Preheating after multifield inflation with nonminimal couplings. III. Dynamical spacetime results

Abstract

This paper concludes our semi-analytic study of preheating in inflationary models comprised of multiple scalar fields coupled nonminimally to gravity. Using the covariant framework of Ref.[1], we extend the rigid-spacetime results of Ref.[2] by considering both the expansion of the universe during preheating, as well as the effect of the coupled metric perturbations on particle production. The adiabatic and isocurvature perturbations are governed by different effective masses that scale differently with the nonminimal couplings and evolve differently in time. The effective mass for the adiabatic modes is dominated by contributions from the coupled metric perturbations immediately after inflation. The metric perturbations contribute an oscillating tachyonic term that enhances an early period of significant particle production for the adiabatic modes, which ceases on a time-scale governed by the nonminimal couplings ξ I . The effective mass of the isocurvature perturbations, on the other hand, is dominated by contributions from the fields' potential and from the curvature of the field-space manifold (in the Einstein frame), the balance between which shifts on a time-scale governed by ξ I . As in Refs.

Some like it hot: R2 heals Higgs inflation, but does not cool it

“…Therefore, even though both R 2 -healed and "pure" Higgs inflation reheat via the generation of longitudinal weak gauge bosons, the underlying dynamics are rather different. In particular, we confirm that the spike in the mass of the longitudinal gauge bosons [24][25][26] does not produce the weak bosons in the amount sufficient for reheating [30].…”

“…This expression gives the estimate for the mass mode with the largest absolute value, and coincides with m 2 H for positive mass, and m 2 L for tachyonic mass. It coincides with the diagonal mass of the mode H k in (25). At Φ 0 < 0 it is positive, while can be negative for positive scalaron.…”

“…Outside of this region, the L and H modes are separable. Furthermore, when ω L and ω H are varying adiabatically slowly, one has WKB solutions to (25) and (26), and a particle interpretation for ϕ (L,H) . This is true for any time when the scalaron is sufficiently far away from Φ 0 = 0, so one may legally quantize ϕ (L,H) during these adiabatic time slots.…”

“…The crucial ingredient -the evolution of longitudinal components of the weak gauge bosonswas missed there. The dependence of this component on the external Higgs field (inflaton) turns out to be spiky [24][25][26], leading to violent production of longitudinal modes of the weak gauge bosons and very rapid reheating of the Universe. This finding is dangerous due to the strong coupling problem, since the reheating dynamics happen right inside the strong coupling domain, making any analysis unreliable.…”

To positivity and beyond, where Higgs-Dilaton inflation has never gone before

“…All physical scales in the low energy Lagrangian are thus given in terms of dimensionless couplings in 1 The gracefulness of this exit has been however recently questioned. See [41][42][43][44][45] and references therein.…”