Inflation, Gravitino and Reheating in Modified Modular invariant Supergravity

Abstract

A new modified string-inspired modular invariant supergravity model is proposed and is applied to realize the slow roll inflation in Einstein frame. Because inflation deals with Planck scale physics, the dilaton can be a strong candidate for identification with the inflaton. The model we used, cleared the $\eta$-problem and negative energy problem of potential at stable point, and appeared to predict successfully the values of observations at the inflation era. We proved that the model explains WMAP observations appropriately. Moreover, a mechanism of SSB and Gravitino production just after the end of inflation is investigated. We have obtained power spectrum of the density perturbation as $\mathcal{P_R}_* \sim 2.438 \times 10^{-9}$ and the scalar spectral index as $n_{s*}\sim 0.9746$ and its tilt as $\alpha_{s*}\sim -4.3 \times 10^{-4}$. The ratio between scalar power spectrum and tensor is predicted as $r\sim 6.8 \times 10^{-2}$, a prediction which seems in the range possibly observed by the Planck satellite soon. The gravitino mass and their production rate from scalar fields are estimated at certain values of parameters in the model. The reheating temperature is estimated by the stability condition of Boltzmann equation by using the decay rate of the dilaton S into gauginos as $T_R({\rm gaugino}) = 3.88 \times 10^{7} \,\, {\rm GeV}$. Though only one example of parameter choices has been discussed here, the other seven candidates of parameter choices that are compatible with WMAP data have already been found by the authors. Some of the examples show that the gauginos can be observed by LHC experiments. The plausible supergravity model of inflation which here we described will open the hope to construct a realistic theory of particle theory and cosmology in this framework.