Gravitational perturbations from oscillons and transients after inflation

Abstract

We study the scalar and tensor perturbations generated by the fragmentation of the inflaton condensate into oscillons or transients after inflation, using nonlinear classical lattice simulations. Without including the backreaction of metric perturbations, we find that the magnitude of scalar metric perturbations never exceeds a few $\times 10^{-3}$, whereas the maximal strength of the gravitational wave signal today is $\mathcal{O}(10^{-9})$ for standard post-inflationary expansion histories. We provide parameter scalings for the $\alpha$-attractor models of inflation, which can be easily applied to other models. We also discuss the likelihood of primordial black hole formation, as well as conditions under which the gravitational wave signal can be at observationally interesting frequencies and amplitudes. Finally, we provide an upper bound on the frequency of the peak of the gravitational wave signal, which applies to all preheating scenarios.

18 pages, 8 figures

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• Preheating in Palatini Higgs inflation
• Classical Decay Rates of Oscillons
• Lighting the Dark: The Evolution of the Post-Inflationary Universe
• Gravitational wave spectra from oscillon formation after inflation
• Time-Scales for Nonlinear Processes in Preheating after Multifield Inflation with Nonminimal Couplings
• Gravitational effects on oscillon lifetimes
• Efficient self-resonance instability from axions
• Numerical renormalization group-based approach to secular perturbation theory
• A review on radiation of oscillons and oscillatons
• Understanding oscillons: standing waves in a ball