Accelerated expansion of the Universe without an inflaton and resolution of the initial singularity from Group Field Theory condensates

Abstract

We study the expansion of the Universe using an effective Friedmann equation obtained from the dynamics of GFT (Group Field Theory) isotropic condensates. The evolution equations are classical, with quantum correction terms to the Friedmann equation given in the form of effective fluids coupled to the emergent classical background. The occurrence of a bounce, which resolves the initial spacetime singularity, is shown to be a general property of the model. A promising feature of this model is the occurrence of an era of accelerated expansion, without the need to introduce an inflaton field with an appropriately chosen potential. We discuss possible viability issues of this scenario as an alternative to inflation.

Group Field Theory Condensate Cosmology: An Appetizer

“…• A careful analysis shows that the identification m 2 j ≡ 3πG N only holds asymptotically for large φ, rendering G N a state-dependent function [28]. This is illustrated in Fig.…”

“…In this picture, a condensate would correspond to a non-perturbative vacuum which comprises of a large number of bosonic GFT quanta and in the context of GFT models of four-dimensional quantum gravity is tentatively interpreted as a continuum geometry. Given this basic premise, the most striking successes and milestone results of the condensate cosmology approach are the recovery of Friedmann-like dynamics of an emergent homogeneous and isotropic geometry [27], an extended accelerated phase of expansion [28,29] right after a cosmological bounce [30], a simple yet effective mechanism for dynamical isotropization of microscopic anisotropies [31,32] and the finding of an approximately scale-invariant and small-amplitude power spectrum of quantum fluctuations of the local volume over a homogeneous background geometry perturbed by small inhomogeneities [34]. In the following, we will quickly review the GFT formalism, give the basic structures behind its condensate cosmology spin-off, highlight the main results and give an outlook for future challenges of this program.…”

Quantum gravity and gravitational-wave astronomy

“…Quantum-gravity theories have mainly implications in the UV regime, hence often recovering an early era of accelerated expansion while avoiding the introduction of an inflaton field with a fined-tuned potential (e.g., [144,145] in the context of group field cosmology). Here we addressed the question of whether such theories can leave an imprint in late-time GW astronomy through dimensional-flow effects.…”

Reconstruction of Mimetic Gravity in a Non-Singular Bouncing Universe from Quantum Gravity

“…For further details on the effective fluid description of quantum gravity corrections in the effective Friedmann equation arising in the group field theory approach, including interactions between quanta, the reader is referred to Refs. [39,44]. For a large universe (i.e.…”