Reheating dynamics affects non-perturbative decay of spectator fields

Abstract

The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g 2 σ 2 Φ 2 , the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling g 10 −3 , the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.

Effective action for cosmological scalar fields at finite temperature

“…Some progress towards an inclusion of medium effects on the effective potential has recently been made e.g. in [34,35,52,53,71,72,75,[89][90][91][92][93], and phenomenological implications have been discussed in [76,[94][95][96][97][98][99][100][101][102], but it is still a long way to go to a complete quantitative understanding of scalar fields in the early universe in realistic models.…”

Gravitational wave production from preheating: parameter dependence

“…Following inflation, the condensate amplitude will oscillate around the minimum of its potential. The paradigmatic example of this is the curvaton scenario [16][17][18][19], where the curvaton field may decay via parametric resonance after inflation, transferring abruptly all its energy to the particle species coupled to it [20][21][22][23]. Another example of a spectator field, naturally decaying through parametric resonance after inflation, is the Higgs field of the Standard Model (SM).…”

The minimal curvaton-higgs model

“…Non-perturbative decay can occur and was discussed in detail for this model in [4,5] (for earlier discussion of nonperturbative curvaton decay, see [14][15][16][17]). For this, it is essential to take into account corrections due to the thermal background of the inflaton decay products.…”

“…Most energy is transferred to the higgs in modes which are initially outside the resonance band. The condition for efficient transfer of energy from the curvaton to the higgs is given by [5] …”