It has been observed that if an extra scalar field (in addition to the inflaton) is present during the inflationary phase, its decay into thermal radiation after baryogenesis gives rise to flucuations in the initially smooth entropy-per-baryon ratio. There was a hope that these perturbations were of the isocurvature type and that they may help explain several observed features in the large-scale structure of the Universe. We study in detail the generation of perturbations in such a two-field inflationary model. We find that the resulting flucuations are not of the isocurvature type, but that the entropy perturbation induces a curvature fluctuation which is larger than the entropic one before the wavelengths of the perturbations enter the Hubble radius. Thus, this model is not a good candidate to provide the initial conditions for the baryon isocurvature perturbations.

• Received 1 November 1989

DOI:https://doi.org/10.1103/PhysRevD.42.313