String Gravity and Cosmology: Some new ideas

TL;DR

This paper argues that string theory reshapes our understanding of gravity and cosmology by showing that geometric and topological notions are effective at low energies and that strong-curvature regimes reveal non-field-theoretic phenomena governed by stringy dualities. Through a simple circle compactification, it demonstrates momentum-winding duality and the $R=\sqrt{\alpha'}$ self-dual point with gauge enhancement, establishing a minimal length scale and non-perturbative symmetries. It then extends these ideas to effective theories, topology change, and black hole/cosmological singularities, illustrating how dual descriptions can smooth apparent singularities and facilitate transitions between geometries. The work highlights a program where exact conformal field theories and dualities guide the understanding of quantum cosmology and gravitational phenomena beyond classical GR, suggesting rich new physics in the gravitational sector.

Abstract

String theory provides the only consistent framework so far that unifies all interactions including gravity. We discuss gravity and cosmology in string theory. Conventional notions from general relativity like geometry, topology etc. are well defined only as low energy approximations in string theory. At small distances physics deviates from the field theoretic intuition. We present several examples of purely stringy phenomena which imply that the physics at strong curvatures can be quite different from what one might expect from field theory. They indicate new possibilities in the context of quantum cosmology.