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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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arXiv IDhep-th/9305016 (version 1)
Pith ID5IFXABAX, Pith's permanent record of this paper and its review
CitationRobert C. Myers, Ted Jacobson. "Entropy of Lovelock Black Holes." arXiv:hep-th/9305016 (1993). https://pith.science/paper/5IFXABAX
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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

In Einstein's theory a black hole's entropy equals one quarter of its horizon area, and that coincidence is usually treated as a hint about quantum gravity. This paper asks what replaces the coincidence when gravity is not Einstein's. Working in Lovelock gravity — the most general metric theory whose field equations remain second order — the authors derive the first law of black hole mechanics from a Hamiltonian boundary term and then integrate it to obtain the entropy. The result is that entropy is still an integral over a cross-section of the horizon, but of a sum of intrinsic curvature invariants rather than area alone, assembled in the same pattern as the Lovelock Lagrangian itself one dimension lower. If the derivation holds, entropy becomes a local property of the horizon's own geometry, defined for any stationary black hole — including rotating ones whose solutions have not yet been found — instead of a number extracted from a particular solution's Euclidean action.

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

Editorial extensions of the paper, not claims the author makes directly.

  • 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.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 2,297 input tokens, $0.0001 reported.

What the abstract itself states, as probabilities: claims first 0.05 · states limitation 0.13 · human participants 0.01 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.18 · compares with prior results 0.44 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; .

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

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
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 kind of paper the classifier reports this is: theoretical result 1.00 · evidence from proof or derivation 1.00.

What was examined, and what was not

sources read
  • arXiv listing abstract v1
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

References
How later papers used it

125 later papers cite it

Evidence: substantial. 119 of the citing papers share no author with it, and 12 of those carry a confident label from Pith's citation classifier.

Pith read 18 of the 200 citing sentences, choosing only those whose citation markers point at this paper alone, and wrote the paraphrases from them. The summary, the counts, the evidence level, the links and the quotes come from code; the summary counts the papers listed below. A later paper is listed under a label when Pith's citation classifier gives one of its sentences that label at probability 0.8 or more (0.95 for support), Pith's reading finds that the citing paper itself did it, and a second check confirms the paraphrase against the sentence. This section lists uses only. It does not list criticism or disagreement, so their absence here says nothing about how the paper has been received. Papers that share an author with this one are listed apart, under "By the same authors". A quote is the citing authors' own sentence, shown when their paper's licence is CC BY, CC BY-SA or CC0. JSON

Builds on it 1 of 2 papers with this label
How the literature uses it

120 arXiv papers cite this in 193 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 150 sentences without a confident label

Builds on it 1 paper
Uses its method or tool 4 papers
Compares with it 5 papers
Cites it as support 2 papers
  • 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

  • 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
  • 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

  • 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

  • * 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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