Cosmological perturbations in warm inflationary models with viscous pressure

Scalar and tensorial cosmological perturbations generated in warm inflationary scenarios whose matter-radiation fluid is endowed with a viscous pressure are considered. Recent observational data from the Wilkinson Microwave Anisotropy Probe experiment are employed to restrict the parameters of the model. Although the effect of this pressure on the matter power spectrum is of the order of a few percent, it may be detected in future experiments. © 2007 The American Physical Society.