Type V singularities with inhomogeneous equations of state

TL;DR

This paper investigates the formation of Type V cosmological singularities under inhomogeneous equations of state across various cosmological models, revealing that the equation of state significantly influences singularity occurrence, especially in f(R) gravity where they are eliminated.

Contribution

It provides a detailed analysis of Type V singularities with inhomogeneous equations of state in multiple cosmological backgrounds, highlighting the dominant role of the equation of state in singularity formation.

Findings

Type V singularities are highly sensitive to the form of the equation of state.

In f(R) gravity, Type V singularities are completely removed.

The background cosmology has less impact on singularity formation than the equation of state.

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. Recent work has seen a proper classification of such singularities into strong and weak based on their strength, with weak singularities being the likes of sudden, w and big freeze singularities and strong singularities like the big rip. This has led to a classification of such singularities in various types like Big rip is Type 1, w-singularity is type V etc. While singularities of type I-type IV have been discussed vividly by taking into account inhomogeneous equations of state (EOS), the same has not been attempted for type V singularities. So in this work we have discussed in detail about the formation of type V singularities in various cosmologies after considering inhomogeneous equations of state. We consider two inhomogeneous forms of the EOS in the context of four different cosmological backgrounds ; standard general relativistic cosmology, an asymptotically safe cosmology, a cosmology inspired by modified area-entropy relations, generalized uncertainty principles, holographic renormalization and Chern-Simons gravity( all of which can be coincidentally described by the same form of the modified Friedmann equation) and an f(R) gravity cosmology. We show in detail that one sees some very big differences in the occurence conditions of type V singularities when one makes such considerations. In the particular case of the f(R) gravity cosmology, we see that the type V singularities get completely removed. This work goes to show that the creation and formation of type V singularities is influenced most strongly by the form of the equation of state that one considers, way more so than what background cosmology one chooses.