950 research outputs found

### Unitarizing Higgs Inflation

We consider a simple extension of the Standard Model Higgs inflation with one
new real scalar field which preserves unitarity up to the Planck scale. The new
scalar field (called sigma) completes in the ultraviolet the theory of Higgs
inflation by linearizing the Higgs kinetic term in the Einstein frame, just as
the non-linear sigma model is unitarized into its linear version. The unitarity
cutoff of the effective theory, obtained by integrating out the sigma field,
varies with the background value of the Higgs field. In our setup, both the
Higgs field and the sigma field participate in the inflationary dynamics,
following the flat direction of the potential. We obtain the same slow-roll
parameters and spectral index as in the original Higgs inflation but we find
that the Hubble rate during inflation depends not only on the Higgs
self-coupling, but also on the unknown couplings of the sigma field.Comment: 16 page

### Induced resonance makes light sterile neutrino Dark Matter cool

We describe two new generation mechanisms for Dark Matter composed of sterile
neutrinos with ${\cal O}(1)$ keV mass. The model contains a light scalar field
which coherently oscillates in the early Universe and modulates the Majorana
mass of the sterile neutrino. In a region of model parameter space, the
oscillations between active and sterile neutrinos are resonantly enhanced. This
mechanism allows us to produce sterile neutrino DM with small mixing angle with
active neutrinos, thus evading the X-ray constraints. At the same time the
spectrum of produced DM is much cooler, than in the case of ordinary
oscillations in plasma, opening a window of lower mass DM, which is otherwise
forbidden by structure formation considerations. In other regions of the model
parameter space, where the resonance does not appear, another mechanism can
operate: large field suppresses the active-sterile oscillations, but instead
sterile neutrinos are produced by the oscillating scalar field when the
effective fermion mass crosses zero. In this case DM component is cold, and
even 1 keV neutrino is consistent with the cosmic structure formation.Comment: 6 pages, 4 figures, PRD accepted versio

### Resonant production of the sterile neutrino dark matter and fine-tunings in the [nu]MSM

The generation of lepton asymmetry below the electroweak scale has a
considerable impact on production of dark matter sterile neutrinos.
Oscillations or decays of the heavier sterile neutrinos in the neutrino minimal
standard model can give rise to the requisite lepton asymmetry, provided the
masses of the heavier neutrinos are sufficiently degenerate. We study the
renormalization group evolution of the mass difference of these singlet
fermions to understand the degree of necessary fine-tuning. We construct an
example of the model that can lead to a technically natural realization of this
low-energy degeneracy.Comment: 8 pages, 5 figure

### Standard Model Higgs boson mass from inflation: two loop analysis

We extend the analysis of \cite{Bezrukov:2008ej} of the Standard Model Higgs
inflation accounting for two-loop radiative corrections to the effective
potential. As was expected, higher loop effects result in some modification of
the interval for allowed Higgs masses m_min<m_H<m_max, which somewhat exceeds
the region in which the Standard Model can be considered as a viable effective
field theory all the way up to the Planck scale. The dependence of the index
n_s of scalar perturbations on the Higgs mass is computed in two different
renormalization procedures, associated with the Einstein (I) and Jordan (II)
frames. In the procedure I the predictions of the spectral index of scalar
fluctuations and of the tensor-to-scalar ratio practically do not depend on the
Higgs mass within the admitted region and are equal to n_s=0.97 and r=0.0034
respectively. In the procedure II the index n_s acquires the visible dependence
on the Higgs mass and and goes out of the admitted interval at m_H below m_min.
We compare our findings with the results of \cite{DeSimone:2008ei}.Comment: 24 paged, 9 figures. Journal version (typos fixed, expanded
discussions

### Magnetic field generation in Higgs inflation model

We study the generation of magnetic field in Higgs-inflation models where the
Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple
the Higgs field to the Electromagnetic fields via a non- renormalizable
dimension six operator suppressed by the Planck scale in the Jordan frame. We
show that during Higgs inflation magnetic fields with present value $10^{-6}$
Gauss and comoving coherence length of $100 kpc$ can be generated in the
Einstein frame. The problem of large back-reaction which is generic in the
usual inflation models of magneto-genesis is avoided as the back-reaction is
suppressed by the large Higgs-curvature coupling.Comment: 10 pages, RevTeX

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