The axion coupling accelerates the Universe through PT-symmetric phases

TL;DR

This paper explores how T-symmetric phases in axion-related gravitational theories could explain the Universe's accelerated expansion, using advanced RG flow analysis including gravitational effects.

Contribution

It provides a systematic analysis of RG flows with gravitational couplings, supporting the idea that T-symmetric phases influence cosmological acceleration.

Findings

T-symmetric phases persist with gravitational couplings

Supports the link between T-symmetry and cosmic acceleration

Offers a new interpretation of Universe's acceleration in string-inspired models

Abstract

The conjecture by two of the authors (N.E.M. and S.S.) that a \cPT-symmetric phase plays a role in understanding singular renormalisation group (RG) flows for a Chern-Simons (CS) gauge theory of axions, has been reexamined and significantly improved. We have used the more complete Wetterich equation, which includes gravitational couplings in a systematic way from the start, to understand the emergence of this phase. The singular structure of the RG flows has persisted on including gravitational-couplings, thereby offering further support to the conjecture that \cPT -symmetric phases of (repulsive) gravity characterise string-effective CS gravitational theories, where the axion is the massless string-model independent axion, which can also play a role of a totally-antisymmetric torsion degree of freedom. This has suggested a novel interpretation of the currently observed acceleration of the expansion of the Universe in terms of such a phase at large (cosmological) scales.