CMB POLARIZATION DURING THE SECONDARY IONIZATION OF MATTER

The cosmic microwave background (CMB) polarization, whose experimental detection must become the next natural step in the study of the CMB r adiation, depends on the dynamics of hydrogen recombination in the Uni verse, on the relation between the power of scalar perturbations and g ravitational waves, and on the presence or absence of secondary ioniza tion. The spectrum of the CMB anisotropy is currently known with an ac curacy that is high enough to draw some conclusions about the cosmolog ical parameters and about the presence of secondary ionization of matt er. The reduction of observational data strongly suggests the presence of secondary ionization. We consider the effect of this ionization at redshifts z < 100 on the CMB polarization generated by the scalar mod e on various angular scales.