String Theory and Inflation

TL;DR

This paper demonstrates that a new mechanism for fixing the values of scalar fields in string theory can resolve cosmological problems and produce stable particles that could account for dark matter.

Contribution

It introduces a mechanism to fix dilaton and moduli fields in string theory, avoiding cosmological issues and enabling these fields to serve as stable dark matter candidates.

Findings

Scalar fields are compatible with inflationary observations.

The mechanism produces ultra-weakly interacting massive particles.

Fields can have masses from 1 TeV to the Planck scale.

Abstract

String theory abounds with light scalar fields (the dilaton and various moduli) which create a host of observational problems, and notably some serious cosmological difficulties similar to the ones associated with the Polonyi field in the earliest versions of spontaneously broken supergravity. We show that all these problems are naturally avoided if a recently introduced mechanism for fixing the vacuum expectation values of the dilaton and/or moduli is at work. We study both the classical evolution and the quantum fluctuations of such scalar fields during a primordial inflationary era and find that the results are naturally compatible with observational facts. In this model, dilatons or moduli within a very wide range of masses (which includes the SUSY-breaking favored 1 TeV value and extends up to the Planck scale) qualify to define a novel type of essentially stable ultra-weakly interacting massive particles able to provide enough mass density to close the universe