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  • richardmitnick 10:42 am on April 26, 2017 Permalink | Reply
    Tags: 10 common misconceptions in physics, , , PI, Slices of PI   

    From PI: “10 common misconceptions in physics” 

    Perimeter Institute
    Perimeter Institute

    The true power of science is that it perpetually refines our understanding based new evidence.

    Apr 26, 2017
    No writer credit

    A key part of a scientist’s job is to question everything – including the things we think we know.

    Through the ages, many ideas considered “facts” have been revealed as common misconceptions. To name a few: the Earth is flat (nope), your tongue has taste “zones” (that map of the tongue you remember from elementary school is wrong), and lightning can’t strike the same place twice (a small area in Venezuela gets roughly 1.2 million strikes each year).

    Indeed, one of the most common scientific misconceptions is that science is full of facts. Rather, science is a field in which the best current models of understanding can either be supported or disproved by evidence.

    Here, we debunk a few of the more common scientific misconceptions.

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    The Event Horizon Telescope Initiative at Perimeter Institute, led by Faculty member Avery Broderick, will analyze and interpret the torrent of data collected by the network’s telescopes, generating humanity’s first image of a black hole and testing fundamental concepts in our understanding of spacetime.

    Event Horizon Telescope Array

    Event Horizon Telescope map

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    Future Array/Telescopes

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

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    Watch Perimeter’s curious cartoon duo, Alice and Bob, explore why the moon doesn’t fall down.

    Uploaded on Oct 13, 2009

    Why doesn’t the moon fall down? Join Alice & Bob in nine fun-filled, animated adventures as they wonder about the world around us. Alice and Bob in Wonderland premiered at Perimeter Institute’s Quantum to Cosmos Festival. http://www.q2cfestival.com.

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    Watch “As We Enter a New Quantum Era,” a public lecture on the incredible advances (and potential pitfalls) of the quantum computing revolution, delivered by Perimeter Institute Associate Faculty member Michele Mosca.

    Published on Oct 6, 2016
    In his public lecture at Perimeter Institute on Oct. 5, 2015, Michele Mosca (Institute for Quantum Computing, Perimeter Institute) explored quantum technologies – those that already exist, and those yet to come – and how they will affect our lives.

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    Check out “20 illuminating, enlightening, day-brightening facts about light.”

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    Watch Alice and Bob explore where energy comes from.

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    Read “What we know (and what we don’t) about dark matter.”

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    See the full article here .

    Please help promote STEM in your local schools.

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    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 1:31 pm on March 28, 2017 Permalink | Reply
    Tags: , , , , , PI, SUPERRADIANCE   

    From PI via GIZMODO: “Mind-Blowing New Theory Connects Black Holes, Dark Matter, and Gravitational Waves” 

    Perimeter Institute
    Perimeter Institute

    GIZMODO

    3.28.17
    Ryan F. Mandelbaum

    The past few years have been incredible for physics discoveries. Scientists spotted the Higgs boson, a particle they’d been hunting for almost 50 years, in 2012, and gravitational waves, which were theorized 100 years ago, in 2016. This year, they’re slated to take a picture of a black hole. So, thought some theorists, why not combine all of the craziest physics ideas into one, a physics turducken? What if we, say, try to spot the dark matter radiating off of black holes through their gravitational waves?

    It’s really not that strange of an idea. Now that scientists have detected gravitational waves, ripples in spacetime spawned by the most violent physical events, they want to use their discovery to make real physics observations. They think they have a way to spot all-new particles that might make up dark matter, an unknown substance that accounts for over 80 percent of all of the gravity in the universe.

    The basic idea is that we’re trying to use black holes… the densest, most compact objects in the universe, to search for new kinds of particles,” Masha Baryakhtar, postdoctoral researcher at the Perimeter Institute for Theoretical Physics in Canada, told Gizmodo. Especially one particle: “The axion. People have been looking for it for 40 years.”

    Black holes are the universe’s sinkholes, so strong that light can’t escape their pull once it’s entered. They’ve got such powerful gravitational fields that they produce gravitational waves when they collide with each other. Dark matter might not be made from particles (specks of mass and energy), but if it was, we might observe it as axions, particles around one quintillion (a billion billion) times lighter than an electron, hanging around black holes. Now that you understand all the terms, here’s how the theory works.

    Baryakhtar and her teammates think that black holes are more than just bear traps for light, but nuclei at the center of a sort of gravitational atom. The axions would be the electrons, so to speak. If you already know about black holes, you know they have incredibly hot, high-energy discs of gas orbiting them, produced by the friction between particles accelerated by the black hole’s gravity. This theory ignores that stuff, since axions wouldn’t interact via friction.

    Keeping with the atom analogy, the axions can jump around the black hole, gaining and losing energy the same way that electrons do. But electrons interact via electromagnetism, so they let out electromagnetic waves, or light waves. Axions interact via gravity, so they let out gravitational waves. But like I said earlier, axions are tiny. Unlike a tiny atom, the black hole in these “gravity atoms” rotates, supercharging the space around it and coaxing it into producing more axions. Despite the axion’s tiny mass, this so-called superradiance process could generate 10^80 axions, the same number of atoms in the entire universe, around a single black hole. Are you still with me? Crazy spinning blob makes lots of crazy stuff.

    Craziest of all, we should be able to hear a gravitational wave hum from these axions moving around and releasing gravitational waves in our detectors, similar to the way you see spectral lines coming off of electrons in atoms in chemistry class. “You’d see this at a particular frequency which would be roughly twice the axion mass,” said Baryakhtar.

    There are giant gravitational wave detectors scattered around the world; presently there’s one called LIGO (Laser Interferometer Gravitational Wave Observatory) in Washington State, another LIGO in Louisiana, and one called Virgo in Italy that are sensitive enough to detect gravitational waves, and with upgrades, to detect axions and prove their theory right.



    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


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



    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Scientists would essentially need to record data, play it back, and tune their analysis like a radio to pick up the signal at just the right frequency.

    There are other ways the team thinks it could spot this superradiance effect, by measuring the spins in sets of colliding black holes. If black holes really do produce axions, scientists would see very few quickly-spinning black holes in collisions, since the superradiance effects would slow down some of the colliding black holes and create a visible effect in the data, according to the research published this month in the journal Physical Review D. The black hole spins would have a specific pattern which we should be able to spot in the gravitational wave detector data.

    Other scientists were immediately excited about this paper. “I’m always super excited about new ways to detect my favorite pet particle, the axion! Also, SUPERRADIANCE!” Dr. Chanda Prescod-Weinstein, the University of Washington axion wrangler, told Gizmodo in an email. “It’s so cool, and I haven’t read a paper that talked about [superradiance] in years. So it was really fun to see superradiance and axions in one paper.”

    There are a few drawbacks, as there are with any theory. These theorized black hole atoms would have to produce axions of a certain mass, but that mass isn’t an ideal one for the axion to be a dark matter particle, said Prescod-Weinstein. Plus, the second detection idea, the one that looks at the spin rate of colliding black holes, might not work. “They say [in the paper] that they don’t take into account the potential influence of another black hole” in the colliding pair, Dr. Lionel London, a research associate at Cardiff University School of Physics and Astronomy specializing in gravitational wave modeling, told Gizmodo. “If this does turn out to be a significant effect and they’re not including it, this could cast doubt on their results.” But there’s hope. “There’s good reason to believe the effect of a companion [black hole] won’t be large.”

    When would we spot these kinds of events? As of now, the LIGO and Virgo gravitational wave detectors probably aren’t ready. “With the current sensitivity we’re on the edge” of detecting axions, said Baryakhtar. “But LIGO will continue improving their instruments and at design sensitivity we might be able to see as many as 1000s of these axion signals coming in,” she said. Thousands of hums from these black hole-atoms.

    So, if you’ve gotten all the way to this point of the story and still don’t understand what’s going on, a recap: We’ve got these gravitational wave detectors that cost hundreds of millions of dollars each, that are good at spotting really crazy things going on in the universe. Theorists have come up with an interesting way to use them to solve one of the most important interstellar mysteries: What the heck is dark matter? As with most new ideas in theoretical physics, this is something cool to think about and isn’t ready for the big time… yet.

    “I think that timescale is always a concern, but we’re just getting started with LIGO discoveries,” said Prescod-Weinstein. “So who knows what’s around the corner over the next 10 years.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 3:52 pm on January 11, 2017 Permalink | Reply
    Tags: , , , , , , , PI   

    From PI via Motherboard: “Dark Matter Hunters Are Hoping 2017 is Their Year” 

    Perimeter Institute
    Perimeter Institute

    Motherboard

    January 3, 2017
    Kate Lunau

    It can be unsettling to realize that only five percent of the universe is made of the kind of matter we know and understand—everything from the planets and stars, to trees and animals and your dining room table.

    Roughly one-quarter is dark matter. This is thought to knit the galaxies together, and has been called the “scaffolding” of the universe, but we’ve never detected it directly. Scientists believe they can see dark matter’s traces in the way that galaxies rotate, but they still have no idea what it is. (Most of the universe, about 70 percent, is dark energy, a mysterious force that permeates space and time. It’s even less well-understood than dark matter.)

    Confirming dark matter’s existence would change humankind’s perspective on the universe. 2016 was a year of dark matter disappointments, as big searches came up empty. Most are looking for WIMPs—weakly interacting massive particles, the leading contender for a dark matter particle.

    2017 might just be the year we finally catch one. And if we don’t, well, it may be that our best theories about dark matter are wrong—that we’re looking in the wrong places, with the wrong instruments. Maybe dark matter, whatever it is, will turn out to be even weirder and more surprising than anyone has so far predicted. Maybe it’s not a WIMP, but some other bizarre kind of particle.

    Then there’s the outside possibility that dark matter doesn’t exist, that it’s an illusion. If that’s the case, we’ll have to consider whether we’ve been fundamentally misreading the universe’s clues.

    Buried deep in a mine near Sudbury in northern Ontario is SNOLAB, a vast underground laboratory where scientists are performing a range of experiments, including looking for dark matter. Often compared to the lair of a Bond villain, it’s an ultra-clean, high-tech facility. Two kilometers of solid rock overhead shield its detectors from cosmic radiation, allowing them to sift for bits of matter from dying stars and the Sun: science done here won the Nobel Prize in Physics, in 2015.

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    A scientist works on the deck of DEAP-3600, a dark matter search at SNOLAB. Image: SNOLAB

    I recently travelled to SNOLAB. To get there, I had to don full mining gear (including a hardhat and headlamp), drop down underground in a rattling dark cage, and hike a kilometre or so to reach the gleaming white facility, which is cleaner inside than an operating room—a startling contrast to the dirty nickel mine that surrounds it.

    After the long hike through the mine, anyone who wants to enter SNOLAB has to undress, shower (with soap and shampoo), and put on lint-free clothing and a hairnet. Any bit of dust from the mine, which is naturally radioactive, can mess up the experiments.

    There, I met research scientist Ken Clark, a congenial physicist with a sandy-coloured beard. Like me, he was wearing safety goggles and a hardhat. Clark has worked on high-profile dark matter searches like CDMS and LUX, and collaborates on the IceCube detector at the South Pole in Antarctica.

    LBL SuperCDMS
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)
    LBL SuperCDMS, at SNOLAB (Vale Inco Mine, Sudbury, Canada)

    LUX Xenon experiment at SURF
    LUX Xenon experiment at SURF, Lead, SD, USA

    U Wisconsin ICECUBE neutrino detector at the South Pole
    IceCube neutrino detector interior
    U Wisconsin ICECUBE neutrino detector at the South Pole

    Now he’s with PICO, a dark matter search that targets the WIMP particle.

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    It was launched in 2013 when two other collaborations, called PICASSO and COUPP, merged.

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    A multi-bubble image of a neutron scattering in the PICO detector. Image: PICO Collaboration

    PICO is a bubble detector: a tank of superheated fluid kept higher than its natural boiling point. If dark matter bumps into the nucleus of another particle in the detector, it should cause a tiny bubble to form. Dark matter courses through the Earth and right through our bodies, so it will reach the detector underground, even through all that rock overhead. But that’s also part of the challenge—dark matter is thought to only rarely interact with normal matter, if at all, so it’s really tricky to catch.

    Clark believes we might just find dark matter in the next year or two. “It’s exciting times,” he said.

    Other searches are due to turn on soon, he explained, and those that are already up-and-working are getting increasingly sensitive. In 2017, Clark said it’s possible we’ll see new results from PICO, DEAP (a different detector, also at SNOLAB), as well as China’s ambitious PandaX project, and another in Italy called XENON1T. Even more searches will turn on in 2018.

    “Provided the models are correct, we should see something soon,” Clark told me.

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    A scientist works on the steel vessel of DEAP-3600. Image: DEAP Collaboration

    Still, there’s no guarantee, and WIMP searches keep turning up empty-handed. For example, in the summer, the highly sensitive LUX—which uses liquid xenon in a South Dakota mine as its detector—announced it had seen zero WIMPs, after looking for more than a year.

    I phoned Lisa Randall, a prominent theoretical physicist and professor at Harvard University, to ask whether she thinks there’s a chance we’ll find dark matter in the next year or two.

    “I would say kind of the opposite,” said Randall, author of Dark Matter and the Dinosaurs. While she agrees that if dark matter is indeed a WIMP, these searches could find it soon, “that’s just one possibility,” she said.

    The WIMP is “lowest-hanging fruit,” Randall continued: this theoretical particle fits snugly within what’s already known about the Standard Model of physics, which explains how the building blocks of the universe interact. And scientists can imagine ways to actually look for WIMPs, unlike some of the more far-out theories, which are much harder to test in experiments.

    “What if it’s not a WIMP?” Randall said. “Could we still learn something about what dark matter is?”

    Other scientists have different strategies for solving the dark matter puzzle.

    Leslie Rosenberg, a professor of physics at the University of Washington in Seattle, is project scientist on the Axion Dark Matter Experiment, or ADMX, which is looking for a theoretical particle called the axion, which is thought to be much lighter than a WIMP.

    ADMX Axion Dark Matter Experiment
    U Washington ADMX
    U Washington ADMX

    It’s being targeted by other searches under development around the world, Rosenberg told me. ADMX, though, is “the only high-sensitivity axion search now,” he said.

    Maybe we’re being fooled into thinking that dark matter is there.

    ADMX, which uses a resonant microwave cavity nested inside a huge superconducting magnet, started out of a collaboration that began in the mid-nineties. It’s been at full sensitivity for about a year now, Rosenberg told me, and will only get better as the team continues to tweak it. He’s hoping they turn up something soon: their next update should come in the summer of 2017.

    “Axions are bound up in our galaxy,” Rosenberg said. “There [should be] an awful lot of them, and we depend on that as the source of our signal.”

    Axions are a mainstream dark matter candidate. Other ideas get weirder.

    “Personally, I’m interested in the idea that dark matter might have nothing to do with the Standard Model,” Randall told me. “One of the possibilities is that it could be some other type of particle. Maybe it interacts [with itself] via its own light, a dark photon.”

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    ESA/Gaia’s first sky map of the Milky Way, based on data collected from July 2014 to Sept. 2015. Image: ESA/Gaia/DPAC

    Randall thinks that one of the best ways to learn about dark matter may be to study the structure of galaxies, and watching the universe at work, to understand how it interacts with itself. The European Space Agency’s Gaia mission, which is making a three-dimensional map of over a thousand million stars, could give insight into some of this, Randall said.

    Asimina Arvanitaki, a theoretical physicist at the Perimeter Institute for Theoretical Physics, suggested to me in a Skype call that dark matter might be detectable through resonant-mass detectors, which are used to hunt for gravitational waves. These ripples in spacetime were detected for the first time in 2016, a hundred years after Albert Einstein predicted their existence.

    Dark matter could also be behaving like a wave, “trapped by gravity and oscillat[ing] at a frequency set by the mass,” she said.

    “The funny thing is you could perhaps even hear dark matter,” Arvanitaki said, “depending on the frequency.”

    Over millions of years, humans have come up with ingenious ways to probe the world around us, from Copernicus and Kepler, through the thousands of scientists involved in the search for the Higgs boson particle at the Large Hadron Collider, and those who are now shaking out the endless diversity of exoplanets that populate our galaxy.

    Because of them, our perspective has changed. When we look up at the night sky today, we understand that just about every star we see hosts at least one planet. The first confirmed exoplanet was announced just over two decades ago.

    Nature can still surprise us.

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    The Bullet cluster, formed by the collision of two large galaxy clusters, provides some of the best evidence yet for dark matter. Image: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

    “There’s a chance that dark matter isn’t necessarily a particle at all,” Clark told me. “Some [theorists] say there’s no dark matter. It’s just that we don’t understand how gravity works at large scales,” he continued. “If that’s the case, we’re being fooled into thinking that dark matter is there.”

    Clark and the other dark matter hunters continue their search. If it’s real, “we’re not even made of what most of the universe is made of,” Rosenberg told me. In the grand scheme of things, then, it isn’t dark matter that’s really so exotic and strange—it’s us.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 8:14 am on October 19, 2016 Permalink | Reply
    Tags: , Particle X, , PI, The lithium problem   

    From PI: “Particle X and the Case of the Missing Lithium” 

    Perimeter Institute
    Perimeter Institute

    October 11, 2016
    Erin Bow

    1
    Maxim Pospelov

    About two-thirds of the lithium that should be in the early universe is missing. Perimeter researcher Maxim Pospelov thinks a hypothetical new particle – particle X – may have kept it from being formed.

    There’s nothing like a good anomaly. In science, anomalies – places where theory contradicts observation – drive progress.

    As Isaac Asimov once said, “The most exciting phrase to hear in science, the one that heralds new discoveries, is not ‘Eureka!’ but ‘That’s funny….’”

    Cosmology, sadly, suffers from a lack of anomalies. Where it makes predictions at all, the standard cosmology tends to be spot on. But there’s an exception: there is not enough lithium-7 in the early universe.

    Perimeter Associate Faculty member Maxim Pospelov has been trying to figure out what happened to that lithium for more than a decade. Now, he and his colleagues have a new idea – one that invokes an unknown particle which they dubbed “particle X.”

    “To me, the lithium problem is quite intriguing,” says Pospelov. “It is a good hard problem that has been around for many years. It’s one of the best cracks through which we might glimpse new ideas.”

    So what exactly is the lithium problem? Using a model called big bang nucleosynthesis, we can calculate the relative amounts of light elements that were produced in the early universe. We can also observe how much of each element was present in the earliest stars. For the most part, the theory and the prediction line up. The model calls for three parts hydrogen to every one part helium, with a dash of deuterium (about 0.01 percent) and even smaller quantities of the two isotopes of lithium, lithium-6 and lithium-7.

    Observations check these ratios and find the predictions to be very accurate. But there is one outlier: lithium-7. That prediction is off by a factor of three. About two-thirds of the lithium-7 predicted by the big bang nucleosynthesis model is missing.

    Is the model of big bang nucleosynthesis simply wrong? That seems unlikely, because its other predictions are so good. Might the lithium be present but somehow hidden? The best efforts to find it have yet to pan out. Might something have happened to the lithium-7 along the way? That’s the line along which Pospelov has been working.

    Pospelov’s research often lies at the intersection of particle physics and cosmology. Working with Josef Pradler – a former Perimeter postdoctoral researcher and long-time collaborator – and Andreas Goudelis of the Institute of High Energy Physics in Austria, Pospelov set out to see if there might be a particle physics solution to the lithium-7 problem.

    As described in the paper A light particle solution to the cosmic lithium problem, published in Physical Review Letters, the team reverse-engineered a hypothetical particle that could destroy lithium without affecting the relative abundance of hydrogen, helium, and deuterium. They called it particle X.

    “I have to stress that this is the realm of speculation,” says Pospelov. “Speculation is a bad word in Russian, but in English it’s fine.” A bad word? “In Russia, speculators are the guys who get put in jail,” he explains, “but in physics it is sometimes good to follow speculative ideas carefully. Sometimes something interesting emerges.”

    In this case, something interesting did emerge: a hypothetical particle that could resolve the lithium anomaly.

    Though any new particle would obviously be outside the Standard Model of known particle physics, there are ones that look reasonable and ones that look out-of-whack. Particle X looks reasonable. Indeed, it looks reasonable enough that the next step in the research is to plan experiments to check for its existence.

    To reverse-engineer particle X, the team first supposed a long lifetime: on the order of 1,000 seconds. That’s long enough that it could have been created during the big bang, and survived the hot and violent first three minutes of the universe to reach the relative calm where the light elements were formed. “A thousand seconds is a benchmark – the period where the most critical reactions for lithium occur,” explains Pospelov. “If there were an input of neutrons right at this time, for instance, you would inhibit the production of lithium.”

    Many previous attempts to tackle the lithium abundance problem with ideas from particle physics have posited a hypothetical heavy particle whose decay produces neutrons. Add neutrons to the mix at the 1,000-second mark, and lithium formation is suppressed.

    But that’s not the only thing those neutrons would do. They would also increase the abundance of deuterium – and that’s not a good thing. The problem with increasing the predicted abundance of deuterium in the universe is that we recently learned to measure the real abundance of deuterium in the early universe.

    “These measurements became as good as a few percent in the last years, and they are bang-on the predictions of big bang nucleosynthesis,” says Pospelov. “Therefore this idea of new particles that produce neutrons doesn’t work. When we learned to measure deuterium abundance, a hundred models died in a moment.

    “Our idea is to work around this. The idea was not introduce new neutrons, but to free up existing neutrons only for a short time.”

    The next assumption the team made was the mass of particle X: about 10 MeV. That’s about 20 times heavier than an electron, and about 100 times lighter than a proton.

    Unlike previous hypothetical particles, it is too light to decay into neutrons. Instead, the team envisions particle X producing neutrons by breaking apart the deuterium, whose nucleus contains one proton and one neutron. “The particle would hit that nucleus and knock the neutron free,” says Pospelov.

    These knocked-free neutrons would enter the soup of the big bang nucleosynthesis, suppressing the formation of lithium. But those neutrons would be quickly swept back up to form deuterium again. As the soup cooled, the ultimate abundance of the deuterium would be unchanged. The team calls the process neutron recycling, and it seems to solve the lithium abundance problem without introducing changes to the otherwise successful model of big bang nucleosynthesis.

    It would be great, lithium-wise, if particle X did exist, but at the moment the idea is still speculative (in the good sense). The team’s next step would be to seek independent lines of evidence for particle X, starting with searches at earthbound particle physics experiments.

    The good news is that the team’s theory is well developed and sophisticated enough to predict experimental signatures. And, at only 10 MeV, particle X should be well within the energy range we can study at particle accelerators. However, it interacts – or “couples,” to use the particle physics language – only weakly, which makes it hard to spot.

    “It’s not like a photon or an electron, or even a pion or kaon,” says Pospelov. “The couplings we’ve introduced are strong enough to have an effect on big bang nucleosynthesis, but that’s not very strong.”

    They might start testing, Pospelov suggests, with the sort of experiments that go by the unpoetic name of beam-dumps. In these experiments, a beam of energetic particles is driven into a thick piece of shielding: the dump. Only fairly long-lived particles can come out the other side. The 1,000-second lifetime for particle X may seem short on the scale of the universe, but on the scale of particle physics, where most exotic particles last for blinks, 1,000 seconds is long enough to qualify as stable or meta-stable.

    “You would look for a particle emerging from the beam dump. It would occasionally interact or decay in the detector.”

    Also, since the particle interacts fairly weakly, it might be good to look for it in experiments that specialize in weakly interacting particles, such as the deep underground ones that look for dark matter or study neutrinos. “All I need is someone willing to let me put a small accelerator next to a big neutrino detector,” says Pospelov, and laughs. It does seem a bit like putting a bandshell in a hospital zone: a hard sell. “These are some small challenges I need to address.”

    Also on the to-do list: building a complete field-theoretical model that would include particle X without making a mess of the Standard Model.

    “Speculations are very nice,” says Pospelov, “but what we need is either a discovery or a firm exclusion.”

    And perhaps, someday, a name for the mysterious particle X.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
  • richardmitnick 5:38 pm on October 14, 2016 Permalink | Reply
    Tags: , , , , PI,   

    From PI: “10 Fascinating Facts About the World’s Most Powerful Telescope” 

    Perimeter Institute
    Perimeter Institute

    October 12, 2016

    It’s a telescope essentially as large as the Earth, and it is shedding light on some of the most mysterious phenomena in the universe.

    A supermassive black hole churns at the heart of the Milky Way galaxy. To see it clearly, we need a telescope the size of the Earth. But building that is impossible.

    So scientists have flipped the problem, and turned the Earth into a telescope.

    The Event Horizon Telescope (EHT) is a global array of interconnected radio telescopes that is expected to soon provide humanity’s first glimpse of a black hole. And that’s just one of the many amazing things about it.

    Here are some fascinating facts about the world’s most remarkable telescope.

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    Access mp4 video here .

    Further Exploration:

    The Event Horizon Telescope Initiative at Perimeter Institute
    Testing General Relativity with Black Holes (story and video)

    Event Horizon Telescope Array

    Event Horizon Telescope map

    The locations of the radio dishes that will be part of the Event Horizon Telescope array. Image credit: Event Horizon Telescope sites, via University of Arizona at https://www.as.arizona.edu/event-horizon-telescope.

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment (APEX)

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM NOEMA interferometer
    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Hawaii SAO
    Submillimeter Array Hawaii SAO

    Future Array/Telescopes

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    Plateau de Bure interferometer
    Plateau de Bure interferometer

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    About Perimeter

    Perimeter Institute is the world’s largest research hub devoted to theoretical physics. The independent Institute was founded in 1999 to foster breakthroughs in the fundamental understanding of our universe, from the smallest particles to the entire cosmos. Research at Perimeter is motivated by the understanding that fundamental science advances human knowledge and catalyzes innovation, and that today’s theoretical physics is tomorrow’s technology. Located in the Region of Waterloo, the not-for-profit Institute is a unique public-private endeavour, including the Governments of Ontario and Canada, that enables cutting-edge research, trains the next generation of scientific pioneers, and shares the power of physics through award-winning educational outreach and public engagement.

     
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