1,629 research outputs found
Gravitino Problem in Supergravity Chaotic Inflation and SUSY Breaking Scale after BICEP2
Gravitinos are generically produced by inflaton decays, which place tight
constraints on inflation models as well as supersymmetry breaking scale. We
revisit the gravitino production from decays of the inflaton and the
supersymmetry breaking field, based on a chaotic inflation model suggested by
the recent BICEP2 result. We study cosmological constraints on thermally and
non-thermally produced gravitinos for a wide range of the gravitino mass, and
show that there are only three allowed regions of the gravitino mass:
eV, --TeV and GeV.Comment: 18 pages, 1 figur
Kinetic Term Anarchy for Polynomial Chaotic Inflation
We argue that there may arise a relatively flat inflaton potential over
super-Planckian field values with an approximate shift symmetry, if the
coefficients of the kinetic terms for many singlet scalars are subject to a
certain random distribution. The inflaton potential generically contains
various shift-symmetry breaking terms, leading to a possibly large deviation of
the predicted values of the spectral index and tensor-to-scalar ratio from
those of the simple quadratic chaotic inflation. We revisit a polynomial
chaotic inflation in supergravity as such.Comment: 16 page
Revisiting the Number-Theory Dark Matter Scenario and the Weak Gravity Conjecture
We revisit the number-theory dark matter scenario where one of the light
chiral fermions required by the anomaly cancellation conditions of U(1)_{B-L}
explains dark matter. Focusing on some of the integer B-L charge assignments,
we explore a new region of the parameter space where there appear two light
fermions and the heavier one becomes a dark matter of mass O(10)keV or
O(10)MeV. The dark matter radiatively decays into neutrino and photon, which
can explain the tantalizing hint of the 3.55keV X-ray line excess.
Interestingly, the other light fermion can erase the AdS vacuum around the
neutrino mass scale in a compactification of the standard model to 3D. This
will make the standard model consistent with the AdS-WGC statement that stable
non-supersymmetric AdS vacua should be absent.Comment: 16 pages, 4 figure
The 3.5 keV X-ray line signal from decaying moduli with low cutoff scale
The recent unidentified 3.5 keV X-ray line signal can be explained by
decaying moduli dark matter with a cutoff scale one order of magnitude smaller
than the Planck scale. We show that such modulus field with the low cutoff
scale follows a time-dependent potential minimum and its abundance is reduced
by the adiabatic suppression mechanism. As a result the modulus abundance can
naturally be consistent with the observed dark matter abundance without any
fine-tuning of the initial oscillation amplitude.Comment: 6 page
Anomaly-free flavor models for Nambu-Goldstone bosons and the 3.5 keV X-ray line signal
We pursue a possibility that a pseudo-Nambu-Goldstone boson is lurking around
or below the intermediate scale. To this end we consider an anomaly-free global
flavor symmetry, and construct models where the pseudo-Nambu-Goldstone boson is
coupled preferentially to leptons. The experimental and astrophysical bounds
derived from couplings to photons and nucleons are significantly relaxed. If
sufficiently light, the pseudo-Nambu-Goldstone boson contributes to dark
matter, and interestingly, it generally decays into photons through couplings
arising from threshold corrections. We show that the recent hint for the X-ray
line at about keV can be explained by the decay of such
pseudo-Nambu-Goldstone boson of mass about keV with the decay constant of
order GeV, if the electron is charged under the flavor symmetry.Comment: 15 page
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