TY - JOUR

T1 - Evaluating the Wald entropy from two-derivative terms in quadratic actions

AU - Brustein, Ram

AU - Gorbonos, Dan

AU - Hadad, Merav

AU - Medved, A. J.M.

PY - 2011/9/9

Y1 - 2011/9/9

N2 - We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.

AB - We evaluate the Wald Noether charge entropy for a black hole in generalized theories of gravity. Expanding the Lagrangian to second order in gravitational perturbations, we show that contributions to the entropy density originate only from the coefficients of two-derivative terms. The same considerations are extended to include matter fields and to show that arbitrary powers of matter fields and their symmetrized covariant derivatives cannot contribute to the entropy density. We also explain how to use the linearized gravitational field equation rather than quadratic actions to obtain the same results. Several explicit examples are presented that allow us to clarify subtle points in the derivation and application of our method.

UR - http://www.scopus.com/inward/record.url?scp=80053918235&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.84.064011

DO - 10.1103/PhysRevD.84.064011

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AN - SCOPUS:80053918235

SN - 1550-7998

VL - 84

JO - Physical Review D - Particles, Fields, Gravitation and Cosmology

JF - Physical Review D - Particles, Fields, Gravitation and Cosmology

IS - 6

M1 - 064011

ER -