GW signatures and spinning axions
Peera Simakachorn (DESY and U. Hamburg)

In presence of a kination era, induced by a fast-moving scalar field dominating the energy density of the universe, stochastic gravitational-wave (GW) backgrounds can be dramatically enhanced. Not only this could boost the detectability of primordial GW from cosmic strings or primordial inflation at current and future-planned GW observatories, but it could also help constraining particle theories that generate the kination phase. We find that kination era at the GeV-EeV scale can induce a GW peak in the window of ET and CE. In this work, we present two classes of spinning axion models in which a phase of matter-domination followed by kination-domination is naturally generated. Ultimately, it is possible to relate the GW signatures to the relic abundance of axion dark matter or to the baryon asymmetry of the universe.