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  • richardmitnick 3:12 pm on October 17, 2014 Permalink | Reply
    Tags: , Black Holes, , ,   

    From Perimeter: “The Last Gasp of a Black Hole” 

    Perimeter Institute
    Perimeter Institute

    October 17, 2014
    No Writer Credit

    New research from Perimeter shows that two of the strangest features of quantum mechanicsentanglement and negative energy – might be two faces of one coin.

    Quantum mechanics is, notoriously, weird. Take entanglement: when two or more particles are entangled, their states are linked together, no matter how far apart they go.

    If the idea makes your classical mind twitch, you’re in good company. At the heart of everything, according to quantum mechanics, nature has a certain amount of irreducible jitter. Even nothing – the vacuum of space – can jitter, or as physicists say, fluctuate. When it does, a particle and its anti-particle can pop into existence.

    For example, an electron and an anti-electron (these are called positrons) might pop into existence out of the vacuum. We know that they each have a spin of one half, which might be either up or down. We also know that these particles were created from nothing and so, to balance the books, the total spin must add up to zero. Finally, we know that the spin of either particle is not determined until it is measured.

    So suppose the electron and the positron fly apart a few metres or a few light years, and then a physicist comes by to measure the spin of, say, the electron. She discovers that the electron is spin up, and in that moment, the electron becomes spin up. Meanwhile, a few metres or a few light years away, the positron becomes spin down. Instantly. That is the strangeness of quantum entanglement.

    Negative energy is less well known than entanglement, but no less weird. It begins with the idea – perhaps already implied by the positron and electron popping out of nowhere – that empty space is not empty. It is filled with quantum fields, and the energy of those fields can fluctuate a little bit.

    In fact, the energy of these fields can dip under the zero mark, albeit briefly. When that happens, a small region of space can, for a short span of time, weigh less than nothing – or at least less than the vacuum. It’s a little bit like finding dry land below sea level.

    Despite their air of strangeness, entanglement and negative energy are both well-explored topics. But now, new research, published as a Rapid Communication in Physical Review D, is hinting that these two strange phenomena may be linked in a surprising way.

    The work was done by Perimeter postdoctoral fellow Matteo Smerlak and former postdoc Eugenio Bianchi (now on the faculty at Penn State and a Visiting Fellow at Perimeter). “Negative energy and entanglement are two of the most striking features of quantum mechanics,” says Smerlak. “Now, we think they might be two sides of the same coin.”

    ms
    Perimeter Postdoctoral Researcher Matteo Smerlak

    man
    Perimeter Visiting Fellow Eugenio Bianchi

    Specifically, the researchers proved mathematically that any external influence that changes the entanglement of a system in its vacuum state must also produce some amount of negative energy. The reverse, they say, is also true: negative energy densities can never be produced without entanglement being directly affected.

    At the moment, the result only applies to certain quantum fields in two dimensions – to light pulses travelling up and down a thin cable, for instance. And it is with light that the Perimeter researchers hope that their new idea can be directly tested.

    “Some quantum states which have negative energy are known, and one of them is called a ‘squeezed state,’ and they can be produced in the lab, by optical devices called squeezers,” says Smerlak. The squeezers manipulate light to produce an observable pattern of negative energy.

    Remember that Smerlak and Bianchi’s basic argument is that if an external influence affects vacuum entanglement, it will also release some negative energy. In a quantum optics setup, the squeezers are the external influence.

    Experimentalists should be able to look for the correlation between the entanglement patterns and the negative energy densities which this new research predicts. If these results hold up – always a big if in brand new work – and if they can make the difficult leap from two dimensions to the real world, then there will be startling implications for black holes.

    Like optical squeezers, black holes also produce changes in entanglement and energy density. They do this by separating entangled pairs of particles and preferentially selecting the ones with negative energy.

    Remember that the vacuum is full of pairs of particles and antiparticles blinking into existence. Under normal circumstances, they blink out again just as quickly, as the particle and the antiparticle annihilate each other. But just at a black hole’s event horizon, it sometimes happens that one of the particles is sucked in, while the other escapes. The small stream of escaping particles is known as Hawking radiation.

    By emitting such radiation, black holes slowly give up their energy and mass, and eventually disappear. Black hole evaporation, as the process is known, is a hot topic in physics. This new research has the potential to change the way we think about it.

    “In the late stages of the evaporation of a black hole, the energy released from the black hole will turn negative,” says Smerlak. And if a black hole releases negative energy, then its total energy goes up, not down. “It means that the black hole will shrink and shrink and shrink – for zillions of years – but in the end, it will release its negative energy in a gasp before dying. Its mass will briefly go up.”

    Call it the last gasp of a black hole.

    See the full article here.

    About Perimeter

    Perimeter Institute is a leading centre for scientific research, training and educational outreach in foundational theoretical physics. Founded in 1999 in Waterloo, Ontario, Canada, its mission is to advance our understanding of the universe at the most fundamental level, stimulating the breakthroughs that could transform our future. Perimeter also trains the next generation of physicists through innovative programs, and shares the excitement and wonder of science with students, teachers and the general public.

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  • richardmitnick 11:15 am on October 15, 2014 Permalink | Reply
    Tags: , Black Holes, Loop Quantum Gravity, , Quantum Gravity, , , White Holes   

    From NOVA: “Are White Holes Real?” 

    PBS NOVA

    NOVA

    Tue, 19 Aug 2014
    Maggie McKee

    Sailors have their krakens and their sea serpents. Physicists have white holes: cosmic creatures that straddle the line between tall tale and reality. Yet to be seen in the wild, white holes may be only mathematical monsters. But new research suggests that, if a speculative theory called loop quantum gravity is right, white holes could be real—and we might have already observed them.

    wh

    A white whole is, roughly speaking, the opposite of a black hole. “A black hole is a place where you can go in but you can never escape; a white hole is a place where you can leave but you can never go back,” says Caltech physicist Sean Carroll. “Otherwise, [both share] exactly the same mathematics, exactly the same geometry.” That boils down to a few essential features: a singularity, where mass is squeezed into a point of infinite density, and an event horizon, the invisible “point of no return” first described mathematically by the German physicist Karl Schwarzschild in 1916. For a black hole, the event horizon represents a one-way entrance; for a white hole, it’s exit-only.

    There is excellent evidence that black holes really exist, and astrophysicists have a robust understanding of what it takes to make one. To imagine how a white hole might form, though, we have to go out on a bit of an astronomical limb. One possibility involves a spinning black hole. According to [Albert] Einstein’s general theory of relativity, the rotation smears the singularity into a ring, making it possible in theory to travel through the swirling black hole without being crushed. General relativity’s equations suggest that someone falling into such a black hole could fall through a tunnel in space-time called a wormhole and emerge from a white hole that spits its contents into a different region of space or period of time.

    Though mathematical solutions to those equations exist for white holes, “they’re not realistic,” says Andrew Hamilton, an astrophysicist at the University of Colorado at Boulder. That is because they describe universes that contain only black holes, white holes and wormholes—no matter, radiation or energy. Indeed, previous research, including Hamilton’s, suggests that anything that falls into a spinning black hole will essentially plug up the wormhole, preventing the formation of a passage to a white hole.

    But there’s a light at the end of the wormhole, so to speak. General relativity, from which Hamilton draws his predictions, breaks down at a black hole’s singularity. “The energy density and the curvature become so large that classical gravity is not a good description of what’s happening there,” says Stephen Hsu, a physicist at Michigan State University in East Lansing. Perhaps a more complete model of gravity—one that works as well on the quantum scale as it does on large ones—would negate the instability and allow for white holes, he says.

    Indeed, a unified theory that merges gravity and quantum mechanics is one of the holy grails of contemporary physics. Applying one such theory, loop quantum gravity, to black holes, theorists Hal Haggard and Carlo Rovelli of Aix-Marseille University in France have shown that black holes could metamorphose into white holes via a quantum process. In July, they published their work online.

    Loop quantum gravity proposes that space-time is made up of fundamental building blocks shaped like loops. According to Haggard and Rovelli, the loops’ finite size prevents a dying star from collapsing all the way down into a point of infinite density, and the shrinking object rebounds into a white hole instead. This process may take just a few thousandths of a second, but thanks to the intense gravity involved, the effects of relativity make the transformation appear to take much, much longer to anyone watching from afar. That means that minuscule black holes born in the infant universe could “now be ready to pop off like firecrackers,” forming white holes, according to a report in Nature. Some of the explosions astronomers thought were supernovae may actually be the wails of newborn white holes.

    The black-to-white conversion could resolve a nettlesome conundrum known as the black hole information paradox. The notion that information can be destroyed is anathema in physics, and general relativity says that anything, including information, that falls into a black hole can never escape. These two statements are not at odds if black holes simply act as locked safes for any information they slurp up, but Stephen Hawking showed 40 years ago that black holes actually evaporate over time. That led to the disturbing possibility that the information contained within them could be lost too, triggering a debate that rages to this day.

    But if a black hole instead turns into a white hole, then “all the information is recovered,” says Haggard. “We are quite excited about this mechanism because it avoids so many of the thorny issues that surround this discussion.”

    The new work is preliminary, however, and it is far from clear whether loop quantum gravity is an accurate description of reality. The only glimpse we get of white holes might turn out to be those we model in labs and kitchen sinks. But Carroll says that’s okay. Just thinking about these possibly mythical cosmic creatures can improve physicists’ intuition, “even if the real world is messy and not like those exact situations,” he says. “That’s the way in which white holes are very useful.”

    See the full article here.

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

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  • richardmitnick 10:54 am on August 19, 2014 Permalink | Reply
    Tags: , , , Black Holes, , ,   

    From SPACE.com: “Supermassive Death: 3 Stars Eaten by Black Holes” 

    space-dot-com logo

    SPACE.com

    August 19, 2014
    Ian O’Neill

    Astrophysicists have analyzed two decades-worth of X-ray data and discovered three events inside galactic cores that can be interpreted in only one way: stellar destruction.

    ANALYSIS: Supermassive Black Hole Jet Mystery Solved

    For any given galaxy, it is estimated that a star will be destroyed by the central supermassive black hole approximately once every 10,000 years. The vast majority of known galaxies are thought to contain at least one supermassive black hole in their cores, having a dramatic effect on galactic and stellar evolution. [Images: Black Holes of the Universe]

    As a star drifts too close to a supermassive black hole, intense tidal stresses rip the star to shreds. As this happens, the shredded material will be dragged into the black hole’s accretion disk — a hot disk of gas that is gradually pulled into the black hole’s event horizon, bulking up the black hole’s mass, or blasted as energetic jets from its poles.

    Should there be a rapid injection of material — i.e. a star becoming blended and ingested into the accretion disk — powerful X-rays of a specific signature will be generated.

    NEWS: Supermassive Black Holes are Not Doughnuts!

    In a new study by the Moscow Institute of Physics and Technology and Space Research Institute of the Russian Academy of Sciences, astrophysicists trawled through observations from two space observatories to discover three likely occasions where stars have been eaten by supermassive black holes. Their work has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.

    Using data from the German ROSAT and European XMM-Newton space observatories, X-ray data from 1990 (to today) could be accessed and three events in different galaxies were positively identified — designated 1RXS J114727.1 + 494302, 1RXS J130547.2 + 641252 and 1RXS J235424.5-102053. Invaluable to this study was the long-duration observations by ROSAT (which operated from 1990 to 1999) and XMM-Newton (launched in 1999) that could detect the moment of stellar death, keeping track of the X-ray emissions over the years as the star’s material was gradually ingested.

    ROSAT Spacecraft
    ROSAT

    ESA XMM Newton
    ESA/XMM-Newton

    NEWS: Intermediate Black Hole Implicated in Star’s Death

    No more than two dozen other stellar death event candidates were seen in the observations, but positive identifications probably won’t be available until the launch of the multi-instrument Spectrum-X-Gamma space observatory in 2016.

    Spectrum GammaX
    Spectrum-X-Gamma space observatory

    This work has added some much needed detail to these rare events, indicating that (on average) one star every 30,000 years in any given galaxy will be destroyed by the central supermassive black hole, though the researchers caution that more observations of stars being eaten by supermassive black holes are needed.

    See the full article here.

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  • richardmitnick 10:24 am on August 18, 2014 Permalink | Reply
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    From SPACE.com: ” It’s Confirmed! Black Holes Do Come in Medium Sizes” 

    space-dot-com logo

    SPACE.com

    August 18, 2014
    Mike Wall

    Black holes do indeed come in three sizes: small, medium and extra large, a new study suggests.

    Astronomers have studied many black holes at either size extreme — “stellar-mass” black holes, which are a few dozen times as weighty as the sun, and supermassive black holes, which can contain millions or billions of times the mass of the sun and lurk at the heart of most, if not all, galaxies.

    Researchers have spotted hints of much rarer medium-size black holes, which harbor between 100 and several hundred thousand solar masses. But it’s tough to weigh these objects definitively — so tough that their existence has been a matter of debate.

    But that debate can now be put to rest, says a research team that has measured an intermediate black hole’s mass with unprecedented precision. A black hole in the nearby galaxy M82 weighs in at 428 solar masses, give or take a hundred suns or so, they report today (Aug. 17) in the journal Nature.

    “Objects in this range are the least expected of all black holes,” study co-author Richard Mushotzky, an astronomy professor at the University of Maryland, said in a statement. “Astronomers have been asking, ‘Do these objects exist, or do they not exist? What are their properties?’ Until now, we have not had the data to answer these questions.”

    Patterns in the light

    Black holes famously gobble up anything that gets too close, including light. But that doesn’t mean astronomers can’t see them; bright X-ray light streams from the superhot disk of material spiraling into a black hole’s mouth.

    About 15 years ago, NASA’s Chandra X-ray Observatory spacecraft spotted such emissions coming from a source in the galaxy M82, which lies about 12 million light-years away from Earth. For a long time, Mushotzky and some other scientists suspected that the object, called M82 X-1, was a medium-size black hole. But those suspicions were tough to confirm.

    NASA Chandra Telescope
    NASA/Chandra

    “For reasons that are very hard to understand, these objects have resisted standard measurement techniques,” Mushotzky said.

    In the new study, a team led by University of Maryland doctoral student Dheeraj Pasham took a closer look at M82 X-1. They studied observations made from 2004 to 2010 by NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, which ceased operations in 2012.

    rxte
    NASA/ RXTE

    The RXTE data revealed a pair of repeating oscillations in M82 X-1’s X-ray emissions. These oscillations occurred 5.1 times per second and 3.3 times per second, respectively — a ratio of three to two. This fact allowed the team to determine the black hole’s mass.

    “In essence, [the] frequency of these 3:2 ratio oscillations scales inverse[ly] with black hole mass,” Pasham told Space.com via email. “Simply put, if the black hole is small, the orbital periods at the innermost circular orbit are shorter, but if the black hole is big, the orbital periods are longer (smaller frequencies).”

    The researchers calculated M82 X-1’s mass at 428 suns, plus or minus 105 solar masses.

    “In our opinion, and as the paper’s referees seem to agree, this is the most accurate mass measurement of an intermediate-mass black hole to date,” Pasham said.

    Learning about black-hole growth

    Confirming the existence of intermediate black holes could help researchers better understand the supermassive monsters at the cores of galaxies.

    Such behemoths apparently first formed in the universe’s very early days, just a few hundred million years after the Big Bang. They could not have grown so big so fast if their “seeds” were small stellar-mass black holes (which result from the collapse of giant stars), Pasham said.

    “Many theories, therefore, have suggested that these initial seed black holes had to have been a few 100 -1,000 times our sun,” he said. “But we did not have firm evidence for such intermediate-mass black holes.”

    Stellar-mass black holes also often feature paired X-ray oscillations that occur in a 3:2 frequency ratio. Therefore, the new observations suggest that medium-size black holes may behave like scaled-up versions of stellar-mass black hole systems, Pasham added.

    The research is detailed in the Aug. 17 edition of the journal Nature.

    See the full article here.

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  • richardmitnick 9:28 am on August 1, 2014 Permalink | Reply
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    From NASA/NuSTAR: “NuSTAR Celebrates Two Years of Science in Space” 

    NASA NuSTAR
    NuSTAR

    July 31, 2014

    NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, a premier black-hole hunter among other talents, has finished up its two-year prime mission, and will be moving onto its next phase, a two-year extension.

    “It’s hard to believe it’s been two years since NuSTAR launched,” said Fiona Harrison, the mission’s principal investigator at the California Institute of Technology in Pasadena. “We achieved all the mission science objectives and made some amazing discoveries I never would have predicted two years ago.”

    In this new chapter of NuSTAR’s life, it will continue to examine the most energetic objects in space, such as black holes and the pulsating remains of dead stars. In addition, outside observers — astronomers not on the NuSTAR team — will be invited to compete for time on the telescope.

    “NuSTAR will initiate a general observer program, which will start execution next spring and will take 50 percent of the observatory time,” said Suzanne Dodd, the NuSTAR project manager at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We are very excited to see what new science the community will propose to execute with NuSTAR.”

    NuSTAR blasted into space above the Pacific Ocean on June 13, 2012, with the help of a plane that boosted the observatory and its rocket to high altitudes. After a 48-day checkout period, the telescope began collecting X-rays from black holes, supernova remnants, galaxy clusters and other exotic objects. With its long mast – the length of a school bus — NuSTAR has a unique design that allows it to capture detailed data in the highest-energy range of X-rays, the same type used by dentists. It is the most sensitive high-energy X-ray mission every flown.

    In its prime mission, NuSTAR made the most robust measurements yet of the mind-bending spin rate of black holes and provided new insight into how massive stars slosh around before exploding. Other observations include: the discovery of a highly magnetized neutron star near the center of our Milky Way galaxy, measurements of luminous active black holes enshrouded in dust, and serendipitous discoveries of supermassive black holes.

    NuSTAR is now funded through fiscal year 2016 in its current extended phase.

    See the full article here.

    NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA’s Jet Propulsion Laboratory, also in Pasadena, for NASA’s Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA’s Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; ATK Aerospace Systems, Goleta, Calif., and with support from the Italian Space Agency (ASI) Science Data Center.

    NuSTAR’s mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission’s outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA’s Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo
    jpl


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  • richardmitnick 12:34 pm on November 19, 2013 Permalink | Reply
    Tags: , , , Black Holes, , ,   

    From Harvard Astronomy: “Shep Doelman: Imaging Black Holes with The Event Horizon Telescope” 

    Harvard Astronomy Banner
    Harvard Astronomy

    November 19, 2013

    Shep Doelman, sdoeleman@cfa.harvard.edu

    Recent technical advances and observations have now demonstrated that the goal of making an image of a black hole is within reach. Using the technique of Very Long Baseline Interferometry (VLBI), in which widely separated radio dishes are linked together to form an Earth-sized array, our group has succeeded in confirming event horizon scale structures in two super massive black holes: Sagittarius A*, the 4 million solar mass black hole at the center of the Milky Way (Nature, 455, 78, ’08), and M87, a 6 billion solar mass black hole in the giant elliptical galaxy Virgo A (Science, 338, 355, ’12). This has been accomplished by extending the VLBI technique to the highest observing frequencies and bandwidths, which has provided the required angular resolution and sensitivity.

    bh

    To achieve true imaging capability, an international collaboration is developing next-generation VLBI instrumentation for deployment on a Global array of mm and submm wavelength facilities. This will extend the current 1.3mm VLBI array to Earth-diameter baselines for which the angular resolution obtained is well matched to the SgrA* and M87 event horizons. Efforts are also aimed at shorter wavelength observations at 0.87mm, where Global baselines can achieve <20 micro arcsecond resolution. This new array is called the Event Horizon Telescope (EHT).

    EHT observations will target modeling and imaging of strong General Relativistic signatures that should become evident hear the black hole. Foremost among these is the black hole ‘shadow’, a consequence of light bending in the black hole’s strong gravity, leading to an annular brightening of the last photon orbit. The size and shape of this shadow is a prediction of Einstein’s GR. Non-imaging analyses of EHT data will be very sensitive to asymmetries caused by orbiting ‘hot-spots’ or Magnetohydrodynamic turbulence in the accretion flow. Observations of M87 will lead to direct imaging of emission at the base of a relativistic AGN jet. The overall goal is to spatially resolve a region of space-time where gravity is dominant, with an aim to test GR and models of black hole accretion and jet formation on Schwarzschild radius scales.

    See the full article here.


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  • richardmitnick 6:57 pm on August 13, 2013 Permalink | Reply
    Tags: , , , Black Holes, , ,   

    From The New York Times: “A Black Hole Mystery Wrapped in a Firewall Paradox” 

    New York Times

    This is copyright protected, so, just a glimpse.

    August 12, 2013
    DENNIS OVERBYE

    “A high-octane debate has broken out among the world’s physicists about what would happen if you jumped into a black hole, a fearsome gravitational monster that can swallow matter, energy and even light. You would die, of course, but how? Crushed smaller than a dust mote by monstrous gravity, as astronomers and science fiction writers have been telling us for decades? Or flash-fried by a firewall of energy, as an alarming new calculation seems to indicate?

    ‘I was a yo-yo on this,’ said one of the more prolific authors in the field, Leonard Susskind of Stanford. He paused and added, ‘I haven’t changed my mind in a few months now.’

    Stephen Hawking, the British cosmologist, stunned the world by showing that when the paradoxical quantum laws that describe subatomic behavior were taken into account, black holes would leak particles and radiation, and in fact eventually explode, although for a hole the mass of a star it would take longer than the age of the universe. It was front-page news in 2004 when Dr. Hawking finally said that he had been wrong, and paid off a bet.

    bh

    Now, however, some physicists say that Dr. Hawking might have conceded too soon. ‘He had good reason,’ said Dr. Polchinski, ‘but he gave up for the wrong reason.’ Nobody, he explained, had yet figured out exactly how information does get out of a black hole.

    That was the task that four researchers based in Santa Barbara — Ahmed Almheiri, Donald Marolf, and James Sully, all from the University of California, Santa Barbara, and Dr. Polchinski of the Kavli Institute set themselves a year ago. The team (called AMPS, after their initials) found, to their surprise, that following the known laws of physics would lead to a contradiction, the firewall paradox.”

    O.K., so much for a glimpse. See the full article here.

    [I had one comment on this article. No where did I see any mention of the "Black Hole War", between Dr. Susskind and Dr. Hawking, or any mention of Dr. Susskind's book of the same name.]

     
  • richardmitnick 2:54 pm on July 25, 2013 Permalink | Reply
    Tags: , , Black Holes, , , , , , Superfluids   

    From M.I.T.: “Superfluid turbulence through the lens of black holes” 

    Study finds behavior of the turbulent flow of superfluids is opposite that of ordinary fluids.

    July 25, 2013
    Jennifer Chu, MIT News Office

    “A superfluid moves like a completely frictionless liquid, seemingly able to propel itself without any hindrance from gravity or surface tension. The physics underlying these materials — which appear to defy the conventional laws of physics — has fascinated scientists for decades.

    fluid
    Black hole physics shows that superfluids in turbulence behave much like cigarette smoke. Image: Christine Daniloff

    Think of the assassin T-1000 in the movie “Terminator 2: Judgment Day” — a robotic shape-shifter made of liquid metal. Or better yet, consider a real-world example: liquid helium. When cooled to extremely low temperatures, helium exhibits behavior that is otherwise impossible in ordinary fluids. For instance, the superfluid can squeeze through pores as small as a molecule, and climb up and over the walls of a glass. It can even remain in motion years after a centrifuge containing it has stopped spinning.

    Now physicists at MIT have come up with a method to mathematically describe the behavior of superfluids — in particular, the turbulent flows within superfluids. They publish their results this week in the journal Science.

    ‘Turbulence provides a fascinating window into the dynamics of a superfluid,’ says Allan Adams, an associate professor of physics at MIT. ‘Imagine pouring milk into a cup of tea. As soon as the milk hits the tea, it flares out into whirls and eddies, which stretch and split into filigree. Understanding this complicated, roiling turbulent state is one of the great challenges of fluid dynamics. When it comes to superfluids, whose detailed dynamics depend on quantum mechanics, the problem of turbulence is an even tougher nut to crack.’

    To describe the underlying physics of a superfluid’s turbulence, Adams and his colleagues drew comparisons with the physics governing black holes. At first glance, black holes — extremely dense, gravitationally intense objects that pull in surrounding matter and light — may not appear to behave like a fluid. But the MIT researchers translated the physics of black holes to that of superfluid turbulence, using a technique called holographic duality.

    Consider, for example, a holographic image on a magazine cover. The data, or pixels, in the image exist on a flat surface, but can appear three-dimensional when viewed from certain angles. An engineer could conceivably build an actual 3-D replica based on the information, or dimensions, found in the 2-D hologram.

    ‘If you take that analogy one step further, in a certain sense you can regard various quantum theories as being a holographic image of a world with one extra dimension,’ says Paul Chesler, a postdoc in MIT’s Department of Physics.

    Taking this cosmic line of reasoning, Adams, Chesler and colleagues used holographic duality as a ‘dictionary’ to translate the very well-characterized physics of black holes to the physics of superfluid turbulence.

    To the researchers’ surprise, their calculations showed that turbulent flows of a class of superfluids on a flat surface behave not like those of ordinary fluids in 2-D, but more like 3-D fluids, which morph from relatively uniform, large structures to smaller and smaller structures. The result is much like cigarette smoke: From a burning tip, smoke unfurls in a single stream that quickly disperses into smaller and smaller eddies. Physicists refer to this phenomenon as an “energy cascade.”

    ‘For superfluids, whether such energy cascades exist is an open question,’ says Hong Liu, an associate professor of physics at MIT. ‘People have been making all kinds of claims, but there hasn’t been any smoking-gun type of evidence that such a cascade exists. In a class of superfluids, we produced very convincing evidence for the direction of this kind of flow, which would otherwise be very hard to obtain.’”

    See the full article here.


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  • richardmitnick 11:36 am on July 17, 2013 Permalink | Reply
    Tags: , , , Black Holes, ,   

    From isgtw: "Mystery solved: X-ray light emitted from black holes" 

    July 17, 2013
    Amber Harmon

    “Exactly how do black holes produce so many high-power X-rays? The answer has remained a mystery to scientists for decades – until now. Supported by 40 years of theoretical progress, astrophysicists have conducted research that finally bridges the gap between theory and observation, demonstrating that gas spiraling toward a black hole inevitably results in X-ray emissions.

    Published in May in The Astrophysical Journal, the study reveals that gas spiraling toward a black hole through an accretion disk (formed by material in orbit, typically around a star) heats up to roughly 10 million degrees Celsius. The main body of the disk is roughly 2,000 times hotter than the sun, and emits low-energy or “soft” X-rays. However, observations also detect “hard” X-rays, which produce up to 100 times higher energy levels. The collaborators showed for the first time that high-energy light emission is an inevitable outcome of gas being drawn into a black hole.

    As the quality and quantity of high-energy light observations improved over the years, increasing evidence showed that photons are created in a hot, tenuous region called the corona. This corona, boiling violently above the comparatively cool accretion disk, is similar to the corona surrounding the sun, which is responsible for much of the ultra-violet and X-ray luminosity seen in the solar spectrum.

    Collaborators on the study include Julian Krolik, professor of physics and astronomy at Johns Hopkins University in Maryland, US, Jeremy Schnittman, lead author and research astrophysicist at the NASA Goddard Space Flight Center in Maryland, US, and Scott Noble, an associate research scientist at the Center for Computational Relativity and Gravitation at Rochester Institute of Technology in New York, US.”

    See the full article here.

    iSGTW is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, iSGTW is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

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  • richardmitnick 12:39 pm on April 18, 2013 Permalink | Reply
    Tags: , , , Black Holes, , ,   

    From SLAC: “Novel Analysis Method Levels the Quasar Playing Field” 

    April 18, 2013
    Lori Ann White

    “In the nearly six decades since quasars were discovered, the list of these energetic galaxies powered by supermassive black holes has grown to more than 100,000 – enough examples to reveal important information about the quasar population as a whole. But attempts to conduct a celestial census of these powerful objects have been limited by a fundamental problem: Although quasars are bright, they also span billions of light years in distance from Earth. Just as with stars in an urban sky, the closest quasars can be seen even if they are dim, while the oldest and most distant ones can be seen only if they are bright. This means astrophysicists have to study a sample with big differences among individual members, including distance, age, brightness and type of radiation emitted.

    qua
    The interaction of a supermassive black hole and a disk of accreting matter, called a quasar, can be seen at the center of a faraway galaxy in this artist’s concept. It consists of a dusty, doughnut-shaped cloud of gas and dust that feeds a central supermassive black hole. As the black hole feeds, the gas and dust heat up and spray out different kinds of light, as illustrated by the white rays.

    Astrophysicists with the Kavli Institute for Particle Astrophysics and Cosmology, a joint SLAC-Stanford institute, found a way to reach past these limitations: They improved an algorithm that homes in on important commonalities of a population of objects while taking into account the limitations and biases for observations made in multiple types of electromagnetic radiation, such as optical light or radio waves – two of the most important wavelengths for studying quasars.

    In the process they shed new light on a contentious question: Are there two types of quasars, with one “louder” in radio than the other, or is there just one type with emissions that vary widely across the electromagnetic spectrum?”

    See the answers in the full article here.

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    SLAC Campus


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