2023/07/03 by Reza Ebadi, Ebadi, Reza, Soubhik Kumar +7 · 4 citations
Economics, Econometrics and Finance · Physics and Astronomy · #Complex Systems and Time Series Analysis #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Phenomenology (hep-ph) #Stochastic processes and financial applications
paper · pdf · doi:10.48550/arxiv.2307.01248
openalex publication_date 2023/07/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We present a novel mechanism for gravitational wave generation in the early Universe. Light spectator scalar fields during inflation can acquire a blue-tilted power spectrum due to stochastic effects. We show that this effect can lead to large curvature perturbations at small scales (induced by the spectator field fluctuations) while maintaining the observed, slightly red-tilted curvature perturbations at large cosmological scales (induced by the inflaton fluctuations). Along with other observational signatures, such as enhanced dark matter substructure, large curvature perturbations can induce a stochastic gravitational wave background (SGWB). The predicted strength of SGWB in our scenario, Ω\rm GWh2 ≃ 10-20 - 10-15, can be observed with future detectors, operating between 10-5 Hz and 10 Hz. We note that, in order to accommodate the newly reported NANOGrav observation, one could consider the same class of spectator models. At the same time, one would need to go beyond the simple benchmark considered here and consider a regime in which a misalignment contribution is also important.