Abstract
Oscillons are spatially localized and relatively stable field fluctuations which can form after inflation under suitable conditions. In order to reheat the universe, the fields which dominate the energy density after inflation have to couple to other degrees of freedom and finally produce the matter particles present in the universe today. In this study, we use lattice simulations in 2+1 dimensions to investigate how such couplings can affect the formation and stability of oscillons. We focus on models of hilltop inflation, where we have recently shown that hill crossing oscillons generically form, and consider the coupling to an additional scalar field which, depending on the value of the coupling parameter, can get resonantly enhanced from the inhomogeneous inflaton field. We find that three cases are realized: without a parametric resonance, the additional scalar field has no effects on the oscillons. For a fast and strong parametric resonance of the other scalar field, oscillons are strongly suppressed. For a delayed parametric resonance, on the other hand, the oscillons get imprinted on the other scalar field and their stability is even enhanced compared to the single-field oscillons.
Highlights
In this paper we have investigated how oscillons, which are spatially localized and relatively stable fluctuations of the inflaton field φ that can form after inflation, are affected by the couplings to other scalar fields
We considered hilltop inflation models of the type studied in [9, 14, 15], where we have recently shown that hill crossing oscillons generically form [14]
In [15] we have shown that when another scalar field χ is coupled to the inflaton, depending on the value of the coupling parameter, the latter can get resonantly enhanced by the inhomogeneous inflaton field
Summary
For the hilltop inflation model of eq (2.1), the initial conditions for observable inflation are generated dynamically via a preinflation mechanism, as shown in [9]. Χ is slowly rolling towards 0 during a phase of preinflation With both φ and χ close to 0, the induced mass term for φ becomes so small that the fields are in a diffusion region where quantum fluctuations dominate over classical rolling. When the fields eventually leave the diffusion region and φ starts rolling down the top of the hill towards one of the minima of the potential at φ = ±v (while χ ≈ 0), this provides suitable initial conditions for the observable phase of inflation to start. The form of the interaction term is fixed by giving Xone unit of U(1)R charge and two units of Zp charge
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