A new non-perturbative time-dependent string configuration

TL;DR

This paper presents a non-perturbative, time-dependent string configuration in graviton and dilaton backgrounds that achieves conformal invariance to all orders, leading to a power-law expanding universe with specific dimensional constraints.

Contribution

It introduces a novel non-perturbative approach to conformal invariance in string theory with time-dependent backgrounds, valid in any target space dimension.

Findings

Achieves Weyl-symmetry beta-functions homogeneous in X^0

Allows reparametrization to cancel beta functions at all orders

Results in a power-law expanding universe with dimension-dependent properties

Abstract

A time-dependent bosonic string configuration is discussed, in graviton and dilaton backgrounds, leading to Weyl-symmetry beta-functions which are homogeneous in X^0, to any order in alpha'. As a consequence, a string reparametrization can always be implemented, such that beta functions can be cancelled, to any order in alpha'. This non-perturbative conformal invariance is valid for any target space dimension, and leads to a power law expanding Universe, for which the power vanishes if a specific relation between the dimension and dilaton amplitude holds. Finally, D=4 is the minimum dimension (in the case of a spherical world sheet) for which this configuration is consistent with a Wick rotation in a Minkowski target space.