Abstract
We revisit the dynamics of the curvaton in detailtaking account of effects from thermal environment,effective potential and decay/dissipation rate for general field values and couplings.We also consider the curvature perturbationgenerated through combinations of various effects:large scale modulation of the oscillation epoch, the effective dissipation rateand the timing at which the equation of state changes.In particular, we find that it tends to be difficult to explain the observed curvature perturbation by the curvaton mechanismwithout producing too large non-Gaussianity if the curvaton energy density is dissipated through thermal effects.In particular, we find that if the renormalizable coupling between the curvaton and light elements is larger thanthe critical value ∼ (mϕ/Mpl)1/2, the curvaton is soon dissipated awayalmost regardless of its initial energy density, contrary to the standard perturbative decay.Therefore, the interaction between them should be suppressedin order for the curvaton to survive the thermal dissipation.
Highlights
We revisit the dynamics of the curvaton in detail taking account of effects from thermal environment, effective potential and decay/dissipation rate for general field values and couplings
Thermal background and/or loop corrections modify the effective potential for φ, which change the properties of the scalar field oscillation
(1) Fluctuations of the initial field value φi yield fluctuations of the energy density of φ as in the ordinary curvaton model, (2) The oscillation epoch of φ may depend on φi [27,28,29], (3) The epoch at which equation of state of φ changes may depend on the amplitude of φ, (4) The effective decay/dissipation rate of φ may depend on the amplitude of φ
Summary
Let us consider the non-perturbative particle production of χ and ψ. ≫ m2th,χ/ψ implies that if thermal mass of χ/ψ is large enough to maintain condition k∗,χ/ψ their adiabaticity, the non-perturbative particle production does not occur. Since the above inequality implies αth,χ/ψ T 2 ≫ k∗,χ/ψ non-perturbative production given in Eq (20) is violated if mφ,eff < mth,χ/ψ In this region, the φ condensation dissipates its energy dominantly via interactions with thermally populated χ/ψ particles. The effective dissipation rates caused by thermally populated χ particles are the followings: eff,slow,χ. Note that even though the homogeneous φ condensation disappears solely by the quartic interaction λ2 φ 2 |χ 2 |, the distribution of produced φ particles is still dominated by the infrared regime which is much smaller than the temperature of thermal plasma. It is shown that whenever the homogeneous φ condensation can disappear completely, the produced φ particles soon cascades toward the UV regime due to the scattering with the thermal plasma via the quartic interaction and participates in the thermal plasma [8]
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