AXION MINICLUSTERS AND BOSE STARS

Evolution of inhomogeneities in the axion field around the QCD epoch i s studied numerically, including for the first time important nonlinea r effects. It is found that perturbations on scales corresponding to c ausally disconnected regions at T approximately 1 GeV can lead to very dense axion clumps, with present density rho(a) greater than or simil ar to 10(-8) g cm-3. This is high enough for the collisional 2a --> 2a process to lead to Bose-Einstein relaxation in the gravitationally bo und clumps of axions, forming Bose stars.