Talk:Acoustic Hawking radiation

message: The article has now been edited (as of Oct 19) to make it NPOV. All further edits should follow suit, by including only statements that are traceable directly to published sources, and by refraining from interjecting personal opinions and musings about the subject. (Erk, this means YOU.) Anything added to the article that is not directly expressing content previosuly published in reputable sources will be deleted, in accord with Wikipedia policy.63.24.56.227 05:22, 20 October 2005 (UTC)
thread_title: How to Proceed With Fixing this Article

message: After changing the title to Acoustic Hawking Radiation, we should revise each of the sentences in the article. To get started, here's the first sentence as it presently exists:
:The famous Hawking radiation effect that quantum mechanics predicts for black holes has a counterpart in some branches of classical physics, but although the “classical” mechanism for indirect radiation through a horizon works in the context of Newtonian physics (see: the old Newtonian emission theory of light), it does not exist in models like Einstein’s general theory of relativity, which inherit the modified non-Newtonian relationships for mechanics derived in the special theory of relativity.
I suggest we delete all the obscurantist anti-relativity crap (i.e., everything after the first comma), so the sentence should be revised to read like this:
:Hawking radiation, an effect that quantum mechanics predicts for black holes in the context of general relativity, has a counterpart in the acoustics of classical media.
All in agreement? If so, we can move on to the second sentence.63.24.53.204 01:14, 17 October 2005 (UTC)
thread_title: First Sentence

message: This article needs at least some stylistic improvements. I reads more like an essay or magazine article than an encyclopedia entry. --Pjacobi 00:10, August 14, 2005 (UTC)
Okay. After rereading it, I agree at least that the opening section needs to be more disciplined. I'll have a go at improving it. Thanks for the feedback. ErkDemon 22:16, 16 October 2005 (UTC)
thread_title: Too much like an essay?

message: This might be a good idea. Brief votes, please, from Wiki account-holders. Also, should all the headings be changed from "Classical…" to "Acoustic…" to match? ErkDemon 22:16, 16 October 2005 (UTC)
thread_title: Rename to "Acoustic Hawking radiation"?

message: I could put in a lot more references, but most of them would say the same thing. I reckoned that that Visser article, plus the big 2005 "Analogue gravity" review piece should be sufficient, but would people prefer to see a wider spread of sources? ErkDemon 22:16, 16 October 2005 (UTC)
thread_title: More references?

message: I'm considering taking out the section on Doppler blueshift and inescapability of gravitational horizons. I thought that it was nice explanation of why GR differs from older models as far as inescapability is concerned (See Thorne's book for diagrams), but perhaps it's taking the article off-topic. Comments? ErkDemon 22:16, 16 October 2005 (UTC)
thread_title: Culling sections?

message: The POV of this article is clear from the statement:
"Although the classical mechanism for Hawking radiation appears to offer a unified worldview in which quantum and classical effects are interchangeable, and where some of the “odder” quantum effects have fairly mundane explanations..."
Need I say more?130.76.32.16 15:28, 11 October 2005 (UTC)
thread_title: Crank POV of the Article

message: Well, yes, you really should have said more, since that was a horrendous example of selective quoting. The "Caveats" section of the article is a single paragraph that essentially says that, although this looks like an easy solution to the BHIP, its not really as easy as all that, because these sorts of descriptions don't work with Einstein's general theory of relativity, which is our current theory of gravitation. 
<BLOCKQUOTE>"Although ... appears to offer ... explanations ... it should be emphasised that our current reference classical theory of gravity is general relativity, which does not support these mechanisms. According to current classical relativistic physics theory, these explanations, though seductive, are simply wrong. This is not how physics operates in an “SR+GR” universe." </BLOCKQUOTE>
Now, please tell me, why you think that the full quote is misleading? I've seen some pretty bad examples of dodgy quoting before, but I've never before seen anyone stoop so low as to quote selectively from a "caveats" section and omit the caveat! That's like taking a sign on a beach that says "Danger: The sea here seems calm and good for swimming, but the region has sharks and very dangerous concealed riptides that can easily kill you. Do not swim here!", and presenting it as saying "The sea here appears calm and good for swimming ...".  
For the benefit of other readers: I'm open to constructive suggestions as to how the article could be improved, or as to any points that could do with clarification, or further explanation or references, or that might seem to be going slightly off-track. I'm in the middle of a minor rewrite, perhaps I might make the start of that queried sentence slightly less flowery, if it's causing folks like 130.76.32.16 to have a kneejerk reaction and not read all the way through to the end of the paragraph.  ErkDemon 00:43, 14 October 2005 (UTC)
thread_title: The rest of the quote ...

message: Well, if you read the very recent literature you'll find that Hawking radiation has now finally been accepted as a wholly mundane effect in fluid mechanics, acoustics, and (apparently) any other situation that involves acoustic metrics. As far as I can work out, the only obvious class of model in which the effect does not arise as a "mundane" effect is in general relativity and in other similar theories of gravitation that are designed to reduce to reduce in a similar way to special relativity - SR's idealised flat Minkowski metric seems to be "too smooth" for the effect to work.<BR> 
This is a bit unfortunate, because that description pretty much defines the set of classical theories of gravitation that we consider credible.
* Steve Carlip, "Quantum gravity: A progress report" Rept. Prog. Phys., 64 (2001), 885. gr-qc/0108040 
 "Hawking radiation is a “semiclassical” prediction, originally discovered in the study of quantum field theory on a fixed curved background [321], and subsequently confirmed in a remarkable number of different computations, ranging from the saddle point approximation of the Euclidean path integral [53] to the investigation of symplectic structure of the space of solutions [197] to the calculation of amplitudes for black hole pair production [322,323]. Any theory that fails to reproduce this prediction is almost surely wrong. ... "
"Another indirect test may come from condensed matter analogs of black holes, which
should emit “Hawking radiation” phonons from sonic horizons, regions at which the fluid flow reaches the speed of sound [345,346]. Tests may be possible in the not-too distant future in Bose-Einstein condensates [347], superfluid helium 3 [348], and “slow light” in dielectrics [349]. 
So, yes, HR does turn out to be really very general, and usually shows up in other contexts without our having to invoke any specially "spooky" QM effects to explain it, such as pair production ... it's just that most published books will still describe the effect as it was generally understood (pre-2000), before the wider generality of the effect was properly recognised , and before that new understanding had trickled down very far. Of course, this still leaves the thorny subject of how the heck we are going to "fix up" current gravitational theory to include the missing effect, without doing something "radical" like swapping out the underlying SR layer for an acoustic metric. Which, for obvious reasons, people are reluctant to do (that would require a full rewrite and rederivation of inertial physics, lots and lots of work). ErkDemon 02:50, 12 October 2005 (UTC)
thread_title: no, not cranky, just too recent for the usual textbooks

message: Please read more carefully. I did not say that we need to swap out SR from GR. My response above said that we still faced the thorny problem of how to fix up GR ==without== swapping out SR. We have still not found a satisfactory way to do this. The subject of classical Hawking radiation is under intense study by many mainstream theoreticians because it offers a way around the black hole information paradox in non-GR physics, and (mostly) because it is hoped that the study of these sorts of non-GR solutions may offer some insights as to how fix the problem in general relativity, without going as far as the "major rewrite" option. It has been suggested by John Preskill that the apparent insolubility of the BHIP might signify that a serious overhaul of current physics may be necessary, but there may be a few other unexplored avenues still to be checked out before we seriously consider that step. ErkDemon 01:27, 14 October 2005 (UTC)
thread_title: anonymous critic again exagerrates, misrepresents

message: : Look, Mr. Baird, it's very simple. Please cite a reference from a reputable published source stating
:: "Hawking Radiation usually shows up in other contexts without our having to invoke any specially "spooky" QM effects to explain it, such as [[pair production]..."
: Please do NOT provide quotes or citations of things that you (as an obvious crackpot) think IMPLY the above statement. It's clear from what you've written above that you are incapable of rationally interpreting what you read. You need to provide a quote from a reputable source (as defined in Wikipedia policies) that says very directly and unambiguously what you claim above. Notice that this must not refer to things being ANALOGOUS to Hawking Radiation, because you claim to be writing about Hawking Radiation itself.
===You didn't notice the provided references?===
I'd already provided a link to Visser's paper [http://xxx.lanl.gov/abs/gr-qc/9712010 "Acoustic black holes: Horizons, ergospheres and Hawking radiation" gr-qc/9712010 ) Class.Quant.Grav. 15 (1998) 1767-1791 in the original article. That ought to be a sufficiently respectable journal, I think!
"In 1981 Unruh developed a way of mapping certain aspects of black hole physics
into problems in the theory of supersonic acoustic flows [1]. The connection
between these two seemingly disparate systems is both surprising and powerful,
and has been independently rediscovered several times over the ensuing decade
and a half [2]. Over the last six years, a respectable body of work has been
developed using this analogy to investigate micro-physical models that might
underly the Hawking radiation process from black holes (or acoustic holes —
“dumb holes”), and to investigate the extent to which the Hawking radiation
process may be independent of the physics of extremely high-energy trans–
Planckian modes [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14].
 ...
... As discussed by Unruh [1], (and subsequent papers [3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14]) an acoustic event horizon will emit Hawking radiation in the form
of a thermal bath of phonons at a temperature 
Here the relationship between acoustic HR and black hole HR is represented as an analogy, but the acoustic HR effect itself is described as being a genuine HR effect, within  acoustics. 
You also seem to have missed or overlooked the relevant "Carlip" quotes presented above.
Finally, if you look at the "in progress" rewrite, you'll see that I've already added a link to the massive review piece that appeared on LANL a few months ago, 
Carlos Barcelo', Stefano Liberati and Matt Visser  "Analogue Gravity" (2005) gr-qc/0505065 (PDF, currently 152 pages)
, which has a similarly massive reference listing at the back, alphabetical, by author. The list illustates how far the field has advanced in the last few years. It has 435 references! 
Scan through that listing and you'll find stacks of articles whose titles refer to "acoustic Hawking radiation", "sonic Hawking radiation", "Hawking radiation in Bose-Einstein condensates", Hawking radiation in sonic/acoustic black holes, and so on. Case closed, I think. ErkDemon 01:44, 14 October 2005 (UTC)
thread_title:  Yes, Cranky 

message: I'd already provided a link to Visser's paper [http://xxx.lanl.gov/abs/gr-qc/9712010 "Acoustic black holes: Horizons, ergospheres and Hawking radiation" gr-qc/9712010 ) Class.Quant.Grav. 15 (1998) 1767-1791 in the original article. That ought to be a sufficiently respectable journal, I think!
"In 1981 Unruh developed a way of mapping certain aspects of black hole physics
into problems in the theory of supersonic acoustic flows [1]. The connection
between these two seemingly disparate systems is both surprising and powerful,
and has been independently rediscovered several times over the ensuing decade
and a half [2]. Over the last six years, a respectable body of work has been
developed using this analogy to investigate micro-physical models that might
underly the Hawking radiation process from black holes (or acoustic holes —
“dumb holes”), and to investigate the extent to which the Hawking radiation
process may be independent of the physics of extremely high-energy trans–
Planckian modes [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14].
 ...
... As discussed by Unruh [1], (and subsequent papers [3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13, 14]) an acoustic event horizon will emit Hawking radiation in the form
of a thermal bath of phonons at a temperature 
Here the relationship between acoustic HR and black hole HR is represented as an analogy, but the acoustic HR effect itself is described as being a genuine HR effect, within  acoustics. 
You also seem to have missed or overlooked the relevant "Carlip" quotes presented above.
Finally, if you look at the "in progress" rewrite, you'll see that I've already added a link to the massive review piece that appeared on LANL a few months ago, 
Carlos Barcelo', Stefano Liberati and Matt Visser  "Analogue Gravity" (2005) gr-qc/0505065 (PDF, currently 152 pages)
, which has a similarly massive reference listing at the back, alphabetical, by author. The list illustates how far the field has advanced in the last few years. It has 435 references! 
Scan through that listing and you'll find stacks of articles whose titles refer to "acoustic Hawking radiation", "sonic Hawking radiation", "Hawking radiation in Bose-Einstein condensates", Hawking radiation in sonic/acoustic black holes, and so on. Case closed, I think. ErkDemon 01:44, 14 October 2005 (UTC)
thread_title: You didn't notice the provided references?

message: As a case in point, consider Mr. Baird's assertion in this article
:Initially the classical effect tended to be described as the sonic “analogue” of Hawking radiation, but in 1998 Matt Visser published a study (gr-qc/9712010) that concluded that this classical leakage effect was technically a “true” form of Hawking radiation, although, the range of theories in which it arose in a gravitational context did not include general relativity.
and compare this with Visser's actual summary of the contents of that paper
:This rather simple physical system is the basis underlying a deep and fruitful ANALOGY between the black holes of Einstein gravity and supersonic fluid flows.
So the citation that Eric uses to justify his (characteristically obscurantist) claim about accoustic Hawking radiation being "true" Hawking radiation (whatever "true" is supposed to mean) is not at all supported by his reference. Eric goes on to admit (obscurely) that this "true" Hawking radiation does not fit within the context of general relativity, so of course it isn't true Hawking radiation at all, which presumably is why he placed the word "true" in quotes. (The very definition of Hawking radiation is from the context of general relativity.) These are all just Eric's contortions to try to insinuate his crackpot ideas into the article while staying "under the radar" of the crackpot detectors. This is just a note to Wikipedia editors - If you check the references that Mr. Baird provides, you will invariably find that they do NOT support the crackpot Point of View expressed in his articles. You will also find that he attempts to disguise his crank POV statements with pseudo-jargon and made-up terms.
63.24.57.138 06:11, 14 October 2005 (UTC)
thread_title: Example of Baird's Misrepresentations

message: Proponents of analog models of gravity often come under heavy fire attack from relativists and high energy physicists who often completely misunderstand the theory. Not too long ago, another proponent George Chapline was savaged by mainstream physicists. Phys 23:10, 21 October 2005 (UTC)
replies: text: Erk is not a "proponent of analog models of gravity" (whatever that is), he is a proponent of the idea that gravity IS a classical fluidic phenomenon. His agenda is to try to smuggle this crackpot belief into a host of Wikipedia articles under the guise of articles on other subjects. If Erk was to write an article on baseball, I have no doubt he would argue that, since baseballs are round and out-fielders wear gloves, it follows that special relativity is wrong and black holes are really dark stars. (And then include a disclaimer like: but current physical theories doesn't support this conclusion, mainly becasuse they rely on special relativity.) Then he would point to a stack of references saying that baseballs are indeed round, and he would claim that his article is therefore based on legitimate sources.63.24.53.246 23:57, 21 October 2005 (UTC)
replies: text:  No, I am not a proponent of the idea of gravity considered as a classical particulate fluid. Some of the mainstream "graviton"/"quantum foam" guys might fit that description, but not me. I tend to think of the gravitational field as being a smooth featureless thing (until we start contaminating it with objects, observers and test particles and their associated gravitoelectomagnetic distortions). Sorry to disappoint. ErkDemon 16:36, 1 January 2006 (UTC)
thread_title:  Wow! Proponents of analog models of gravity have it hard! 

message: Hawking radiation in analog models is still a quantum effect. Because of this, I will rename this article acoustic Hawking radiation. Phys 00:39, 22 October 2005 (UTC)
replies: text: Let me try to clarify myself. Classically, it's possible to move faster than "light" (i.e. sound) as thus escape from the "event horizon" but the actual acoustic Hawking radiation itself requires quantum mechanics. Phys 00:42, 22 October 2005 (UTC)
thread_title:  The title is inappropriate 

message: Okay, here's the promised (overdue) total rewrite of the "Classical Hawking radiation" article. Almost everything from the original article has gone.
I retained the recently-added Visser quote by another editor in the "Analogy vs. identity" section and supplemented it with a more recent quote saying that the idea that the analogies might be argued to be more than just analogies is a (secondary) reason for study. I'm hoping that this section, with the two quotes (without further commentary) will be considered as striking a NPOV balance. The two statements don’t necessarily conflict, one is about general relativity, the other, quantum gravity. The attempt to eventually obtain a theory that obeys QG principles seems to be is a recurring motivation in a lot of this research.
I've added a substantial reference section, partly because (without it) some people didn’t seem to believe that this was an actual subject, and partly because I think this reading list should be a useful research resource. I think that its range is reasonably comprehensive. There does not (yet) seem to be any published reference book on this subject. ErkDemon 09:00, 25 October 2005 (UTC)
thread_title:  Version 2.0