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  • richardmitnick 9:52 pm on October 11, 2021 Permalink | Reply
    Tags: , , Holography, , , "The Search for Quantum Gravity"   

    From The University of California-Santa Barbara (US) : “The Search for Quantum Gravity” 

    UC Santa Barbara Name bloc

    From The University of California-Santa Barbara (US)

    October 11, 2021

    Sonia Fernandez
    sonia.fernandez@ucsb.edu

    With support from The Heising-Simons Foundation (US), theoretical physicists take a new approach to the search for quantum gravity.

    1
    Quantum Gravity Illustration

    About a century ago, Albert Einstein amazed the world with his groundbreaking theory of relativity, and ever since he shared this profound understanding of gravity and spacetime, physicists everywhere have worked hard to prove, refine and extend it. In the intervening decades, numerous observations have borne Einstein out, with phenomena such as gravitational lensing and redshift, shifts in planetary orbit and, more recently, gravitational waves and observations of black holes.

    However, for all the advances we’ve made in witnessing the more readily observable, macro effects of gravity, there remains a gap — a chasm, really — in our ability to understand gravity in the context of another profound discovery: quantum mechanics, the physics of matter and energy at their smallest scales.

    “There is the longstanding problem, perhaps the greatest remaining from 20th century physics, of reconciling quantum mechanics with gravity,” said UC Santa Barbara theoretical physicist Steven Giddings. The universe is quantum, and unlike the other fundamental forces — the electromagnetic, the weak and the strong nuclear forces — which have been described within quantum field theory, what we know of gravitation remains solidly in the realm of classical physics.

    “Associated with that problem is a gulf between theory and observation,” said Giddings, who specializes in high energy and gravitational theory, as well as quantum black holes, quantum cosmology and other quantum aspects of gravity. Traditional thinking leads one to believe that quantum aspects of gravity are only observable if we explore incredibly short distances, he said, such as the Planck length (10-35 meter), thought to be the smallest length in the universe and the length at which quantum gravity effects become important. It’s also far beyond observational reach.

    But what if it was possible to detect quantum gravity at longer, observable length scales? Giddings, and fellow theorists Kathryn Zurek and Yanbei Chen at The California Institute of Technology (US), Cynthia Keeler and Maulik Parikh at The Arizona State University (US), and Ben Freivogel and Erik Verlinde at The University of Amsterdam [Universiteit van Amsterdam](NL), think that could be the case.

    “Various theoretical developments have indicated that quantum gravity effects may become important at much greater distances in certain contexts, and that is truly exciting and worth exploring,” Giddings said. “We are taking this seriously.”

    And, thanks to support from the Heising-Simons Foundation, the team is poised to bridge that chasm, by exploring ways in which quantum gravity may be observed, via effects a longer length scales.

    “We are thrilled that the Heising-Simons Foundation has chosen to support this vision of exploring new effects, particularly at long distances, in quantum gravity, and the possibility that they lead to observational effects,” Giddings said of the $3.1 million in multi-institution grants to help the team push the boundaries of our knowledge of quantum gravity. “Their support should really move this research forward.”

    Quantum Effects at Longer Lengths

    Reconciling relativity to quantum mechanics has challenged physicists for the better part of a century, with puzzles such as the black hole information paradox. That’s where relativity and quantum mechanics violently conflict on the issue of what happens to information that falls into a black hole, those extremely high-gravity voids in spacetime. A relativistic picture indicates that the information gets destroyed as the black hole slowly evaporates, while quantum mechanics states that that information cannot be destroyed.

    A suggested approach to that conundrum and other similarly complex issues emerges with the proposed holographic principle, a fundamentally new idea about the possible behavior of quantum gravity.

    “There are different ways to explain it, but one is that the amount of information you can put in a volume is not proportional to the volume but to the surface area surrounding the volume,” Giddings explained. A consistent theory incorporating this principle might explain how information is not destroyed, resulting in a relativistic object, such as a black hole, obeying quantum rules.

    “When one tries to reconcile the existence of black holes with the principles of quantum mechanics, one seems to be led to the conclusion that new quantum gravity effects must become important not just at short distances, but at distances comparable to the size of the black hole in question — for the largest black holes we know, many times the size of our solar system,” Giddings said.

    The principle, which started out originally with black holes, has been suggested to extend to the universe in general — what we perceive as our three-dimensional reality may even, in a sense, have an underlying two-dimensional description. This could make its mathematical description more elegant and compelling.

    “This is a big departure from the properties of quantum field theories that describe other forces of nature — like electromagnetism and the strong force — and is a feature of gravity that strongly suggests that a theory of gravity has a very different underlying structure,” he added. This fundamentally different structure might be part of a description with novel properties, in which information is preserved.

    A related argument for the observability of quantum gravity at greater distances comes from the notion that very high energy collisions, though far beyond what we have been able to accomplish, start producing quantum gravitational effects at increasingly large distances.

    “When one considers extremely high energy collisions of particles, one is not probing shorter distances any longer — as has been true at accessible energies — but instead one starts to see effects at longer distances, due to basic properties of gravity,” Giddings said.

    Quantum Gravity at Work

    Recent developments in experimental observations have made it possible to detect and measure new effects of gravity, such as with Caltech’s Laser Interferometer Gravitational Wave Observatory (LIGO), the Virgo interferometer in Italy, and the Kamioka Gravitational Wave Detector (KAGRA) in Japan.

    _______________________________________________________________________________________
    LIGOVIRGOKAGRA

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    KAGRA Large-scale Cryogenic Gravitational Wave Telescope Project (JP)
    _______________________________________________________________________________________
    Each of those facilities is turned to space to sense gravitational waves coming from major events, such as the mergers of massive celestial bodies like black holes and neutron stars. These, as well as observations of light from near black holes by The Event Horizon Telescope-EHT, may also be sensitive to long-range quantum effects. In addition, ideas related to holography suggest the possibility of new quantum effects in lab-based settings, and newer experiments with interferometers may provide novel ways to test them.

    The task for the researchers as they resolve foundational issues and understand aspects of the fundamental description of quantum gravity, is to develop “effective descriptions” that can connect theory with observations coming in from the interferometers and other instruments.

    “In physics, we have often been in the situation where we don’t have the complete theory, but we have an approximate description that captures certain important properties of that theory,” Giddings explained. “Often, such ‘effective descriptions’ can be surprisingly powerful, and lead to deeper insight about the more fundamental theory.”

    The group’s diverse mix of backgrounds is a strength of this collaboration, with specializations ranging from quantum gravity to particle physics, string theory to gravitational wave physics. Through a series of meetings to be held over four years the collaboration will progress from foundational issues, such as sharpening the description of holography and understanding the mathematical structure of gravity, to studying models that may describe behavior of quantum gravity, its interactions and potentially observable effects, to developing specific observational tests with the interferometers and observations of black holes.

    Along the way, the collaboration will grow, starting with the seven core members and adding postdoctoral fellows and graduate students, and finally broadening activities to include additional physicists to discuss collaboration results and related theoretical advances from the broader community.

    “If we are able to observe quantum effects of black holes, that will be truly revolutionary,” Giddings said. “It would also likely help guide the conceptual revolution of reconciling quantum mechanics with gravity, which we expect to likely be as profound as the revolutionary discovery of quantum mechanics.”

    See the full article here .


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    UC Santa Barbara Seal

    The University of California-Santa Barbara (US) is a public land-grant research university in Santa Barbara, California, and one of the ten campuses of the University of California (US) system. Tracing its roots back to 1891 as an independent teachers’ college, The University of California-Santa Barbara joined the University of California system in 1944, and is the third-oldest undergraduate campus in the system.

    The university is a comprehensive doctoral university and is organized into five colleges and schools offering 87 undergraduate degrees and 55 graduate degrees. It is classified among “R1: Doctoral Universities – Very high research activity”. According to the National Science Foundation (US), The University of California-Santa Barbara spent $235 million on research and development in fiscal year 2018, ranking it 100th in the nation. In his 2001 book The Public Ivies: America’s Flagship Public Universities, author Howard Greene labeled The University of California-Santa Barbara a “Public Ivy”.

    The University of California-Santa Barbara is a research university with 10 national research centers, including the Kavli Institute for Theoretical Physics (US) and the Center for Control, Dynamical-Systems and Computation. Current University of California-Santa Barbara faculty includes six Nobel Prize laureates; one Fields Medalist; 39 members of the National Academy of Sciences (US); 27 members of the National Academy of Engineering (US); and 34 members of the American Academy of Arts and Sciences (US). The University of California-Santa Barbara was the No. 3 host on the ARPANET and was elected to the Association of American Universities in 1995. The faculty also includes two Academy and Emmy Award winners and recipients of a Millennium Technology Prize; an IEEE Medal of Honor; a National Medal of Technology and Innovation; and a Breakthrough Prize in Fundamental Physics.
    The University of California-Santa Barbara Gauchos compete in the Big West Conference of the NCAA Division I. The Gauchos have won NCAA national championships in men’s soccer and men’s water polo.

    History

    The University of California-Santa Barbara traces its origins back to the Anna Blake School, which was founded in 1891, and offered training in home economics and industrial arts. The Anna Blake School was taken over by the state in 1909 and became the Santa Barbara State Normal School which then became the Santa Barbara State College in 1921.

    In 1944, intense lobbying by an interest group in the City of Santa Barbara led by Thomas Storke and Pearl Chase persuaded the State Legislature, Gov. Earl Warren, and the Regents of the University of California to move the State College over to the more research-oriented University of California system. The State College system sued to stop the takeover but the governor did not support the suit. A state constitutional amendment was passed in 1946 to stop subsequent conversions of State Colleges to University of California campuses.

    From 1944 to 1958, the school was known as Santa Barbara College of the University of California, before taking on its current name. When the vacated Marine Corps training station in Goleta was purchased for the rapidly growing college Santa Barbara City College moved into the vacated State College buildings.

    Originally the regents envisioned a small several thousand–student liberal arts college a so-called “Williams College (US) of the West”, at Santa Barbara. Chronologically, The University of California-Santa Barbara is the third general-education campus of the University of California, after The University of California-Berkeley (US) and The University of California-Los Angeles (US) (the only other state campus to have been acquired by the UC system). The original campus the regents acquired in Santa Barbara was located on only 100 acres (40 ha) of largely unusable land on a seaside mesa. The availability of a 400-acre (160 ha) portion of the land used as Marine Corps Air Station Santa Barbara until 1946 on another seaside mesa in Goleta, which the regents could acquire for free from the federal government, led to that site becoming the Santa Barbara campus in 1949.

    Originally only 3000–3500 students were anticipated but the post-WWII baby boom led to the designation of general campus in 1958 along with a name change from “Santa Barbara College” to “University of California-Santa Barbara,” and the discontinuation of the industrial arts program for which the state college was famous. A chancellor- Samuel B. Gould- was appointed in 1959.

    In 1959 The University of California-Santa Barbara professor Douwe Stuurman hosted the English writer Aldous Huxley as the university’s first visiting professor. Huxley delivered a lectures series called The Human Situation.

    In the late ’60s and early ’70s The University of California-Santa Barbara became nationally known as a hotbed of anti–Vietnam War activity. A bombing at the school’s faculty club in 1969 killed the caretaker Dover Sharp. In the spring of 1970 multiple occasions of arson occurred including a burning of the Bank of America branch building in the student community of Isla Vista during which time one male student Kevin Moran was shot and killed by police. The University of California-Santa Barbara ‘s anti-Vietnam activity impelled then-Gov. Ronald Reagan to impose a curfew and order the National Guard to enforce it. Armed guardsmen were a common sight on campus and in Isla Vista during this time.

    In 1995 The University of California-Santa Barbara was elected to the Association of American Universities– an organization of leading research universities with a membership consisting of 59 universities in the United States (both public and private) and two universities in Canada.

    On May 23, 2014 a killing spree occurred in Isla Vista, California, a community in close proximity to the campus. All six people killed during the rampage were students at The University of California-Santa Barbara. The murderer was a former Santa Barbara City College student who lived in Isla Vista.

    Research activity

    According to the National Science Foundation (US), The University of California-Santa Barbara spent $236.5 million on research and development in fiscal 2013, ranking it 87th in the nation.

    From 2005 to 2009 UCSB was ranked fourth in terms of relative citation impact in the U.S. (behind Massachusetts Institute of Technology (US), California Institute of Technology(US), and Princeton University (US)) according to Thomson Reuters.

    The University of California-Santa Barbara hosts 12 National Research Centers, including the Kavli Institute for Theoretical Physics, the National Center for Ecological Analysis and Synthesis, the Southern California Earthquake Center, the UCSB Center for Spatial Studies, an affiliate of the National Center for Geographic Information and Analysis, and the California Nanosystems Institute. Eight of these centers are supported by The National Science Foundation (US). UCSB is also home to Microsoft Station Q, a research group working on topological quantum computing where American mathematician and Fields Medalist Michael Freedman is the director.

    Research impact rankings

    The Times Higher Education World University Rankings ranked The University of California-Santa Barbara 48th worldwide for 2016–17, while the Academic Ranking of World Universities (ARWU) in 2016 ranked https://www.nsf.gov/ 42nd in the world; 28th in the nation; and in 2015 tied for 17th worldwide in engineering.

    In the United States National Research Council rankings of graduate programs, 10 University of California-Santa Barbara departments were ranked in the top ten in the country: Materials; Chemical Engineering; Computer Science; Electrical and Computer Engineering; Mechanical Engineering; Physics; Marine Science Institute; Geography; History; and Theater and Dance. Among U.S. university Materials Science and Engineering programs, The University of California-Santa Barbara was ranked first in each measure of a study by the National Research Council of the NAS.

    The Centre for Science and Technologies Studies at

     
  • richardmitnick 1:00 pm on August 22, 2019 Permalink | Reply
    Tags: , , , , Holography, ,   

    From Symmetry: “Holography class gives students new perspective” 

    Symmetry Mag
    From Symmetry

    [I must say, nothing in this article tells me why this is An important subject for Symmetry.]

    08/22/19
    Bailey Bedford

    A holography class at the Ohio State University combines art and physics to provide a more complete picture of how we understand the world around us.

    Art and science are often seen as incompatible lenses through which to view the world. Science provides one perspective, characterized by detachment and certainty, and art provides another, characterized by emotion and unpredictability, and never the twain shall meet.

    But sometimes you need more than one perspective to understand the whole picture. Harris Kagan, an Ohio State University physics professor and collaborator on the ATLAS experiment at the Large Hadron Collider at CERN, proves this in his classes about the art and science of holography.

    The word “holography” derives from two Greek words that together mean “entire picture.” A hologram is essentially a 3-D picture that is designed to provide a complete image including different perspectives and parallax—the way an object’s position appears to vary for different lines of sight.

    In physics terms, each part of a hologram records an interference pattern to recreate the light that was emitted or reflected from the subject of the image. This method allows the viewer to move around and see the object from different angles like they could if the object were on the opposite side of a window.

    “My philosophy is that art and science are really the same thing,” he says. “The techniques you use to create a new idea in science are very, very similar [to the ones used in art]. To create a new idea in art, you’re using different tools, maybe different fundamentals, but the goals are the same; the honesty is the same.”

    3
    Courtesy of Harris Kagan

    4
    Courtesy of Harris Kagan

    Marrying art and science

    Kagan has been teaching holography classes since the mid-1980s. When OSU art professor Susan Dallas-Swan saw a hologram that he had produced for display using equipment from a laboratory class he taught, she arranged for Kagan to work with an art graduate student using the medium.

    The success with the graduate student led the pair of professors to set the blueprint for the classes. Some of Kagan’s classes have been in the physics department and some in the art department, with students from a variety of backgrounds mixed together in each. Kagan teaches beginner, advanced and honors undergraduate holography courses as well as a graduate course.

    Students in the class are not required to have any background in art or physics. The classes are meant to help students explore both subjects and how they intersect with math and visual perception. They include elements usually associated with science classes, such as unsupervised time in the lab working with lasers, and elements usually associated with art classes, such as artistic critiques of the students’ work. The students perform a series of projects culminating in an original piece for an art show.

    One point the critique process drove home was that the students’ art for the class should be concept-driven, says Shreyas Muralidharan, who participated as an undergraduate majoring in electrical and computer engineering and physics. By that, Kagan meant “that you need to really be able to clearly define what you want to achieve with this piece of art,” Muralidharan says. “From a physics and more scientific background, I haven’t really been exposed to [that idea].”

    Muralidharan, now a graduate student, says that Kagan would often challenge students to simplify the language in their explanations of their pieces and processes. Asking the students to explain concepts in simple terms ensured they actually understood them—a practice that he says remains useful in giving scientific presentations.

    Muralidharan says that idea encouraged him to think outside the box in his science classes as well. “A lot of the time, you can get stuck in the method of thinking in math,” he says. “We think of integrals, numbers, probability. And you kind of step back, and you realize that maybe you don’t have a good intuition for what’s actually happening.”

    Both art students and physics students benefited from the class, Muralidharan says. “I think talking to each other across that bridge helped solidify concepts.”

    Beyond the classroom

    Kagan estimates that between 2000 and 3000 students have gone through his classes. Those students have gone on to a wide variety of careers.

    “What comes with these lessons is a perspective with which to do art or to do science—a perspective with which you understand your role in the universe,” Kagan says.

    Jeff Hazelden, who took Kagan’s classes as a photography major, says Kagan’s classes introduced him to characteristics of light that are still useful in his career as a photographer and art teacher. He says he also uses parts of Kagan’s structured format for artistic critiques with his students that are new to the critique process.

    Katherine Hanlon, another former photography major, now works as a medical imaging specialist. She helps identify skin diseases by taking specialized photos using lasers and 3-D modeling. Kagan’s class introduced her to important aspects of those techniques.

    “I look back and realize that a lot of what I ended up doing in my career and my skill level and knowledge level was influenced specifically by this class,” Hanlon says. “I think it was easily the most important class I ever took in any of my education.”

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 3:21 pm on November 26, 2017 Permalink | Reply
    Tags: Einstein, ER - for Einstein-Rosen bridges, ER = EPR - (the EPR paradox named for its authors - Einstein Boris Podolsky and Nathan Rosen), Eventually Susskind — in a discovery that shocked even him — realized (with Gerard ’t Hooft) that all the information that fell down the hole was actually trapped on the black hole’s two-dimen, Holography, , , , , The particles still inside the hole would be directly connected to particles that left long ago,   

    From Quanta: “Wormholes Untangle a Black Hole Paradox” 2015 but Worth It. 

    Quanta Magazine
    Quanta Magazine

    April 24, 2015
    K.C. Cole

    1
    Hannes Hummel for Quanta Magazine

    One hundred years after Albert Einstein developed his general theory of relativity, physicists are still stuck with perhaps the biggest incompatibility problem in the universe. The smoothly warped space-time landscape that Einstein described is like a painting by Salvador Dalí — seamless, unbroken, geometric. But the quantum particles that occupy this space are more like something from Georges Seurat: pointillist, discrete, described by probabilities. At their core, the two descriptions contradict each other. Yet a bold new strain of thinking suggests that quantum correlations between specks of impressionist paint actually create not just Dalí’s landscape, but the canvases that both sit on, as well as the three-dimensional space around them. And Einstein, as he so often does, sits right in the center of it all, still turning things upside-down from beyond the grave.

    Like initials carved in a tree, ER = EPR, as the new idea is known, is a shorthand that joins two ideas proposed by Einstein in 1935. One involved the paradox implied by what he called “spooky action at a distance” between quantum particles (the EPR paradox, named for its authors, Einstein, Boris Podolsky and Nathan Rosen). The other showed how two black holes could be connected through far reaches of space through “wormholes” (ER, for Einstein-Rosen bridges). At the time that Einstein put forth these ideas — and for most of the eight decades since — they were thought to be entirely unrelated.

    1
    When Einstein, Podolsky and Rosen published their seminal paper pointing out puzzling features of what we now call entanglement, The New York Times treated it as front-page news. The New York Times

    But if ER = EPR is correct, the ideas aren’t disconnected — they’re two manifestations of the same thing. And this underlying connectedness would form the foundation of all space-time. Quantum entanglement — the action at a distance that so troubled Einstein — could be creating the “spatial connectivity” that “sews space together,” according to Leonard Susskind, a physicist at Stanford University and one of the idea’s main architects. Without these connections, all of space would “atomize,” according to Juan Maldacena, a physicist at the Institute for Advanced Study in Princeton, N.J., who developed the idea together with Susskind. “In other words, the solid and reliable structure of space-time is due to the ghostly features of entanglement,” he said. What’s more, ER = EPR has the potential to address how gravity fits together with quantum mechanics.

    Not everyone’s buying it, of course (nor should they; the idea is in “its infancy,” said Susskind). Joe Polchinski, a researcher at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara, whose own stunning paradox about firewalls in the throats of black holes triggered the latest advances, is cautious, but intrigued. “I don’t know where it’s going,” he said, “but it’s a fun time right now.”

    The Black Hole Wars

    3
    Juan Maldacena at the Institute for Advanced Study in Princeton, N.J. Andrea Kane/Institute for Advanced Study

    The road that led to ER = EPR is a Möbius strip of tangled twists and turns that folds back on itself, like a drawing by M.C. Escher.

    A fair place to start might be quantum entanglement. If two quantum particles are entangled, they become, in effect, two parts of a single unit. What happens to one entangled particle happens to the other, no matter how far apart they are.

    Maldacena sometimes uses a pair of gloves as an analogy: If you come upon the right-handed glove, you instantaneously know the other is left-handed. There’s nothing spooky about that. But in the quantum version, both gloves are actually left- and right-handed (and everything in between) up until the moment you observe them. Spookier still, the left-handed glove doesn’t become left until you observe the right-handed one — at which moment both instantly gain a definite handedness.

    Entanglement played a key role in Stephen Hawking’s 1974 discovery that black holes could evaporate. This, too, involved entangled pairs of particles. Throughout space, short-lived “virtual” particles of matter and anti-matter continually pop into and out of existence. Hawking realized that if one particle fell into a black hole and the other escaped, the hole would emit radiation, glowing like a dying ember. Given enough time, the hole would evaporate into nothing, raising the question of what happened to the information content of the stuff that fell into it.

    But the rules of quantum mechanics forbid the complete destruction of information. (Hopelessly scrambling information is another story, which is why documents can be burned and hard drives smashed. There’s nothing in the laws of physics that prevents the information lost in a book’s smoke and ashes from being reconstructed, at least in principle.) So the question became: Would the information that originally went into the black hole just get scrambled? Or would it be truly lost? The arguments set off what Susskind called the “black hole wars,” which have generated enough stories to fill many books. (Susskind’s was subtitled My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics.)

    4
    Leonard Susskind at home in Palo Alto, Calif. Jeff Singer

    5
    Stephen Hawking. No image credit

    Eventually Susskind — in a discovery that shocked even him — realized (with Gerard ’t Hooft) that all the information that fell down the hole was actually trapped on the black hole’s two-dimensional event horizon, the surface that marks the point of no return. The horizon encoded everything inside, like a hologram. It was as if the bits needed to re-create your house and everything in it could fit on the walls. The information wasn’t lost — it was scrambled and stored out of reach.

    Susskind continued to work on the idea with Maldacena, whom Susskind calls “the master,” and others. Holography began to be used not just to understand black holes, but any region of space that can be described by its boundary. Over the past decade or so, the seemingly crazy idea that space is a kind of hologram has become rather humdrum, a tool of modern physics used in everything from cosmology to condensed matter. “One of the things that happen to scientific ideas is they often go from wild conjecture to reasonable conjecture to working tools,” Susskind said. “It’s gotten routine.”

    Holography was concerned with what happens on boundaries, including black hole horizons. That left open the question of what goes on in the interiors, said Susskind, and answers to that “were all over the map.” After all, since no information could ever escape from inside a black hole’s horizon, the laws of physics prevented scientists from ever directly testing what was going on inside.

    Then in 2012 Polchinski, along with Ahmed Almheiri, Donald Marolf and James Sully, all of them at the time at Santa Barbara, came up with an insight so startling it basically said to physicists: Hold everything. We know nothing.

    The so-called AMPS paper (after its authors’ initials) presented a doozy of an entanglement paradox — one so stark it implied that black holes might not, in effect, even have insides, for a “firewall” just inside the horizon would fry anyone or anything attempting to find out its secrets.

    Scaling the Firewall

    Here’s the heart of their argument: If a black hole’s event horizon is a smooth, seemingly ordinary place, as relativity predicts (the authors call this the “no drama” condition), the particles coming out of the black hole must be entangled with particles falling into the black hole. Yet for information not to be lost, the particles coming out of the black hole must also be entangled with particles that left long ago and are now scattered about in a fog of Hawking radiation. That’s one too many kinds of entanglements, the AMPS authors realized. One of them would have to go.

    The reason is that maximum entanglements have to be monogamous, existing between just two particles. Two maximum entanglements at once — quantum polygamy — simply cannot happen, which suggests that the smooth, continuous space-time inside the throats of black holes can’t exist. A break in the entanglement at the horizon would imply a discontinuity in space, a pileup of energy: the “firewall.”


    Video: David Kaplan explores one of the biggest mysteries in physics: the apparent contradiction between general relativity and quantum mechanics. Filming by Petr Stepanek. Editing and motion graphics by MK12. Music by Steven Gutheinz.

    The AMPS paper became a “real trigger,” said Stephen Shenker, a physicist at Stanford, and “cast in sharp relief” just how much was not understood. Of course, physicists love such paradoxes, because they’re fertile ground for discovery.

    Both Susskind and Maldacena got on it immediately. They’d been thinking about entanglement and wormholes, and both were inspired by the work of Mark Van Raamsdonk, a physicist at the University of British Columbia in Vancouver, who had conducted a pivotal thought experiment suggesting that entanglement and space-time are intimately related.

    “Then one day,” said Susskind, “Juan sent me a very cryptic message that contained the equation ER = EPR. I instantly saw what he was getting at, and from there we went back and forth expanding the idea.”

    Their investigations, which they presented in a 2013 paper, “Cool Horizons for Entangled Black Holes,” argued for a kind of entanglement they said the AMPS authors had overlooked — the one that “hooks space together,” according to Susskind. AMPS assumed that the parts of space inside and outside of the event horizon were independent. But Susskind and Maldacena suggest that, in fact, particles on either side of the border could be connected by a wormhole. The ER = EPR entanglement could “kind of get around the apparent paradox,” said Van Raamsdonk. The paper contained a graphic that some refer to half-jokingly as the “octopus picture” — with multiple wormholes leading from the inside of a black hole to Hawking radiation on the outside.

    4
    The ER = EPR idea posits that entangled particles inside and outside of a black hole’s event horizon are connected via wormholes. Olena Shmahalo/Quanta Magazine.

    In other words, there was no need for an entanglement that would create a kink in the smooth surface of the black hole’s throat. The particles still inside the hole would be directly connected to particles that left long ago. No need to pass through the horizon, no need to pass Go. The particles on the inside and the far-out ones could be considered one and the same, Maldacena explained — like me, myself and I. The complex “octopus” wormhole would link the interior of the black hole directly to particles in the long-departed cloud of Hawking radiation.

    Holes in the Wormhole

    No one is sure yet whether ER = EPR will solve the firewall problem. John Preskill, a physicist at the California Institute of Technology in Pasadena, reminded readers of Quantum Frontiers, the blog for Caltech’s Institute for Quantum Information and Matter, that sometimes physicists rely on their “sense of smell” to sniff out which theories have promise. “At first whiff,” he wrote, “ER = EPR may smell fresh and sweet, but it will have to ripen on the shelf for a while.”

    Whatever happens, the correspondence between entangled quantum particles and the geometry of smoothly warped space-time is a “big new insight,” said Shenker. It’s allowed him and his collaborator Douglas Stanford, a researcher at the Institute for Advanced Study, to tackle complex problems in quantum chaos through what Shenker calls “simple geometry that even I can understand.”

    To be sure, ER = EPR does not yet apply to just any kind of space, or any kind of entanglement. It takes a special type of entanglement and a special type of wormhole. “Lenny and Juan are completely aware of this,” said Marolf, who recently co-authored a paper describing wormholes with more than two ends. ER = EPR works in very specific situations, he said, but AMPS argues that the firewall presents a much broader challenge.

    Like Polchinski and others, Marolf worries that ER = EPR modifies standard quantum mechanics. “A lot of people are really interested in the ER = EPR conjecture,” said Marolf. “But there’s a sense that no one but Lenny and Juan really understand what it is.” Still, “it’s an interesting time to be in the field.”

    See the full article here .

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  • richardmitnick 10:10 am on August 26, 2014 Permalink | Reply
    Tags: , , Holography   

    From Symmetry: “Holographic universe experiment begins” 

    Symmetry

    August 26, 2014
    No Writer Credit

    The Holometer experiment will test whether our universe is coded into 2-D packets many trillion times smaller than an atom.

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    Photo by Reidar Hahn, Fermilab

    A unique experiment at Fermi National Accelerator Laboratory has started collecting data that will answer some mind-bending questions about our universe—including whether we live in a hologram.

    Much like characters on a television show would not know that their seemingly 3-D world exists only on a 2-D screen, we could be clueless that our 3-D space is just an illusion. The information about everything in our universe could actually be encoded in tiny packets in two dimensions.

    Get close enough to your TV screen and you’ll see pixels, small points of data that make a seamless image if you stand back. Scientists think that the universe’s information may be contained in the same way and that the natural “pixel size” of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale.

    “We want to find out whether space-time is a quantum system just like matter is,” says Craig Hogan, director of Fermilab’s Center for Particle Astrophysics and the developer of the holographic noise theory. “If we see something, it will completely change ideas about space we’ve used for thousands of years.”

    Quantum theory suggests that it is impossible to know both the exact location and the exact speed of subatomic particles. If space comes in 2-D bits with limited information about the precise location of objects, then space itself would fall under the same theory of uncertainty. The same way that matter continues to jiggle (as quantum waves) even when cooled to absolute zero, this digitized space should have built-in vibrations even in its lowest energy state.

    Essentially, the experiment probes the limits of the universe’s ability to store information. If there is a set number of bits that tell you where something is, it eventually becomes impossible to find more specific information about the location—even in principle. The instrument testing these limits is Fermilab’s Holometer, or holographic interferometer, the most sensitive device ever created to measure the quantum jitter of space itself.

    Now operating at full power, the Holometer uses a pair of interferometers placed close to one another. Each one sends a 1-kilowatt laser beam (the equivalent of 200,000 laser pointers) at a beam splitter and down two perpendicular 40-meter arms. The light is then reflected back to the beam splitter where the two beams recombine, creating fluctuations in brightness if there is motion. Researchers analyze these fluctuations in the returning light to see if the beam splitter is moving in a certain way, being carried along on a jitter of space itself.

    “Holographic noise” is expected to be present at all frequencies, but the scientists’ challenge is not to be fooled by other sources of vibrations. The Holometer is testing a frequency so high—millions of cycles per second—that motions of normal matter are not likely to cause problems. Rather, the dominant background noise is more often due to radio waves emitted by nearby electronics. The Holometer experiment is designed to identify and eliminate noise from such conventional sources.

    “If we find a noise we can’t get rid of, we might be detecting something fundamental about nature—a noise that is intrinsic to space-time,” says Fermilab physicist Aaron Chou, lead scientist and project manager for the Holometer. “It’s an exciting moment for physics. A positive result will open a whole new avenue of questioning about how space works.”

    The Holometer experiment, funded by the US Department of Energy Office of Science and other sources, is expected to gather data over the coming year.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.


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