REVIEW
Entropy of Lovelock Black Holes
High Energy Physics - Theory · Submitted 6 May 1993 · 29 references
Pith's verdict: The standard derivation of Lovelock black hole entropy: a general intrinsic-curvature formula from the Hamiltonian first law, with the Killing-horizon assumption openly flagged.
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Referee report
The paper
The paper claims
In Lovelock gravity, black hole entropy is not one quarter of the horizon area but a sum of curvature invariants integrated over the horizon.
The reading
What carries the argument
The load-bearing device is the Hamiltonian boundary term evaluated at the bifurcation surface. The authors take the Sudarsky–Wald method: for a stationary solution, evolve along the Killing field $t^a = chi^a$ that is null on the horizon, so the volume term of Hamilton's equations drops out because the Lie derivatives of the metric and momentum vanish. What survives is a surface term $delta H_B$ at the inner boundary, the bifurcation surface $B$ where $chi^a$ vanishes and whose extrinsic curvature vanishes. Varying the curvature in the constraint $H_{(m) perp}$ produces, after two integrations by parts, a boundary integral containing $D_a N$; at $B$ this equals $kappa v_a$, so the surface gravity factors out and the antisymmetrized Kronecker deltas project everything into $B$. The projected curvature is then the intrinsic curvature of the $(D-2)$-metric on the horizon cross-section, and the surviving variation is recognised as the variation of $4pi m c_m int L_{m-1}(tilde h)$. Dividing by the temperature $kappa/2pi$ gives the entropy.
Extended reading notes
Core claim
The paper's central claim is Eq. (4): for a stationary black hole in $D$-dimensional Lovelock gravity with couplings $c_m$, the entropy is $$S = 2.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt=1.5pt
Load-bearing premise
The derivation assumes the black hole's event horizon is a Killing horizon with generators that can be extended backwards as complete geodesics, so that a bifurcation surface exists; Hawking's proof that stationary horizons are Killing horizons is established in four-dimensional Einstein gravity but is not carried over to Lovelock gravity here.
Editorial extensions
If this is right
- The first law $delta M - Omega_{(alpha)} delta J_{(alpha)} = (kappa/2pi) delta S$ holds for any stationary Lovelock black hole, with $S$ given by the curvature sum rather than by area.
- Entropy is a local functional of the intrinsic geometry of the horizon, so it can be written down for rotating Lovelock black holes whose metrics have not yet been constructed.
- For black holes much larger than the length scale set by the couplings $c_m$, the area term dominates and the Einstein result is recovered, so the correction is a controlled small-black-hole effect.
- In even dimensions the sum includes a topological term (the Euler constant of the horizon cross-section), which is a fixed constant in four dimensions but can vary in higher dimensions where horizon topology is not unique.
- The derivation extends to Maxwell and Yang-Mills fields with the usual $Phi delta Q$ term, leaving the entropy formula unchanged.
Reading between the lines
- If entropy is a sum of curvature invariants, two horizons with identical area but different intrinsic geometry carry different entropies; that makes the formula a sharp test of any proposal that counts horizon microstates geometrically.
- The topological term suggests a selection rule: in dimensions above four, black hole coalescence could change the horizon topology and with it the constant piece of the entropy, which is where the authors themselves flag a possible second-law problem.
- Because the entropy is fixed by the first law alone, any independent microscopic derivation in a Lovelock theory — string-inspired or otherwise — must reproduce this same curvature sum, not the area, in the small-black-hole regime where the correction is large.
- The unresolved question is whether the curvature sum never decreases under arbitrary horizon evolution; a positive-energy theorem for Lovelock gravity, or an area-theorem analogue for this functional, would close that gap.
Original abstract
A general formula for the entropy of stationary black holes in Lovelock gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section of the horizon.
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
A general formula for the entropy of stationary black holes in Lovelock gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section of the horizon.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | A general formula for the entropy of stationary black holes in Lovelock gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. | contribution 0.70 | 0.90 | 0.52 | asserted 1.00 |
| s1 | The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section of the horizon. | result 0.99 | 0.82 | 0.66 | asserted 1.00 |
What was examined, and what was not
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References
How later papers used it
125 later papers cite it
1 later paper by other authors is listed below: 1 built on it.
Builds on it 1 of 2 papers with this label
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Applied the same reasoning to this paper's Lovelock gravity results and modified the equation for δM to replace GδM with δ(GM).
Smarr Formula and an Extended First Law for Lovelock Gravity (2010) · 0.99 · paraphrased: the licence does not allow quoting
How the literature uses it
120 arXiv papers cite this in 193 sentences
Papers citing it · 150 sentences without a confident label
Builds on it 1 paper
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Applying this same reasoning to the results of [ref] in Lovelock gravity, we modify the equation for $δM$ to replace $GδM$ with $δ(GM)$ giving
Smarr Formula and an Extended First Law for Lovelock Gravity · Varying Newton's constant · 0.99
Uses its method or tool 4 papers
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We adopt the approach of [ref] , which relates entanglement entropy to the area of a co-dimension two bulk hypersurface that extremizes the Jacobson-Myers functional [ref] .
Entanglement entropy and its linear response following a global quench in holographic Gauss-Bonnet gravity · Introduction · 1.00
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The Regge-Teitelboim type construction of the ADM mass in [ref] yields an expression of the form
Mass and Free Energy of Lovelock Black Holes · ADM Mass · 0.81
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The Hamiltonian formulation of Lovelock gravity given in [ref] was used in [ref] to derive a first law and the expression ([ref]) for the gravitational entropy in Lovelock theories.
Smarr Formula and an Extended First Law for Lovelock Gravity · Hamiltonian formulation · 0.95
Compares with it 5 papers
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Choosing $T_m$ as Eq. ([ref]) and substituting it into the above equations, we get [equation] The central term reads [equation] from which we can read off the central charge $C$ and zero mode $Q_0$ as [equation] Using the Cardy formula, we obtain the entropy [equation] which is exactly the Wald entropy of the Gauss-Bonnet black holes [ref] .
Surface term, Virasoro algebra, and Wald entropy of black holes in higher-curvature gravity · Entropy of a Gauss-Bonnet black hole · 0.89
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A comparison to the results found in Riemannian theories with quadratic curvature Lagrangians [ref] , as well as in the general PG models [ref] , reveals how black holes react to different dynamical frameworks.
Thermodynamics of Riemannian Kerr-AdS black holes in Poincar\'e gauge theory · Introduction · 0.99
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The entropy calculation presented here is compatible with these results and the Wald entropy [ref] emerges at leading order (with correct prefactor for the analytic continuation $β→±i/2$).
Black hole entropy from loop quantum gravity in higher dimensions · Comments · 0.87
Cites it as support 2 papers
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In the case of General Relativity, as pointed out by [ref] , the gravitational charge does acquire such a topological contribution (the Euler number of \(B\)) when the Euler density is added to the Einstein-Hilbert Lagrangian in \(4\)-dimensions even though the equations of motion are unaffected (also see <ref>).
The First Law of Black Hole Mechanics for Fields with Internal Gauge Freedom · The first law for gauge-invariant Lagrangians · 0.96
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This additional inequality ensures that the coefficient of the Gauss-Bonnet term is strictly positive, and can be motivated to hold based on scattering amplitudes [ref] , the second law of thermodynamics [ref] , weak gravity conjecture [ref] , consistency of EFT strings [ref] , and holography [ref] .
Towards a complete classification of 6D supergravities · Consistency conditions · 0.96
Cites it as background 25 papers
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For example, in the gravity theory with higher-curvature corrections, the entropy is described by Wald entropy, which contains properly the contributions of higher-curvature corrections [ref] .
Surface term, Virasoro algebra, and Wald entropy of black holes in higher-curvature gravity · Introduction · 0.85
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First, there is Wald's entropy formula [ref] , which can be applied for any covariant gravity action, and then an earlier result derived specifically for Lovelock gravity [ref] .
On Holographic Entanglement Entropy and Higher Curvature Gravity · A few preliminaries · 0.96
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* The Wald entropy can be constructed for arbitrary $α$ with $=0$. * In [ref] the authors construct entropy functions for theories where the higher derivative Lagrangian is written solely in terms of the Ricci scalar (the so-called $f(R)$ theories), for a finite range of $α$, and arbitrary $$ and $ω$. * In recent years, [ref] first constructed an entropy functional that was valid for higher derivative interactions of the Lovelock form (see below) for small amplitude departures from equilibrium $≪1$.
Towards a second law for Lovelock theories · Introduction · 0.83
Discussion
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