Whether or not information can truly be lost is a major issue in the study of black holes. Stephen Hawking’s work in the 1970s offered a mechanism for black hole evaporation. Vacuum fluctuations would cause a particle and its antiparticle to appear just beyond the black hole’s event horizon, with one of the two falling into the black hole while the other escaped. A ‘virtual’ particle, in other words, would become a real particle. Black holes, in this view, would be able to lose mass through quantum effects, a theory that the soon to be launched GLAST satellite will try to confirm.
But ingenious as Hawking’s theory was, it produced a conundrum. Black holes that fail to gain more matter will eventually vanish, with information, such as the identity of matter drawn into the black hole, becoming permanently lost. It being a linchpin of quantum mechanics that information cannot be lost, this presents a problem. Enough of one that physicist John Preskill (Caltech) bet Hawking and Kip Thorne (also at Caltech) that information could not be lost in black holes. Hawking conceded in 2005, and now a team of physicists has suggested a new way of seeing black holes that would indeed allow information to escape.
Image: An artist’s depiction of the accretion of a thick ring of dust into a supermassive black hole. The accretion produces jets of gamma rays and X-rays. Credit: ESA / V. Beckmann (NASA-GSFC).
The idea behind this work, led by Abhay Ashtekar (Penn State), is that the disappearance of information is only an illusion. Think of spacetime as a series of individual building blocks. Ashtekar’s team believes that the idea of a continuum is but an approximation of a larger reality, one in which singularities, as Ashtekar himself says, “…are merely artifacts of our insistence that space-time should be described as a continuum.” Thus:
“Information only appears to be lost because we have been looking at a restricted part of the true quantum-mechanical space-time. Once you consider quantum gravity, then space-time becomes much larger and there is room for information to reappear in the distant future on the other side of what was first thought to be the end of space-time.”
The work, to be published in the Physical Review Letters, draws on mathematical studies of black holes in two dimensions, an approach the team believes accurately applies to real black holes in four-dimensions, although directly studying the latter is what Ashtekar and company are now proceeding to do. If confirmed, their work would validate Hawking’s decision to pay off the bet with Preskill, which he did by giving the physicist what he had asked for, a baseball encyclopedia. Thorne has yet to concede the bet, for Hawking’s own take on how black holes might leak information is as controversial as Ashtekar’s is likely to be.
When one considers this theory that even blackholes represent a ‘restricted part’ of space-time reality, the hypothesized ‘mega-verse’ is going to be a horse pill to swallow with the mainstream crowd.
Of course this opens up a whole philisophical discussion about the nature of reality that seems never-ending as it is.
I applaud and welcome it with open arms!
I should point out that when physicists say “information” in this context what they mean is specific types of information such as electrical charge, isospin, baryon and lepton number. Our current understanding of physics holds that these quantities, and others, are preserved in specific ways. As pointed out, certain interpretations of the way black holes might work would result in this information being lost forever. If black holes didn’t evaporate this might not be a problem, the information would just be cut off from the rest of the universe, but evaporation eventually leads to the disappearance of the black hole, while apparently inputting random bits of “information” back into the universe. Thus the conundrum.
Hi Folks;
Given the conceptual framework that black holes have “no hair”, I have often wondered whether or not the super symmetric analogue of the electromagnetic force involving the sparticles of squarks, sleptons, and the photino would violate this conjecture. Naturally, we have heard that the only characteristics that define a black hole from outside the event horizon are its electric charge, angular momentum, and mass.
I have often wondered about black hole concepts or analogues involving the super symmetric partner to the graviton, otherwise known as the gravitino.
As I mentioned, recently in another Tau Zero thread, with all of the particles and fields that are or have been proposed to exist, perhaps there are other ways that black holes may have hair. Even though properties such as quark flavor, baryon number and lepton type would seem to appear to be lossed, perhaps some of these additional particles and fields may provide a way for the information allegedly lossed in terms of the in falling baryonic matter and other normal mattergy to be conserved. Perhaps between normal (or traditional non-super symmetric mattergy) and super symmetric mattergy and other proposed and/or yet to be conjectured fields, there is some sort of quantum information equivalence principle(s) such that given the entirely of the possible particles and fields, the quantum information can never be lossed. Perhaps such an equivalence principle allows the so-called lossed information to be imprinted in an alternate but equivalent form on these other particles and/or fields. This might be the case even if space-time is a continuum.
Thanks;
Jim
Perhaps I am not qualified to comment on this story, but I am an interested layman who has read a number of the recent books on black holes.
I was under the impression that quantum gravity was by no means a “done deal” in the sense that the details of the theory is well established.
If it’s not, isn’t this paper a bit of a stretch? Correct me if I’m wrong.
Introduction to black holes
Authors: Gustavo E. Romero
(Submitted on 14 May 2008)
Abstract: Black holes are perhaps the most strange and fascinating objects known to exist in the universe. Our understanding of space and time is pushed to its limits by the extreme conditions found in these objects. They can be used as natural laboratories to test the behavior of matter in very strong gravitational fields. Black holes seem to play a key role in the universe, powering a wide variety of phenomena, from X-ray binaries to active galactic nuclei. In this article we will review the basics of black hole physics.
Comments: 25 pages, 6 figures, Lecture Notes from the First La Plata International School on Astronomy and Geophysics
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0805.2082v1 [astro-ph]
Submission history
From: Gabriela S. Vila [view email]
[v1] Wed, 14 May 2008 15:04:44 GMT (325kb)
http://arxiv.org/abs/0805.2082
Frank, you’re absolutely right about quantum gravity not being a done deal. And yes, the paper discussed in this post is bound to be controversial as we continue to sort out just how to merge the mercurial quantum world with the theories, like General Relativity, that have been so effective in describing our universe. We’re unquestionably a long way from that merger, with many detours along the way.
Hawkings 2005 work, ‘Information Loss In Black Holes’ if I’m correct, purports that black holes might shed ‘information’ into the ‘multiverse’ and that the quantum perturbations of the event horizon also leaks information out.
As Robin noted, this seems that the info release is random, although current theories speculate this should be preserved.
But information is information, is it not? Even if the black holes spit out random pieces and ship the rest to universes without black holes (white holes instead?), it doesn’t mean information was destroyed, just changed and transported.
Or am I misunderstanding how this works?
Dad2059, read my post above. “Information” is not a generic term in this context, it has very specific meaning. Consider the types of “information” we know are conserved by black holes: mass and electrical charge. However, there are other quantities which we know to be conserved given our understanding of the laws of physics. A good example is lepton number. If you have an electron, for example, you can’t simply destroy it and remove it from reality, you can transform it’s energy into other kinds of particles, but only in certain ways. If you combine an electron and a proton to create a neutron you will also end up with an electron neutrino, the electron neutrino has the same “lepton number” as an electron, thus preserving the lepton number in this reaction. There are many other examples for different quantities.
However, our current understanding of black holes does not have any mechanism for preserving lepton number. Indeed, Hawking radiation appears to be a way to violate the preservation of lepton number in a wholesale fashion. This is just another way in which blackholes highlight the seeming incompatibility between quantum mechanics and general relativity. It’s not surprising that quantum gravity may hold an answer to this problem.
@Robin: Okay, I understand now. It’s just that ‘information loss’ and black holes get bandied about nilly-willy. The electrons can get broken up into particles, but they can’t get lost, or shouldn’t anyway, thus the Hawking Radiation problem.
So yeah, I can see where gravitons can come in handy now.
Nearly seeing Hawking radiation?
Astrophysicists have known for more than three decades that black holes
shouldn’t be totally black…
http://physicsworld.com/blog/2008/05/nearly_seeing_hawking_radiatio_1.html
Hi Folks;
I have a particular interest in extreme limits of mass/energy density, miniscule spatial and temporal dimensions, and the possible breakdown of the laws of physics near the heart of a black hole.
We have all heard of the general relativistic notion of a point-like singularity at the center of a non-rotating or slowly enough rotating black hole. We have also heard of the concept of a quantum mechanically smeared out or finite size to the dimensional extent of the so-called black hole singularity. We obviously have heard of quantum gravity concepts like loop quantum gravity, holographic information theory, and the like wherein space-time would be discreetized into finite size differential volumetric elements.
However, I wonder if the so-called singularity inside the black hole is really the limit. Presumably there would be some boundary between the space-time just out side the singularity, even if smeared out by some uncertainty principle, and the what I will call the outer surface of the singularity itself. I wonder if the interior of the singularity goes through some sort of phase transition in terms of the laws of physics that apply, any boundary condition analogous to the passing through the event horizon from out side the black hole, or where a much broader mathematical physical formulation becomes necessary above and beyond the descriptive, analytical, or numerical methods of current quantum gravity paradigms or approaches.
Perhaps further “inside the singularity” for lack of a better phrase yet another phase transition or set of boundary conditions arises. Who knows, perhaps even a further level yet and so on. If such interiorly phase transitions exist or something analogous to them does within the singularity, perhaps such remains forever hidden or at least almost impossible or effectively hard to access just as any existent so-called hidden variables in quantum mechanics might exist but be essentially forever hidden from us.
Thanks;
Jim
Jim, Paul, and all
Here’s the straight scoop according to me. Wish all questions and answers were this easy <:-).
When EM radiation enters a black hole the waves of the radiation are long before broken up in the event horizon along with the photons which these waves contain. The energy of their velocity is transferred to the event horizon vortex. This vortex accelerates both atomic matter and particles. An accelerating vortex excites electrons that emit new high-energy EM radiation some of which escapes this area. Atomic matter is steadily ionized by the velocity of this vortex so that high-energy electrons are emitted. To think that the memory of any of this would be retained is straight from quantum theory, AKA quantum fantasy.
Ultimately that energy of those particles that are not radiated away are absorbed by the black hole. If it is a young galaxy then some of this energy will enhance the energy of the galactic jets and the spin velocity of the Black Hole. If it’s an older galaxy, without jets, then the increased energy would be used to more quickly crush entering matter into strings of dark matter that will end up being pushed into the dark matter compaction of the Black Hole. If there is enough new energy it can also reinforce the spin rate of the Black Hole.
To believe that info could be recovered from this — please contact me. I have a bridge I would like to sell <:-). Are quantum theorists really that gullible?
The 100% honest answer is: you betcha.
your friend forrest
Information ‘not lost’ in black holes
The end may be in sight for the black hole “information paradox”
http://physicsworld.com/cws/article/news/34239
Hi Forrest and other Folks;
It occurred to me that perhaps the so-called lost information from the black holes is somehow transferred to parallel histories that branch of from our universe with every instance of so-called quantum mechanical de-coherence.
Regarding quantum acts of de-coherence and parallel histories, perhaps solar energy harnessing apparatus could be somehow set up in parallel histories that have a Sun Earth system wherein the energy would be piped into our history via technology that somehow bridges the gap between the macroscopic aspects of such parallel histories . The caveat here would be that such parallel histories actually exist and are not merely abstract philosophical or calculational contrivances.
If no such real parallel histories exist, perhaps energy can still somehow be piped in from parallel universes if such universes exist. Such huge stellar, or whatever, energy supplies might be used to boost manned space craft to extreme gamma factors via beamed energy schemes thus allowing manned time travel to locations far into the future by human representatives from our era.
Thanks;
Your Friend Jim
Black hole mimickers: regular versus singular behavior
Authors: José P. S. Lemos, Oleg B. Zaslavskii
(Submitted on 4 Jun 2008)
Abstract: Black hole mimickers are possible alternatives to black holes, they would look observationally almost like black holes but would have no horizon. The properties in the near-horizon region where gravity is strong can be quite different for both type of objects, but at infinity it could be difficult to discern black holes from their mimickers.
To disentangle this possible confusion, we examine the near-horizon properties, and their connection with far away properties, of some candidates to black mimickers. We study spherically symmetric uncharged or charged but non-extremal objects, as well as spherically symmetric charged extremal objects. Within the uncharged or charged but non-extremal black hole mimickers, we study non-extremal $\epsilon$-wormholes on the threshold of the formation of an event horizon, of which a subclass are called black foils, and gravastars. Within the charged extremal black hole mimickers we study extremal $\epsilon$-wormholes on the threshold of the formation of an event horizon, quasi-black holes, and wormholes on the basis of quasi-black holes from Bonnor stars. We elucidate, whether or not the objects belonging to these two classes remain regular in the near-horizon limit.
The requirement of full regularity, i.e., finite curvature and absence of naked behavior, up to an arbitrary neighborhood of the gravitational radius of the object enables one to rule out potential mimickers in most of the cases. A list ranking the best mimickers up to the worse is given. Since, in observational astrophysics it is difficult to find extremal configurations (the best mimickers in the ranking), whereas non-extremal configurations are really bad mimickers, the task of distinguishing black holes from their mimickers seems to be less difficult than one could think of.
Comments: 30 pages, 1 figure
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics
(astro-ph); High Energy Physics – Theory (hep-th)
Cite as: arXiv:0806.0845v1 [gr-qc]
Submission history
From: Jose’ P. S. Lemos [view email]
[v1] Wed, 4 Jun 2008 19:49:09 GMT (38kb)
http://arxiv.org/abs/0806.0845
HIROSI OOGURI: SEMINAR DAY 2008: BLACK HOLES AND THE FATE OF DETERMINISM
(PHYSICS)
New Streaming Theater Presentation: When Stephen Hawking discovered
that black holes are not completely dark but emit thermal radiation
by quantum effects and may evaporate in some cases, he seriously
challenged causal determinism, which is a basic tenet of the
physical sciences. Physicists’ attempts to solve this puzzle have
inspired important theoretical innovations toward the unification of
general relativity and quantum mechanics. Hirosi Ooguri, Fred Kavli
Professor of Theoretical Physics, explains how superstring theory
has met the challenge and uncovered surprising properties of quantum
black holes.
Details: http://today.caltech.edu/theater/
Hawking radiation as seen by an infalling observer
Authors: Eric Greenwood, Dejan Stojkovic
(Submitted on 3 Jun 2008)
Abstract: We investigate an important question of Hawking-like radiation as seen by an infalling observer during gravitational collapse. Using the functional Schrodinger formalism we are able to probe the time dependent regime which is out of the reach of the standard approximations like the Bogolyubov method.
We calculate the occupation number of particles registered by an infalling observer and demonstrate that the distribution is not quite thermal, though it becomes thermal once the black hole is formed in his frame. We approximately fit the temperature and find that the local temperature increases as the horizon is approached. This is in agreement with what is generically expected in the absence of backreaction.
Comments: Seven pages and three figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics – Theory (hep-th)
Cite as: arXiv:0806.0628v1 [gr-qc]
Submission history
From: Eric Greenwood [view email]
[v1] Tue, 3 Jun 2008 20:03:19 GMT (310kb)
http://arxiv.org/abs/0806.0628
Magnetic Beacons May Signal Invisible “Micro Black Holes”
Throughout the Universe
Black holes are the most fascinating features of space time yet discovered, regions where mass is compacted so densely that the values literally go off the scales and physics breaks down.
Now it seems that these galactic vacuum cleaners aren’t just gravitationally attractive – they’re magnetic too.
Full article here:
http://www.dailygalaxy.com/my_weblog/2008/06/magnetic-black.html
Resource Letter BH-2: Black Holes
Authors: Elena Gallo, Don Marolf (UCSB)
(Submitted on 13 Jun 2008)
Abstract: This resource letter is designed to guide students, educators, and researchers through (some of) the literature on black holes. Both the physics and astrophysics of black holes are discussed. Breadth has been emphasized over depth, and review articles over primary sources. We include resources ranging from non-technical discussions appropriate for broad audiences to technical reviews of current research.
Topics addressed include classification of stationary solutions, perturbations and stability of black holes, numerical simulations, collisions, the production of gravity waves, black hole thermodynamics and Hawking radiation, quantum treatments of black holes, black holes in both higher and lower dimensions, and connections to nuclear and condensed matter physics.
On the astronomical end, we also cover the physics of gas accretion onto black holes, relativistic jets, gravitationally red-shifted emission lines, evidence for stellar-mass black holes in binary systems and super-massive black holes at the centers of galaxies, the quest for intermediate mass black holes, the assembly and merging history of super-massive black holes through cosmic time, and their effects on the evolution of galaxies.
Comments: For the American Journal of Physics (15 pages). A Resource Letter is in large part an annotated bibliography. Comments and suggestions are welcome, though the goal is to keep the letter as brief as possible
Subjects: Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)
Cite as: arXiv:0806.2316v1 [astro-ph]
Submission history
From: Elena Gallo [view email]
[v1] Fri, 13 Jun 2008 21:14:56 GMT (31kb)
http://arxiv.org/abs/0806.2316
Quantum Black Holes As Elementary Particles
Authors: Yuan K. Ha
(Submitted on 30 Dec 2008)
Abstract: Are black holes elementary particles? Are they fermions or bosons? We investigate the remarkable possibility that quantum black holes are the smallest and heaviest elementary particles. We are able to construct various fundamental quantum black holes: the spin-0, spin 1/2, spin-1, and the Planck-charge cases, using the results in general relativity.
Quantum black holes in the neighborhood of the Galaxy could resolve the paradox posed by the Greisen-Zatsepin-Kuzmin limit on the energy of cosmic rays from distant sources. They could also play a role as dark matter in cosmology.
Comments: Quantum black holes with a typical mass of 10^{-5} gm are semiclassical objects. Like a heavy nucleus of an atom, they may subject to the rules of quantum mechanics but not necessarily to the rules of quantum field theory. 12 pages
Subjects: General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics – Theory (hep-th)
Cite as: arXiv:0812.5012v1 [gr-qc]
Submission history
From: Yuan K. Ha [view email]
[v1] Tue, 30 Dec 2008 19:20:51 GMT (6kb)
http://arxiv.org/abs/0812.5012
Are Alice and Rob really protected by statistics as she falls into a black hole?
Authors: E. Martin-Martinez, J. Leon
(Submitted on 11 Jul 2009 (v1), last revised 14 Jul 2009 (this version, v2))
Abstract: We analyze Alice and Rob entanglement degradation due to Unruh effect when considering an arbitrary number of accessible modes. A fermion field under single mode approximation (SMA) only has a few accessible levels due to Pauli exclusion principle, in opposition to bosonic fields which have an infinite number of excitable levels. This has been argued to justify entanglement survival in the fermionic case in the SMA infinite acceleration limit.
Here we relax SMA. Hence, an infinite number of modes are excited as Rob accelerates even for a fermion field. We will prove that, despite this analogy with the bosonic case, entanglement loss is limited. We will show this comes from fermionic statistics through the characteristic structure it imposes on the infinite dimensional density matrix for Rob. This is independent of the specific entangled state chosen and the number of accessible modes considered.
We shall discuss the nature of this surviving entanglement and the insights it gives concerning the black hole information paradox.
Comments: 4 pages, revtex4
Subjects: Quantum Physics (quant-ph)
Cite as: arXiv:0907.1960v2 [quant-ph]
Submission history
From: Eduardo Martin-Martinez [view email]
[v1] Sat, 11 Jul 2009 12:22:41 GMT (10kb)
[v2] Tue, 14 Jul 2009 08:53:19 GMT (10kb)
http://arxiv.org/abs/0907.1960