PUB - Publikationen an der Universität Bielefeld

In theories with low energy supersymmetry breaking, the effective potential for squarks and sleptons has generically nearly Rat directions, V(phi) similar to M-4(log(phi/M))(n). This guarantees the existence of stable non-topological solitons, Q-balls, that carry large baryon number, B greater than or similar to (M/m(p))(4), where m(p) is the proton mass. We study the behaviour of these objects in a high temperature plasma. We show that in an infinitely extended system with a finite density of the baryon charge, the equilibrium state is not homogeneous and contains Q-balls at any temperature. In a system with a finite volume, Q-balls evaporate at a volume-dependent temperature. In the cosmological context, we formulate the conditions under which Q-balls, produced in the early Universe, survive till the present time. Finally, we estimate the baryon to cold dark matter ratio in a cosmological scenario in which Q-balls are responsible for both the net baryon number of the Universe and its dark matter. We find out naturally the correct orders of magnitude for M similar to 1-10 TeV: eta similar to 10(-10) (M/TeV)(-2)(B/10(26))(-1/2). (C) 1998 Elsevier Science B.V.