Explore Inert Dark Matter Blind Spots with Gravitational Wave Signatures

Motivated by the absence of dark matter signals in direct detection experiments and the discovery of gravitational waves (GWs) at aLIGO, we discuss the possibility to explore a generic classes of scalar dark matter models using the complementary searches via phase transition gravitational waves and the future lepton collider signatures. We focus on the inert scalar multiplet dark matter models and the mixed inert scalar dark matter models, which could undergo a strong first-order phase transitions during the evolution of the early universe, and might produce detectable phase transition GW signals at future GW experiments, such as eLISA, DECIGO and BBO. We find that the future GW signature, together with circular electron-positron collider, could further explore the model's blind spot parameter region, at which the dark matter-Higgs coupling is identically zero, thus avoiding the dark matter spin-independent direct detection constraints.