The Quantum Cosmological Wavefunction at Very Early Times for a Quadratic Gravity Theory

TL;DR

This paper derives the quantum cosmological wavefunction for a quadratic gravity theory from heterotic string action, showing that including scalar field derivatives ensures regularity at the universe's initial singularity.

Contribution

It demonstrates that incorporating scalar field derivatives leads to a sixth-order differential equation, resolving singularities in the wavefunction at early times in quadratic gravity models.

Findings

Wavefunction is singular without scalar derivatives

Including scalar derivatives yields a regular wavefunction

Scalar field inclusion is essential for early universe quantum cosmology

Abstract

The quantum cosmological wavefunction for a quadratic gravity theory derived from the heterotic string effective action is obtained near the inflationary epoch and during the initial Planck era. Neglecting derivatives with respect to the scalar field, the wavefunction would satisfy a third-order differential equation near the inflationary epoch which has a solution that is singular in the scale factor limit $a(t)\to 0$. When scalar field derivatives are included, a sixth-order differential equation is obtained for the wavefunction and the solution by Mellin transform is regular in the $a\to 0$ limit. It follows that inclusion of the scalar field in the quadratic gravity action is necessary for consistency of the quantum cosmology of the theory at very early times.