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

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.

The emergence of expanding space-time in a novel large-$N$ limit of the Lorentzian type IIB matrix model

“…where 𝛾 is the Lorentz invariant "mass" parameter. This term was introduced for the first time in [21] as an IR regulator, and has been studied at the perturbative level in [22][23][24][25][26][27][28][29][30][31][32][33][34]. Especially in [28], the authors found that for 𝛾 > 0, typical classical solutions of fixed dimensionality describe the emergence of an expanding (3+1)-dimensional space-time.…”

The emergence of expanding space-time in the Lorentzian type IIB matrix model with a novel regularization

“…The model with this mass term has been studied at the classical and perturbative levels in Refs. [27][28][29][30][31][32][33][34][35][36][37][38][39][40]. In Ref.…”