Abstract
Current measurements of Standard Model parameters suggest that the electroweak vacuum is metastable. This metastability has important cosmological implications, because large fluctuations in the Higgs field could trigger vacuum decay in the early universe. For the false vacuum to survive, interactions which stabilize the Higgs during inflation -- e.g., inflaton-Higgs interactions or non-minimal couplings to gravity -- are typically necessary. However, the post-inflationary preheating dynamics of these same interactions could also trigger vacuum decay, thereby recreating the problem we sought to avoid. This dynamics is often assumed catastrophic for models exhibiting scale invariance since these generically allow for unimpeded growth of fluctuations. In this paper, we examine the dynamics of such "massless preheating" scenarios and show that the competing threats to metastability can nonetheless be balanced to ensure viability. We find that fully accounting for both the backreaction from particle production and the effects of perturbative decays reveals a large number of disjoint "islands of (meta)stability" over the parameter space of couplings. Ultimately, the interplay among Higgs-stabilizing interactions plays a significant role, leading to a sequence of dynamical phases that effectively extend the metastable regions to large Higgs-curvature couplings.
Highlights
A remarkable implication of the currently measured Standard Model (SM) parameters is that the electroweak vacuum is metastable
We find that fully accounting for both the backreaction from particle production and the effects of perturbative decays reveals a large number of disjoint “islands ofstability” over the parameter space of couplings
Some amount of degeneracy often exists in inflationary models in the sense that observational constraints may be satisfied over a degenerate subspace of the model parameters
Summary
A remarkable implication of the currently measured Standard Model (SM) parameters is that the electroweak vacuum is metastable. During inflation, the nonminimal gravitational interaction is effectively scale invariant, so such couplings fit naturally within the purview of scale-invariant theories of inflation [35,36,37,38,39,40,41,42] In this way, our study provides an analysis of the preheating dynamics that emerges from this wellmotivated class of inflationary models. In Appendix A, we provide an overview of vacuum metastability in the context of “massive preheating,” where the inflaton potential is approximately quadratic after inflation and the scale invariance of the inflaton potential broken These scenarios have been studied in the literature [20,21,23,24], and we reproduce their findings for the purpose of comparing and contrasting to our results. In Appendix B, we include the analytical calculations for the tachyonic resonance which are not given in the main body of the paper, and, in Appendix C, we provide the relevant details of our numerical methods
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
