Sneutrinos as Mixed Inflaton and Curvaton

TL;DR

This paper explores a model where sneutrinos act as mixed inflaton and curvaton, reducing tensor-to-scalar ratio and predicting non-Gaussianities, with strong ties to neutrino physics and observational constraints.

Contribution

It introduces a sneutrino-based mixed inflaton-curvaton scenario that links neutrino parameters to inflationary observables and non-Gaussianity predictions.

Findings

The scenario evades current bounds on r and n_s.

Predicts specific levels of local non-Gaussianity (f_NL and τ_NL).

Constrains sneutrino mass using cosmological data.

Abstract

We investigate a scenario where the supersymmetric partners of two right-handed neutrinos (sneutrinos) work as mixed inflaton and curvaton, motivated by the fact that the curvaton contribution to scalar perturbations can reduce the tensor-to-scalar ratio $r$ so that chaotic inflation models with a quadratic potential are made consistent with the experimental bound on $r$. After confirming that the scenario evades the current bounds on $r$ and the scalar perturbation spectral index $n_s$, we make a prediction on the local non-Gaussianity in bispectrum, $f_{\rm NL}$, and one in trispectrum, $\tau_{\rm NL}$. Remarkably, since the sneutrino decay widths are determined by the neutrino Dirac Yukawa coupling, which can be estimated from the measured active neutrino mass differences in the seesaw model, our scenario has a strong predictive power about local non-Gaussianities, as they heavily depend on the inflaton and curvaton decay rates. Using this fact, we can constrain the sneutrino mass from the experimental bounds on $n_s$, $r$ and $f_{\rm NL}$.