REVIEW
Black holes with unusual topology
General Relativity and Quantum Cosmology · Submitted 5 May 1997 · 41 references
Pith's verdict: A careful, honest thermodynamics paper: the S = A/4 fix for higher-genus AdS black holes is real but rests on a background choice the paper argues for rather than derives.
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Referee report
The paper
The paper claims
Black holes in anti-de Sitter space can have horizons shaped like tori or higher-genus Riemann surfaces, and their thermodynamics becomes well behaved — positive mass, entropy equal to one quarter the horizon area — once the zero of energy,
The reading
What carries the argument
The load-bearing object is the lapse function $V=kappa-k'/r+r^2/ell^2$, which satisfies $R_{ab}=Lambda g_{ab}$ with $Lambda=-3ell^{-2}$ for any constant-curvature two-metric $sigma_{ij}$ with $R_{ij}=kappa,sigma_{ij}$. Rescaling sets $kappa=-1$ for $g>1$ and $kappa=0$ for the torus, giving $V=-1-2eta/r+r^2/ell^2$ and $V=-2eta/r+r^2/ell^2$ respectively, with the horizon at the positive root $r_+$. The temperature comes from requiring the Euclidean section to close smoothly at $r_+$: $beta_+=4piell^2 r_+/(3r_+^2-ell^2)$ for $g>1$ and $beta_+=4piell^2/(3r_+)$ for the torus. The mass comes from the Hamiltonian boundary term $-frac{1}{8pi}int_{S_g}sqrt{V}(Theta-Theta_0),r^2sqrt{sigma},d^2x$ evaluated at large radius, which forces the background to carry the same genus as the solution. The entropy comes from the off-shell Euclidean action with the Gauss-Bonnet conical-defect contribution $frac{A}{16pi}frac{beta_+}{beta}(beta_+-beta)$ for both solution and background.
Extended reading notes
Core claim
The central claim is that the whole family of topological anti-de Sitter black holes, from the torus up through every genus, forms a thermodynamically consistent sequence once the reference background used to define energy is chosen to be the extreme solution with $eta_0=-ell/(3sqrt{3})$ (equivalently $r_0=r_c=ell/sqrt{3}$). The mass formula $M=(eta-eta_0)(g-1)+eta|mathrm{Im},tau|,delta(g,1)/(4pi)$ ties the mass to the horizon geometry, the first law $dM=kappa,dA/8pi$ holds for every genus, and the off-shell Euclidean action $I=beta M-A/4+[1-delta(r_0,r_c)]A_0/4$ reproduces both the mean energy and the entropy. With the extreme background the indicator factor $[1-delta(r_0,r_c)]$ switches off, the conical contribution of the background disappears, and the entropy reduces to exactly one quarter of the horizon area, $S=A/4-pi r_0^2(g-1)[1-delta(r_0,r_c)]$. The author reads this as evidence that the negative-mass and negative-entropy branches found under the other subtraction were an artifact of the wrong zero of energy, and that the third law of thermodynamics lines up with the third law of black hole mechanics: the zero-temperature state is the extreme solution, which is a naked singularity rather than a black hole.
Load-bearing premise
The argument rests on treating the extreme solution — the one whose Euclidean section stays regular at any imaginary-time period — as the physically correct zero of energy, a choice the paper defends by regularity and by the disappearance of a negative entropy term rather than by deriving it from the dynamics; the author concedes there is freedom in where the zero of energy is placed.
Editorial extensions
If this is right
- For every genus $g$, the first law $dM=kappa,dA/8pi$ holds in vacuum, and the mass is a monotonically increasing function of temperature, so the specific heat is positive and the canonical ensemble is stable.
- The toroidal black hole has $r_+=(8piell^2M/|mathrm{Im},tau|)^{1/3}$, so its size is set by the mass and the torus's conformal class rather than by the cosmological constant; small toroidal black holes can exist at any mass.
- Higher-genus black holes have no small-mass limit: their minimum size is of order $ell$, so they are cosmological objects that could only have existed when the cosmological constant was large.
- The density of states grows as $rho(E)simexp(C_1E^{2/3})$ with exponent fixed by $A/4$, matching the behaviour of a massless gas in two spatial dimensions.
- The genus, and for the torus the Teichmüller parameter $tau$, enter the metric as free non-dynamical parameters, so the spectrum contains disconnected sectors labelled by horizon topology.
Reading between the lines
- If the entropy really is $A/4$ independent of subtraction, then the negative-entropy branch is a diagnostic of a bad reference frame rather than a physical instability, which suggests a general rule: any candidate zero of energy whose Euclidean section is not regular at arbitrary period should be suspect in anti-de Sitter thermodynamics.
- The genus label behaving as a fixed external parameter is the sharpest loose end; a path-integral treatment that sums over horizon topologies would turn it into a dynamical variable and could in principle allow transitions between genus sectors, which the paper explicitly says it cannot rule out.
- The same subtraction ambiguity should show up in the charged topological black holes, where an inner horizon gives a second natural candidate for the zero of energy; checking whether the extreme charged solution plays the same regularizing role would test whether the mechanism is about extremality rather than about this particular uncharged family.
- Because the toroidal solution survives in a nearly flat universe while higher-genus ones do not, the observable content of this family is concentrated in the $g=1$ case, which makes the torus's conformal class the one free parameter worth asking about physically.
Original abstract
The Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. Hence there is no fundamental reason that black hole's horizons should have spherical topology. In anti-de Sitter space the Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus $g$. The case $g=0$ is the asymptotically anti-de Sitter black hole first studied by Hawking-Page, which has spherical topology. The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. The genus $g>1$ black hole has no other free parameters apart from the mass and the charge. All such black holes exhibits a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite.
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
The Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. Hence there is no fundamental reason that black hole's horizons should have spherical topology. In anti-de Sitter space the Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus $g$. The case $g=0$ is the asymptotically anti-de Sitter black hole first studied by Hawking-Page, which has spherical topology. The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. The genus $g>1$ black hole has no other free parameters apart from the mass and the charge. All such black holes exhibits a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The Einstein's equations with a negative cosmological constant admit solutions which are asymptotically anti-de Sitter space. | background 1.00 | 0.06 | 0.04 | asserted 0.99 |
| s1 | Matter fields in anti-de Sitter space can be in stable equilibrium even if the potential energy is unbounded from below, violating the weak energy condition. | background 0.87 | 0.13 | 0.07 | asserted 0.86 |
| s2 | Hence there is no fundamental reason that black hole's horizons should have spherical topology. | interpretation 0.79 | 0.16 | 0.47 | asserted 0.94 |
| s3 | In anti-de Sitter space the Einstein's equations admit black hole solutions where the horizon can be a Riemann surface with genus $g$. | result 0.59 | 0.48 | 0.47 | asserted 0.98 |
| s4 | The case $g=0$ is the asymptotically anti-de Sitter black hole first studied by Hawking-Page, which has spherical topology. | background 0.98 | 0.06 | 0.06 | asserted 1.00 |
| s5 | The genus one black hole has a new free parameter entering the metric, the conformal class to which the torus belongs. | result 0.88 | 0.63 | 0.06 | asserted 1.00 |
| s6 | The genus $g>1$ black hole has no other free parameters apart from the mass and the charge. | result 0.93 | 0.66 | 0.10 | asserted 1.00 |
| s7 | All such black holes exhibits a natural temperature which is identified as the period of the Euclidean continuation and there is a mass formula connecting the mass with the surface gravity and the horizon area of the black hole. | result 0.95 | 0.68 | 0.17 | asserted 1.00 |
| s8 | The Euclidean action and entropy are computed and used to argue that the mass spectrum of states is positive definite. | result 0.84 | 0.85 | 0.21 | asserted 0.98 |
What was examined, and what was not
- arXiv listing abstract v3
- full text
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- references and citing sentences
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References
How later papers used it
71 later papers cite it
3 later papers by other authors are listed below: 1 used its method or tool and 2 cited it as support.
Uses its method or tool 1 paper
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Used the standard ADM result, as in this paper, to compute the mass.
Black hole and BTZ-black string in the Einstein-SU(2) Skyrme model (2018) · 0.96 · paraphrased: the licence does not allow quoting
Cites it as support 2 papers
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Said that this supports the consideration of some of these extremal solutions as groundstates, citing this paper.
Cosmic censorship in Lovelock theory (2013) · 0.98 · paraphrased: the licence does not allow quoting
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Said that this supports the consideration of some of these extremal solutions as groundstates, citing this paper.
Lovelock gravity, black holes and holography (2015) · 0.99 · paraphrased: the licence does not allow quoting
How the literature uses it
65 arXiv papers cite this in 99 sentences
Papers citing it · 51 sentences without a confident label
Builds on it 1 paper
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Les trous noirs topologiques rencontr�s � la sous-section [ref] en dimension $D=4$ [ref] se g�n�ralisent facilement en dimension $D ≥4$ [ref] .
Black hole solutions of modified gravity theories · La solution de Tangherlini et ses versions topologiques · 0.87
Uses its data or values 1 paper
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The Hawking temperature of the MTBH is equal to [ref] – [ref] [equation] and from the QNF ([ref]) of the massless Dirac field we find [equation] We see that the first expression in formulas ([ref]) saturates the inequality ([ref]) and that the second expression does not satisfy the previously mentioned inequality.
Quasinormal frequencies of the Dirac field in the massless topological black hole · Hod's bound · 0.89
Compares with it 1 paper
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We also note from ([ref]) and ([ref]) that the mass becomes negative at zero temperature [equation] This is somewhat similar to the AdS-Schwarzschild with negative curvature horizon [ref] .
Dissipative force on an external quark in heavy quark cloud · Introduction · 0.87
Cites it as support 1 paper
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This supports the consideration of some of these extremal solutions as groundstates [ref] .
Cosmic censorship in Lovelock theory · The puzzle of multi horizon black holes · 0.98
Cites it as background 38 papers
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The general Schwarzschild-anti-de Sitter metric ansatz we will study is [equation] where $dΣ_k^2$ is a metric on a locally homogeneous three-dimensional surface of constant curvature $k$ ($k=+1$, $k=0$, and $k=-1$ correspond to three-dimensional sphere, flat, and hyperboloid, respectively) [ref] .
Probing extra dimension through gravitational wave observations of compact binaries and their electromagnetic counterparts · Null geodesics in five-dimensional AdS space-time · 0.87
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These black holes are known as topological black holes [ref] .
Hawking Radiation via Gravitational Anomalies in Non-spherical Topologies · Mode Analysis of the Wave Equation of a Scalar Field in the Background of a TBH · 0.91
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For the uncharged topological black holes of Einstein's theory the first law of the thermodynamics reads [ref] – [ref] [equation] where $M$ stands for the mass of the black hole, $κ$ denotes the surface gravity of the event horizon, and $A$ stands for the horizon area.
Entropy spectrum of the D-dimensional massless topological black hole · Introduction · 0.82
Discussion
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