REVIEW
Universal Entropy and Hawking Radiation of Near-Extremal AdS$_4$ Black Holes
High Energy Physics - Theory · Submitted 25 Sep 2020 · 73 references
Pith's verdict: The two gravity-side derivations match and are worth reporting; the boundary-ABJM match is normalized by fiat, so the three-way universality claim is overstated.
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Referee report
The paper
The paper claims
The paper argues that near-extremal electrically charged rotating AdS4 black holes obey one universal entropy formula, S = S* + (C/TH)*TH, reproduced exactly by gravity, the near-horizon Kerr/CFT correspondence, and ABJM microstate…
The reading
What carries the argument
The load-bearing identity is the linear near-extremal expansion S = S* + (C/TH)*TH, where the ratio (C/TH)* = (dS/dTH)* is evaluated in the BPS limit and is the single quantity all three methods must reproduce. The argument is carried by the near-horizon geometry obtained through the Bardeen-Horowitz scaling, a circle fibration over AdS2 whose asymptotic symmetry algebra yields the Kerr/CFT central charges and whose hidden conformal symmetry fixes the Frolov-Thorne temperatures. On the field-theory side, the boundary computation uses the ABJM entropy function, a quartic equation for a Lagrange multiplier Λ whose imaginary root gives the BPS entropy; the near-extremal correction comes from perturbing that equation, with the temperature dependence entering through the relation 2πiδTH = 2η.
Extended reading notes
Core claim
The paper's central discovery is a universal near-extremal entropy formula for electrically charged rotating AdS4 black holes in the equal-charge sector δ1 = δ2: S_BH = S* + (C/TH)*TH with S* = 2π $g^{{-2}}$($e^{{4δ1}}$-3) and (C/TH)* = 8√2 $π^{2}$($e^{{4δ1}}$-1)^{3/2}[$g^{3}$($e^{{4δ1}}$-3)($e^{{8δ1}}$+$10e^{{4δ1}}$-7)]^{-1}. The same expression is obtained from the gravity-side expansion, from a Kerr/CFT Cardy computation in which the left and right central charges are equal, c_L = c_R = 24√2($e^{{4δ1}}$-1)[$g^{2}$($e^{{8δ1}}$+$10e^{{4δ1}}$-7)]^{-1}, with the right Frolov-Thorne temperature proportional to TH, and from perturbing the ABJM entropy function. The authors take the equality as evidence that a near-horizon CFT2 describes these black holes, and they derive a Hawking radiation rate from the right sector proportional to the horizon area times the Planckian factor $e^{{-k0/TR}}$/(1-$e^{{-k0/TR}}$), which they argue is unitary.
Load-bearing premise
The load-bearing premise is that the boundary ABJM calculation may assume a fixed proportionality between its perturbation parameter and the gravitational change in Hawking temperature; if the ABJM theory does not determine that normalization on its own, the exact match between the boundary computation and the two gravity-side computations is partly engineered.
Editorial extensions
If this is right
- If the three-way match is right, the near-extremal entropy of these black holes is determined by BPS data plus one temperature, with no new free parameters in the leading correction.
- The Kerr/CFT correspondence, originally formulated for extremal black holes, applies to near-extremal AdS4 black holes, with equal left and right central charges and a right temperature proportional to the Hawking temperature.
- Hawking radiation from near-extremal AdS4 black holes has a microscopic description as emission from the right-moving sector of the near-horizon CFT2, with a thermal spectrum and a rate proportional to the horizon area.
- The universal picture that held for BPS AdS black holes now extends to near-extremal ones, supporting the existence of a near-horizon CFT2 for a broader class of AdS black holes.
- The boundary ABJM microstate count fixes the near-extremal heat capacity, so the temperature correction is a genuine microstate prediction and not only a gravity-side fit.
Reading between the lines
- If the universal formula is right, the leading near-extremal correction is fixed by BPS data alone, so any independent microscopic model that reproduces the BPS entropy will automatically reproduce the temperature correction without extra input.
- Computing the O(TH^2) term in the ABJM perturbed entropy function would test whether the universality extends beyond the linear approximation or whether the three-way match is a leading-order coincidence.
- Deriving the relation between the CFT perturbation parameter and δTH from the ABJM partition function itself would convert the three-way match into a parameter-free prediction; until then, the boundary computation carries one undetermined normalization.
- The same near-extremal expansion should apply to AdS5, AdS6 and AdS7 near-BPS black holes, and the AdS4 case is the clearest place to check whether the outer-horizon radius alone fixes (C/TH)*.
Original abstract
We compute the Bekenstein-Hawking entropy of near-extremal asymptotically AdS$_4$ electrically charged rotating black holes using three different methods: (i) from the gravity solution, (ii) from the near-horizon Kerr/CFT correspondence and (iii) from the boundary conformal field theory. The results from these three different approaches match exactly, giving us a unique and universal expression for the entropy and the microstate counting of near-extremal AdS black holes via the AdS/CFT correspondence. In the second method, we extend the Kerr/CFT correspondence to the near-extremal case to compute the left and right central charges. We also use hidden conformal symmetry of the near-horizon geometry to compute the Frolov-Thorne temperatures. From the results of the near-extremal AdS$_4$ black hole entropy, we provide a microscopic foundation for Hawking radiation.
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 compute the Bekenstein-Hawking entropy of near-extremal asymptotically AdS$_4$ electrically charged rotating black holes using three different methods: (i) from the gravity solution, (ii) from the near-horizon Kerr/CFT correspondence and (iii) from the boundary conformal field theory. The results from these three different approaches match exactly, giving us a unique and universal expression for the entropy and the microstate counting of near-extremal AdS black holes via the AdS/CFT correspondence. In the second method, we extend the Kerr/CFT correspondence to the near-extremal case to compute the left and right central charges. We also use hidden conformal symmetry of the near-horizon geometry to compute the Frolov-Thorne temperatures. From the results of the near-extremal AdS$_4$ black hole entropy, we provide a microscopic foundation for Hawking radiation.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We compute the Bekenstein-Hawking entropy of near-extremal asymptotically AdS$_4$ electrically charged rotating black holes using three different methods: (i) from the gravity solution, (ii) from the near-horizon Kerr/CFT correspondence and (iii) from the boundary conformal field theory. | contribution 0.67 | 0.96 | 0.08 | asserted 1.00 |
| s1 | The results from these three different approaches match exactly, giving us a unique and universal expression for the entropy and the microstate counting of near-extremal AdS black holes via the AdS/CFT correspondence. | result 0.96 | 0.94 | 0.87 | asserted 1.00 |
| s2 | In the second method, we extend the Kerr/CFT correspondence to the near-extremal case to compute the left and right central charges. | method 0.93 | 0.95 | 0.04 | asserted 1.00 |
| s3 | We also use hidden conformal symmetry of the near-horizon geometry to compute the Frolov-Thorne temperatures. | method 0.98 | 0.94 | 0.03 | asserted 1.00 |
| s4 | From the results of the near-extremal AdS$_4$ black hole entropy, we provide a microscopic foundation for Hawking radiation. | interpretation 0.80 | 0.90 | 0.19 | asserted 1.00 |
What was examined, and what was not
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References
How the literature uses it
15 arXiv papers cite this in 23 sentences
Papers citing it · 17 sentences without a confident label
Uses its method or tool 1 paper
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Based on the analyses in [ref] , the quantum temperature $T_q$ can be estimated using the heat capacity of the AdS$_4$ black hole (or black brane).
Quantum Corrections to Holographic Strange Metal at Low Temperature · A sweet spot scenario for quantum corrections · 0.82
Compares with it 1 paper
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This quantity is extracted from the classical heat capacity and agrees (in the $δ_1=δ_2=δ≠0$ limit) with the expression presented in [ref] .
Universality in Logarithmic Temperature Corrections to Near-Extremal Rotating Black Hole Thermodynamics in Various Dimensions · Lichnerowicz operator and the zero modes · 0.97
Cites it as background 4 papers
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The temperature dependence is then shown to be controlled by a specific mode in the metric described by (super)JT gravity [Other papers studying different aspects regarding the connection of JT gravity and near extremal black holes are [ref] .].
Revisiting the Logarithmic Corrections to the Black Hole Entropy · Introduction · 0.93
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[An incomplete subset of relevant references in both gravity and field theory sides is [ref] [ref] [ref] [ref] [ref] [ref] [ref] [ref] , [ref] .
From multi-gravitons to Black holes: The role of complex saddles · Introduction and summary · 0.92
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For example, Davida and Nian [ref] investigated the universal entropy and Hawking radiation of near-extremal $AdS_4$ black holes.
The emergence of universal relations in the AdS black holes thermodynamics · Literature Survey and Motivation · 0.89
What it cites · 78 sentences without a confident label
Contests 4 papers
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The two conditions [ref] and [ref] in [ref] contain typos, which have been corrected in [ref] and also [ref] .
Dyonic AdS black holes in maximal gauged supergravity · AdS$_4$ Black Hole Solution · contest 0.85
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The two conditions [ref] and [ref] in [ref] contain typos, which have been corrected in [ref] and also [ref] .
Entropy functions of BPS black holes in AdS$_4$ and AdS$_6$ · AdS$_4$ Black Hole Solution · contest 0.85
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The two conditions [ref] and [ref] in [ref] contain typos, which have been corrected in [ref] and also [ref] .
The BPS limit of rotating AdS black hole thermodynamics · AdS$_4$ Black Hole Solution · contest 0.85
Builds on 6 papers
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Therefore, our results use a concrete example to support the existence of a near-horizon CFT$_2$, which accounts for the black hole entropy, and show that the Kerr/CFT correspondence [ref] , which was originally applied only to extremal black holes, can also be extended to the near-extremal black holes.
The Kerr/CFT Correspondence · Introduction · 0.93
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Therefore, our results use a concrete example to support the existence of a near-horizon CFT$_2$, which accounts for the black hole entropy, and show that the Kerr/CFT correspondence [ref] , which was originally applied only to extremal black holes, can also be extended to the near-extremal black holes.
Kerr-AdS/CFT Correspondence in Diverse Dimensions · Introduction · 0.93
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Therefore, our results use a concrete example to support the existence of a near-horizon CFT$_2$, which accounts for the black hole entropy, and show that the Kerr/CFT correspondence [ref] , which was originally applied only to extremal black holes, can also be extended to the near-extremal black holes.
Extremal Black Hole/CFT Correspondence in (Gauged) Supergravities · Introduction · 0.93
Uses the method or tool of 10 papers
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For the first method, the central charge can be computed using the following integral [ref] 1/8 πG ∫_∂Σ k_ζ_(m) [ℒ_ζ_(n) g, g] = - i/12 c_L (m^3 + αm) δ_m+n, 0 , where $g$ denotes the near-horizon metric of the near-extremal AdS$_4$ black hole in global coordinates [ref].
The Kerr/CFT Correspondence · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.87
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For the first method, the central charge can be computed using the following integral [ref] 1/8 πG ∫_∂Σ k_ζ_(m) [ℒ_ζ_(n) g, g] = - i/12 c_L (m^3 + αm) δ_m+n, 0 , where $g$ denotes the near-horizon metric of the near-extremal AdS$_4$ black hole in global coordinates [ref].
Kerr-AdS/CFT Correspondence in Diverse Dimensions · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.87
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For the first method, the central charge can be computed using the following integral [ref] 1/8 πG ∫_∂Σ k_ζ_(m) [ℒ_ζ_(n) g, g] = - i/12 c_L (m^3 + αm) δ_m+n, 0 , where $g$ denotes the near-horizon metric of the near-extremal AdS$_4$ black hole in global coordinates [ref].
Extremal Black Hole/CFT Correspondence in (Gauged) Supergravities · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.87
Uses data or values from 1 paper
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We have seen in [ref] that for the BPS case $T_R = 0$.
Gravitational Cardy Limit and AdS Black Hole Entropy · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.83
Compares with 9 papers
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However, the supersymmetric solutions considered [ref] have $1/2$-BPS supersymmetry instead of $1/4$-BPS supersymmetry discussed in [ref] , which makes some features of the black holes different.
Charged Rotating Black Holes in Four-Dimensional Gauged and Ungauged Supergravities · AdS$_4$ Black Hole Solution · 0.97
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However, the supersymmetric solutions considered [ref] have $1/2$-BPS supersymmetry instead of $1/4$-BPS supersymmetry discussed in [ref] , which makes some features of the black holes different.
Thermodynamics of Kerr-Newman-AdS Black Holes and Conformal Field Theories · AdS$_4$ Black Hole Solution · 0.97
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However, the supersymmetric solutions considered [ref] have $1/2$-BPS supersymmetry instead of $1/4$-BPS supersymmetry discussed in [ref] , which makes some features of the black holes different.
Rotating Black Holes in Gauged Supergravities; Thermodynamics, Supersymmetric Limits, Topological Solitons and Time Machines · AdS$_4$ Black Hole Solution · 0.97
Cites as background 25 papers
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The Kerr/CFT correspondence was originally posed for asymptotically flat extremal Kerr black holes [ref] and was later shown to also be valid for asymptotically AdS black holes [ref] .
The Kerr/CFT Correspondence · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.96
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The Kerr/CFT correspondence was originally posed for asymptotically flat extremal Kerr black holes [ref] and was later shown to also be valid for asymptotically AdS black holes [ref] .
Kerr-AdS/CFT Correspondence in Diverse Dimensions · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.96
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The Kerr/CFT correspondence was originally posed for asymptotically flat extremal Kerr black holes [ref] and was later shown to also be valid for asymptotically AdS black holes [ref] .
Extremal Black Hole/CFT Correspondence in (Gauged) Supergravities · Near-Extremal AdS$_4$ Black Hole Entropy from Cardy Formula · 0.96
Discussion
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