REVIEW
Black holes and asymptotics of 2+1 gravity coupled to a scalar field
High Energy Physics - Theory · Submitted 22 Jan 2002 · 17 references
Pith's verdict: The asymptotic analysis and the hairy black hole family are solid and worth engaging; the printed temperature in (3.5) is wrong by a factor of Θ_ν², and the algebra argument is terse but the standard c-number logic holds.
T0 · AI review
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Referee report
The paper
The paper claims
Three-dimensional gravity with a negative cosmological constant keeps its conformal asymptotic symmetry, and its central charge, even when a scalar field reaches infinity too slowly to count as localized matter.
The reading
What carries the argument
Two pieces of machinery carry the argument. The first is the divergence cancellation between gravitational and scalar contributions to the canonical charge, computed with the Regge-Teitelboim surface-integral method: because the leading correction to $gives$ is tied to the scalar's leading coefficient $gives$, the $O(r)$ pieces of $gives$ and $gives$ cancel and leave a finite charge. The second is a conformal-frame construction: the potential family $gives$ is obtained by the rescaling $gives$ with $gives$ and $gives$ from an action whose matter part is conformally invariant for every value of the parameter $gives$, which is what makes the exact hairy solutions tractable. The horizon radius is read off as the first zero of the Schuster function $gives$, and consistency of the boundary conditions with the field equations is claimed to force the potential into the form $gives$ with $gives$ an arbitrary smooth function.
Extended reading notes
Core claim
The paper's central claim is that the asymptotic conditions $gives$, $gives$ and $gives$ — in which the radial metric component falls off one power of $r$ more slowly than in pure gravity — are left invariant by exactly the same asymptotic Killing vectors that generate the conformal group in the vacuum theory. The reason the symmetry survives is a cancellation: the variation of the scalar charge $gives$ contains a term linear in $r$ that would diverge, and it is cancelled by a divergent piece of the gravitational charge $gives$ precisely because, to leading order, $gives$. The total charge $gives$ is then finite, and the algebra of canonical generators is stated to be two copies of the Virasoro algebra with the same central extension as in pure gravity, since the vacuum is taken to be the standard massless black hole and the central-charge computation is therefore identical. On top of this, the authors exhibit exact black hole solutions with regular scalar hair for the potential family $gives$, with horizon at $gives$, mass $gives$, temperature $gives$, and entropy $S = A/4$; the specific heat equals the entropy, exactly as for the standard black hole. The authors themselves flag one loose end: applying Cardy's formula to the unchanged central charge would give an entropy larger than $A/4$ for $gives$, which they leave unresolved.
Load-bearing premise
The central-charge argument assumes that the reference configuration for this slower-falloff class is the standard massless black hole with vanishing scalar field, even though the same class also contains the $gives$ metric that the paper itself calls a degenerate ground state, and the paper does not show that these two are the same state or that the central charge is independent of which one is used as the reference.
Editorial extensions
If this is right
- The Brown-Henneaux central charge $c = 3l/2G$ applies to a boundary-condition class in which the matter stress tensor does not vanish at infinity, so the correspondence between 2+1 gravity and a boundary conformal theory is not restricted to localized matter.
- For every $gives$ there is an explicit hairy black hole with $gives$, $gives$ and $gives$, so the thermodynamic identities of the standard black hole carry over to the dressed solutions unchanged, including the equality of specific heat and entropy.
- Because there is only one integration constant $B$, fixing the mass fixes the scalar profile: the scalar cannot be switched off at fixed mass, so each mass admits two distinct black holes, one with $gives$ and one with nontrivial hair.
- The limit $gives$ gives a configuration of vanishing mass, temperature and entropy, which the paper treats as a degenerate ground state continuously connected to the rest of the family.
- Consistency of the asymptotic conditions with the field equations restricts the admissible self-interactions to the family $gives$, so only a specific class of scalar potentials supports this slow-falloff behavior.
Reading between the lines
- If the central charge really is a property of the asymptotic class rather than of the chosen reference configuration, the same argument should extend to other matter that reaches the boundary slowly, such as gauge fields with logarithmic falloff or dilatonic couplings, which would turn this into a general statement about non-normalizable matter in AdS$_3$.
- The acknowledged mismatch between Cardy counting and the area law may be a signal that the Cardy formula should be applied to the $gives$ configuration rather than the standard massless black hole, or with a shifted zero-point energy; checking which choice reproduces $S = A/4$ would identify the state the boundary theory actually counts.
- The paper's charge formula already carries a rotational term $gives$, so a rotating generalization of the hairy family is a natural next check; if rotation preserves the same central extension, the robustness claim is strengthened considerably.
- Because $gives$ interpolates between a previously known solution at $gives$ and the degenerate ground state at $gives$, the family looks like a continuous deformation of the dual theory, which could be probed by computing quasi-normal mode frequencies as a function of $gives$.
Original abstract
We consider 2+1 gravity minimally coupled to a self-interacting scalar field. The case in which the fall-off of the fields at infinity is slower than that of a localized distribution of matter is analyzed. It is found that the asymptotic symmetry group remains the same as in pure gravity (i.e., the conformal group). The generators of the asymptotic symmetries, however, acquire a contribution from the scalar field, but the algebra of the canonical generators possesses the standard central extension. In this context, new massive black hole solutions with a regular scalar field are found for a one-parameter family of potentials. These black holes are continuously connected to the standard zero mass black hole.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We consider 2+1 gravity minimally coupled to a self-interacting scalar field. The case in which the fall-off of the fields at infinity is slower than that of a localized distribution of matter is analyzed. It is found that the asymptotic symmetry group remains the same as in pure gravity (i.e., the conformal group). The generators of the asymptotic symmetries, however, acquire a contribution from the scalar field, but the algebra of the canonical generators possesses the standard central extension. In this context, new massive black hole solutions with a regular scalar field are found for a one-parameter family of potentials. These black holes are continuously connected to the standard zero mass black hole.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We consider 2+1 gravity minimally coupled to a self-interacting scalar field. | contribution 0.57 | 0.66 | 0.03 | asserted 0.89 |
| s1 | The case in which the fall-off of the fields at infinity is slower than that of a localized distribution of matter is analyzed. | contribution 0.90 | 0.63 | 0.04 | asserted 0.86 |
| s2 | It is found that the asymptotic symmetry group remains the same as in pure gravity (i.e., the conformal group). | result 1.00 | 0.91 | 0.28 | asserted 1.00 |
| s3 | The generators of the asymptotic symmetries, however, acquire a contribution from the scalar field, but the algebra of the canonical generators possesses the standard central extension. | result 1.00 | 0.90 | 0.22 | asserted 1.00 |
| s4 | In this context, new massive black hole solutions with a regular scalar field are found for a one-parameter family of potentials. | result 0.98 | 0.96 | 0.31 | asserted 1.00 |
| s5 | These black holes are continuously connected to the standard zero mass black hole. | result 0.98 | 0.86 | 0.14 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v2
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Figures
Figures reproduced from arXiv:hep-th/0201170 by the authors.
References
How the literature uses it
47 arXiv papers cite this in 96 sentences
Papers citing it · 66 sentences without a confident label
Builds on it 1 paper
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Thus, if one considers the static hairy black hole of Ref. [ref] [equation] which has the same scalar field given in ([ref]), and performs the following boost [equation] where the constant $ω$ is restricted to satisfy $ω^2<1$, one directly obtains the rotating hairy solution described by Eqs. ([ref])-([ref]).
Rotating hairy black hole and its microscopic entropy in three spacetime dimensions · Rotating hairy scalar black hole in three dimensions · 0.95
Uses its method or tool 1 paper
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In fact, by using Eq. (22) of Ref. [ref] (see also [ref] and [ref] ) the mass $M$ and the angular momentum $J$ of the hairy black hole described by Eqs. ([ref])-([ref]) are found to be [equation] which depend on the integration constants $B$ and $ω$.
Rotating hairy black hole and its microscopic entropy in three spacetime dimensions · Mass, angular momentum and thermodynamics · 0.85
Compares with it 3 papers
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The class of hairy black holes found here was shown to have positive mass and it can be seen that they share many of the features with the one previously found in [ref] .
Hairy black hole entropy and the role of solitons in three dimensions · Microscopic entropy of hairy black holes: Soliton mass and its role in the asymptotic growth of the number of states. · 0.96
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A similar behavior has been observed in a setup leading to relaxed AdS boundary conditions due to a slowly decaying scalar field at infinity [ref] .
New boundary conditions in Einstein-scalar gravity in three dimensions · Surface charges · 0.93
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It is worth pointing out that a similar effect occurs in the case of hairy black holes with scalar fields with slow fall-off at infinity [ref] .
Higher spin gravity in 3D: black holes, global charges and thermodynamics · Introduction · 0.93
Cites it as background 23 papers
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The first analytic example of a black hole solution endowed with minimally coupled scalar hair was found in [ref] , precisely for the self-interaction under discussion [ref] in the case of $Λ<0$ and $ν≥-1$.
Gravity coupled to a scalar field from a Chern-Simons action: describing rotating hairy black holes and solitons with gauge fields · Rotating hairy black hole · 0.81
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The entropy of static hairy scalar black holes has been computed, by means of Cardy formula, in the case of potentials defined by one [ref] and two coupling constants [ref] .
Rotating hairy black hole and its microscopic entropy in three spacetime dimensions · Introduction · 0.81
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On the other hand, there exists a black hole solution to three-dimensional gravity with a minimally coupled self-interacting scalar, called the scalar black hole (SBH) [ref] .
Phase transition for black holes with scalar hair and topological black holes · Introduction · 0.94
Discussion
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