1301.7041 (Yasha Neiman)

The imaginary part of the gravity action and black hole entropy    [PDF]

Yasha Neiman

As observed recently in arXiv:1212.2922, the action of General Relativity (GR) in finite spacetime regions has an imaginary part that resembles the Bekenstein entropy. In this paper, we expand on that argument, with attention to different causal types of boundaries. We then focus on the special case of stationary black holes. In such stationary spacetimes, we identify a class of bounded regions for which the action's imaginary part precisely reproduces the black hole entropy. These derivations are successfully repeated for Lovelock gravity. Our results for the imaginary action apply just as well to non-stationary spacetimes. We speculate on their relation to a non-stationary definition of entropy.

View original: http://arxiv.org/abs/1301.7041