Future singularity avoidance in phantom dark energy models

TL;DR

This paper investigates quantum cosmology approaches to avoid future singularities like the big rip, finding that such singularities may persist or change form depending on the model and corrections used.

Contribution

It critically examines the effectiveness of quantum cosmology methods, especially loop quantum cosmology, in avoiding future singularities and highlights potential inconsistencies in previous results.

Findings

Big rip persists in modified gravity with phantom energy.

Holonomy corrections can replace big rip with a bounce.

Inconsistencies may lead to different singularity outcomes.

Abstract

Different approaches to quantum cosmology are studied in order to deal with the future singularity avoidance problem. Our results show that these future singularities will persist but could take different forms. As an example we have studied the big rip which appear when one considers the state equation $P=\omega\rho$ with $\omega<-1$, showing that it does not disappear in modified gravity. On the other hand, it is well-known that quantum geometric effects (holonomy corrections) in loop quantum cosmology introduce a quadratic modification, namely proportional to $\rho^2$, in Friedmann's equation that replace the big rip by a non-singular bounce. However this modified Friedmann equation could have been obtained in an inconsistent way, what means that the obtained results from this equation, in particular singularity avoidance, would be incorrect. In fact, we will show that instead of a non-singular bounce, the big rip singularity would be replaced, in loop quantum cosmology, by other kind of singularity.