Pseudosmooth Tribrid Inflation in $SU(5)$

TL;DR

This paper presents a realistic $SU(5)$ GUT model of sneutrino inflation with a pseudosmooth trajectory, predicting specific inflationary parameters, successful reheating, leptogenesis, and gauge coupling unification.

Contribution

It introduces a novel pseudosmooth inflationary trajectory in an $R$-symmetric $SU(5)$ GUT, addressing monopole, gravitino, and unification issues with new symmetry breaking and field content.

Findings

Predicted scalar spectral index $n_s=0.968$

Tensor-to-scalar ratio $r \,\lesssim 0.0027$

Gauge symmetry breaking scale between $5\times 10^{16}$ and $5\times 10^{17}$ GeV

Abstract

A realistic tribrid model of sneutrino inflation is constructed in an $R$-symmetric $SU(5)$ grand unified theory (GUT). To avoid the monopole problem, a pseudosmooth inflationary trajectory is generated with the help of an additional $Z_5$ symmetry which is broken during and after inflation. The predictions of inflationary parameters are made at the central value of the scalar spectral index, $n_s =0.968$. The largest possible value of the tensor to scalar ratio, $r\lesssim 0.0027$, is obtained with sub-Planckian field values ($\lesssim m_P$). A successful realization of reheating and leptogenesis is achieved by avoiding the gravitino problem with a reheat temperature as low as $10^6$ GeV. The predicted range of the gauge symmetry breaking scale, $ 5 \times 10^{16} \lesssim M/\text{GeV} \lesssim 5 \times 10^{17}$, turns out to be somewhat larger than the typical GUT scale. With additional vector-like families, a successful gauge coupling unification is achieved by avoiding the no-go theorem related to $R$-symmetric $SU(5)$ GUT.