Joint Theory Seminar
Speaker: Yasha Neiman
Title: The imaginary part of the action in Lorentzian gravity
Host: Steve Carlip
Room: 432
Abstract: The action of classical gravity in a Lorentzian region has an imaginary part, arising from the boundary term. The expression for this imaginary part is directly related to the black hole entropy formula. The result continues to hold for higher-derivative gravity and in the presence of matter couplings. I show how the action's imaginary part can be directly calculated, and also how its key properties can be established abstractly. I evaluate the imaginary action on a selection of interesting regions involving horizons and asymptotic boundaries. Finally, I speculate on possible implications for quantum gravity.
