Gravitational waves as a probe of SUSY scale

We investigate the sources of the Hubble-induced mass for a flat direction in supersymmetric theories and show that the sign of the Hubble-induced mass generally changes just after the end of inflation. This implies that global cosmic strings generally form after the end of inflation in most supersymmetric models, including the Minimal Supersymmetric Standard Model. The cosmic strings emit gravitational waves whose frequency corresponds to the Hubble scale, until they disappear when the Hubble parameter decreases down to the soft mass of the flat direction. As a result, the peak frequency of gravitational waves is related to the supersymmetric scale. The observation of this gravitational wave signal will give us information of supersymmetric scale and reheating temperature.