(P)reheating after minimal plateau inflation and constraints from CMB
In this paper we have investigated the preheating phase for a class of plateau inflationary model considering the four-legs interaction term (1/2)g2ϕ2χ2 between the inflaton (ϕ) and reheating field (χ). We specifically focus on the effects of our model parameter ϕ* which controls inflationary dynamics. For ϕ* < Mp, the departure of the inflaton potential from the usual power-law behavior ϕn significantly modifies the microscopic behavior of the preheating dynamics. We analyze and compare the efficiency of production, thermalization behavior and the final equation of states of the system for different values of n = 2,4,6 considering two different values of ϕ*. Most importantly as we increase n, or decrease ϕ*, the preheating occurs very efficiently with the final equation of state to be that of the radiation, w = 1/3. However, for n = 2, the final equation of state turned out to be w ≃ 0.2. In the non-perturbative framework complete decay of inflaton could not be achieved with the four-legs interaction for any model under consideration. Therefore, in order to complete the reheating process, we perform the perturbative analysis for the second stage of the reheating phase. With the appropriate initial condition set by the non-perturbative dynamics, we solved a set of homogeneous Boltzmann equations for both the fields supplemented by the constraints coming from the subsequent entropy conservation. In so doing, we calculated the reheating temperature which was otherwise ill-defined right after the end of preheating. The temperature can be uniquely fixed for a given inflaton decay constant and the CMB temperature. We also compare our results with the conventional reheating constraint analysis and discuss the limits on the inflaton decay constant from the field theory perspective.