Comment to ``Quantization of FRW spacetimes in the presence of a cosmological constant and radiation''

TL;DR

This paper critically re-evaluates previous claims that quantum effects in FRW spacetimes with a negative cosmological constant prevent singularities, showing that such singularities are not avoided and that earlier results lacked numerical precision.

Contribution

It demonstrates that previous conclusions about singularity avoidance are incorrect and provides more accurate numerical analysis using the variational sinc collocation method.

Findings

Quantum probability of singularities is higher than classical.

Previous results lacked numerical precision.

Singularities are not avoided at the quantum level.

Abstract

The quantization of the Friedmann-Robertson-Walker spacetime in the presence of a negative cosmological constant was used in a recent paper to conclude that there are solutions that avoid singularities (big bang--big crunch) at the quantum level. We show that a proper study of their model{\sl does not prevent} the occurrence of singularities at the quantum level, in fact the quantum probability of such event is larger than the classical one. Our numerical simulations based on the powerful variational sinc collocation method (VSCM) also show that the precision of the results of that paper is much lower than the 20 significant digits reported by the authors.