Preheating and reheating effects of the Kähler moduli inflation I model

We investigate reheating in the string-theory-motivated Kähler moduli inflation I potential, coupled to a light scalar field $\chi$ and produce constraints and forecasts based on cosmic microwave background and gravitational wave observables. We implement a Markov chain Monte Carlo sampling method to compute the adopted model’s parameter ranges allowed by the current cosmic microwave background observations. Floquet analysis and numerical lattice simulations are performed to analyze the nonlinear effects of the model’s (p)reheating phase. We derive bounds on the $\mathrm{\Lambda }$-cold dark matter parameters $A_s$, $n_s$, $n_{\mathrm{run}}$, and $r$ based on Planck results, finding that correlations between model parameters severely constrain the range of these parameters allowed within this model. While the Kähler moduli inflation I potential’s nonvanishing minimum may provide a possible source for the observed dark energy density ${\rho }_{\mathrm{DE}}$ this cannot be tested with current observations. We estimate the 95% CI bounds on the inflaton mass $m_{\varphi }$ and reheating temperature $T_{\mathrm{reh}}$ to be $2.1\times {10}^{13}\mathrm{GeV}\lesssim m_{\varphi }\lesssim 3.2\times {10}^{13}\mathrm{GeV}$ and $T_{\mathrm{reh}}\gtrsim 1.8\times {10}^3\mathrm{GeV}$, respectively. We observe both self-resonance and parametric resonance instability band structures in our Floquet analysis results. Finally, we do not observe any formation of oscillon configurations in our lattice simulations; however, our results predict a stochastic gravitational wave background generated during preheating that would be observable today in the ${10}^9–{10}^{11}\mathrm{Hz}$ frequency range.