Multifield reheating after modular j-inflation

Abstract

In the inflationary framework of cosmology the initial phase of rapid expansion has to be followed by a reheating stage, which is envisioned to end in a radiation dominated big bang. Key parameters that characterize this big bang state are the temperature at the end of the reheating stage and the baryon asymmetry. For general interacting theories these parameters are difficult to obtain analytically because of the involved structure of the potential. In this paper multifield reheating is considered for interacting theories in which the inflaton trajectory is weakly curved. This scenario is realized in the model of j-inflation, a particular example of modular inflation, allowing an estimate of the reheat temperature.

Modular inflation at higher levelN

“…It was shown in refs. [7,18,19] that the resulting inflationary model is compatible with the CMB observations of WMAP and Planck.…”

“…Associated to the isocurvature perturbations S IJ are the power spectra P RS IJ and P S IJ S KL and their spectral indices n RS IJ and n S IJ S KL , which can be explicitly computed as well. The power spectrum P SS of the isocurvature projection (10) coincides with that of P RR at horizon crossing n SS = n RR (19) and there is no cross correlation P RS = 0. Hence at horizon crossing the correlation coefficient γ corr , defined by…”

“…Reheating aspects of this model were furthermore discussed in [19,29]. In the present section we generalize the framework considered in [7,18] to subgroups at higher levels N > 1.…”

“…Recall that all modular inflation models have the same target space geometry given by the Poincaré metric. The different potentials of h N -inflation, as well as j-inflation [7,18,19], however lead to different neighborhoods U N (τ I * ) and U j (τ I * ) of the domain in which the slow-roll parameters are small. Hence the degree of the deviation from the flat limit of the geometry is different for these models as N varies.…”

Hidden symmetries of two-field cosmological models

“…Notice that the Hesse symmetry generating function Λ is not assumed to be rotationally symmetric, even though we assume that the scalar manifold metric is.3 Generalized two-field α-attractors extend ordinary two-field α-attractor models[25][26][27][28][29][30][31][32] (whose target space is the hyperbolic disk) to models whose target space is allowed to be an arbitrary complete hyperbolic surface. As explained in[21][22][23][24], such models can be approached through uniformization theory, which relates them to the framework of modular inflation developed and studied in[33][34][35][36][37].…”