Q-ball formation in the wake of Hubble-induced radiative corrections

Abstract

We discuss some interesting aspects of the $\mathrm{Q}$-ball formation during the early oscillations of the flat directions. These oscillations are triggered by the running of soft $(\mathrm{mass}{)}^2$ stemming from the nonzero energy density of the Universe. However, this is quite different from the standard $\mathrm{Q}$-ball formation. The running in presence of gauge and Yukawa couplings becomes strong if $m_{1/2}/m_0$ is sufficiently large. Moreover, the $\mathrm{Q}$-balls which are formed during the early oscillations constantly evolve, due to the redshift of the Hubble-induced soft mass, until the low-energy supersymmtery breaking becomes dominant. For smaller $m_{1/2}/m_0$, $\mathrm{Q}$-balls are not formed during early oscillations because of the shrinking of the instability band due to the Hubble expansion. In this case the $\mathrm{Q}$-balls are formed only at the weak scale, but typically carry smaller charges, as a result of their amplitude redshift. Therefore, the Hubble-induced corrections to the flat directions give rise to a successful $\mathrm{Q}$-ball cosmology.

Comments: 7 revtex pages, few references corrected and added, final version to appear in Phys. Rev. D