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Why is it called "no-hair" theorem or whatever? I can't find any information in the article about the origin of "no-hair" name. 83.10.102.254 ( talk) 10:35, 19 February 2009 (UTC)
I would like to opine that the title is wrong! The no hair "conjecture", or whatever you want to call it, is not a theorem. A theorem is something you prove. Once you prove it, it is true. The uniqueness theorems are theorems. The only stationary black hole solutions in electro-vacuum Einstein-Maxwell are the the Kerr-Newman class. That's a theorem. Read Heusler's book. You can't have counterexamples to theorems, you can only have examples that have different assumptions. The Einstein-Yang-Mills, Einstein non-minimally couple scalar field etc solutions are counterexamples to the no hair "conjecture" but don't violate the uniqueness theorems. Theorems don't fail by definition (unless someone made a booboo).-- Eujin16 ( talk) 02:01, 24 March 2008 (UTC)
This sentence makes no (or very little) sense, but I don't feel qualified to make any amends (First para):
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.
"The no-hair theorem postulates" - in my knowledge (and according to the New Oxford American Dictionary embedded in Mac OS X 10.6.7) a theorem is: "a truth established by means of accepted truths", i.e. a result of reasoning. A postulate is "a thing suggested or assumed as true as the basis for reasoning, discussion, or belief". Ouroboros just entered the building. I think "The no-hair theorem states" might be better wording. Sorry, it just bugged me. —Preceding unsigned comment added by 60.236.82.124 ( talk) 06:51, 7 May 2011 (UTC)
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)
I would say there's no problem. Uniqueness theorems have nothing to do with identifying microstates. If they did then the string theorists would be barking mad, which, well, make your own minds up.-- Eujin16 ( talk) 02:06, 24 March 2008 (UTC)
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)
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)
I thought it was from that book. Thanks. David618 15:39, 15 March 2006 (UTC)
The article used to source the name from JAW. For some reason this has been lost. Why? -- Michael C. Price talk 17:01, 19 February 2009 (UTC)
"Black holes have no hair." <-- What does this mean, exactly? Is 'hair' something like information?
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)
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)
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?
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).
http://arxiv.org/abs/gr-qc/0702006 "No hair theorems for positive $\Lambda$" which starts off:
seems to extend the non-hair theorem for black holes to universes which have a cosmological constant.-- Michael C. Price talk 02:11, 1 July 2007 (UTC)
http://arxiv.org/abs/gr-qc/9606008 "Eluding the No-Hair Conjecture for Black Holesstates"
which also seems relevant. -- Michael C. Price talk 02:19, 1 July 2007 (UTC)
Is this "black holes have no hair" statement related to the "hairy ball" observation? A "hairy ball" (e.g. the physiscist's standard spherical vacuum-racing hamster) cannot have all of the hair smoothed down perfectly flat. In at least two points (" boojums" if you'd like more physics-related neologisms) the hair must either come to either a radial point, or a point of extreme curl. As such points aren't observable from outside the event horizon, we can infer that there's no "hair" on a black hole, where this "hair" analogy can be extended to a number of forms of possible "texture" in its surface. Andy Dingley ( talk) 11:15, 15 April 2008 (UTC)
No. This conjecture is about a very different type of 'hair'. 130.237.201.40 ( talk) 14:12, 21 October 2008 (UTC)
Hmmm, "a very different type of 'hair'"? Is there no similarity between combing & frame-dragging? Does a 2-sphere black hole not have 2 frame-dragging "dead" spots whereas a 2-torus frame-drags everywhere? 86.135.127.147 ( talk) 04:25, 10 October 2010 (UTC)
Is the final word supposed to be 'isentropy' and not 'isotropy'? I thought we were talking about entropy, and not space... 128.171.31.11 ( talk) 02:27, 30 April 2008 (UTC)
Surely a hypothesis that the black hole is stationary should be included in the first sentence. I think a hypothesis that the space-time is real analytic is also necessary. 130.237.201.40 ( talk) 14:30, 21 October 2008 (UTC)
Misner, Thorne, & Wheeler (1973) says that although a series of theorems by Hawking, Carter, and Israel "come close" to proving it, it was not technically proven. Ludvigson (1999) says it's proven except for "details". Hall, Pulham (1996) regard it as proven and give an outline. Chow (2008) says it was proved by Carter, Hawking, Israel, Robinson, and Price. So I guess the article should say it's "regarded as proven"? -- Chetvorno TALK 08:10, 28 March 2010 (UTC)
In the book Recent Advances in General Relativity: Essays in Honour of Ted Newman (1992), Israel writes:
This source is twenty years old and I don't know if the status has changed. If it hasn't been properly proven, then it would be wrong to label this as a 'theorem'. Does anyone have up-to-date information on this matter? -- JB Gnome ( talk) 04:27, 20 January 2012 (UTC)
This is a long, uncited section, and it seems to me that it is mostly unrelated to the article topic. -- 192.75.48.150 ( talk) 15:51, 3 April 2013 (UTC)
The Example currently mentions two black holes with identical properties, except that one is made of ordinary matter, while the other is made of anti-matter. The example states that to an outside observer, the two holes are indistinguishable. Fine. If two such black holes were to collide, I imagine that the result would be different from a collision involving two black holes made of the same type of matter. In other words in the event of a collision, it would become clear if the two holes were or were not made of the same type of matter. Would it be possible to expand the explanation to briefly include the case of a collision of the two mentioned black holes ? Lklundin ( talk) 08:27, 6 April 2013 (UTC)
Is there any intuitive way of understanding why a magnetic moment is not possible? Given tthat a charge is possible, and that angular momentum is possible, plain-old gut sense suggests that a magnetic dipole moment should be possible. I can think of hand-waving arguments to banish higher-order magnetic moments, but not the dipole. But surely, there is a way to do this? 67.198.37.16 ( talk) 21:56, 30 July 2015 (UTC)
There's a new publication about "soft hair" on black holes retaining some of the information: [1]. Could someone with more knowledge of the subject than me please edit that in? 2A02:810D:14C0:5A0C:20B7:15AE:50A5:C945 ( talk) 21:06, 8 June 2016 (UTC)
References
I guess, the "theorem" conditions should state that it is limited to isolated black holes in equilibrium. Because, for example, when two black holes merge to form a single black hole, this non-stationary solution has more degrees of freedom than just the total mass, charge and angular momentum (see Binary black hole § Ringdown). Or when something falls into a black hole, it also breaks the BH symmetry and creates "ripples" on its event horizon (leading to radiation of gravitational waves as the BH equilibrates). — Mikhail Ryazanov ( talk) 05:00, 12 January 2020 (UTC)
The article explains the "results" of the theorem, ie what the theorem states, what the implications are. But what is the rationale behind the conjecture? How was it derived? For example "why" wouldn't it make a difference if the black hole was composed of matter or antimatter? Feldercarb ( talk) 01:04, 15 July 2022 (UTC)
If the black hole no longer has sufficient feed and radiates outward more energy than absorbed, it shrinks. This means that the event horizon is also shrinking, which in turn means that some information AKA 'hair' may yet be observed, if and when that information is stuck within the outer edge of the event horizon. This may constitute 'hair' and therefore shrinking black holes may yet not be (entirely) baldies.
More seriously, if we can find a black hole that is shrinking 'fast' and is nearing the minimum size of a black hole, then we may yet also experience/observe what the black hole is made of once it decompresses completely. At least we'd see how far a black hole can shrink before undergoing such decompression.
This
level-5 vital article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||
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Why is it called "no-hair" theorem or whatever? I can't find any information in the article about the origin of "no-hair" name. 83.10.102.254 ( talk) 10:35, 19 February 2009 (UTC)
I would like to opine that the title is wrong! The no hair "conjecture", or whatever you want to call it, is not a theorem. A theorem is something you prove. Once you prove it, it is true. The uniqueness theorems are theorems. The only stationary black hole solutions in electro-vacuum Einstein-Maxwell are the the Kerr-Newman class. That's a theorem. Read Heusler's book. You can't have counterexamples to theorems, you can only have examples that have different assumptions. The Einstein-Yang-Mills, Einstein non-minimally couple scalar field etc solutions are counterexamples to the no hair "conjecture" but don't violate the uniqueness theorems. Theorems don't fail by definition (unless someone made a booboo).-- Eujin16 ( talk) 02:01, 24 March 2008 (UTC)
This sentence makes no (or very little) sense, but I don't feel qualified to make any amends (First para):
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.
"The no-hair theorem postulates" - in my knowledge (and according to the New Oxford American Dictionary embedded in Mac OS X 10.6.7) a theorem is: "a truth established by means of accepted truths", i.e. a result of reasoning. A postulate is "a thing suggested or assumed as true as the basis for reasoning, discussion, or belief". Ouroboros just entered the building. I think "The no-hair theorem states" might be better wording. Sorry, it just bugged me. —Preceding unsigned comment added by 60.236.82.124 ( talk) 06:51, 7 May 2011 (UTC)
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)
I would say there's no problem. Uniqueness theorems have nothing to do with identifying microstates. If they did then the string theorists would be barking mad, which, well, make your own minds up.-- Eujin16 ( talk) 02:06, 24 March 2008 (UTC)
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)
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)
I thought it was from that book. Thanks. David618 15:39, 15 March 2006 (UTC)
The article used to source the name from JAW. For some reason this has been lost. Why? -- Michael C. Price talk 17:01, 19 February 2009 (UTC)
"Black holes have no hair." <-- What does this mean, exactly? Is 'hair' something like information?
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)
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)
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?
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).
http://arxiv.org/abs/gr-qc/0702006 "No hair theorems for positive $\Lambda$" which starts off:
seems to extend the non-hair theorem for black holes to universes which have a cosmological constant.-- Michael C. Price talk 02:11, 1 July 2007 (UTC)
http://arxiv.org/abs/gr-qc/9606008 "Eluding the No-Hair Conjecture for Black Holesstates"
which also seems relevant. -- Michael C. Price talk 02:19, 1 July 2007 (UTC)
Is this "black holes have no hair" statement related to the "hairy ball" observation? A "hairy ball" (e.g. the physiscist's standard spherical vacuum-racing hamster) cannot have all of the hair smoothed down perfectly flat. In at least two points (" boojums" if you'd like more physics-related neologisms) the hair must either come to either a radial point, or a point of extreme curl. As such points aren't observable from outside the event horizon, we can infer that there's no "hair" on a black hole, where this "hair" analogy can be extended to a number of forms of possible "texture" in its surface. Andy Dingley ( talk) 11:15, 15 April 2008 (UTC)
No. This conjecture is about a very different type of 'hair'. 130.237.201.40 ( talk) 14:12, 21 October 2008 (UTC)
Hmmm, "a very different type of 'hair'"? Is there no similarity between combing & frame-dragging? Does a 2-sphere black hole not have 2 frame-dragging "dead" spots whereas a 2-torus frame-drags everywhere? 86.135.127.147 ( talk) 04:25, 10 October 2010 (UTC)
Is the final word supposed to be 'isentropy' and not 'isotropy'? I thought we were talking about entropy, and not space... 128.171.31.11 ( talk) 02:27, 30 April 2008 (UTC)
Surely a hypothesis that the black hole is stationary should be included in the first sentence. I think a hypothesis that the space-time is real analytic is also necessary. 130.237.201.40 ( talk) 14:30, 21 October 2008 (UTC)
Misner, Thorne, & Wheeler (1973) says that although a series of theorems by Hawking, Carter, and Israel "come close" to proving it, it was not technically proven. Ludvigson (1999) says it's proven except for "details". Hall, Pulham (1996) regard it as proven and give an outline. Chow (2008) says it was proved by Carter, Hawking, Israel, Robinson, and Price. So I guess the article should say it's "regarded as proven"? -- Chetvorno TALK 08:10, 28 March 2010 (UTC)
In the book Recent Advances in General Relativity: Essays in Honour of Ted Newman (1992), Israel writes:
This source is twenty years old and I don't know if the status has changed. If it hasn't been properly proven, then it would be wrong to label this as a 'theorem'. Does anyone have up-to-date information on this matter? -- JB Gnome ( talk) 04:27, 20 January 2012 (UTC)
This is a long, uncited section, and it seems to me that it is mostly unrelated to the article topic. -- 192.75.48.150 ( talk) 15:51, 3 April 2013 (UTC)
The Example currently mentions two black holes with identical properties, except that one is made of ordinary matter, while the other is made of anti-matter. The example states that to an outside observer, the two holes are indistinguishable. Fine. If two such black holes were to collide, I imagine that the result would be different from a collision involving two black holes made of the same type of matter. In other words in the event of a collision, it would become clear if the two holes were or were not made of the same type of matter. Would it be possible to expand the explanation to briefly include the case of a collision of the two mentioned black holes ? Lklundin ( talk) 08:27, 6 April 2013 (UTC)
Is there any intuitive way of understanding why a magnetic moment is not possible? Given tthat a charge is possible, and that angular momentum is possible, plain-old gut sense suggests that a magnetic dipole moment should be possible. I can think of hand-waving arguments to banish higher-order magnetic moments, but not the dipole. But surely, there is a way to do this? 67.198.37.16 ( talk) 21:56, 30 July 2015 (UTC)
There's a new publication about "soft hair" on black holes retaining some of the information: [1]. Could someone with more knowledge of the subject than me please edit that in? 2A02:810D:14C0:5A0C:20B7:15AE:50A5:C945 ( talk) 21:06, 8 June 2016 (UTC)
References
I guess, the "theorem" conditions should state that it is limited to isolated black holes in equilibrium. Because, for example, when two black holes merge to form a single black hole, this non-stationary solution has more degrees of freedom than just the total mass, charge and angular momentum (see Binary black hole § Ringdown). Or when something falls into a black hole, it also breaks the BH symmetry and creates "ripples" on its event horizon (leading to radiation of gravitational waves as the BH equilibrates). — Mikhail Ryazanov ( talk) 05:00, 12 January 2020 (UTC)
The article explains the "results" of the theorem, ie what the theorem states, what the implications are. But what is the rationale behind the conjecture? How was it derived? For example "why" wouldn't it make a difference if the black hole was composed of matter or antimatter? Feldercarb ( talk) 01:04, 15 July 2022 (UTC)
If the black hole no longer has sufficient feed and radiates outward more energy than absorbed, it shrinks. This means that the event horizon is also shrinking, which in turn means that some information AKA 'hair' may yet be observed, if and when that information is stuck within the outer edge of the event horizon. This may constitute 'hair' and therefore shrinking black holes may yet not be (entirely) baldies.
More seriously, if we can find a black hole that is shrinking 'fast' and is nearing the minimum size of a black hole, then we may yet also experience/observe what the black hole is made of once it decompresses completely. At least we'd see how far a black hole can shrink before undergoing such decompression.