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Register a new userThe Secret Higgstory of the Highest Temperature during Reheating
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We study the role of the Standard Model Higgs condensate, formed during cosmological inflation, in the epoch of reheating that follows. We focus on the scenario where the inflaton decays slowly and perturbatively, so that there is a long period between the end of inflation and the beginning of radiation domination. The Higgs condensate decays non-perturbatively during this period, and we show that it heats the primordial plasma to much higher temperatures than would result from the slowly-decaying inflaton alone. We discuss the effect of this hot plasma on the thermalization of the inflatons decay products, and study its phenomenological implications for the formation of cosmological relics like dark matter, with associated isocurvature fluctuations, and the restoration of the electroweak and Peccei-Quinn symmetries.
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The simplest possibility to explain the baryon asymmetry of the Universe is to assume that radiation is created asymmetrically between baryons and anti-baryons after the inflation. We propose a new mechanism of this kind where CP-violating flavor oscillations of left-handed leptons in the reheating era distribute the lepton asymmetries partially into the right-handed neutrinos while net asymmetry is not created. The asymmetry stored in the right-handed neutrinos is later washed out by the lepton number violating decays, and it ends up with the net lepton asymmetry in the Standard Model particles, which is converted into the baryon asymmetry by the sphaleron process. This scenario works for a range of masses of the right-handed neutrinos while no fine-tuning among the masses is required. The reheating temperature of the Universe can be as low as $O(10)$~TeV if we assume that the decays of inflatons in the perturbative regime are responsible for the reheating. For the case of the reheating via the dissipation effects, the reheating temperature can be as low as $O(100)$~GeV.
The preheating process in the mixed Higgs-$ R^2 $ model has been investigated in depth recently, but the analysis of perturbative reheating is still missing. In this paper, we discuss the effect of perturbative decay during (p)reheating in this model. It is shown that perturbative decay can play an important role throughout the whole reheating process. Depending on the model parameters, perturbative decay can affect different stages of the reheating. We study the perturbative reheating with and without the presence of early preheating stage, and calculate the reheating temperature and the duration of the whole perturbative process. We find that the detail of the early preheating stage may not affect the final reheating temperature while it can affect the number of e-folds of reheating.
Using 3+1 classical lattice simulations, we follow the symmetry breaking pattern and subsequent non-linear evolution of a spectator field non-minimally coupled to gravity when the post-inflationary dynamics is given in terms of a stiff equation-of-state parameter. We find that the gradient energy density immediately after the transition represents a non-negligible fraction of the total energy budget, steadily growing to equal the kinetic counterpart. This behaviour is reflected on the evolution of the associated equation-of-state parameter, which approaches a universal value $1/3$, independently of the shape of non-linear interactions. Combined with kination, this observation allows for the generic onset of radiation domination for arbitrary self-interacting potentials, significantly extending previous results in the literature. The produced spectrum at that time is, however, non-thermal, precluding the naive extraction of thermodynamical quantities like temperature. Potential identifications of the spectator field with the Standard Model Higgs are also discussed.
We study the parametric amplification of super-Hubble-scale scalar metric fluctuations at the end of inflation in some specific two-field models of inflation, a class of which is motivated by hybrid inflation. We demonstrate that there can indeed be a large growth of fluctuations due to parametric resonance and that this effect is not taken into account by the conventional theory of isocurvature perturbations. Scalar field interactions play a crucial role in this analysis. We discuss the conditions under which there can be nontrivial parametric resonance effects on large scales.
We show that, for values of the axion decay constant parametrically close to the GUT scale, the Peccei-Quinn phase transition may naturally occur during warm inflation. This results from interactions between the Peccei-Quinn scalar field and the ambient thermal bath, which is sustained by the inflaton field through dissipative effects. It is therefore possible for the axion field to appear as a dynamical degree of freedom only after observable CMB scales have become super-horizon, thus avoiding the large-scale axion isocurvature perturbations that typically plague such models. This nevertheless yields a nearly scale-invariant spectrum of axion isocurvature perturbations on small scales, with a density contrast of up to a few percent, which may have a significant impact on the formation of gravitationally-bound axion structures such as mini-clusters.
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