Inflation from Geometrical Tachyons

TL;DR

This paper introduces a novel geometrical tachyon inflation model based on D3-brane motion around NS5-branes, demonstrating its consistency with slow roll conditions, small metric perturbations, and potential reheating mechanisms.

Contribution

It presents a new geometrical tachyon framework for inflation that overcomes issues of open-string tachyon models, aligning with effective 4D theory and perturbative string coupling.

Findings

Slow roll conditions are satisfied in the model.

Metric perturbations remain small and consistent.

A potential minimum suggests a reheating mechanism.

Abstract

We propose an alternative formulation of tachyon inflation using the geometrical tachyon arising from the time dependent motion of a BPS $D3$-brane in the background geometry due to $k$ parallel $NS$5-branes arranged around a ring of radius $R $. Due to the fact that the mass of this geometrical tachyon field is $\sqrt{2/k} $ times smaller than the corresponding open-string tachyon mass, we find that the slow roll conditions for inflation and the number of e-foldings can be satisfied in a manner that is consistent with an effective 4-dimensional model and with a perturbative string coupling. We also show that the metric perturbations produced at the end of inflation can be sufficiently small and do not lead to the inconsistencies that plague the open string tachyon models. Finally we argue for the existence of a minimum of the geometrical tachyon potential which could give rise to a traditional reheating mechanism.