A comparative analysis of dissipation coefficients in warm inflation

In the warm inflation scenario, the early cosmic acceleration is driven by the inflaton coupled to thermal fields, decaying into radiation and leaving a hot universe populated by relativistic particles after the end of inflation. The interaction is usually modeled by a dissipation coefficient $\mathrm{{\rm Y}}$ that contains the microphysics of the model. In this work, we adopt a well-motivated potential $V(\phi )=\frac{\lambda }{4}{\phi }^4$ and constrain a variety of $\mathrm{{\rm Y}}$ parameterizations by using updated Cosmic Microwave Background data from the $\mathit{\text{Planck}}$ and $\mathit{\text{BICEP/Keck}}\mathit{\text{Array}}$ collaborations. We also use a Bayesian statistical criterion to compare the observational viability of these models. Our results show a significant improvement in the constraints over past results reported in the literature and also that some of these warm inflation models can be competitive compared to Starobinsky inflation.