On the violent preheating in the mixed Higgs-R2 inflationary model

Abstract

It has been argued that the mixed Higgs-R 2 model acts as the UV extension of the Higgs inflation, pushing up its cut-off scale in the vacuum close up to the Planck scale. In this letter, we study the inflaton oscillation stage after inflation, focusing on the effective mass of the phase direction of the Higgs field, which can cause a violent preheating process. We find that the "spikes" in the effective mass of the phase direction observed in the Higgs inflation still appear in the mixed Higgs-R 2 model. While the spikes appear above the cut-off scale in the Higgs-only case, they appear below the cut-off scale when the model is extended with R 2 term though reheating cannot be completed in the violent particle production regime since the spikes get milder.

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].…”

“…While the last term in the equation above, being rapidly oscillating, generically sources the particle production, in our case with functional form (28) and rather small Higgs field immediately after inflation the production is not very efficient, see Ref. [30] for details. However, the situation is different for the longitudinal modes, which also obey the Klein-Gordon equationẄ…”

“…To study the preheating dynamics, the mode functions for W L , and (L, H) scalar perturbations were evolved numerically according to (23), (24) and (30), subject to the vacuum initial conditions. The total energy in the inhomogeneous excitations of each type was calculated using (39).…”

Dynamical emergence of scalaron in Higgs inflation

“…Indeed, Refs. [71,72] have studied the reheating dynamics of this model in detail. The former studies particle production at the first oscillation for a generic parameter space, while the latter finds that the reheating temperature is as high as 10 15 GeV (or N e 59) at least for a tuned parameter space.…”

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.…”