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(27.04) The off-shell string effective action and black hole entropy
Amr Ahmadain (Cambridge)
27.04.2023 at 16:15
Taking string theory off shell requires breaking Weyl invariance on the worldsheet, i.e. the worldsheet theory is now a QFT instead of a CFT. I will explain Tseytlin’s first-quantized approach to taking the worldsheet theory off-shell in a consistent manner, with a particular emphasis on the subtleties involved in calculating the sphere amplitude. This approach allows for the derivation of a classical string action which gives rise to the correct equations of motion and S-matrix, to all orders in perturbation theory. I'll also explain the underlying conceptual structure of the Susskind and Uglum black hole entropy argument. There I will show explicitly how the classical (tree-level) effective action and entropy S = A/4G_N may be calculated from the sphere diagrams. Time permitting, I will discuss ongoing efforts to derive the Ryu-Takayanagi formula in string theory. Based on arXiv:2211.08607 and arXiv:2211.16448.
via ZOOM