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BTZ Black Hole with Chern-Simons and Higher Derivative Terms

High Energy Physics - Theory · Submitted 31 Jan 2006 · 16 references

Pith's verdict: An honest methodological paper: the BTZ entropy numbers were already known, but the covariant 2D-reduction route to them is new and the authors are upfront about the one step they could not derive.

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arXiv IDhep-th/0601228 (version 1)
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CitationAshoke Sen, Bindusar Sahoo. "BTZ Black Hole with Chern-Simons and Higher Derivative Terms." arXiv:hep-th/0601228 (2006). https://pith.science/paper/BHQBATHV
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The paper

The paper claims

By treating the angular direction of a BTZ black hole as a compact circle, the authors show that Wald's Noether-charge method reproduces the known entropy even when a parity-violating gravitational Chern-Simons term and higher-derivativecur

The reading

The paper asks whether Wald's Noether-charge method — the standard modern way to define black hole entropy in theories with curvature-squared and higher terms — can be made to work for a three-dimensional BTZ black hole once a gravitational Chern-Simons term is added. That term is the obstruction: it cannot be written in a manifestly coordinate-invariant way in three dimensions, so Wald's construction, which assumes a covariant Lagrangian, does not apply directly. The authors' move is to shrink the angular coordinate $y$ to a compact circle of period $2$ and rewrite the whole theory as a two-dimensional one with a metric, a gauge field $A_$ and a scalar $'$; in that language the Chern-Simons term becomes an ordinary covariant expression built from a curvature times a field strength plus a cubic term in $F$. Wald's formula then goes through essentially mechanically. The payoff is a closed expression for the entropy of a non-extremal BTZ black hole, $E = 2pi sqrt{c_L q_L / 6} + 2pi sqrt{c_R q_R / 6}$, which matches the earlier Euclidean-action computation, and which shows that the left-right central-charge difference $c_L - c_R = 48 pi K$ is fixed entirely by the Chern-Simons coefficient, independent of the higher-derivative terms.

What carries the argument

The load-bearing device is the dimensional reduction of the gravitational Chern-Simons term to two dimensions, which turns a non-covariant three-dimensional object into the covariant density $sqrt{-g} L_1 = K pi [ (1/2) R epsilon^{mu nu} F_{mu nu} + (1/2) epsilon^{mu nu} F_{mu tau} F^{tau sigma} F_{sigma nu} ]$. This is what makes Wald's Noether-charge machinery applicable at all. The second device is the entropy function: a function of the near-horizon values of the scalar $'$, the $AdS_2$ radius-squared $v$, and the electric field $e$, whose extremum with respect to those variables gives both the near-horizon parameters and the entropy. For the non-extremal case the authors exhibit an analogous extremization principle, $E = 2pi [ q_L e_L + q_R e_R - (1/e_L + 1/e_R) g(l) + pi K (1/e_L - 1/e_R) ]$, with $e_L = l/(ho_+ - ho_-)$ and $e_R = l/(ho_+ + ho_-)$, though they state they have not derived it from Wald's formula.

Extended reading notes

Core claim

The central claim is that the entropy of a BTZ black hole in a theory with arbitrary higher-derivative corrections plus a gravitational Chern-Simons term can be computed by Wald's Noether-charge method, provided one first reduces the theory along the compact angular direction. In the reduced two-dimensional theory the Chern-Simons term is manifestly covariant, so the Noether charge of diffeomorphisms is well defined. For extremal black holes the authors use the entropy function $E(u,v,e,q) = 2pi (e q - f(u,v,e))$, extremized subject to the BTZ-specific constraint $v = e^2$ that follows from local $AdS_3$ symmetry; for non-extremal holes they evaluate the Noether charge directly, splitting it into a higher-derivative piece $E_0 = 8 pi^2 C l^{-1} ho_+$ and a Chern-Simons piece $E_1 = -8 pi^2 K l^{-1} ho_-$. The two combine into the left-right symmetric form $E = 2pi sqrt{c_L q_L / 6} + 2pi sqrt{c_R q_R / 6}$ with $q_L = (M-J)/2$, $q_R = (M+J)/2$, reproducing the Euclidean result of Kraus and Larsen. Along the way the authors note that the Chern-Simons term does not affect the determination of the $AdS_3$ radius $l$, because its contribution to the equations of motion involves a covariant derivative of the Ricci tensor, which vanishes for BTZ.

Load-bearing premise

The paper assumes that the two-dimensional Chern-Simons Lagrangian obtained after dropping total derivative terms is a faithful starting point for Wald's Noether charge, even though dropping a total derivative can shift that charge by a boundary term, and it does not show those discarded terms vanish at the horizon.

Editorial extensions

If this is right

  • Wald's Noether-charge method, previously unusable for parity-odd three-dimensional gravity, becomes a practical alternative to the Euclidean action for BTZ entropy computations.
  • The left-right central-charge difference is pinned to the Chern-Simons coefficient alone, $c_L - c_R = 48 pi K$, while the sum $c_L + c_R = -48 g(l)$ is fixed by the higher-derivative sector, so the two kinds of correction separate cleanly.
  • Because the extremal entropy takes the Cardy form $2pi sqrt{c_L q_L/6} + 2pi sqrt{c_R q_R/6}$, a two-dimensional conformal-field-theory account of the microstates survives the addition of higher-derivative and Chern-Simons terms, with the central charges shifted as above.
  • The BTZ radius $l$ is unaffected by the Chern-Simons term, since that term's contribution to the equations of motion vanishes on the locally $AdS_3$ background.

Reading between the lines

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

  • If the reduction step is exact, the same trick should give a general recipe for any odd-dimensional theory with a gravitational Chern-Simons term: reduce along a Killing circle first, then apply Noether-charge methods in the even-dimensional quotient.
  • The agreement with the Euclidean computation is a check on the whole chain, but it is also the only independent check reported; a direct three-dimensional covariant treatment, or a holographic computation of $c_L$ and $c_R$ from the boundary stress tensor, would test the reduction independently.
  • The un-derived non-extremal extremization principle in equation (4.15) is a concrete target: if it follows from Wald's formula plus the equations of motion, the entropy-function formalism extends beyond the near-horizon $AdS_2$ setting in which it was introduced.
Original abstract

The entropy of a BTZ black hole in the presence of gravitational Chern-Simons terms has previously been analyzed using Euclidean action formalism. In this paper we treat the BTZ solution as a two dimensional black hole by regarding the angular coordinate as a compact direction, and use Wald's Noether charge method to calculate the entropy of this black hole in the presence of higher derivative and gravitational Chern-Simons terms. The parameters labelling the black hole solution can be determined by extremizing an entropy function whose value at the extremum gives the entropy of the 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.

Compiled by classifier-1.13-20260917 via OpenRouter, question bank abstract-p1-20260923, 2026-09-23: 1 request, 3,025 input tokens, $0.0001 reported.

What the abstract itself states, as probabilities: claims first 0.05 · states limitation 0.07 · human participants 0.01 · controlled comparison 0.04 · randomized assignment 0.01 · states quantitative result 0.05 · compares with prior results 0.45 · mentions code or data availability 0.01.

The abstract, sentence by sentence

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

The entropy of a BTZ black hole in the presence of gravitational Chern-Simons terms has previously been analyzed using Euclidean action formalism. In this paper we treat the BTZ solution as a two dimensional black hole by regarding the angular coordinate as a compact direction, and use Wald's Noether charge method to calculate the entropy of this black hole in the presence of higher derivative and gravitational Chern-Simons terms. The parameters labelling the black hole solution can be determined by extremizing an entropy function whose value at the extremum gives the entropy of the black hole.

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 The entropy of a BTZ black hole in the presence of gravitational Chern-Simons terms has previously been analyzed using Euclidean action formalism. background 1.00 0.03 0.03 asserted 1.00
s1 In this paper we treat the BTZ solution as a two dimensional black hole by regarding the angular coordinate as a compact direction, and use Wald's Noether charge method to calculate the entropy of this black hole in the presence of higher derivative and gravitational Chern-Simons terms. method 0.58 0.95 0.16 asserted 1.00
s2 The parameters labelling the black hole solution can be determined by extremizing an entropy function whose value at the extremum gives the entropy of the black hole. method 0.92 0.73 0.27 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.98 · evidence from proof or derivation 1.00.

What was examined, and what was not

sources read
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  • references and citing sentences
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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 the literature uses it

44 arXiv papers cite this in 62 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 · 47 sentences without a confident label

Builds on it 1 paper
Uses its method or tool 5 papers
Compares with it 1 paper
  • Importantly, the new entropy is given by the Bekenstein-Hawking entropy as [equation] which is slightly different from the shifted-entropy $S_c$ of Eq.([ref]) expressed as [ref] [equation] Here we check easily that the first-law of thermodynamics [equation] is satisfied for the CS-BTZ black hole.

    Entropy of black holes in topologically massive gravity · Thermodynamics and entropy for CS-BTZ black hole · 0.91

Cites it as background 8 papers
  • Later this was generalized to higher derivative theories of gravity [ref] , where the lagrangian density contains arbitrary powers of Riemann tensor and its covariant derivatives as well as gravitational Chern-Simons terms [ref] , both in the Euclidean action formalism [ref] and in Wald's formalism [ref] .

    AdS_3, Black Holes and Higher Derivative Corrections · Introduction · 0.92

  • The Wald entropy of the BTZ black hole in TMG receives a non-trivial contribution which has been well documented and studied in [ref] .

    Gravitational Anomalies in nAdS$_2$/nCFT$_1$ · Thermodynamics near Extremality · 0.82

  • The attractor mechanism has been observed for asymptotically flat as well as asymptotically $AdS$ black holes and in theories with higher derivative interactions, and there is a long list of papers where this subject has been studied widely [ref] .

    The fate of flat directions in higher derivative gravity · Introduction and summary · 1.00

Discussion

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