Speaker
Dr
Kiyoharu Kawana
(SNU)
Description
In this talk, I discuss a possibility that the CMB anisotropy is dominantly generated by the primordial fluctuations of QCD axion under a circumstance that usual fluctuations by inflaton is too small to explain the anisotropy. The following conditions must be satisfied in this scenario: (i) sufficient amplitudes of the CMB anisotropy (ii) isocurvature constraint and (iii) non Gaussianity constraint. By carefully studying those conditions, I show that a large energy fraction $\Omega_A$ of the axion is necessary at the QCD phase transition, but simultaneously, it must become tiny at the present era due to the isocurvature constraint.
