Talk:No hair theorem
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This sentence makes no (or very little) sense, but I don't feel qualified to make any amends (First para):
- All other information about the matter which formed a black hole or infalling into it, "disappear" behind the black-hole event horizon and are therefore permanently inaccessible to external observers.
First of all, 'information' is singularis, so it should be 'disappears', but 'infalling'? Could someone knowledgeable fix it? Asav 13 Dec. 2005
Igorivanov 14:24, 23 Jul 2004 (UTC) Color is not a pseudo-charge. It is linked to the gauge group, just like the usual charge, so it must be conserved. But, I guess, due to confinement, this is just of academic interest.
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[edit] Microstates and macrostates ?
If the surface of a black hole has entropy S, doesn't that imply that the event surface is in one of (1/k) exp (S) microstates at a microscopic level, just by inverting S = k ln W ?
Why should the fact that its macroscopic properties are determined completely by the no hair theorem worry us any more than any other thermodynamic object which has a well-defined macrostate, but is in an unknown one of many possible microstates ? What is the big problem here ? -- Jheald 22:48, 2 November 2005 (UTC)
[edit] What about volume?
Since volume doesn't depend on mass, charge, or spin, does the No-Hair Theorem state that black holes have zero volume, or that they all have identical volume, or what? ---63.26.160.105 02:19, 2 February 2006 (UTC)
- Well, volume doesn't really make sense in this context. See for example the discussion of the so-called Einstein-Rosen bridge (wormhole of a kind) in the discussion of nonrotating black holes modeled by the Schwarzschild vacuum solution in MTW, Gravitation; see General relativity resources for full citation. On the other hand, you could ask for the area of the event horizon. This has no immediate physical meaning but it is mathematically well defined and has a profound meaning in terms of the global structure of a black hole spacetime. Then the brief answer to your question is that it can be computed in terms of the parameters mentioned in the no hair theorem. See for example Frolov & Novikov, Black Hole Physics (full citation given in the article just mentioned). ---CH 03:16, 2 February 2006 (UTC)
[edit] John Wheeler
I believe I read in one of Kip Thorne's books that John Wheeler coined the term: "Black holes have no hair." Is this correct? David618 02:52, 12 March 2006 (UTC)
- Yes. The book was no doubt Black Holes And Time Warps : Einstein's Outrageous Legacy, a popular book which contains many anecdotes about the Golden age of general relativity. ---CH 16:45, 14 March 2006 (UTC)
I thought it was from that book. Thanks. David618 15:39, 15 March 2006 (UTC)
[edit] Students beware
I edited earlier versions of this article and had been monitoring it for bad edits, but I am leaving the WP and am now abandoning this article to its fate. And WikiProject GTR is presumably defunct.
Just wanted to provide notice that I am only responsible (in part) for the last version I edited; see User:Hillman/Archive. I emphatically do not vouch for anything you might see in more recent versions, although I hope for the best.
Good luck in your search for information, regardless!---CH 02:28, 1 July 2006 (UTC)
[edit] Conserved quantities
Mustn't all conserved quantities be conserved in a black hole as well? Granted most particle quantum numbers are violated in one process or another, but what about exact laws like conservation of color charge, or B−L? 164.55.254.106 19:55, 18 July 2006 (UTC)
- The no hair theorem deals only with classical gravitational and electromagnetic fields, under classical general relativity. If you were to add in new additional classical fields, it seems to me entirely likely that you would get new additional conserved quantities (but I'll leave it to the real GR experts here to pronounce definitively).
- Note also that the quantum case is an entirely different ball game. If black holes have an entropy S, that implies that there are exp(S/k) conceptually identifiable different quantum states asscociated with each classical state. Jheald 21:27, 18 July 2006 (UTC).
[edit] What about Momentum (non angular)?
I don't understand why this theorem explicitly states that black holes retain mass and angular momentum but says nothing about normal, linear momentum. I suppose it's considered obvious to an expert in the field? I can't imagine that a rapidly moving star ceases to move when it collapses in to a black hole (as if there were some coordinates throughout the universe such that non movement could even be defined). If I wanted to characterize a black hole COMPLETELY, I would need one number for mass, one signed number for charge, one 2 vector for direction of movement and a scalar for magnitude of movement, and one two vector for axis of rotation and a scalar for speed of rotation. Is that correct?
- Momentum isn't considered a property of the black hole as it depends on reference frame. We only consider the frame-independent magnitude of the momentum, which is the mass. (Similarly, we only consider the magnitude of the angular momentum as a property, but not the direction) Ben Standeven 23:34, 29 November 2006 (UTC)
[edit] Possible Reference to be included
I am not an expert in the field, but one might include "Black Hole Uniqueness Theorems" by Markus Heusler, Peter Goddard (editor) and Julia Yeomans (editor) because it gives an overview about the subject (without quantum gravity).
