Abstract
We perform an extensive analysis of linear fluctuations during preheating in Higgs inflation in the Einstein frame, where the fields are minimally coupled to gravity, but the field-space metric is nontrivial. The self-resonance of the Higgs and the Higgsed gauge bosons are governed by effective masses that scale differently with the nonminimal couplings and evolve differently in time. Coupled metric perturbations enhance Higgs self-resonance and make it possible for Higgs inflation to preheat solely through this channel. For $\xi\gtrsim 100$ the total energy of the Higgs-inflaton condensate can be transferred to Higgs particles within $3$ $e$-folds after the end of inflation. For smaller values of the nonminimal coupling preheating takes longer, completely shutting off at around $\xi\simeq 30$. The production of gauge bosons is dominated by the gauge boson mass and the field space curvature. For large values of the nonminimal coupling $\xi \gtrsim 1000$, it is possible for the Higgs condensate to transfer the entirety of its energy into gauge fields within one oscillation. For smaller values of the nonminimal coupling gauge bosons decay very quickly into fermions, thereby shutting off Bose enhancement. Estimates of non-Abelian interactions indicate that they will not suppress preheating into gauge bosons for $\xi \gtrsim 1000$.
Highlights
While the discovery of the Higgs boson at CERN [1] solidified our understanding of the Standard Model (SM), its behavior in the early Universe, above the electroweak symmetry-breaking scale, remains unclear
We perform an extensive analysis of linear fluctuations during preheating in Higgs inflation in the Einstein frame, where the fields are minimally coupled to gravity, but the field-space metric is nontrivial
For large values of the nonminimal coupling ξ ≳ 1000, it is possible for the Higgs condensate to transfer the entirety of its energy into gauge fields within one oscillation
Summary
While the discovery of the Higgs boson at CERN [1] solidified our understanding of the Standard Model (SM), its behavior in the early Universe, above the electroweak symmetry-breaking scale, remains unclear. Despite the difficulty of directly observing reheating due to the very short length scales involved, knowledge of how the equation of state of the Universe transitioned from w ≃ −1 to w 1⁄4 1=3 is crucial, since it affects how one relates the observed cosmic microwave background (CMB) modes to the time during inflation when they exited the horizon [39,40,41,42,43,44,45,46] This becomes increasingly relevant as new data shrink the experimental bounds on primordial observables. [64], multifield models of inflation with nonminimal couplings to gravity can exhibit more efficient preheating behavior than previously thought, due to the contribution of the fieldspace structure to the effective mass of the fluctuations
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