Mean-field phase transitions in TGFT quantum gravity

TL;DR

This paper justifies the use of mean-field theory to describe phase transitions in tensorial group field theory models of quantum gravity, supporting the emergence of continuum gravitational physics from discrete quantum structures.

Contribution

It demonstrates that realistic TGFT models inherently support mean-field phase transitions, strengthening the case for continuum gravity in quantum gravity frameworks.

Findings

Mean-field phase transition assumption is justified in realistic TGFT models.

Supports the emergence of continuum gravitational physics from quantum discrete structures.

Enhances the phenomenological applicability of group-field and spin-foam quantum gravity.

Abstract

Controlling the continuum limit and extracting effective gravitational physics are shared challenges for quantum gravity approaches based on quantum discrete structures. The description of quantum gravity in terms of tensorial group field theory (TGFT) has recently led to much progress in its application to phenomenology, in particular cosmology. This application relies on the assumption of a phase transition to a nontrivial vacuum (condensate) state describable by mean-field theory, an assumption that is difficult to corroborate by a full renormalization group flow analysis due to the complexity of the relevant TGFT models. Here we demonstrate that this assumption is justified due to the specific ingredients of realistic quantum geometric TGFT models: combinatorially non-local interactions, matter degrees of freedom and Lorentz group data together with the encoding of micro-causality. This greatly strengthens the evidence for the existence of a meaningful continuum gravitational regime in group-field and spin-foam quantum gravity, the phenomenology of which is amenable to explicit computations in a mean-field approximation.