We discuss the production of gravity waves from the fragmentation of a supersymmetric condensate in the early Universe. Supersymmetry predicts the existence of flat directions in the potential. At the end of inflation, the scalar fields develop large time-dependent vacuum expectation values along these flat directions. Under some general conditions, the scalar condensates undergo a fragmentation into nontopological solitons, $Q$-balls. We study this process numerically and confirm the recent analytical calculations showing that it can produce gravity waves observable by the Advanced Laser Interferometer Gravitational Wave Observatory, Laser Interferometer Space Antenna, and Big Bang Observer. The fragmentation can generate gravity waves with an amplitude as large as ${\Omega }_{\mathrm{GW}}{h}^2\sim {10}^{-11}$ and with a peak frequency ranging from 1 mHz to 10 Hz, depending on the parameters. The discovery of such a relic gravitational background radiation can open a new window on the physics at the high scales, even if supersymmetry is broken well above the electroweak scale.

• Received 13 February 2009

DOI:https://doi.org/10.1103/PhysRevD.79.124034