2025/12/03 by Marcos A. G. García, Garcia, Marcos A. G., Sarunas Verner +1 · 2 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Pulsars and Gravitational Waves Research #Dark Matter and Cosmic Phenomena
paper · pdf · doi:10.48550/arxiv.2512.04240
We present a mechanism for gravitational wave (GW) production from isocurvature perturbations in spectator scalar fields during inflation. These energetically subdominant fields develop blue-tilted power spectra through inflationary dynamics, generating second-order scalar perturbations that source a stochastic GW background. The mechanism naturally satisfies CMB constraints at large scales while producing enhanced signals at smaller scales across a broad frequency range 10-20 - 1 Hz. We perform comprehensive numerical and analytical calculations of the complete isocurvature spectrum evolution, including gravitational particle production, reheating dynamics, and scalar-induced GW generation. For spectator fields with effective masses 0.5 \lesssim mχ,eff/HI, the resulting GW energy density reaches ΩGW h2 ∼ 10-20-10-12, accessible to pulsar timing arrays, space-based interferometers, and next-generation CMB experiments. Our analysis reveals that GW-induced constraints exceed current isocurvature bounds. We examine both unstable (curvaton-like) and stable (dark matter) spectator fields, demonstrating strong sensitivity to reheating temperature, inflaton-spectator coupling, and decay dynamics. This framework establishes isocurvature-sourced GWs as a powerful probe of early universe physics, enabling simultaneous constraints on inflationary dynamics, dark matter production, and reheating through coordinated multi-frequency GW observations.