Second Law of Black Holes Thermodynamics in Non-Quasi-Static Processes

Abstract: The Bekenstein-Hawking entropy satisfies the generalized second law of black hole thermodynamics for arbitrary thermodynamic evolution within Einstein-Maxwell theory. In contrast, the black hole entropy that satisfies the second law in low-energy effective modified gravity theories related to quantum gravity is derived solely by considering linear perturbations within quasi-static processes. Since astrophysical processes are typically non-quasi-static, deriving a rigorous expression for entropy within the quasi-static framework is not feasible. By treating the effective quantum corrections as first-order perturbations, the black hole entropy in Einstein-Maxwell gravity with generalized quadratic corrections for arbitrary dynamical processes is derived. This entropy is distinct from the Iyer-Wald and Dong-Wald entropies and is applicable to non-quasi-static processes. Furthermore, it is shown that the black hole entropy is consistent with the generalized covariant entropy boundary. This work establishes a framework for examining the generalized second law of black hole thermodynamics in non-static processes within modified gravity theories.