354 research outputs found
Supergravity Minimal Inflation and its Spectral Index Revisited
Natural supergravity models of new inflation are reconsidered as minimal
inflationary models within slow-roll approximation. Their running spectral
index is derived in a revised form with recent observational results and future
refinements in mind. This will possibly determine essential model parameters
with respect to Planck-suppressed operators.Comment: 7 pages, late
Affleck-Dine mechanism with negative thermal logarithmic potential
We investigate whether the Affleck-Dine (AD) mechanism works when the
contribution of the two-loop thermal correction to the potential is negative in
the gauge-mediated supersymmetry breaking models. The AD field is trapped far
away from the origin by the negative thermal correction for a long time until
the temperature of the universe becomes low enough. The most striking feature
is that the Hubble parameter becomes much smaller than the mass scale of the
radial component of the AD field, during the trap. Then, the amplitude of the
AD field decreases so slowly that the baryon number is not fixed even after the
onset of radial oscillation. The resultant baryon asymmetry crucially depends
on whether the Hubble parameter, , is larger than the mass scale of the
phase component of the AD field, , at the beginning of oscillation.
If holds, the formation of Q balls plays an essential role to
determine the baryon number, which is found to be washed out due to the
nonlinear dynamics of Q-ball formation. On the other hand, if
holds, it is found that the dynamics of Q-ball formation does not affect the
baryon asymmetry, and that it is possible to generate the right amount of the
baryon asymmetry.Comment: 18 pages, RevTeX4, 9 postscript figures included, final version to
appear in Phys.Rev.
Hadronic Axion Model in Gauge-Mediated Supersymmetry Breaking and Cosmology of Saxion
Recently we have proposed a simple hadronic axion model within gauge-mediated
supersymmetry breaking. In this paper we discuss various cosmological
consequences of the model in great detail. A particular attention is paid to a
saxion, a scalar partner of an axion, which is produced as a coherent
oscillation in the early universe. We show that our model is cosmologically
viable, if the reheating temperature of inflation is sufficiently low. We also
discuss the late decay of the saxion which gives a preferable power spectrum of
the density fluctuation in the standard cold dark matter model when compared
with the observation.Comment: 24 pages, 3 figure
Cosmological Moduli Problem and Thermal Inflation Models
In superstring theories, there exist various dilaton and modulus fields which
masses are expected to be of the order of the gravitino mass . These
fields lead to serious cosmological difficulties, so called ``cosmological
moduli problem'', because a large number of moduli particles are produced as
the coherent oscillations after the primordial inflation. We make a
comprehensive study whether the thermal inflation can solve the cosmological
moduli problem in the whole modulus mass region
predicted by both hidden sector supersymmetry (SUSY) breaking and
gauge-mediated SUSY breaking models. In particular, we take into account the
primordial inflation model whose reheating temperature is so low that its
reheating process finishes after the thermal inflation ends. We find that the
above mass region survives from
various cosmological constraints in the presence of the thermal inflation.Comment: 49 pages, 17 figure
Where to find a dark matter sterile neutrino?
We propose a strategy of how to look for dark matter (DM) particles
possessing a radiative decay channel and derive constraints on their parameters
from observations of X-rays from our own Galaxy and its dwarf satellites. When
applied to the sterile neutrinos in keV mass range, it allows a significant
improvement of restrictions to its parameters, as compared with previous works.Comment: 5 pp, revtex; v3: 1-sigma limits have been replaced by more
conservative 3-sigma limits, a picture illustrating the data analysis methods
has been ade
On the Moduli Problem and Baryogenesis in Gauge-mediated SUSY Breaking Models
We investigate whether the Affleck-Dine mechanism can produce sufficient
baryon number of the universe in the gauge-mediated SUSY breaking models, while
evading the cosmological moduli problem by late-time entropy production. We
find that the Q-ball formation renders the scenario very difficult to work,
irrespective of the detail mechanism of the entropy production.Comment: 11 pages, RevTeX, 5 postscript figures include
Some constraints on the Yukawa parameters in the neutrino modification of the Standard Model (nuMSM) and CP-violation
The equations connecting elements of the Yukawa matrix to elements of the
active neutrino mass matrix in the \nu MSM theory (an extension of the Standard
Model by a singlet of three right-handed neutrinos) was analyzed, and explicit
relations for the ratio of the Yukawa matrix elements through elements of the
active neutrino mass matrix were obtained. This relation can be used for
getting more accurate constraints on the model parameters. Particularly, with
the help of the obtained results we investigated CP-violating phase in the \nu
MSM theory. We demonstrate that even in the case when elements of the active
neutrino mass matrix are real the baryon asymmetry can be generated also.Comment: 14 pages, 2 figures, many clarifications and references adde
Late Reheating, Hadronic Jets and Baryogenesis
If inflaton couples very weakly to ordinary matter the reheating temperature
of the universe can be lower than the electroweak scale. In this letter we show
that the late reheating occurs in a highly non-uniform way, within narrow areas
along the jets produced by ordinary particles originated from inflaton decays.
Depending on inflaton mass and decay constant, the initial temperature inside
the lumps of the overheated plasma may be large enough to trigger the
unsuppressed sphaleron processes with baryon number non-conservation, allowing
for efficient local electroweak baryogenesis.Comment: 4 pages, 2 figures, revtex
New inflation in supergravity with a chaotic initial condition
We propose a self-consistent scenario of new inflation in supergravity.
Chaotic inflation first takes place around the Planck scale, which solves the
longevity problem, namely, why the universe can live much beyond the Planck
time, and also gives an adequate initial condition for new inflation. Then, new
inflation lasts long enough to generate primordial fluctuations for the large
scale structure, which generally has a tilted spectrum with the spectral index
. The successive decay of the inflaton leads to the reheating
temperature low enough to avoid the overproduction of gravitinos in a wide
range of the gravitino mass.Comment: 11 pages. To appear in Phys. Rev.
Reheating-temperature independence of cosmological baryon asymmetry in Affleck-Dine leptogenesis
In this paper we point out that the cosmological baryon asymmetry in our
universe is generated almost independently of the reheating temperature
in Affleck-Dine leptogenesis and it is determined mainly by the mass of the
lightest neutrino, , in a wide range of the reheating temperature
-- GeV. The present baryon asymmetry predicts the
in a narrow region, -- eV.
Such a small mass of the lightest neutrino leads to a high predictability on
the mass parameter contributing to the neutrinoless double
beta decay. We also propose an explicit model in which such an ultralight
neutrino can be naturally obtained.Comment: 22 pages, LaTeX, 9 eps figure
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