage of clever laboratory setups. (SXS, THE SIMULATING EXTREME SPACETIMES (SXS) PROJECT (BLACK-HOLES.ORG))

    We know, in principle, that the gravitational field should remain localized around the electron’s position, just as it would for any mass. But what does this mean when the electron’s position is inherently uncertain? Does the gravitational field always go primarily through one slit or the other? And does the act of observing (or not observing) change the gravitational field? And if so, how?

    The gravitational field of the electron is weak; we cannot observe it in practice. Equations developed by Wheeler, Feynman, and DeWitt in the 1960s describe the expected behavior of a particle in the weak-field limit of quantum gravity, but those equations have never been experimentally tested. To do so is presently beyond the realm of what we’re capable of, but there is hope.

    10
    The experimental setup that’s enabled the measurement of gravitational fields and effects down to milligram-scale masses, From “A micromechanical proof-of-principle experiment for measuring the gravitational force of milligram masses.”

    There are proposed experimental setups that would allow us to measure the gravitational field more precisely than ever before: down to milligram masses. On the other hand, we’ve managed to bring relatively large objects (compared to fundamental particles) into quantum superpositions of states: up to nanogram-scale masses. The exact energy levels of these states depend on the total gravitational self-energy of the system, making this a realistic, plausible test to determine whether gravity is quantized or not. When technology and experimental techniques advance far enough, these two scales will intersect. When that moment comes, we’ll be able to probe the quantum gravitational regime.

    11
    The energy levels of a nanogram-scale disk of osmium, and how the effect of self-gravitation will (right) or won’t (left) affect the specific values of those energy levels. The disk’s wavefunction, and how it’s affected by gravitation, may lead to the first experimental test of whether gravity is truly a quantum force. (ANDRÉ GROSSARDT ET AL. (2015); ARXIV:1510.0169)

    The description that General Relativity puts forth — that of matter telling space how to curve, and curved space telling matter how to move — needs to be augmented to include an uncertain position that has a probability distribution to it. Whether gravity is quantized or not is still an unknown, and has everything to do with the outcome of such a hypothetical experiment. How an uncertain position translates into a gravitational field, exactly, remains an unsolved problem on the road to a full quantum theory of gravity. The principles that underlie quantum mechanics must be universal, but how those principles apply to gravity, and in particular to a particle passing through a double slit, is a great unknown of our time.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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