On the propagation across the big bounce in an open quantum FLRW cosmology

TL;DR

This paper investigates how scalar fields propagate through a big bounce in an open quantum FLRW cosmology derived from IKKT matrix theory, revealing that particles can traverse the bounce and the propagator remains well-defined.

Contribution

It provides a detailed analysis of scalar field propagation across the big bounce in a quantum cosmological model, combining classical geodesic analysis with quantum-field-theoretic propagator evaluation.

Findings

Particles can travel across the big bounce.

The scalar propagator resembles Minkowski space at late times.

A well-defined correlation exists across the bounce.

Abstract

The propagation of a scalar field in an open FLRW bounce-type quantum spacetime is examined, which arises within the framework of the IKKT matrix theory. In the first part of the paper, we employ general-relativity tools to study null and timelike geodesics at the classical level. This analysis reveals that massless and massive non-interacting particles can travel across the big bounce. We then exploit quantum-field-theory techniques to evaluate the scalar field propagator. In the late-time regime, we find that it resembles the standard Feynman propagator of flat Minkowski space, whereas for early times it governs the propagation across the big bounce and gives rise to a well-defined correlation between two points on opposite sheets of the spacetime.