Bremsstrahlung-induced Gravitational Waves in Monomial Potentials during Reheating

Abstract

We discuss the production of primordial gravitational waves (GW) from radiative inflaton decay during the period of reheating, assuming perturbative decay of the inflaton either into a pair of bosons or fermions, leading to successful reheating satisfying constraint from Big Bang nucleosynthesis. Assuming that the inflaton $\phi$ oscillates in a general monomial potential $V(\phi)\propto \phi^n$, which results in a time-dependent inflaton decay width, we show that the resulting stochastic GW background can have optimistic detection prospects, especially in detectors that search for a high-frequency GW spectrum, depending on the choice of $n$ that determines the shape of the potential during reheating. We also discuss how this GW energy density may affect the measurement of $\Delta N_{\text{eff}}$ for bosonic and fermionic reheating scenarios.