Dynamical Black Hole Entropy in Effective Field Theory

Article Physics, Particles & Fields

The second law of black hole mechanics in effective field theory

Stefan Hollands et al.

Summary: This article investigates the second law of black hole mechanics in gravitational theories with higher derivative terms. The author describes a method for defining an entropy that satisfies the second law to linear and quadratic orders in perturbations, treating the higher derivative terms as effective field theory. Additionally, the author addresses some outstanding issues with the method, such as gauge invariance and its relation to the Iyer-Wald entropy.

JOURNAL OF HIGH ENERGY PHYSICS (2022)

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Article Physics, Particles & Fields

The zeroth law of black hole thermodynamics in arbitrary higher derivative theories of gravity

Sayantani Bhattacharyya et al.

Summary: This article examines diffeomorphism invariant theories of gravity as corrections to Einstein's general relativity. It presents a proof of the zeroth law of black hole thermodynamics in such theories. By assuming that stationary black hole solutions in higher derivative theories can be obtained from corresponding solutions in general relativity via perturbative corrections, the constancy of surface gravity on the horizon is proven. The article also explores the relationship between the constancy of surface gravity and the equations of motion in these theories, using a boost symmetry in the near horizon spacetime.

JOURNAL OF HIGH ENERGY PHYSICS (2022)

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Article Physics, Particles & Fields

An entropy current and the second law in higher derivative theories of gravity

Sayantani Bhattacharyya et al.

Summary: In this work, a proof of the second law of thermodynamics is established in an arbitrary diffeomorphism invariant theory of gravity, working within the approximation of linearized dynamical fluctuations around stationary black holes. This proof is achieved by establishing the existence of an entropy current defined on the horizon of dynamically perturbed black holes in such theories, providing a mechanism for black holes to approach equilibrium configurations via entropy production. Additionally, an alternative proof of the physical process version of the first law applicable to arbitrary higher derivative theories of gravity is also provided using the same setup.

JOURNAL OF HIGH ENERGY PHYSICS (2021)

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Article Astronomy & Astrophysics

Causality in gravitational theories with second order equations of motion

Harvey S. Reall

Summary: This paper explores diffeomorphism invariant theories of gravity coupled to matter, focusing on second order equations of motion. It delves into specific theories such as Einstein-Maxwell and Einstein-scalar field theory, demonstrating how causality is governed by characteristic polynomials and identifying surfaces analogous to Fresnel surfaces in crystal optics. It also discusses the implications of Killing horizons and the zeroth law of black hole mechanics in these theories.

PHYSICAL REVIEW D (2021)

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Article Physics, Particles & Fields