Abstract

In this talk, I will give a brief overview of Susskind’s and Uglum’s work with a special focus on their closed string off-shell derivation of the tree-level black hole entropy in a conical manifold.

Since conformal invariance is broken (due to the conical singularitiy), the nonlinear sigma model living on the worldsheet is a QFT rather than a CFT . Susskind and Uglum used Tseytlin’s nonlinear sigma model-based prescription for constructing off-shell classical effective actions. Their calculation gets the factor of 1/4 of the black hole entropy correct.

I will briefly mention some novel justifications for Tseytlin’s sphere prescriptions, in particular, how to use it to obtain (i) Witten’s i\varepsilon prescription for the Lorentzian S-matrix, and time permitting (ii) the correct equations of motion in Euclidean signature. This is based on work with Aron Wall.