Correlated hybrid fluctuations from inflation with thermal dissipation

We investigate the primordial scalar perturbations in thermal dissipative inflation where the radiation component (thermal bath) persists and the density fluctuations are thermally originated. The perturbation generated in this model is hybrid; i.e., it consists of both adiabatic and isocurvature components. We calculate the fractional power ratio (S) and the correlation coefficient [Formula Presented] between the adiabatic and the isocurvature perturbations at the commencing of the radiation regime. Since the adiabatic or isocurvature decomposition of hybrid perturbations generally is gauge dependent at superhorizon scales, when there is substantial energy exchange between the inflaton and the thermal bath, we carefully perform a proper decomposition of the perturbations. We find that the adiabatic and the isocurvature perturbations are correlated, even though the fluctuations of the radiation component are considered uncorrelated with that of the inflaton. We also show that both S and [Formula Presented] depend mainly on the ratio between the dissipation coefficient [Formula Presented] and the Hubble parameter H during inflation. The correlation is positive [Formula Presented] for strong dissipation cases where [Formula Presented] and is negative for weak dissipation instances where [Formula Presented] Moreover, S and [Formula Presented] in this model are not independent of each other. The predicted relation between S and [Formula Presented] is consistent with the Wilkinson Microwave Anisotropy Probe observation. Other testable predictions are also discussed.