Early universe in quantum gravity
Abstract
We present a new picture of the early universe in finite nonlocal quantum gravity, which is Weyl invariant at the classical and quantum levels. The high-energy regime of the theory consists of two phases, a Weyl invariant trans-Planckian phase and a post-Planckian or Higgs phase described by an action quadratic in the Ricci tensor and where the cosmos evolves according to the standard radiation-dominated model. In the first phase, all the issues of the hot big bang such as the singularity, flatness, and horizon problems find a universal and simple non-inflationary solution by means of Weyl invariance, regardless of the microscopic details of the theory. In the second phase, once Weyl symmetry is spontaneously broken, primordial perturbations are generated around a background that asymptotically evolves as a radiation-dominated flat Friedmann--Lema\^{i}tre--Robertson--Walker universe.
Cite
@article{arxiv.2206.06384,
title = {Early universe in quantum gravity},
author = {Leonardo Modesto and Gianluca Calcagni},
journal= {arXiv preprint arXiv:2206.06384},
year = {2024}
}
Comments
1+43 pages, 7 figures. v2: nature of beta coefficients and solution of flatness problem clarified, discussion on spontaneous symmetry breaking expanded. v3: discussions on background metrics and on singularity problem resolution substantially clarified, derivation of cosmological spectra moved to companion paper arXiv:2206.07066, references added. Main results unchanged. v4: typos corrected