Deriving General Relativity from String Theory

Abstract

Weyl symmetry of the classical bosonic string Lagrangian is broken by quantization, with profound consequences described here (along with a review of string theory for philosophers of physics). Reimposing symmetry requires that the background space-time satisfy the equations of general relativity: general relativity, hence classical space-time as we know it, arises from string theory. We investigate the logical role of Weyl symmetry in this explanation of general relativity: it is not an independent physical postulate but required in quantum string theory, so from a certain point of view it plays only a formal role in the explanation.