Avoidance of future singularities in loop quantum cosmology

TL;DR

This paper investigates how loop quantum cosmology's quantum effects can resolve various future singularities, such as Big Rip and sudden singularities, leading to a non-singular, oscillatory universe.

Contribution

It demonstrates that loop quantum cosmology's quantum geometric effects can universally resolve future singularities in Friedmann dynamics.

Findings

Quantum effects prevent Big Rip singularity, resulting in a recollapsing universe.

Sudden singularities can be avoided if energy density exceeds a critical value.

The universe can become oscillatory, avoiding singularities, depending on energy density ratios.

Abstract

We consider the fate of future singularities in the effective dynamics of loop quantum cosmology. Non-perturbative quantum geometric effects which lead to $\rho^2$ modification of the Friedmann equation at high energies result in generic resolution of singularities whenever energy density $\rho$ diverges at future singularities of Friedmann dynamics. Such quantum effects lead to the avoidance of a Big Rip, which is followed by a recollapsing universe stable against perturbations. Resolution of sudden singularity, the case when pressure diverges but energy density approaches a finite value depends on the ratio of the latter to a critical energy density of the order of Planck. If the value of this ratio is greater than unity, the universe escapes the sudden future singularity and becomes oscillatory.