Exactly solvable models of two-dimensional dilaton cosmology with quantum backreaction

TL;DR

This paper presents a comprehensive analysis of exactly solvable two-dimensional dilaton cosmological models incorporating quantum backreaction, revealing diverse regular solutions with various asymptotic behaviors, including inflation and singularity-free universes.

Contribution

It introduces a unified framework for exactly solvable 2D dilaton cosmologies with quantum effects, encompassing previous models and discovering new regular solutions with rich asymptotic properties.

Findings

Existence of regular solutions with different asymptotics including inflation and deflation.

Some models exhibit spacetime regularity despite infinite quantum backreaction.

Solutions include universes with singularities only in the infinite past or future.

Abstract

We consider general approach to exactly solvable 2D dilaton cosmology with one-loop backreaction from conformal fields taken into account. It includes as particular cases previous models discussed in literature. We list different types of solutions and investigate their properties for simple models, typical for string theory. We find a rather rich class of everywhere regular solutions which exist practically in every type of analyzed solutions. They exhibit different kinds of asymptotic behavior in past and future, including inflation, superinflation, deflation, power expansion or contraction. In particular, for some models the dS spacetime with a time-dependent dilaton field is the exact solution of field equations. For some kinds of solutions the weak energy condition is violated independent of a specific model. We find also the solutions with a singularity which is situated in an infinite past (or future), so at any finite moment of a comoving time the universe is singularity-free. It is pointed out that for some models the spacetime may be everywhere regular even in spite of infinitely large quantum backreaction in an infinite past.