New inflation in supergravity with a chaotic initial condition

TL;DR

This work addresses a self-consistent supergravity inflationary scenario that begins with chaotic inflation near the Planck scale to resolve the longevity problem and to set initial conditions for a subsequent slow-roll inflation. A single supermultiplet with a shift-symmetric Kähler potential and a symmetry-breaking superpotential realizes chaotic inflation via the imaginary component and a later new inflation via the real component, yielding a tilted spectrum with $n_s<1$ and a low reheating temperature $T_R$ that mitigates the gravitino problem. COBE normalization fixes model parameters so that $v \\simeq 2.3\times 10^{-2} \\sqrt{c} \, e^{-cN/2}$ at $N\approx 60$ with $0<c<0.1$ (so $1<g<1.05$) and $H \\simeq v^2/\\sqrt{3}$ during new inflation; the amplitude of curvature perturbations follows the standard one-field expression during this phase. The framework also accommodates leptogenesis and discusses potential observational traces of the chaotic stage, depending on the duration of the subsequent inflation, highlighting its significance for connecting Planck-scale physics to large-scale structure observations.

Abstract

We propose a self-consistent scenario of new inflation in supergravity. Chaotic inflation first takes place around the Planck scale, which solves the longevity problem, namely, why the universe can live much beyond the Planck time, and also gives an adequate initial condition for new inflation. Then, new inflation lasts long enough to generate primordial fluctuations for the large scale structure, which generally has a tilted spectrum with the spectral index $n_{s} < 1$. The successive decay of the inflaton leads to the reheating temperature low enough to avoid the overproduction of gravitinos in a wide range of the gravitino mass.