Conformal GUT inflation, proton lifetime and non-thermal leptogenesis

TL;DR

This paper extends conformal GUT inflation models with singlet fields, deriving inflationary predictions, estimating proton lifetime, and exploring non-thermal leptogenesis, linking cosmology with particle physics and neutrino mass generation.

Contribution

It introduces a conformal GUT inflation framework with singlet fields, connecting inflation, proton decay, and neutrino masses in a unified model.

Findings

Inflation predictions: n_s ~ 1 - 2/N, r ~ 12/N^2 for N=50-60.

Proton lifetime estimated as τ_p ≲ 10^40 years.

Reheating temperature constrained between 10^6 and 10^9 GeV.

Abstract

In this paper, we generalize Coleman-Weinberg (CW) inflation in grand unified theories (GUTs) such as $\text{SU}(5)$ and $\text{SO}(10)$ by means of considering two complex singlet fields with conformal invariance. In this framework, inflation emerges from a spontaneously broken conformal symmetry. The GUT symmetry implies a potential with a CW form, as a consequence of radiative corrections. The conformal symmetry flattens the above VEV branch of the CW potential to a Starobinsky plateau. As a result, we obtain $n_{s}\sim 1-\frac{2}{N}$ and $r\sim \frac{12}{N^2}$ for $N\sim 50-60$ e-foldings. Furthermore, this framework allow us to estimate the proton lifetime as $\tau_{p}\lesssim 10^{40}$ years, whose decay is mediated by the superheavy gauge bosons. Moreover, we implement a type I seesaw mechanism by weakly coupling the complex singlet, which carries two units of lepton number, to the three generations of singlet right handed neutrinos (RHNs). The spontaneous symmetry breaking of global lepton number amounts to the generation of neutrino masses. We also consider non-thermal leptogenesis in which the inflaton dominantly decays into heavy RHNs that sources the observed baryon asymmetry. We constrain the couplings of the inflaton field to the RHNs, which gives the reheating temperature as $10^{6}\text{ GeV}\lesssim T_{R}<10^{9}$ GeV.