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  • richardmitnick 10:44 am on January 21, 2019 Permalink | Reply
    Tags: , , , , , Hawking radiation, , , ,   

    Weizmann Institute of Science via Science Alert: “We Just Got Lab-Made Evidence of Stephen Hawking’s Greatest Prediction About Black Holes” 

    Weizmann Institute of Science logo

    Weizmann Institute of Science

    via

    ScienceAlert

    Science Alert

    21 JAN 2019
    MICHELLE STARR

    Scientists may have just taken a step towards experimentally proving the existence of Hawking radiation. Using an optical fibre analogue of an event horizon – a lab-created model of black hole physics – researchers from Weizmann Institute of Science in Rehovot, Israel report that they have created stimulated Hawking radiation.

    Under general relativity, a black hole is inescapable. Once something travels beyond the event horizon into the heart of the black hole, there’s no return. So intense is the gravitational force of a black hole that not even light – the fastest thing in the Universe – can achieve escape velocity.

    Under general relativity, therefore, a black hole emits no electromagnetic radiation. But, as a young Stephen Hawking theorised in 1974, it does emit something when you add quantum mechanics to the mix.

    This theoretical electromagnetic radiation is called Hawking radiation; it resembles black body radiation, produced by the temperature of the black hole, which is inversely proportional to its mass (watch the video below to get a grasp of this neat concept).

    This radiation would mean that black holes are extremely slowly and steadily evaporating, but according to the maths, this radiation is too faint to be detectable by our current instruments.

    So, cue trying to recreate it in a lab using black hole analogues. These can be built from things that produce waves, such as fluid and sound waves in a special tank, from Bose-Einstein condensates, or from light contained in optical fibre.

    “Hawking radiation is a much more general phenomenon than originally thought,” explained physicist Ulf Leonhardt to Physics World. “It can happen whenever event horizons are made, be it in astrophysics or for light in optical materials, water waves or ultracold atoms.”

    These won’t, obviously, reproduce the gravitational effects of a black hole (a good thing for, well, us existing), but the mathematics involved is analogous to the mathematics that describe black holes under general relativity.

    This time, the team’s method of choice was an optical fibre system developed by Leonhardt some years ago.

    The optical fibre has micro-patterns on the inside, and acts as a conduit. When entering the fibre, light slows down just a tiny bit. To create an event horizon analogue, two differently coloured ultrafast pulses of laser light are sent down the fibre. The first interferes with the second, resulting in an event horizon effect, observable as changes in the refractive index of the fibre.

    The team then used an additional light on this system, which resulted in an increase in radiation with a negative frequency. In other words, ‘negative’ light was drawing energy from the ‘event horizon’ – an indication of stimulated Hawking radiation.

    While the findings were undoubtedly cool, the end goal for such research is to observe spontaneous Hawking radiation.

    Stimulated emission is exactly what it sounds like – emission that requires an external electromagnetic stimulus. Meanwhile the Hawking radiation emanating from a black hole would be of the spontaneous variety, not stimulated.

    There are other problems with stimulated Hawking radiation experiments; namely, they are rarely unambiguous, since it’s impossible to precisely recreate in the lab the conditions around an event horizon.

    With this experiment, for example, it’s difficult to be 100 percent certain that the emission wasn’t created by an amplification of normal radiation, although Leonhardt and his team are confident that their experiment did actually produce Hawking radiation.

    Either way, it’s a fascinating achievement and has landed another mystery in the team’s hands, too – they found the result was not quite as they expected.

    “Our numerical calculations predict a much stronger Hawking light than we have seen,” Leonhardt told Physics World.

    “We plan to investigate this next. But we are open to surprises and will remain our own worst critics.”

    The research has been published in the journal Physical Review Letters.

    See the full article here .

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    Weizmann Institute Campus

    The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 7:24 am on August 30, 2018 Permalink | Reply
    Tags: An eternal cycle of Big Bang events, Big Bang, , Conformal Cyclic Cosmology, , Hawking Points- anomalous high energy features in the CMB, Hawking radiation, Roger Penrose, ,   

    From University of Oxford via COSMOS: “Black holes from a previous universe shine light on our own” 

    U Oxford bloc

    From University of Oxford

    via

    COSMOS

    30 August 2018
    Stephanie Rowlands

    Cold spots are a hot topic in Conformal Cyclic Cosmology.

    1
    Stephen Hawking suggested evidence of previous universes could be detected in the cosmic microwave background. Has he been proved right? Jemal Countess/Getty Images

    Cosmologists say they have found remnants of a bygone universe in the afterglow of the Big Bang found in the Cosmic Microwave Background (CMB).

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    The discovery gives weight to the controversial theory of Conformal Cyclic Cosmology, or CCC, that suggests our universe is just one of many, built from the remains of a previous one in the Big Bang 13.6 billion years ago.

    The theory describes an eternal cycle of Big Bang events, repeating into the far distant future, the end of our universe giving rise to a new one.

    A team led by Oxford University mathematics emeritus Roger Penrose, a former collaborator of the late Stephen Hawking, claims in a new paper lodged on the preprint server arXiv to have found signs of so-called Hawking Points, anomalous high energy features in the CMB.

    3
    Inside Penrose’s universe
    06 Dec 2010
    Cycles of Time: An Extraordinary New View of the Universe
    Roger Penrose
    2010 Bodley Head £25.00 hb 320pp

    https://people.maths.ox.ac.uk/lmason/RP80/paul.pdf

    Penrose and colleagues say that these anomalies were made from the last moments of black holes evaporating through “Hawking radiation”.

    Although black holes are famous for never releasing any light, Hawking proposed a subtle way for light and particles to escape over time.

    Through quantum mechanical effects, every black hole slowly shrinks and fades, losing its energy through Hawking radiation.

    “This burst of energy from a now decayed black hole then spreads out quickly in our newly formed universe, leaving a warm central point with a cooling spot around it,” says astronomer Alan Duffy from Australia’s Swinburne University and Lead Scientist of the Royal Institution of Australia, who was not involved in the research.

    “In other words, they have proposed that we can search for an echo of a previous universe in the CMB.”

    Conformal Cyclic Cosmology strongly conflicts with the current standard model explaining the evolution of the universe.

    “Unlike previous cyclic universe models, there is no ‘Big Crunch’ where everything comes together again,” explains Duffy.

    “Instead CCC links the similarity of the current accelerating expansion of the universe by dark energy with early expansion of inflation in the Big Bang.”

    While mathematically the two epochs of expansion are similar, not all cosmologists are convinced that the Big Bang eventually leads to another Big Bang from a future empty universe.

    The results from Penrose and colleagues are likely to be met with skepticism by many mainstream cosmologists.

    Penrose first claimed [Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity] to have detected Hawking points in 2010. Other researchers shot down the claim in flames, arguing that his discoveries were nothing more than random noise contained in the data.

    NASA/WMAP 2001 to 2010


    Inflationary Universe. NASA/WMAP


    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    See the full article here.


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    U Oxford campus

    Oxford is a collegiate university, consisting of the central University and colleges. The central University is composed of academic departments and research centres, administrative departments, libraries and museums. The 38 colleges are self-governing and financially independent institutions, which are related to the central University in a federal system. There are also six permanent private halls, which were founded by different Christian denominations and which still retain their Christian character.

    The different roles of the colleges and the University have evolved over time.

     
  • richardmitnick 10:01 am on January 26, 2017 Permalink | Reply
    Tags: Accelerating mirror, , Black hole paradox, , Hawking radiation, , , Shooting electron waves through plasma could reveal if black holes permanently destroy information,   

    From Science Alert: “Shooting electron waves through plasma could reveal if black holes permanently destroy information” 

    ScienceAlert

    Science Alert

    25 JAN 2017
    MIKE MCRAE

    1
    Interstellar/Paramount Pictures

    Without having to enter a black hole ourselves…

    One of the greatest dilemmas in astrophysics is the black hole paradox – if black holes really do destroy every scrap of information that enters them.

    Now, physicists might have finally come up with a way to test the paradox once and for all, by accelerating a wave of negatively charged electrons through a cloud of plasma.

    As far as objects in space go, black holes need little introduction. Get too close, and their concentrated mass will swallow you, never to return.

    But in the 1970s, physicists including Stephen Hawking proposed that black holes weren’t necessarily forever.

    Thanks to the peculiarities of quantum mechanics, particles did indeed radiate away from black holes, Hawking hypothesised, which means, theoretically, black holes could slowly evaporate away over time.

    This poses the paradox. Information – the fundamental coding of stuff in the Universe – can’t just disappear. That’s a big rule. But when a black hole evaporates away, where does its bellyful of information go?

    A clue might be found in the nature of the radiation Hawking described. This form of radiation arises when a pair of virtual particles pops into existence right up against a black hole’s line of no return – the ‘event horizon’.

    Usually, such paired particles cancel each other out, and the Universe is none the wiser. But in the case of Hawking radiation, one of these particles falls across the horizon into the gravitational grip of the black hole. The other barely escapes off into the Universe as a bona fide particle.

    Physicists have theorised that this escaped particle preserves the information of its twin thanks to the quirks of quantum dynamics. In this case, the phenomenon of entanglement would allow the particles to continue share a connection, even separated by time and space, leaving a lasting legacy of whatever was devoured by the black hole.

    To demonstrate this, physicists could catch a particle that has escaped a black hole’s event horizon, and then wait for the black hole to spill its guts in many, many years, to test if there’s indeed a correlation between one of the photons and its entangled twin. Which, let’s face it, isn’t exactly practical.

    Now, Pisin Chen from the National Taiwan University and Gerard Mourou from École Polytechnique in France have described a slightly easier method.

    They suggest that a high-tech ‘accelerating mirror’ should provide the same opportunity of separating entangled particles.

    That sounds strange, but as a pair of particles zips into existence in this hypothetical experiment, one would reflect from the accelerating mirror as the other became trapped at the boundary. Just as it might happen in a black hole.

    Once the mirror stopped moving, the ‘trapped’ photon would be freed, just as the energy would be released from a dying black hole.

    Chen’s and Mourou’s mirror would be made by pulsing an X-ray laser through a cloud of ionised gas in a plasma wakefield accelerator. The pulse would leave a trail of negatively charged electrons, which would serve nicely as a mirror.

    By altering the density of the plasma on a small enough scale, the ‘mirror’ would accelerate away from the laser pulse.

    As clever as the concept is, the experiment is still in its ‘thought bubble ‘stage. Even with established methods and trusted equipment, entanglement is tricky business to measure.

    And Hawking radiation itself has yet to be observed as an actual thing.

    Yet Chen’s and Mourou’s model could feasibly be built using existing technology, and as the researchers point out in their paper, could also serve to test other hypotheses on the physics of black holes.

    It sounds far more appealing than waiting until the end of time in front of a black hole, at least.

    This research was published in Physical Review Letters.

    See the full article here .

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  • richardmitnick 7:35 pm on August 15, 2016 Permalink | Reply
    Tags: , Hawking radiation,   

    From Technion: “Technion Scientist is First to Observe Hawking Radiation” 

    Technion bloc

    Technion

    August 15, 2016
    Kevin Hattori

    The eminent British scientist Stephen Hawking made predictions, 42 years ago, about elusive radiation emanating from black holes.

    Known as Hawking radiation, this phenomenon is too weak to observe with current techniques, and remained a “holy grail” for the fields of atomic physics, nonlinear optics, solid state physics, condensed matter superfluids, astrophysics, cosmology, and particle physics. It remained as such until Prof. Jeff Steinhauer’s observations of Hawking radiation in an analogue (model) black hole created at his Atomic Physics Lab in the Technion-Israel institute of Technology Faculty of Physics.

    1
    Technion-Israel Institute of Technology Professor Jeff Steinhauer

    Steinhauer’s latest findings, published today in Nature Physics, describe the first observation of thermal, quantum Hawking radiation in any system. “We observe a thermal distribution of Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole,” says Steinhauer. “This confirms Hawking’s prediction regarding black hole thermodynamics.”

    Pairs of phonons (particles of sound) appear spontaneously in the void at the event horizon (in layman’s terms, this is “the point of no return” in spacetime, beyond which events cannot affect an outside observer) of the analogue black hole. One of the phonons travels away from the black hole as Hawking radiation, and the other partner phonon falls into the black hole. The pairs have a broad spectrum of energies. It is the correlations between these pairs that allow for the detection of the Hawking radiation.

    The Hawking and partner particles within a pair can have a quantum connection called “entanglement.” Steinhauer explains: “Using a technique we developed, we saw that high energy pairs were entangled, while low energy pairs were not. This entanglement verifies an important element in the discussion of the information paradox (the idea that information that falls into a black hole is destroyed or lost) as well as the firewall controversy (the theory that a wall of fire – resulting from the breaking of the entanglement between the Hawking particles and their partners – exists at the event horizon of a black hole).”

    This observation of Hawking radiation, performed in a Bose-Einstein condensate (a quantum state of matter where a clump of super-cold atoms behaves like a single atom), verifies Hawking’s semiclassical calculation, which is viewed as a milestone in the quest for quantum gravity. The observation of its entanglement verifies important elements in the discussion of information loss in a real black hole.

    Steinhauer has been working exclusively on the proof since 2009 in his hand-assembled lab, replete with lasers and dozens of mirrors, lenses, and magnetic coils to simulate a black hole. Motivated by an overriding curiosity regarding the laws of physics since he was a child, Steinhauer says that evidence for the existence of quantum Hawking radiation brings us one step further in our endless journey of discovering the laws of the universe. This understanding itself is important to human beings, as is the applications of the laws of physics in society.

    Through the Wormhole, a Science Channel TV show hosted and narrated by Academy Award winner Morgan Freeman, featured Steinhauer back in 2012. Here, he discussed his creation of an analogue black hole in the lab and his hopes of using it to observe Hawking radiation. The analogue black hole takes advantage of his pioneering ultra-high resolution imaging system.

    In 2014, Steinhauer succeeded in doing this, publishing his results in a top science journal of the first observation of Hawking radiation in any system. This earlier work demonstrated self-amplifying Hawking radiation, which reflected from the inner horizon, returned to the outer horizon, and caused additional Hawking radiation. In contrast, his latest research endorses the existence of quantum Hawking radiation, the spontaneous appearance of Hawking pairs.

    See the full article here .

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    Technion Campus

    A science and technology research university, among the world’s top ten,
    dedicated to the creation of knowledge and the development of human capital and leadership,
    for the advancement of the State of Israel and all humanity.

     
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