Singularity avoidance and time in quantum gravity

TL;DR

This paper investigates quantum cosmology by quantizing a Friedmann-Robertson-Walker universe, showing that the choice of time variable influences the presence of singularities, with no semiclassical wave packet avoiding the Big Bang.

Contribution

It introduces a reduced square root Hamiltonian using the scale factor as time and analyzes its implications for singularity avoidance in quantum gravity.

Findings

No semiclassical wave packet avoids the Big Bang singularity

The choice of time variable affects singularity resolution

Quantization leads to a spinor equation in quantum cosmology

Abstract

We consider the quantization of a Friedmann-Robertson-Walker universe. We derive a reduced square root Hamiltonian by choosing the scale factor as time variable and quantize the theory using the Dirac method. From the resulting spinor equation we show that there is no semiclassical wave packet that avoids the Big Bang singularity. Our work raises the question concerning the relationship between the choice of time and singularity avoidance.