2.4k citations · 12k across the 222 of their papers we have counts for
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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…
Cosmological perturbations in -essence model
Kazuharu Bamba, Jiro Matsumoto, Shin'ichi Nojiri
Subhorizon approximation is often used in cosmological perturbation theory. In this paper, however, it is shown that the subhorizon approximation is not always a good approximation…
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…
Large-scale magnetic fields from inflation due to a -even Chern-Simons-like term with Kalb-Ramond and scalar fields
Kazuharu Bamba, C. Q. Geng, S. H. Ho +1
We investigate the generation of large-scale magnetic fields due to the breaking of the conformal invariance in the electromagnetic field through the -even dimension-six Chern…
Domain wall solution in gravity and variation of the fine structure constant
Kazuharu Bamba, Shin'ichi Nojiri, Sergei D. Odintsov
We construct a domain wall solution in gravity. We reconstruct a static domain wall solution in a scalar field theory. We also reconstruct an explicit gravity model i…
Screening of cosmological constant for De Sitter Universe in non-local gravity, phantom-divide crossing and finite-time future singularities
Kazuharu Bamba, Shin'ichi Nojiri, Sergei D. Odintsov +1
We investigate de Sitter solutions in non-local gravity as well as in non-local gravity with Lagrange constraint multiplier. We examine a condition to avoid a ghost and discuss a s…
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…