Search

We study the nonperturbative dynamics of the standard model (SM) after inflation, in the regime where the SM is decoupled from (or weakly coupled to) the inflationary sector. We use classical lattice simulations in an expanding box in (3 + 1) dimensions, modeling the SM gauge interactions with both global and Abelian-Higgs analogue scenarios. We consider different postinflationary expansion rates. During inflation, the Higgs forms a condensate, which starts oscillating soon after inflation ends. Via non-perturbative effects, the oscillations lead to a fast decay of the Higgs into the SM species, transferring most of the energy into Z and W± bosons. All species are initially excited far away from equilibrium, but their interactions lead them into a stationary stage, with exact equipartition among the different energy components. From there on, the system eventually reaches equilibrium. We have characterized in detail, in the different expansion histories considered, the evolution of the Higgs and of its dominant decay products until equipartition is established. We provide a useful mapping between simulations with different parameters, from which we derive a master formula for the Higgs decay time as a function of the coupling constants, Higgs initial amplitude and postinflationary expansion rate. [ABSTRACT FROM AUTHOR]

We study the postinflationary dynamics of the Standard Model (SM) Higgs field in the presence of a nonminimal coupling ξ|Φ|²R to gravity, both with and without the electroweak gauge fields coupled to the Higgs field. We assume a minimal scenario in which inflation and reheating are caused by chaotic inflation with a quadratic potential, and no additional new physics is relevant below the Planck scale. By using classical real-time lattice simulations with a renormalization group improved effective Higgs potential and by demanding the stability of the Higgs vacuum after inflation, we obtain upper bounds for ξ, taking into account the experimental uncertainty of the top-Yukawa coupling. We compare the bounds in the absence and presence of the electroweak gauge bosons and conclude that the addition of gauge interactions has a rather minimal impact. In the unstable cases, we parametrize the time when such instability develops. For a top-quark mass mt≈173.3 GeV, the Higgs vacuum instability is triggered for ξ≳4-5, although a slightly lower mass of mt≈172.1 GeV pushes up this limit to ξ≳11-12. This, together with the estimation ξ≳0.06 for stability during inflation, provides tight constraints to the Higgs field-curvature coupling within the SM. [ABSTRACT FROM AUTHOR]