Oscillon decay via parametric resonance: the case of three-point scalar interactions

Abstract

We investigate the decay dynamics of oscillons through interactions with an external scalar field. To examine how robust the decay dynamics of oscillons via parametric resonance we previously found in Li et al. 2025 are to the specific form of the coupling, we extend the analysis to include a three-point interaction $g_3\phi\chi^2$. We compute the Floquet exponents of the external field $\chi$ under an oscillating oscillon background and analyze how the instability bands depend on the coupling constants and the oscillon shapes. Numerical simulations of the two-field system show that, similar to the four-point case, the parametric resonance may cease before the oscillon is destroyed, leaving a smaller oscillon that decays only perturbatively. This indicates that the partial decay of oscillons through parametric resonance is a generic phenomenon of oscillon-scalar couplings, qualitatively insensitive to the specific interaction form, while the shape of instability bands, parameter dependence, and the precise critical oscillon energies depend on the specific coupling. Our findings provide further insights into the decay dynamics of oscillons and their potential role in the post-inflationary reheating process.