  In this paper, we extensively analyzed the reheating dynamics after inflation
and looked into its possible implication on dark matter (DM) and inflaton
phenomenology. We studied the reheating through various possible channels of
inflaton going into massless scalars (bosonic reheating) and fermions
(fermionic reheating) via non-gravitational and gravity-mediated decay
processes. We further include the finite temperature effect on the decay
process. Along with their precise roles in governing the dynamics, we compared
the relative importance of different temperature-corrected decay channels in
the gradual process of reheating depending on the reheating equation of state
(EoS), which is directly related to inflaton potential. Particularly, the
universal gravitational decay of inflaton is observed to play a very crucial
role in the reheating process for a large range of inflaton decay parameters.
For our study, we consider typical $\alpha$-attractor inflationary models. We
further establish the intriguing connection among those different inflaton
decay channels and the CMB power spectrum that can have profound implications
in building up a unified model of inflation, reheating, and DM. We analyze both
fermion and scalar DM with different physical processes being involved, such as
gravitational scattering, thermal bath scattering, and direct inflaton decay.
Gravitational decay can again be observed to play a crucial role in setting the
maximum limit on DM mass that has already been observed earlier in the
literature [52]. Depending on the coupling strength, we have analyzed in detail
the production of both FIMP and WIMP-like DM during reheating and their
detailed phenomenological implications from the perspective of various
cosmological and laboratory experiments.
