Effect of arbitrary matter-geometry coupling on thermodynamics in f(R) theories of gravity

In this paper, the thermodynamics of the Friedmann-Lemaitre-Robertson-Walker universe have been explored in f(R) theories of gravity with arbitrary matter-geometry coupling. The equivalence between the modified Friedmann equations with any spatial curvature and the first law of thermodynamics is confirmed, where the assumption of the entropy plays a crucial role. Then laws of thermodynamics in our considering case are obtained. They can reduce to the ones given in Einstein's general theory of relativity under certain conditions. Moreover, a particular model is investigated through the obtained generalized second law of thermodynamics with observational results of cosmographic parameters.

Automated summary

This paper explores the thermodynamics of the Friedmann-Lemaitre-Robertson-Walker universe in f(R) theories of gravity with arbitrary matter-geometry coupling, confirming the equivalence between modified Friedmann equations and the first law of thermodynamics. Laws of thermodynamics are obtained and validated through observational results.