The final state and thermodynamics of dark energy universe

TL;DR

This paper investigates the final states of dark energy universes, showing quantum effects can prevent or soften future singularities like the Big Rip and discussing implications for entropy and black hole mass loss.

Contribution

It demonstrates that quantum effects dominate near Big Rip singularities, altering the universe's fate and refining entropy bounds in dark energy cosmologies.

Findings

Quantum effects can prevent or soften Big Rip singularities.

Black hole masses do not vanish due to phantom accretion.

Quantum-corrected entropy bounds become well-defined near singularities.

Abstract

As it follows from the classical analysis, the typical final state of the dark energy universe where dominant energy condition is violated is finite time, sudden future singularity (Big Rip). For a number of dark energy universes (including scalar phantom and effective phantom theories as well as specific quintessence model) we demonstrate that quantum effects play the dominant role near Big Rip, driving the universe out of future singularity (or, at least, making it milder). As a consequence, the entropy bounds with quantum corrections become well-defined near Big Rip. Similarly, black holes mass loss due to phantom accretion is not so dramatic as it was expected: masses do not vanish to zero due to transient character of phantom evolution stage. Some examples of cosmological evolution for negative, time-dependent equation of state are also considered with the same conclusions. The application of negative entropy (or negative temparature) occurence in the phantom thermodynamics is briefly discussed.