Singularity formation in asymptotically safe cosmology with inhomogeneous equation of state

TL;DR

This paper investigates the formation of various cosmological singularities in an asymptotically safe universe with an inhomogeneous equation of state, revealing unique conditions and challenges for singularity occurrence and removal.

Contribution

It is the first study to analyze singularity formation in asymptotically safe cosmology with an inhomogeneous EOS, highlighting differences from standard cosmology without free parameters.

Findings

Type I - Type IV singularities can occur in this cosmology.

Singularities can occur in finite or infinite time.

Standard removal methods are ineffective in this framework.

Abstract

Interest in cosmological singularities has remarkably grown in recent times, particularly on future singularities with the discovery of late-time acceleration of the universe and dark energy. While such explorations have previously been done in various modified gravity and quantum gravitationally inspired cosmologies (besides standard general relativistic cosmology), no such an endeavour has been taken up till now in the realms of renormalization group approaches to cosmology and we have hence took up on this journey. In this work, we consider the formation of cosmological singularities in an asymptotically safe cosmology where the cut off scale is proportional to the Hubble parameter. We consider a well motivated inhomogeneous form of the equation of state(EOS) as well. We firstly delve into some basics of this cosmology and show that such a scenario permits a transition between phantom and quintessence forms of universal evolution. We then show that one can have Type I - Type IV singularities in such a cosmology for various version of the EOS and that the singularities can occur both in finite and infinite time. The conditions in which these singularities occur is significantly different than how they occur in the standard cosmology, with the formulations being even more involved. Interestingly this difference comes about without the need of any free parameters in the cosmological models, which is usually what one observes when one goes for the same pursuit via various modified gravity/ QG inspired cosmological approaches. Furthermore, we showed that usual singularity removal methods like conformal anomaly effects and f(R) gravity effects do not offer much hope for singularity removal in this cosmology.