On Climbing Scalars in String Theory

TL;DR

This paper explores how certain exponential potentials in string theory, arising from brane supersymmetry breaking, can influence early universe cosmology by causing scalar fields to climb potentials and potentially trigger inflation.

Contribution

It demonstrates that these string-derived potentials lead to unique scalar field dynamics, including climbing behavior, with implications for cosmological evolution and inflation.

Findings

Scalar fields climb potentials at a critical slope

Potential trapping of scalar fields during cosmological evolution

Possible connection to inflationary phase initiation

Abstract

In string models with "brane supersymmetry breaking" exponential potentials emerge at (closed-string) tree level but are not accompanied by tachyons. Potentials of this type have long been a source of embarrassment in flat space, but can have interesting implications for Cosmology. For instance, in ten dimensions the logarithmic slope |V'/V| lies precisely at a "critical" value where the Lucchin--Matarrese attractor disappears while the scalar field is \emph{forced} to climb up the potential when it emerges from the Big Bang. This type of behavior is in principle perturbative in the string coupling, persists after compactification, could have trapped scalar fields inside potential wells as a result of the cosmological evolution and could have also injected the inflationary phase of our Universe.