Gravitational Wave Signals of Pseudo-Goldstone Dark Matter in the ${\mathbb{Z}}_3$ Complex Singlet Model

We study pseudo-Goldstone dark matter in the ${\mathbb{Z}}_3$ complex scalar singlet model. Because the direct detection spin-independent cross section is suppressed, such dark matter is allowed in a large mass range. Unlike in the original model stabilized by a parity, due to the cubic coupling of the singlet the ${\mathbb{Z}}_3$ model can accommodate first-order phase transitions that give rise to a stochastic gravitational wave signal potentially observable in future space-based detectors.