This paper studies the stability of warm inflationary solutions when the viscous pressure is taken into account. The latter is a very natural and physically motivated ingredient of warm inflation and is seen to widen the stability range of warm inflation. The spectral index parameters, ns, UT, and their ratio are derived. The corresponding WMAP7 data are used to fix some parameters of the model. Two specific examples are discussed in detail: (i) a potential given by V((φ),T) = vi((φ)) + V2(T), and (ii) a potential of the form V(φ,T) = αv1((φ) v2(T). In both cases, the viscosity has little impact on the said ratio.
- Cosmological perturbation theory