Event Horizons and Black Holes

Stephen Hawking enters the recent debate around black holes and firewalls – by suggesting event horizons may not exist!

Dr Tony Padilla and Professor Ed Copeland discuss Hawking’s recent paper.

Read it yourself at: http://arxiv.org/pdf/1401.5761.pdf
Firewall paper: http://arxiv.org/pdf/1207.3123.pdf

Our previous firewall video: http://youtu.be/XE5PNbsUERE

And some more papers suggested by Dr Padilla:
http://arxiv.org/pdf/1306.0533.pdf
http://arxiv.org/pdf/1310.6334.pdf
http://arxiv.org/pdf/1310.6335.pdf
http://arxiv.org/pdf/1301.4504.pdf

Read more at sixtysymbols

Advertisements

Information Preservation and Weather Forecasting for Black Holes

S. W. Hawking

It has been suggested [1] that the resolution of the information paradox for evaporating black holes is that the holes are surrounded by firewalls, bolts of outgoing radiation that would destroy any infalling observer. Such firewalls would break the CPT invariance of quantum gravity and seem to be ruled out on other grounds.
A different resolution of the paradox is proposed, namely that gravitational collapse produces apparent horizons but no event horizons behind which information is lost. This proposal is supported by ADS-CFT and is the only resolution of the paradox compatible with CPT.
The collapse to form a black hole will in general be chaotic and the dual CFT on the boundary of ADS will be turbulent.
Thus, like weather forecasting on Earth, information will effectively be lost, although there would be no loss of unitarity.

Some time ago [2] I wrote a paper that started a controversy that has lasted until the present day. In the paper I pointed out that if there were an event horizon, the outgoing state would be mixed. If the black hole evaporated completely without leaving a remnant, as most people believe and would be required by CPT, one would have a transition from an initial pure state to a mixed final state and a loss of unitarity. On the other hand, the ADS-CFT correspondence indicates that the evaporating black hole is dual to a unitary conformal field theory on the boundary of ADS. This is the information paradox.

Recently there has been renewed interest in the information paradox [1]. The authors of [1] suggested that the most conservative resolution of the information paradox would be that an infalling observer would encounter a firewall of outgoing radiation at the horizon.

There are several objections to the firewall proposal. First, if the firewall were located at the event horizon, the position of the event horizon is not locally determined but is a function of the future of the spacetime.

Another objection is that calculations of the regularized energy momentum tensor of matter fields are regular on the extended Schwarzschild background in the Hartle-Hawking state [3, 4]. The outgoing radiating Unruh state differs from the Hartle-Hawking state in that it has no incoming radiation at infinity. To get the energy momentum tensor in the Unruh state one therefore has to subtract the energy momentum tensor of the ingoing radiation from the energy momentum in the Hartle-Hawking state. The energy momentum tensor of the ingoing radiation is singular on the past horizon but is regular on the future horizon. Thus the energy momentum tensor is regular on the horizon in the Unruh state.
So no firewalls.

For a third objection to firewalls I shall assume that if firewalls form around black holes in asymptotically flat space, then they should also form around black holes in asymptotically anti deSitter space for very small lambda. One would expect that quantum gravity should be CPT invariant. Consider a gedanken experiment in which Lorentzian asymptotically anti deSitter space has matter fields excited in certain modes. This is like the old discussions of a black hole in a box [5]. Non-linearities in the coupled matter and gravitational field equations will lead to the formation of a black hole [6]. If the mass of the asymptotically anti deSitter space is above the Hawking-Page mass [7], a black hole with radiation will be the most common configuration. If the space is below that mass the most likely configuration is pure radiation.

Whether or not the mass of the anti deSitter space is above the Hawking-Page mass the space will occasionally change to the other configuration, that is the black hole above the Hawking-Page mass will occasionally evaporate to pure radiation, or pure radiation will condense into a black hole. By CPT the time reverse will be the CP conjugate. This shows that, in this situation, the evaporation of a black hole is the time reverse of its formation (modulo CP), though the conventional descriptions are very different. Thus if one assume quantum gravity is CPT invariant, one rules out remnants, event horizons, and firewalls.

Further evidence against firewalls comes from considering asymptotically anti deSitter to the metrics that fit in an S1 cross S2 boundary at infinity. There are two such metrics: pe- riodically identified anti deSitter space, and Schwarzschild anti deSitter. Only periodically identified anti deSitter space contributes to the boundary to boundary correlation func- tions because the correlation functions from the Schwarzschild anti deSitter metric decay exponentially with real time [8, 9]. I take this as indicating that the topologically trivial periodically identified anti deSitter metric is the metric that interpolates between collapse to a black hole and evaporation. There would be no event horizons and no firewalls.

The absence of event horizons mean that there are no black holes – in the sense of regimes from which light can’t escape to infinity. There are however apparent horizons which persist for a period of time. This suggests that black holes should be redefined as metastable bound states of the gravitational field. It will also mean that the CFT on the boundary of anti deSitter space will be dual to the whole anti deSitter space, and not merely the region outside the horizon.

The no hair theorems imply that in a gravitational collapse the space outside the event horizon will approach the metric of a Kerr solution. However inside the event horizon, the metric and matter fields will be classically chaotic. It is the approximation of this chaotic metric by a smooth Kerr metric that is responsible for the information loss in gravitational collapse. The chaotic collapsed object will radiate deterministically but chaotically. It will be like weather forecasting on Earth. That is unitary, but chaotic, so there is effective information loss. One can’t predict the weather more than a few days in advance.

[1] A. Almheiri, D. Marolf, J. Polchinski, J. Sully, Black Holes: Complementarity or Firewalls?, J. High Energy Phys. 2, 062 (2013)
[2] S. W. Hawking, Breakdown of Predicatability in Gravitational Collapse, Phys. Rev. D 14, 2460 (1976)
[3] M. S. Fawcett, The Energy-Momentum Tensor near a Black Hole Commun. Math. Phys. 89, 103-115 (1983)

[4] K. W. Howard, P. Candelas, Quantum Stress Tensor in Schwarzschild Space-Time, Physical Review Letters 53, 5 (1984)

[5] S. W. Hawking, Black holes and Thermodynamics, Phys. Rev. D 13, 2 (1976)

[6] P. Bizon, A. Rostworowski, Weakly Turbulent Instability of Anti-de Sitter Space, Phys. Rev. Lett. 107, 031102 (2011)

[7] S. W. Hawking, D. N. Page, Thermodynamics of Black Holes in Anti-de Sitter Space, Commun. Math. Phys. 87, 577-588 (1983)

[8] J. Maldacena, Eternal black holes in anti-de Sitter, J. High Energy Phys. 04, 21 (2003) [9] S. W. Hawking, Information Loss in Black Holes, Phys. Rev. D 72, 084013 (2005)
…. Read more at http://arxiv.org/pdf/1401.5761v1.pdf

Read also: Stephen Hawking questions nature of black holes and Stephen Hawking’s new theory offers black hole escape

Hawking: Great Scientist, Bad Gambler

Not a Gambler? Lt. Commander Data plays a game of poker with holographic representations of Sir Isaac Newton, Albert Einstein, and Stephen Hawking in the 1993 Star Trek: TNG episode “Descent.” Credit: Paramount Domestic

Not a Gambler? Lt. Commander Data plays a game of poker with holographic representations of Sir Isaac Newton, Albert Einstein, and Stephen Hawking in the 1993 Star Trek: TNG episode “Descent.” Credit: Paramount Domestic

World-renowned physicist Stephen Hawking has conceded that he was likely wrong about his view that the Higgs boson doesn’t exist — an outcome he doesn’t find very exciting.

Speaking at the Beckman Auditorium in Caltech, Pasadena, Calif., on Tuesday (April 16), the British physicist who is famous for developing the theory behind evaporating black holes gave a public lecture on “The Origins of the Universe,” summarizing new revelations in modern astrophysics and cosmology. The auditorium was full and hundreds of fans poured onto campus to watch the “physics superstar” give his lecture on a huge screen set up on the lawn outside Beckman.

Hawking honed-in on the question “why something rather than nothing?” reasserting his point of view that a supernatural “god” is not needed to create the universe — quantum fluctuations helped shape our evolving universe at the Big Bang, adding the conditions were “just right” for life (and therefore us) to be asking these profound questions.

Hawking believes the answer to this big question lies in M-theory, an extension to superstring theory, and that the Large Hadron Collider (LHC), located on the Franco-Swiss border near Geneva, Switzerland, could start detecting hints of supersymmetric particles in the not-so-distant future.

Although much of the discussion was based around black holes, multiverses and the apparent incompatibilities of Einstein’s general theory of relativity and quantum mechanics, he did have some time to comment on the recent discovery of the much-sought after Higgs boson.

“It looks like I’ve lost another bet,” Hawking joked during his presentation to the capacity audience.

Hawking famously placed a $100 bet against fellow physicist Gordon Kane of Michigan University on the Higgs boson not being discovered. But shortly after CERN announced that the LHC had discovered a “Higgs-like particle” on July 4, 2012, he admitted the odds of him winning the bet had become very slim.

“This is an important result and should earn Peter Higgs the Nobel Prize,” said Hawking in 2012. “But it is a pity in a way because the great advances in physics have come from experiments that gave results we didn’t expect.”

He reaffirmed this disappointment at Tuesday’s Caltech lecture, saying that although the world was wrapped up in excitement for the Higgs boson discovery, he “didn’t feel the same” — a sentiment shared by many of his colleagues…..

…. Read more at http://news.discovery.com/space/hawking-higgs-discovery-lost-bet-130417.htm?utm_source=twitterfeed&utm_medium=twitter

5 Of Physics’s Greatest Sex Scandals

Physicists need love, too. Just ask Paul Frampton, the physics professor who was sentenced recently after an alleged scam involving drugs and a bikini model.
We know it can be hard to resist the temptation of bikini models on the Internet, but physicist Paul Frampton was duped pretty bad. The University of North Carolina professor flew to Bolivia to meet up with model Denise Milani, but Milani never showed up. Instead, a man with a briefcase claiming to be Milani’s intermediary sent Frampton on a drug smuggling mission. Frampton was arrested before he made it back the United States and convicted last week. We’re all fools in love, huh?

Frampton isn’t the only physicist to get caught up in a love scandal. Though most of them haven’t ended up in an Argentine prison, some did have awkward run-ins with the media. Check out these physicists who probably wish their sex lives were as invisible as dark matter.

Albert Einstein’s theory of relatives
The father of relativity wasn’t very good to his second first wife, Mileva Maric. He made her do all the housework, and in return, she got… well, nothing much in the love department. That’s because he was too busy taking lovers, including his cousin Elsa whom he later married. When asked about his love life, he would probably say, “It’s all relatives.” Zing!

Marie Curie’s radioactive love
Apparently, two Nobel prizes aren’t enough to get people off your back about that one affair you had. After Marie Curie’s husband died, she fell in love with his former student, Pierre Langevin. The man was married, so the French press made a big stink about it and started calling her a homewrecker and a Jew. For the record, Curie was not cheating on anyone herself (and was also not Jewish.)

Erwin Schrodinger’s mistresses
Here we have another physicist who wanted little do with his wife. Austrian physicist Erwin Schrodinger had several mistresses, one being the wife of his assistant, Arthur March. The weird part: March was cool with it and stepped in as the father of the child while his wife Hilde moved into the Schrodinger household.

Stephen Hawking and the sex clubs
It doesn’t really seem fair to pick on Hawking for a few reasons, the main one being that he currently doesn’t have a wife to cheat on, but the media did it anyway. Hawking apparently frequents the sex clubs, and the only reason that’s a scandal is because it is now horrendously public. No one’s getting hurt here, at the very least.
Read more: www.popsci.com

Even a theory of everything has limits

Stephen Hawking’s new series attempts to comprehend the cosmos – but no ‘grand design’ can give us all the answers

What we call ‘the universe’ could be an infinitely small part of the cosmic whole

By Martin Rees
We humans haven’t changed much since our remote ancestors roamed the African savannah. Our brains evolved to cope with the human-scale environment. So it is surely remarkable that we can make sense of phenomena that confound everyday intuition: in particular, the minuscule atoms we’re made of, and the vast cosmos that surrounds us.
Thanks to powerful telescopes, and to instruments such as the Large Hadron Collider in Geneva, we can map billions of galaxies, and trace cosmic history back to some mysterious “beginning” nearly 14 billion years ago. But as always in science, each advance brings into focus some new questions that couldn’t previously have even been posed.
In a new three-part series for the Discovery Channel, Stephen Hawking’s Grand Design, my old friend and colleague explores some of the biggest issues in science today – in particular, how close we are to arriving at a “theory of everything” that explains the final mysteries of the universe. But the mystery is even deeper. For, as I argued at a Royal Society debate last week, there’s an equally fascinating question: namely whether we, as humans, will ever be able to understand our cosmos and the complexities within it.
We’ve known for a long time that, when confronting the overwhelming mystery of what banged in the Big Bang and why it banged, Einstein’s theory isn’t enough. That’s because it treats space and time as smooth and continuous. We know, however, that no material can be chopped into arbitrarily small pieces: eventually, you get down to discrete atoms. Likewise, space itself has a grainy and “quantised” structure – but on a scale a trillion trillion times smaller.
During the very earliest instants after the Big Bang, everything was so immensely squeezed that this “graininess” is crucial. But theorists are still baffled about the bedrock nature of space and time on the very smallest scale: in the fashion of ancient cartographers, we must still write: “Here be dragons.

On the largest scale, we may be even further from grasping the full extent of physical reality. The domain that astronomers call “the universe” – the space, extending more than 10 billion light years around us and containing billions of galaxies, each with billions of stars, billions of planets and maybe billions of biospheres – could be an infinitesimal part of the totality. Indeed, the results of our Big Bang could extend so far that somewhere there are assemblages of atoms in all possible configurations and combinations – including replicas of ourselves.
And that’s not all. “Our” Big Bang may not even be the only one. An idea called “eternal inflation”, developed by the Russian cosmologist Andrei Linde, envisages Big Bangs popping off ad infinitum, in an ever-expanding cascade. This process depends on the physics that prevails at ultra-high densities: there are genuine prospects that physicists may, in the coming decades, be able to pin down the relevant equations well enough to be able to infer whether the prerequisites for eternal inflation are indeed fulfilled – and whether our universe is just one island in a vast cosmic archipelago. This cosmic environment would be on scales so vast that our purview would be restricted to a tiny fragment: we wouldn’t be directly aware of the big picture, any more than a plankton whose “universe” is a spoonful of water is aware of the Empire State Building.
The question then arises of what these other universes are like. By analysing cosmic light, we can infer that the atoms in distant stars behave just like those we study in the lab. But does this uniformity extend beyond our horizon? The most comprehensive theories – known as M-theory, and pioneered by Ed Witten, the undisputed leader of this subject – suggest that the answer is no, and that the wider cosmos might display immense variety, with different universes being governed by different bylaws. Were this the case, our universe would belong to the subset where there was a “lucky draw” of cosmic numbers conducive to the emergence of complexity: life couldn’t exist if gravity were overwhelmed by an overly strong repulsive force, nor if there were no atoms, nor if there were insufficient space and time for complexity to emerge.
During a recent conference at Stanford University, some theorists investigating this concept of a multiverse were asked how strongly they believed in their ideas: would they bet their goldfish? Their dog? Themselves? I said that I was about at the dog level. Linde, however, was far more confident – after all, he’d devoted 25 years of his life to eternal inflation. The great theorist Steven Weinberg later commented that he’d happily bet Martin Rees’s dog and Andre Linde’s life. I think Stephen Hawking, who’s been known to make a bet or too, would place the same wager.
To prove or refute these conjectures – to turn them into firm science – we need to achieve the unified understanding that Hawking and Leonard Mlodinow call the “Grand Design” (after which the new series is named). Success, if achieved, would triumphantly conclude an intellectual quest that began with Newton, who unified the force that made the apple fall with the force that held the moon and planets in their orbits. The quest continued through the insights of Faraday and Maxwell, who unified electric and magnetic forces.
Yet while such a theory would bring Big Bangs and multiverses within the remit of rigorous science, it wouldn’t signal the end of discovery. Indeed, it wouldn’t impinge on the greatest scientific challenges of all. Ultimately, phrases like “theory of everything” are hubristic and misleading – and those who speculate about
M-theory and rival ideas, are not necessarily confronting the biggest challenges.
Suppose you’d never seen chess being played. You could, by watching a few games, infer the rules. But learning how the pieces move is just the start of the absorbing progression from novice to grandmaster: the beauty of the game lies in the rich variety that the rules allow.
Likewise, the Grand Design would be irrelevant to the 99 per cent of scientists who are neither particle physicists nor cosmologists, and who are challenged by the baffling complexity of our everyday world. It may seem incongruous that scientists can make confident statements about remote galaxies, or about exotic sub-atomic particles, while being baffled about issues closer to hand – diet and disease, for instance. Yet even the smallest insects embody intricate structures that render them far more mysterious than atoms or stars.
Nearly all scientists are “reductionists” in so far as they think that everything, however complicated, obeys the basic equations of physics. But even if we had a hypercomputer that could solve those equations for (say) breaking waves, migrating birds or human brains, an atomic-level explanation wouldn’t yield the enlightenment we really seek. The brain is an assemblage of cells, and a painting is an assemblage of chemical pigment. But in both cases, what’s important and interesting is the pattern and structure – the emergent complexity.
This is why the Grand Design has no relevance to most of the things that humans value. True, if you believe God is some magician who lit the blue touchpaper to set our universe expanding, you need to modify your beliefs. But nothing in modern physics – and here I disagree with Hawking and Mlodinow – need give Rowan Williams (for instance) any intellectual discomfort.
Will scientists ever fathom all nature’s complexities? Perhaps they will. But we should be open to the possibility that we might, far down the line, encounter limits – hit the buffers – because our brains don’t have enough conceptual grasp. As I remarked earlier, it’s amazing that we can comprehend so much of the counter-intuitive cosmos. But there may be some aspects of reality are intrinsically beyond us – just as quantum theory was beyond the first primates.
Here, we astronomers can offer a special perspective. Our biosphere, as everyone bar the creationists accepts, is the outcome of several billion years of Darwinian evolution. But astronomers are mindful that the future is potentially far longer than the past. Our Sun formed 4.5 billion years ago, but its fuel won’t run out for another six billion years. And the expanding universe will continue – perhaps for ever. Future evolution, here on Earth or far beyond, could be as prolonged as the Darwinian process that has led to us – and even more wonderful.
Whether the really long-range future lies with organic post-humans or with intelligent machines is a matter for debate. But we would be anthropocentric to believe that all of science is within humanity’s grasp, and that no enigmas will remain to challenge our descendents. There may be things that humans will never understand – but that doesn’t mean that they will never be understood.

Lord Rees is the Astronomer Royal. ‘Stephen Hawking’s Grand Design’ starts on Thursday at 9pm on the Discovery Channel with ‘The Key To The Cosmos’
Read more: www.telegraph.co.uk

See Stephen Hawking Perform With Orbital at Paralympics Opener


Stephen Hawking appeared onstage with Orbital for a moving rendition of “Where Is It Going?” during the Paralympic Games opening ceremony Wednesday night in London.

The techno tune, from the recent Orbital album Wonky, samples the voice of Hawking, the theoretical physicist the BBC called “the most famous disabled person in the world.”

“The Large Hadron Collider at CERN is the largest, most complex machine in the world, possibly the universe,” Hawking says, as the British electronica duo’s lush and poignant synthesized sounds soar behind him. “By smashing particles together at enormous energies, it re-creates conditions of the Big Bang. The recent discovery of what looks like the Higgs particle is a triumph of human endeavor and international collaboration. It will change our perception of the world, and has the potential to offer insights into a complete theory of everything.”

The Olympic Stadium stage then transformed into a colorful vision of the Large Hadron Collider, with rows of people dressed as red particles rushing out of the center of the stage. (See the performance in the video above.)

Suddenly, the graceful, expansive “Where Is It Going?” morphed into the aggressive stomper “Spasticus Autisticus” by Ian Dury. The late singer, who became crippled after contracting polio at a young age, wrote the song in the early 1980s to protest what he perceived as patronizing treatment of the disabled; the song was subsequently banned by the BBC.

During the Paralympics opener Wednesday, the song came alive once again onstage. The live broadcast drew 11.2 million viewers, according to the BBC.

If the video of the performance doesn’t make you shed a tear about the wonders of science and the triumphs of humankind, then, well, nothing will.
Read more: www.wired.com


http://youtu.be/KfmpxaLl6c4

Scientists to ‘hack’ Hawking’s brain …

… in bid to help him communicate more easily

By DANIEL BATES
Scientists are working out a way to ‘hack’ into Stephen Hawking’s brain to enable him to communicate more easily.
The world-famous physicist has been trying out the ‘iBrain’ which picks up his brain waves and sends them to a computer for analysis.
Hawking was fitted with a black headband which has a series of neurotransmitters inside it and was told to think about scrunching his right hand into a ball.

Professor Steven Hawking is having his brain ‘hacked’ into by scientists so they can try and help him communicate more easily

He was able to create a pattern which the researchers hope they can one day convert into letters, words and sentences.
Hawking has been unable to speak for the last 30 years due to the motor neurone disease which is ravaging his body and weakening his muscles.
He famously uses a computer to communicate with a robot-like voice which he until seven years ago he used to activate by a clicker.
Now because the muscles in his hand are too weak an infra-red sensor superglued to his glasses monitors his cheek movements which are translated into text by a computer on his wheelchair.
The iBrain has been developed by Philip Low, a professor at Stanford University in the US.
It is about the size of a matchbox and is very light so does not weigh down Hawking’s head.
Professor Low said he hopes that it will be able to monitor him in real time, regardless of what he is doing.
He said: ‘We’d like to find a way to bypass his body, pretty much hack his brain.
‘This is very exciting for us because it allows us to have a window into the brain.
‘We’re building technology that will allow humanity to have access to the human brain for the first time.
‘The emergence of such biomarkers opens the possibility to link intended movements to a library of words and convert them into speech, thus providing motor neurone sufferers with communication tools more dependent on the brain than on the body.’
Mr Low will unveil his latest findings next month at a conference in Cambridge, and Hawking may demonstrate the technology.
It could also be used to treat sleep disorders and possibly help to quickly diagnose autism.

Read more: www.dailymail.co.uk