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Résumé |
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 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 will also briefly describe
the Susskind-Uglum derivation of the black hole entropy S = A/4G from the off-shell string worldsheet. |
