de Sitter Excited State in Heterotic E_8 x E_8 Theory

TL;DR

This paper introduces a new duality approach to study late-time cosmology in heterotic E_8 x E_8 theory, revealing a transient de Sitter phase without NEC violation, with implications for axionic cosmology.

Contribution

It presents a novel duality sequence in heterotic E_8 x E_8 theory that uncovers a transient de Sitter phase in four dimensions without NEC violation.

Findings

No violation of NEC in the four-dimensional theory

Presence of a transient de Sitter phase within trans-Planckian bounds

Potential for addressing cosmological and phenomenological issues

Abstract

We devise a novel duality sequence to study late-time cosmology in the heterotic E_8 x E_8 setup of Horava and Witten with dynamical walls that are moving towards each other. Surprisingly, we find that the dimensionally reduced four-dimensional theory does not violate NEC and therefore we do not see either a bouncing or an ekpyrotic phase. Instead, our four-dimensional setup shows a transient de Sitter phase that lies well within the trans-Planckian bound. This opens up a myriad of possibilities of addressing both phenomenological and cosmological issues, and here we concentrate on one such interesting model, an axionic cosmology with temporally varying axionic coupling.