3,079 research outputs found
On the Solution to the Polonyi Problem with No-Scale Type Supergravity
We study the solution to the Polonyi problem in the framework of no-scale
type supergravity. In such a model, Polonyi field can weigh as
and decay just before the big-bang nucleosynthesis. It is shown that in spite
of a large entropy production by the decay of the Polonyi field, one can
naturally explain the present value of the baryon-to-entropy ratio, if the Affleck-Dine mechanism for baryogenesis works. It
is pointed out, however, that there is another cosmological problem related to
the abundance of the lightest superparticles produced by the decay of the
Polonyi field.Comment: Talk given at the Yukawa International Seminar '95 in Kyoto, 21 - 26
August, 199
Gravitino Production in the Early Universe and Its Implications to Particle Cosmology
Effects of the unstable gravitino on the big-bang nucleosynthesis (BBN) and
its implications to particle cosmology are discussed. If the gravitino mass is
smaller than \sim 20 TeV, lifetime of the gravitino becomes longer than \sim
1sec and its decay may spoil the success of the standard BBN. In order to avoid
such a problem, upper bound on the reheating temperature after the inflation is
obtained, which may be as low as \sim 10^{5-6} GeV. For a successful
baryogenesis with such low reheating temeprature, a consistent scenario based
on the large cutoff supergravity (LCSUGRA) hypothesis of supersymmetry
breaking, where the gravitino and sfermion become as heavy as \sim O(1-10 TeV),
is proposed. In the LCSUGRA, non-thermal leptogenesis can produce large enough
baryon asymmetry. We also see that, in the LCSUGRA scenario, relic density of
the lightest superparticle becomes consistent with the WMAP value of the dark
matter density in the parameter region required for the successful non-thermal
leptogenesis. In this case, the dark matter density may be reconstructed with
the future e^+e^- linear collider.Comment: Talk given at PASCOS05, Gyeongju, Korea (June 2005). 13 pages, 5
figure
Effects of the right-handed neutrinos on \Delta S = 2 and \Delta B = 2 processes in supersymmetric SU(5) model
We discuss an extra source of CP and flavor violations in supersymmetric
SU(5) grand unified model with the right-handed neutrinos. In such a model, the
right-handed down-type squarks \tilde{d}_R interact with the right-handed
neutrinos above the GUT scale, and the renormalization group effect can
generate sizable off-diagonal elements in the mass matrix of \tilde{d}_R.
Because of new Yukawa phases which exist in the SU(5) model, these off-diagonal
elements have, in general, large CP violating phases. The renormalization group
induced off-diagonal elements affect the K and B decays. In particular, in this
model, supersymmetric contribution to the \epsilon_K parameter can be as large
as the currently measured experimental value, and hence the effect might be
seen as an anomaly in the on-going test of the Cabibbo-Kobayashi-Maskawa
triangle.Comment: 13 pages, 3 figures, typo correcte
A Solution to the Polonyi Problem in the Minimum SUSY-GUT
We show that the Polonyi problem is solved in the minimum SUSY-GUT model in
which a self-coupling strength for a heavy Higgs , ,
is very small . It is stressed that with this small
the mass of the physical becomes m_{\Sigma} \sim
10^{12}\GEV and the unification scale is raised up to the gravitational one,
M\simeq 2\times 10^{18}\GEV. A potential problem, however, is also pointed
out in this GUT model
Early Decay of Peccei-Quinn Fermion and the IceCube Neutrino Events
IceCube observed high-energy neutrino flux in the energy region from TeV to
PeV. The decay of a massive long-lived particle in the early universe can be
the origin of the IceCube neutrino events, which we call an "early decay
scenario." In this paper, we construct a particle physics model that contains
such a massive long-lived particle based on the Peccei-Quinn model. We
calculate the present neutrino flux, taking account of realistic initial energy
distributions of particles produced by the decay of the massive long-lived
particle. We show that the early decay scenario naturally fits into the
Peccei-Quinn model, and that the neutrino flux observed by IceCube can be
explained in such a framework. We also see that, based on that model, a
consistent cosmological history that explains the abundance of the massive
long-lived particle is realized.Comment: 20 pages, 2 figures; v2: references added; v3: version accepted for
publication in PL
Electromagnetic Cascade in the Early Universe and its Application to the Big-Bang Nucleosynthesis
We investigate the electromagnetic cascade initiated by injection of very
high energy photons in the early Universe and calculate the cascade spectrum by
solving a set of Boltzmann equations numerically. In the calculation we take
account of Compton scattering off the background electrons and pair creation
off the background nucleons as well as photon-photon processes and inverse
Compton scattering. We also apply our cascade spectrum to the big bang
nucleosynthesis with photo-dissociation processes due to heavy unstable
particles and obtain the constraint on their lifetime and abundance.Comment: 21pages (compressed and uuencoded postscript file including 6
figures
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