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Thermodynamics of cosmological horizons in gravity
Kazuharu Bamba, Chao-Qiang Geng
We explore thermodynamics of the apparent horizon in gravity with both equilibrium and non-equilibrium descriptions. We find the same dual equilibrium/non-equilibrium formul…
Phantom crossing in viable theories
Kazuharu Bamba, Chao-Qiang Geng, Chung-Chi Lee
We review the equation of state for dark energy in modified gravity theories. In particular, we summarize the generic feature of the phantom divide crossing in the past and future…
Thermodynamics in Modified Gravity Theories
Kazuharu Bamba, Chao-Qiang Geng, Shinji Tsujikawa
We demonstrate that there does exist an equilibrium description of thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified grav…
Time-dependent matter instability and star singularity in gravity
Kazuharu Bamba, Shin'ichi Nojiri, Sergei D. Odintsov
We investigate a curvature singularity appearing in the star collapse process in gravity. In particular, we propose an understanding of the mechanism to produce the curvatur…