Einstein gravity with Gauss-Bonnet entropic corrections
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Abstract
A toy model of Einstein gravity with a Gauss-Bonnet classically ``entropic'' term mimicking a quantum correction is considered. The static black hole solution due to Tomozawa is found and generalized with the inclusion of nontrivial horizon topology, and its entropy is evaluated, deriving the first law by equations of motion. As a result the Bekenstein-Hawking area law turns out to be corrected by a logarithmic area term. A Misner-Sharp expression for the mass of a black hole is found. Within a Friedmann-Lema\^{\i}tre-Robertson-Walker cosmological setting, the model is used in order to derive modified Friedmann equations. Such new equations are shown to reproduce the first law with the same formal entropy and quasilocal energy of the static case, but here within a Friedmann-Lema\^{\i}tre-Robertson-Walker space-time interpreted as a dynamical cosmological black hole. A detailed analysis of cosmological solutions is presented, and it is shown that the presence of the correction term provides regular solutions and interesting phases of acceleration and deceleration, as well as, with negligible matter, exact de Sitter solutions.