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arXiv · 1902.04859

Thermodynamics of $f(R)$ Gravity with Disformal Transformation

Chao-Qiang Geng·Wei-Cheng Hsu·Jhih-Rong Lu·Ling-Wei Luo
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Abstract

We study thermodynamics in $f(R)$ gravity with the disformal transformation. The transformation applied to the matter Lagrangian has the form of $\g_{\m\n} = A(\phi,X)g_{\m\n} + B(\phi,X)\pa_\m\f\pa_\n\f$ with the assumption of the Minkowski matter metric $\g_{\m\n} = \e_{\m\n}$, where $\phi$ is the disformal scalar and $X$ is the corresponding kinetic term of $\phi$. We verify the generalized first and second laws of thermodynamics in this disformal type of $f(R)$ gravity in the Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. In addition, we show that the Hubble parameter contains the disformally induced terms, which define the effectively varying equations of state for matter.

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Chao-Qiang Geng, Wei-Cheng Hsu, Jhih-Rong Lu, Ling-Wei Luo. 2019-02-13. Thermodynamics of $f(R)$ Gravity with Disformal Transformation. https://doi.org/10.3390/e21020172

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