Speaker
Description
The chiral gravitational wave background (GWB) can be generated by axion‑like fields in the early universe. The conventional notion of an audible axion relies on couplings between axions and gauge fields. Here we consider an axion‑like mechanism coupled to the gravitational topological term, which enables direct and efficient production of gravitational waves during the radiation‑dominated era of the early Universe. We compute the energy spectral density of the chiral gravitational wave background and the comoving energy density of axion‑like fields. Using our numerical results, we explore the parameter space of axion masses and decay constants that yield detectable gravitational wave signals for both pulsar timing arrays and space‑based gravitational wave detectors.[2604.08141 & 2412.18420].
