Non-Singular String-Cosmologies From Exact Conformal Field Theories

TL;DR

This paper constructs non-singular string cosmologies in two and three dimensions using exact conformal field theories, showing that quantum effects can remove classical singularities and allow for various cosmological scenarios including inflation.

Contribution

It demonstrates the construction of non-singular string cosmologies from exact CFTs, revealing that quantum effects can eliminate classical singularities and enable diverse cosmological models.

Findings

All classical curvature singularities are canceled in the exact theories.

Non-singular oscillating, expanding, and inflationary cosmologies are constructed.

Higher-dimensional generalizations suggest anisotropy and the avoidance of singularities are common features.

Abstract

Non-singular two and three dimensional string cosmologies are constructed using the exact conformal field theories corresponding to SO(2,1)/SO(1,1) and SO(2,2)/SO(2,1). {\it All} semi-classical curvature singularities are canceled in the exact theories for both of these cosets, but some new quantum curvature singularities emerge. However, considering different patches of the global manifolds, allows the construction of non-singular spacetimes with cosmological interpretation. In both two and three dimensions, we construct non-singular oscillating cosmologies, non-singular expanding and inflationary cosmologies including a de Sitter (exponential) stage with positive scalar curvature as well as non-singular contracting and deflationary cosmologies. Similarities between the two and three dimensional cases suggest a general picture for higher dimensional coset cosmologies: Anisotropy seems to be a generic unavoidable feature, cosmological singularities are generically avoided and it is possible to construct non-singular cosmologies where some spatial dimensions are experiencing inflation while the others experience deflation.