“Firewall” of black holes stumped theoretical physics




“Firewall” of black holes stumped theoretical physics March 13, 2013

A black hole. Illustration.

If a new hypothesis about a “wall of fire» (firewal l) in the value of people grown fond of the event horizon of black holes is correct, at least one of the three fundamental concepts in theoretical physics will be called into question. This question is being studied by physicists for about a year, and the recent conference only warmed up the interest of people from science. And upset them.

Should warn at once, that to fully understand the problem, you need to know at least the basic concepts of quantum mechanics. You probably know that in the micro-particles act not only as a baseball balls, but as waves. Provide some quantum processes – can drive you mad, but it will be interesting with physicists puzzled problem firewall.

Alice and Bob, the favorite characters of various thought experiments in quantum mechanics, were in a terrible trap. Adventurous and slightly reckless Alice jumping into a huge black hole, leaving the poor thing for Bob’s event horizon – beyond the point of no return of the black hole, which may be going in one direction with no chance of return. What’s next?

Typically, physicists believe that if a black hole is large enough, Alice will not notice anything unusual as the intersection of the event horizon (more human experience in such a situation we have described here .) In this scenario, which is colorfully called the “okay”, the gravitational forces are extreme, until the girl will move toward the point of singularity. And then Alice becomes a pasta.

A new hypothesis suggests that poor Alice waiting to more drama than she expected. Possible until the unsuspecting Alice will cross the event horizon, it will face a firewall, which incinerate it at the time. If the hypothesis is correct, at least one of the three fundamental concepts in theoretical physics, as we have said, will no longer be a matter of discussion.

When last summer to discuss the script was passed “fiery death” Alice, many of the luminaries of science were puzzled.

“My first reaction was: yes, you’re kidding,” – says Rafael Busse (Raphael Bousso), a physicist at the University of Carolina at Berkley.

First physicist decided that a powerful counter-argument put upstart hypothesis in place. But after a heated discussion topic among physicists powerful, she was given carte blanche on the Rights of the paradox. Paradoxes in quantum mechanics – the mass, and one of them, we have recently discussed in an attempt to understand whether the universe be higher intelligence? (Yes, except representation Hi-News.ru in Twitter). But in this case, other forces – fire – were involved in a dispute.

Firewall – is a computer term. Literally – the firewall, do not miss what is not allowed to pass. In this article, the firewall will take exactly the same meaning, but located between the event horizon of the black hole and its singularity.
“Infernal brew”

Квантовая запутанность

Monogamy of quantum entanglement.

Physical paradox is an original way to solve the key problems. At the heart of the puzzle that we are trying to unravel the lies the conflict between the three postulates, loved by many physicists. These are:

1. First, based on the equivalence principle of general relativity, paints the scenario of “okay”: because Alice is in free fall, crossing the event horizon, and there is no difference between free fall and inertial motion, she should not feel the influence of extreme gravity.

2. The second postulate is based on unitarity, the assumption that the laws of quantum mechanics, the information to be pushed into a black hole, there will be irretrievably lost. Unitarity in quantum mechanics – it is an axiom that every possible event probability equal to unity.

3. Third – the “normal” physics, that is, the assumption that the black hole physics will be business as usual, even if at some point will throw tricks – or at the singularity at the event horizon.

Together, these three concepts are what is in the hearts of Busse calls a “hellish brew.” To solve the paradox, one of the three must be sacrificed, but physicists can not decide whom to execute, and who pardon.

Physicists are not easy to abandon the postulates proven. That’s why many considered the appearance of “firewall” just malicious. “It’s not natural,” – said John Preskill at the informal conference at the California Institute of Technology, hosted by Leonard Susskind. For two days, about fifty physicists throw in crazy ideas, trying to resolve the paradox, followed by frantic knocking crayons to the order of the equation on the board. But to everyone’s regret, even the most desperate critics hypothesis of “fire wall” had to surrender: finding a solution is far from complete.

According to Joseph Polchinski, a theoretician of string theory at Caltech, the easiest solution would be that the principle of equivalence is falling apart at the event horizon, creating a firewall. Polchinski and he believes that the idea is insane, but the “wall of fire” is the least radical resolution of potential issues.

If the hypothesis of a “fire wall” and there is an error, it is not obvious. And this, in turn, threatens the appearance of strong scientific paradox. And all this against the background of the fact that theoretical physicists are concerned about a strong position on the conscience of the Standard Model because of the recent discovery of the Higgs boson. Information is scarce, but paradoxes are multiplying.

But if a group led by Polchinskogo mistaken physics must make great strides forward, and maybe even get close to the theory of quantum gravity. black hole physicists interested in the first place, because it applies to the general theory of relativity and quantum mechanics – which is not said of other objects in the Universe, with the subatomic level which corresponds to the quantum mechanics, and in the macrocosm – the general theory of relativity. Two of these “code of laws” work well separately, but physicists madly want to combine them in order to shed light on the anomalies such as black holes, and hence the origin of the universe. What was there before the Big Bang – a lot of theories we previously dismantled .

This preamble. Come on, let’s move on to dessert, and find out on what physicists scratching their heads.
The paradox of entanglement


The problem is very subtle and complex – if they were simple, there would be a paradox – but most of the arguments of Polchinskogo (which in the world of physics called AMPS – the first letters of the names of four members of the team) uses the principle of monogamy quantum entanglement. You only get one type of confusion at a time. AMPS think you need two different types of quantum entanglement that all three postulates “hellish brew” was correct. But since according to the rules of quantum mechanics, you can not be two different complexity, one of the three postulates must be removed.

Quantum entanglement – which Albert Einstein derided as “frightening action at a distance” – a well-known feature of quantum mechanics. As a thought experiment, Alice and Bob are a pair of entangled particles. When subatomic particles collide, they may not be visible related, though physically – separated. Even at a distance, they are inextricably linked and act as a single entity (the distance can be as great, but experimentally managed to “teleport” entangled particles at a distance of 97 kilometers). This means that one partner can instantly see the status of the other. Only snag is that confuse certain way (read – with a certain type) only one pair of particles simultaneously. Now explain.

In classical physics, told Preskill, Alice and Bob can have a copy of the same newspaper, and therefore have access to the same information. Creating such a link is defined as a “strong correlation”. The third character – Carrie – can also buy a copy of the newspaper and have access to the same information as the first two. This does not weaken the correlation of Bob and Alice. Roughly speaking, anyone can buy the same newspaper and become a member of strong correlation.

But in quantum mechanics, everything goes wrong. To Bob and Alice were maximally entangled, their papers must be in the same position from top to bottom and left to right. And when the newspapers will be targeted in the same way, Alice and Bob will have access to the same information.

“Since there is only one way to read the newspaper and many classic – read newspaper quantum, quantum correlation is much stronger than the classic” – explains Preskill. Therefore, if Bob will be very confused with Carrie have to sacrifice entanglement with Alice.

The problem is that there is more than one type of involvement in the case of a black hole, and on the hypothesis of AMPS, two are in conflict. This confusion between Alice falling into a black hole, and Bob, which is needed for the script of “nothing wrong.” There is another confusion that comes from another paradox in physics, address the issue of the disappearance of the information in the black hole. In 1970, Stephen Hawking has suggested that black holes are not really black at all. Although Alice did not notice anything strange when crossing the event horizon, Bob sees a piece of burning coal – Hawking radiation.

Hawking radiation – the result of virtual particles emitted from the quantum vacuum near the black hole. Usually they face and annihilate with the emission of energy, but sometimes one flies into a black hole, and the other – into space. Mass of the black hole, which should be slightly reduced, offsetting this effect and making sure that energy is conserved, if the “winks” to us. The rate of evaporation of a black hole depends on its size: the larger the black hole, the slower it evaporates.

Hawking has suggested that once the radiation escapes, any information about the black hole contained in the radiation will be lost.

“God not only plays dice, he sometimes throws us collisions, throwing them where we can not see” – he once said.

Together with physicist Kip Thorne of Caltech, they even argued with Preskill in 1990 (the results of betting can see here ) about whether the information disappears into a black hole or not. Preskill was the second choice. Hawking and Thorne – the first. As a result, physicists have come to the conclusion that the information is saved: as the evaporation of a black hole, Hawking radiation should become more confusing with the area outside the event horizon. So, while Bob watches radiation, it extracts the information.

And the main question: what would happen if Bob compare their information with Alice after it crosses the event horizon?

“It will be a disaster” – says Busse. – “For Bob, the outside observer sees the same information in the Hawking radiation [because it contains a quantum particle entangled with particles inside the black hole], so if he wants to discuss it, there will be a quantum” copying “, which is strictly forbidden in quantum mechanics “.

Physics headed by Susskind said that the difference between these two points of view on the black hole will be perfectly observed, while Alice and Bob will share their information. This concept is called the complementarity just will not involve direct contradiction, since no single observer can not be both outside and inside the event horizon. If Alice crossed it will see the stars outside and wants to talk to Bob about it, the general theory of relativity will find ways to stop her intentions.

Susskind argument that the information can be recovered without the quantum “Copy”, was so convincing that Hawking admitted his defeat in 2004. But it’s possible that Thorn, who until recently resisted, was still right.

The firewall comes due the following: if, as most physicists prefer to think of the information in a black hole is lost (after getting there with the matter surrounding the black hole of the world) and it can be restored to the Hawking radiation emitted by the hole, then there is a contradiction between the quantum entanglement of Alice and Bob and the quantum entanglement of the black hole and its environment. Bob, it seems equally strongly coupled quantum immediately and with Alice, and with the “third party”, which physicists call Carrie. However, quantum mechanics forbids equally strong quantum entanglement between more than two particles: quantum entanglement “monogamous” or Bob can not be in the same strongly coupled together at once, and with Alice, and with Carrie.

Busse decided that complementarity can resolve the paradox of “firewall.” But I soon realized that this is not enough. Complementarity – the theoretical concept designed to solve a specific problem, namely the harmonization of the two points of view of observers inside and outside the event horizon. But the “wall of fire” is quite a bit outside the event horizon, giving Alice and Bob to one point of view for two, and thus will not resolve the issue complementarity.
Somewhere about quantum gravity


If you want to get rid of the physics of fire walls and save the script, “okay”, they will have to find a new theoretical understanding of this unique situation, or to admit that Hawking was probably right in saying that the information is lost, and then have to return the favor Preskill. Overall, Preskill was surprised, knowing that he and his colleagues will have to reconsider the possibility of data loss. Although we did not see any sense in quantum mechanics without unitarity, “this does not mean that it is designed to end,” said Preskill. In any case, his life on the unitarity he would not put.

Polchinski insists that Alice and Bob have to be complicated to keep the script, “okay”, and to the Hawking radiation to be confused with the zone outside the event horizon to keep quantum information. But not both simultaneously. If you donate to the intricacies of the Hawking radiation area of ​​the event horizon, you will lose information. If you sacrifice the intricacies of Alice and Bob, you will receive a “firewall,” which simply destroys Alice and not allow to display information.

“Quantum mechanics does not give both be there,” – says Polchinski. – “If you lose entanglement between the incident Alice and Bob, that is, the observers, you breed a certain instability in the quantum state of the event horizon. If you sever the chain, in a sense, a broken chain will require energy. And so there will be a firewall that will not allow this to happen. ” Magic.

This follows from the fact that the entanglement between the area outside the event horizon and Hawking radiation should be increased in proportion as the black hole evaporates. When about half of the mass of the black hole evaporates to nothing, a black hole is the most confusing and experiencing a bit of mid-life crisis. Preskill explained: “It’s like a singularity, which we expect to find deep in the black hole, is right behind the event horizon, the black hole too old.” The collision of the singularity and the event horizon, and there is this terrible firewall.

Even the idea of ​​the singularity of the abyss migrated closer to the black hole event horizon, upset physicists. This is a terrible blow to the general theory of relativity, according to Busse.

With all the skepticism regarding the firewall, he deserved to be the culprit celebration. Busse, who believes that this is the most interesting thing that has happened to him since he became a physicist. And physics truly lucky to catch the birth of this paradox.

Death of Alice’s firewall, seems to have become a classic thought experiment in physics. The more physicists learn about quantum gravity, the greater the difference appears in the background of well-known paintings of the universe. Physicists put their faith on the altar for the sake of scientific and technical progress. Now they will have to sacrifice either the screenplay for “okay”, or unitary, well or severely revise quantum field theory. Even if the firewall – it’s a terrible mistake, physicists certainly learn something new.

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Tags: Hawking radiation , Quantum mechanics , Firewall , Black Holes



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