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  • richardmitnick 11:02 pm on December 9, 2020 Permalink | Reply
    Tags: "Physics professor advances research on black hole paradox", Black Hole Information Paradox, , It turns out that a powerful way to learn about one black hole is to study two black holes., Late physicist Stephen Hawking showed that when quantum effects are included black holes do have a temperature.,   

    From Cornell Chronicle: “Physics professor advances research on black hole paradox” 

    From Cornell Chronicle

    December 9, 2020
    Kate Blackwood

    Thomas Hartman, right, associate professor of physics, and Amirhossein Tajdini, Ph.D. ’20, diagram in 2019 a replica wormhole, a concept associated with quantum gravity. They were two authors of “Replica Wormholes and the Entropy of Hawking Radiation,” a paper important to recent progress on the black hole paradox. Credit: Dave Burbank/Cornell University.

    Do black holes emit information?

    For decades, physicists have theorized on this high-stakes question. At the heart of the so-called “black hole information paradox” is a fundamental incompatibility between the two pillar theories of theoretical physics: general relativity and quantum mechanics.

    But in the past two years, a series of breakthrough calculations by researchers – including Tom Hartman, associate professor of physics in the College of Arts and Sciences – have led to proclamations in the field of theoretical physics that “the most famous paradox in physics,” according to Quanta Magazine, is nearing its end.

    “It’s fair to say that these calculations have given us a new way to think about black hole information and given us hints about how to make sense of quantum gravity,” Hartman said, confirming the progress and his significant contribution. “It solves some corner of the paradox.”

    Hartman researches quantum gravity, a theory to reconcile quantum mechanics and general relativity. His paper published in May in the Journal of High Energy Physics, reports a mathematical technique for calculating the physics of a black hole. Collaborators on the paper included former Cornell postdoctoral researcher Edgar Shaghoulian, now a postdoc at the University of Pennsylvania; and Amir Tajdini, Ph.D. ’20, now a postdoc at the University of California, Santa Barbara.

    “Black holes are a place where both quantum mechanics and gravity can be important at the same time,” Hartman said. “If you’re thinking about quantum gravity and how to put the two theories together, black holes are a great way to study that problem.”

    Although we think of black holes as having nothing coming out from them, Hartman said, late physicist Stephen Hawking showed that when quantum effects are included, black holes do have a temperature.

    This leads to the paradox: The fact that black holes have a temperature, Hartman said, means that particles are escaping the black hole. Hawking found that these particles are “pure thermal radiation,” or radiation that is completely random and does not carry any information, Hartman said. If this is true, then when a black hole evaporates away and disappears, the information that was originally contained in the black hole has been destroyed, he said.

    “It is a fundamental principle of quantum mechanics that information cannot be destroyed,” Hartman said. “So the paradox is a contradiction between quantum mechanics and Hawking’s calculation showing that black holes radiate randomly.”

    In the paper, Hartman and collaborators used a mathematical trick involving extra copies of the black hole called “replicas” to calculate the physics of a single black hole.

    “It turns out that a powerful way to learn about one black hole is to study two black holes,” he said. “The reason is that there are statistical properties of radiation that are hard to understand if you look at one black hole but easier to understand if you look at two at once.”

    Using this technique, they found evidence that the particles emitted in Hawking radiation are not random, after all.

    In November, Hartman published further research in the Journal of High Energy Physics. In the paper, he and Shaghoulian, along with Yikun Jiang, a Ph.D. student in the field of physics, explore the possibility that the new theory of Hawking radiation could also apply to the early universe.

    Hartman co-organized a virtual workshop on this and related topics in November with researchers from Stanford and the University of California, San Diego, joined by 40 participants from around the world.

    Far from being near an end, the information paradox is a problem that multiplies as physicists look into it, Hartman said. What started as one paradox has grown into a whole field of study.

    “There are many aspects of it,” he said. “It’s something thousands of people will work on for decades.”

    See the full article here .


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

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

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

  • richardmitnick 10:47 am on March 14, 2018 Permalink | Reply
    Tags: , Black Hole Information Paradox, , Stephen Hawking has died   

    From Science Alert: “Here’s Stephen Hawking’s Incredible Solution to His Black Hole Information Paradox” 


    Science Alert

    14 MAR 2018

    His mind was truly incomparable.

    ESA/V. Beckmann (NASA-GSFC).

    Stephen Hawking, one of the greatest minds of our lifetime, has passed away – leaving behind a lot of heartbroken science fans.

    Stephen Hawking

    While he was publishing papers right up until the months before his death, it was in 2016 that he released one of his most talked about journal articles – a long-awaited solution to his black hole information paradox.

    The paper was finally released in Physical Review Letters, published 6 June 2016 – and it made headlines around the world.

    To understand why it was such a big deal, and what the black hole information paradox really is, we need to go back to where it all started.

    Our original understanding of black holes, according to Einstein’s generally theory of relativity, is that everything that crosses the event horizon – the boundary of a black hole – is lost forever. Even light can’t escape its clutches, which is why black holes are called black holes (and also why it’s impossible for us to actually see one).

    But then in the 1970s, Hawking proposed that radiation actually can escape from a black hole, because of the laws of quantum mechanics. Put very simply, he suggested that when a black hole swallows one half of a particle-antiparticle pair, the other particle radiates away into space, stealing a little energy from the black hole as it leaves.

    Because of this, eventually, black holes can disappear, and the only remaining trace would be the electromagnetic radiation they emitted – which is known as ‘Hawking radiation’.

    The problem is that, according to Hawking’s best calculations, that radiation would contain no useful information about what the black hole ate – the information swallowed up would have been lost forever.

    And that doesn’t gel with our understanding of modern physics, which states that it’s always possible to reverse time. In theory, at least, processes in the Universe will look the same if they’re running forwards or backwards.

    As Dennis Overbye explains over at The New York Times full article:

    “The Universe, like a kind of supercomputer, is supposed to be able to keep track of whether one car was a green pickup truck and the other was a red Porsche, or whether one was made of matter and the other antimatter. These things may be destroyed, but their ‘information’ – their essential physical attributes – should live forever.”

    Hence the paradox. And it’s actually a big deal not just for astrophysicists, because if the rules of quantum mechanics don’t hold up for black holes, then what’s to say they apply to the rest of us?

    But in 2016 Hawking proposed a solution to the problem – black holes might actually have a halo of ‘soft hair’ surrounding them, which are capable of storing information.

    That ‘hair’ isn’t actually hair – as you might have already assumed – but is actually low-energy quantum excitations that carry with them a signature pattern of everything that’s been swallowed up by the black hole, long after it evaporates.

    “That pattern, like the pixels on your iPhone or the wavy grooves in a vinyl record, contains information about what has passed through the horizon and disappeared,” wrote Overbye at the time.

    To come to this conclusion, Hawking identified two underlying problems with his original assumptions, which is why he says his original calculations – which suggested that the information inside a black hole would be lost forever – were wrong.

    Those two assumptions were that the vacuum in quantum gravity is unique, and that black holes have no quantum ‘hair’.

    That’s getting a little complex, but what you need to know is that Hawking has since revised his calculations, and is fairly sure that black holes have ‘soft hair’ haloed around them.

    This hypothesis was peer-reviewed and published in Physical Review Letters [link is above], and researchers are claiming that, while there’s more work to be done, it’s a promising step towards solving the information paradox.

    “It is important to note that this paper does not solve the black hole information problem,” wrote physicist Gary Horowitz from the University of California, Santa Barbara, in Physics.

    Physics Figure 1: Hawking, Perry, and Strominger suggest that black holes might have “soft hair,” low-energy quantum excitations that release information when the black hole evaporates. APS/Alan Stonebraker.

    “First, the analysis must be repeated for gravity, rather than just electromagnetic fields. The authors are currently pursuing this task, and their preliminary calculations indicate that the purely gravitational case will be similar,” he added.

    “More importantly, the soft hair they introduce is probably not enough to capture all the information about what falls into a black hole.”

    His criticism is that it’s still unclear whether all the information swallowed up by a black hole really can be transferred to the soft hair – rather than just an energy signature of everything that’s been lost.

    But he admitted: “It is certainly possible that, following the path indicated by this work, further investigation will uncover more hair of this type, and perhaps eventually lead to a resolution of the black hole information problem.”

    And that would certainly be a red-letter day in physics. Because we’d be one step closer to understanding some of the biggest enigmas in the known Universe – the weirdness that are black holes.

    What does that mean for the rest of us? As Hawking explained in a talk in 2015: “[Black holes] are not the eternal prisons they were once thought. If you feel you are trapped in a black hole, don’t give up. There is a way out.”

    And there might just be a little trace of you lingering on the outside, too.

    Stephen Hawking, we miss you already.

    A version of this article was originally published in June 2016.

    See the full article here .

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  • richardmitnick 6:53 am on March 13, 2018 Permalink | Reply
    Tags: , , , Black Hole Information Paradox, , ,   

    From ScienceNews: “Superconductors may shed light on the black hole information paradox” 


    March 9, 2018
    Emily Conover

    Scientists are trying to understand what happens to information that falls into a black hole.

    MIRROR, MIRROR When black holes evaporate, where does the trapped information go? One potential explanation, that the black hole reflects the information instead of trapping it, has parallels with the behavior of materials that conduct electricity without resistance. NASA Goddard Space Flight Center.

    Insights into a black hole paradox may come from a down-to-Earth source.

    Superconductors, materials through which electrons can move freely without resistance, may share some of the physics of black holes, physicist Sreenath Kizhakkumpurath Manikandan of the University of Rochester in New York reported March 7 at a meeting of the American Physical Society. The analogy between the two objects could help scientists understand what happens to information that gets swallowed up in a black hole’s abyss.

    When a black hole gobbles up particles, information about the particles’ properties is seemingly trapped inside. According to quantum mechanics, such information cannot be destroyed. Physicist Stephen Hawking determined in 1974 that black holes slowly evaporate over time, emitting what’s known as Hawking radiation before eventually disappearing. That fact implies a conundrum known as the black hole information paradox (SN: 5/31/14, p. 16): When the black hole evaporates, where does the information go?

    One possible solution, proposed in 2007 by physicists Patrick Hayden of Stanford University and John Preskill of Caltech, is that the black hole could act like a mirror, with information about infalling particles being reflected outward, imprinted in the Hawking radiation. Now, Manikandan and physicist Andrew Jordan, also of the University of Rochester, report that a process that occurs at the interface between a metal and a superconductor is analogous to the proposed black hole mirror [Physical Review D].

    The effect, known as Andreev reflection, occurs when electrons traveling through a metal meet a superconductor. The incoming electron carries a quantum property known as spin, similar to the spinning of a top. The direction of that spin is a kind of quantum information. When the incoming electron meets the superconductor, it pairs up with another electron in the material to form a duo known as a Cooper pair. Those pairings allow electrons to glide easily through the material, facilitating its superconductivity. As the original electron picks up its partner, it also leaves behind a sort of electron alter ego reflecting its information back into the metal. That reflected entity is referred to as a “hole,” a disturbance in a material that occurs when an electron is missing. That hole moves through the metal as if it were a particle, carrying the information contained in the original particle’s spin.

    Likewise, if black holes act like information mirrors, as Hayden and Preskill suggested, a particle falling into a black hole would be followed by an antiparticle coming out — a partner with the opposite electric charge — which would carry the information contained in the spin of the original particle. Manikandan and Jordan showed that the two processes were mathematically equivalent.

    It’s still not clear whether the black hole mirror is the correct solution to the paradox, but the analogy suggests experiments with superconductors could clarify what happens to the information, Jordan says. “That’s something you can’t ever do with black holes: You can’t do those detailed experiments because they’re off in the middle of some galaxy somewhere.”

    The theory is “intriguing,” says physicist Justin Dressel of Chapman University in Orange, Calif. Such comparisons are useful in allowing scientists to take insights from one area and apply them elsewhere. But additional work is necessary to determine how strong an analogy this is, Dressel says. “You may find with further inspection the details are different.”

    See the full article here .

    Science News is edited for an educated readership of professionals, scientists and other science enthusiasts. Written by a staff of experienced science journalists, it treats science as news, reporting accurately and placing findings in perspective. Science News and its writers have won many awards for their work; here’s a list of many of them.

    Published since 1922, the biweekly print publication reaches about 90,000 dedicated subscribers and is available via the Science News app on Android, Apple and Kindle Fire devices. Updated continuously online, the Science News website attracted over 12 million unique online viewers in 2016.

    Science News is published by the Society for Science & the Public, a nonprofit 501(c) (3) organization dedicated to the public engagement in scientific research and education.

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