Conserved charges in gravity and entropy
 Date
 December 10 at 13:00  14:30, 2020 (JST)
 Speaker

 Dr. Shinya Aoki (Professor, Yukawa Institute for Theoretical Physics, Kyoto University)
 Venue
 via Zoom
 Language
 English
We propose a manifestly covariant definition of a conserved charge in gravity. We first define a charge density from the energy momentum tensor with a Killing vector, if exists in the system, and calculate the energy (and angular momentum) of the black hole by a volume integral. Our definition of energy leads to a correction of the known mass formula of a compact star, which includes the gravitational interaction energy and is shown to be 68\% of the leading term in some case. Secondly we propose a new method to define a conserved charge in the absence of Killing vectors, and argue that the conserved charge can be regarded as entropy, by showing the 1st law of thermodynamic for a special case. We apply this new definition to the expanding universe, gravitational plane waves and the black hole. We discuss future directions of our research.
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References
 S. Aoki, T. Onogi, S. Yokoyama, arXiv:2005.13233
 S. Aoki, T. Onogi, S. Yokoyama, arXiv:2010.07660