Collider tests of nanohertz gravitational waves

\nRecently, compelling evidence of nanohertz gravitational waves is indicated by the pulsar timing array collaborations. We present an MeV-scale first-order phase transition from a minimal dark sector to explain the gravitational waves, with a focus on the collider tests via the Higgs portal interaction. We demonstrate that to explain the observed gravitational waves, the Higgs portal coupling should be so sizable that it can be probed through Higgs invisible decay at the LHC and future colliders such as HL-LHC, CEPC, ILC, and FCC-ee. It opens up a promising avenue to uncover the physical origin of the nanohertz gravitational waves via colliders and to hear and see the minimal dark sector.\n