We present WarmSPy, a numerical code in Python designed to solve for the
perturbations' equations in warm inflation models and compute the corresponding scalar power
spectrum at CMB horizon crossing. In models of warm inflation, a radiation bath of temperature T
during inflation induces a dissipation (friction) rate of strength Q ∝ Tc
/ϕm
in the
equation of motion for the inflaton field ϕ. While for a temperature-independent dissipation
rate (c = 0) an analytic expression for the scalar power spectrum exists, in the case of a
non-zero value for c the set of equations can only be solved numerically. For c > 0 (c < 0), the
coupling between the perturbations in the inflaton field and radiation induces a growing
(decaying) mode in the scalar perturbations, generally parameterized by a multiplicative function
G(Q) which we refer to as the scalar dissipation function. Using WarmSPy, we provide an
analytic fit for G(Q) for the cases of c = {3,1,-1}, corresponding to three cases that have
been realized in physical models. Compared to previous literature results, our fits are more
robust and valid over a broader range of dissipation strengths
Q ∈ [10-7,104]. Additionally, for the first time, we numerically assess the stability of
the scalar dissipation function against various model parameters, inflationary histories as well
as the effects of metric perturbations. As a whole, the results do not depend appreciably on most
of the parameters in the analysis, except for the dissipation index c, providing evidence for
the universal behaviour of the scalar dissipation function G(Q).