Inflation in Symmergent Metric-Palatini Gravity

TL;DR

This paper explores how symmergent gravity, which unifies gravity with the standard model through matter loop corrections, can drive cosmic inflation consistent with observational data, depending on specific matter sector parameters.

Contribution

It demonstrates that symmergent gravity's parameters can produce inflationary results compatible with observations, linking matter sector properties to inflation.

Findings

Inflation occurs when the quadratic curvature coefficient is negative.

Vacuum energy and quadratic curvature enable inflation under certain matter sector conditions.

Results depend on the matter sector's fermion and boson dominance and mass degeneracy deviations.

Abstract

In this paper, we study the cosmological inflation phenomenon in symmergent gravity theory. Symmergent gravity is a novel framework which merges gravity and the standard model (SM) so that the gravity emerges from the matter loops and restores the broken gauge symmetries along the way. Symmergent gravity is capable of inducing the gravitational constant $G$ and the quadratic curvature coefficient $c_O$ from the loop corrections of the matter sector in a flat space-time. In the event that all the matter fields, including the beyond the standard model (BSM) sector, are mass degenerate, the vacuum energy can be expressed in terms of $G$ and $c_O$. The parameter which measures the deviation from the mass degeneracy is dubbed $\hat{\alpha}$. The parameters, $c_O$ and $\hat{\alpha}$, of symmergent gravity convey the information about the fermion and boson balance in the matter (SM+BSM) sector in number and in mass, respectively. In our analysis, we have investigated the space of the symmergent parameters $c_O$ and $\hat{\alpha}$ wherein they produce results that comply with the inflationary observables $n_s$, $r$, and $\mathrm{d}n_s/\mathrm{d}\ln k$. We have shown that the vacuum energy together with the quadratic curvature term arising in the symmergent gravity prescription are capable of inflating the universe provided that the quadratic curvature coefficient $c_O$ is negative (which corresponds to fermion dominance in number in the matter sector) and the deviation from the mass degeneracy in the matter sector is minute for both boson mass dominance and fermion mass dominance cases.