Description
A scalar field undergoing coherent oscillations can exhibit parametric resonance, leading to resonant amplification of field fluctuations that can source gravitational waves with characteristic spectra. We illustrate two key implications of this framework. First, such oscillating spectator scalar fields can naturally accommodate a candidate for the (ultralight) dark matter or dark radiation. Second, in a low-energy realization of Affleck–Dine baryogenesis, a light scalar field with mass of order a few GeV generates the baryon asymmetry while sourcing gravitational waves peaking in the CE/DECIGO frequency band. We highlight a compelling complementarity between gravitational-wave observations, cosmology, and laboratory searches for physics beyond the Standard Model.
