Detectable Gravitational Wave Signals from Inflationary Preheating
  We consider gravitational wave (GW) production during preheating in hybrid
inflation models where an axion-like waterfall field couples to Abelian gauge
fields. Based on a linear analysis, we find that the GW signal from such models
can be within the reach of a variety of foreseeable GW experiments such as
LISA, AEDGE, ET and CE, and is close to that of LIGO A+, both in terms of
frequency range and signal strength. Furthermore, the resultant GW signal is
helically polarized and thus may distinguish itself from other sources of
stochastic GW background. Finally, such models can produce primordial black
holes that can compose dark matter and lead to merger events detectable by GW
detectors.
