Gravitational waves in metastable supersymmetry breaking

Abstract

If supersymmetry is broken in metastable vacua, it is not clear why we are now in there rather than supersymmetric vacua. Moreover, it is natural to expect that we were in supersymmetric vacua, which have higher symmetry than metastable vacua, in the early universe. In this paper, we reexamine and improve the previous analysis on the cosmological evolution of the vacuum structure in the ISS model of metastable supersymmetry breaking by taking into account constraints on the reheating temperature, which is needed to avoid the overproduction of gravitinos. It turns out that the desired phase transition from a supersymmetric vacuum to a metastable vacuum is allowed only in the light gravitino mass region $m_{3/2} < 4.7$ eV. This is achieved by either rolling down potential or tunneling processes depending on the reheating temperature. We show that when the tunneling processes are realized, abundant gravitational waves could be produced from collisions of runaway bubbles. The resulting gravitational waves are detectable with the future gravitational wave interferometers like LISA and DECIGO.