Cosmological evolution as squeezing: a toy model for group field cosmology

TL;DR

This paper introduces a simple quantum cosmology model based on group field theory, describing universe evolution as quantum squeezing, leading to a bounce connecting contracting and expanding phases, with results aligning with loop quantum cosmology.

Contribution

It presents a novel toy model of GFT cosmology where universe evolution is described as quantum squeezing, providing insights without requiring full GFT formalism.

Findings

Universe evolution modeled as squeezing in GFT framework

Effective Friedmann equation with quantum bounce derived

Model parameter linked to Newton's constant

Abstract

We present a simple model of quantum cosmology based on the group field theory (GFT) approach to quantum gravity. The model is formulated on a subspace of the GFT Fock space for the quanta of geometry, with a fixed volume per quantum. In this Hilbert space, cosmological expansion corresponds to the generation of new quanta. Our main insight is that the evolution of a flat FLRW universe with a massless scalar field can be described on this Hilbert space as squeezing, familiar from quantum optics. As in GFT cosmology, we find that the three-volume satisfies an effective Friedmann equation similar to the one of loop quantum cosmology, connecting the classical contracting and expanding solutions by a quantum bounce. The only free parameter in the model is identified with Newton's constant. We also comment on the possible topological interpretation of our squeezed states. This paper can serve as an introduction into the main ideas of GFT cosmology without requiring the full GFT formalism; our results can also motivate new developments in GFT and its cosmological application.