Multi-step phase transitions and gravitational waves in the inert doublet model

The inert doublet model is a well-motivated extension of the Standard Model that contains dark matter candidate and modifies dynamics electroweak symmetry breaking. In order to detail its phenomenology, we perform comprehensive study cosmic phase transitions gravitational wave signals implied by framework, accounting for latest results collider experiments. We require neutral scalar constitute, at least, subdominant part observed abundance. While most proceed through single step, identify regions parameter space where vacuum reached after multiple transitions. resulting spectrum generally dominated single-step and, in space, falls within reach future detectors such as LISA, BBO or DECIGO. find direct detection experiments efficiently probe associated with multi-step transitions, which remain unconstrained only Higgs resonance region testable monojet searches. implications new determination $W$ boson mass are also discussed.