202 research outputs found
Stability of Neutral Fermi Balls with Multi-Flavor Fermions
A Fermi ball is a kind of non-topological soliton, which is thought to arise
from the spontaneous breaking of an approximate symmetry and to
contribute to cold dark matter. We consider a simple model in which fermion
fields with multi-flavors are coupled to a scalar field through Yukawa
coupling, and examine how the number of the fermion flavors affects the
stability of the Fermi ball against the fragmentation. (1)We find that the
Fermi ball is stable against the fragmentation in most cases even in the lowest
order thin-wall approximation. (2)We then find that in the other specific
cases, the stability is marginal in the lowest order thin-wall approximation,
and the next-to-leading order correction determines the stable region of the
coupling constants; We examine the simplest case where the total fermion number
and the Yukawa coupling constant of each flavor are common to
the flavor, and find that the Fermi ball is stable in the limited region of the
parameters and has the broader region for the larger number of the flavors.Comment: 10 pages, 3 eps figures, ReVTeX
On suppressing the Higgsino-mediated proton decay in SUSY SO(10) GUT's
Using the freedom in SO(10) GUT's one can generalize the existing models
without changing the mass spectrum of fermions to obtain a significant
suppression of proton decay resulting from the baryon number violating
operators of dimension 5. In some limiting cases, their contributions can be
made negligible compared to the dimension 6 operators resulting from the heavy
gauge bosons exchange.Comment: 19 pages, 3 Postscript figures, 2 mpost figures, rearranged plots,
corrected typo
Low-Energy Predictions of Lopsided Family Charges
We consider the Froggatt-Nielsen (FN) mechanism reproducing the observed mass
hierarchies and mixing angles for quarks and leptons. The large - mixing suggested from recent Superkamiokande experiments on the
atmospheric neutrinos implies lopsided FN U(1) charges for the lepton doublets.
There are two possible charge assignments to generate the large - mixing. We point out that the two models with different charge
assignments have distinct low-energy predictions and hence they are
distinguishable in future neutrino experiments on such as CP violation and
decay.Comment: 14 pages,11 figures, Several discussions are sophisticate
Exact Schwarzschild-Like Solution for Yang-Mills Theories
Drawing on the parallel between general relativity and Yang-Mills theory we
obtain an exact Schwarzschild-like solution for SU(2) gauge fields coupled to a
massless scalar field. Pushing the analogy further we speculate that this
classical solution to the Yang-Mills equations shows confinement in the same
way that particles become confined once they pass the event horizon of the
Schwarzschild solution. Two special cases of the solution are considered.Comment: 11 pages LaTe
CP and T violation in neutrino oscillations
The conditions to induce appreciable CP-and T-odd effects in neutrino
oscillations are discussed. The propagation in matter leads to fake CP-and
CPT-odd asymmetries, besides a Bohm-Aharonov type modification of the
interference pattern. We study the separation of fake and genuine CP violation
by means of energy and distance dependence.Comment: To appear in the Proceedings of TAUP 99 Worksho
CP Violation and Matter Effect in Long Baseline Neutrino Oscillation Experiments
We show simple methods how to separate pure CP violating effect from matter
effect in long baseline neutrino oscillation experiments with three generations
of neutrinos. We give compact formulae for neutrino oscillation probabilities
assuming one of the three neutrino masses (presumably tau-neutrino mass) to be
much larger than the other masses and the effective mass due to matter effect.
Two methods are shown: One is to observe envelopes of the curves of oscillation
probabilities as functions of neutrino energy; a merit of this method is that
only a single detector is enough to determine the presence of CP violation. The
other is to compare experiments with at least two different baseline lengths;
this has a merit that it needs only narrow energy range of oscillation data.Comment: 17 pages + 9 eps figures, LaTeX, errors are correcte
Untangling CP Violation and the Mass Hierarchy in Long Baseline Experiments
In the overlap region, for the normal and inverted hierarchies, of the
neutrino-antineutrino bi-probability space for appearance,
we derive a simple identity between the solutions in the (, ) plane for the different hierarchies. The
parameter sets the scale of the
appearance probabilities at the atmospheric eV whereas controls the amount of CP
violation in the lepton sector. The identity between the solutions is that the
difference in the values of for the two hierarchies equals twice
the value of divided by the {\it critical} value
of . We apply this identity to the two proposed
long baseline experiments, T2K and NOA, and we show how it can be used to
provide a simple understanding of when and why fake solutions are excluded when
two or more experiments are combined. The identity demonstrates the true
complimentarity of T2K and NOA.Comment: 15 pages, Latex, 4 postscript figures. Submitted to New Journal of
Physics, ``Focus on Neutrino Physics'' issu
On the measurement of leptonic CP violation
We show that the simultaneous determination of the leptonic CP-odd phase
and the angle from the subleading transitions
and results generically, at
fixed neutrino energy and baseline, in two degenerate solutions. In light of
this, we refine a previous analysis of the sensitivity to leptonic CP violation
at a neutrino factory, in the LMA-MSW scenario, by exploring the full range of
and .
Furthermore, we take into account the expected uncertainties on the solar and
atmospheric oscillation parameters and in the average Earth matter density
along the neutrino path. An intermediate baseline of O(3000) km is still the
best option to tackle CP violation, although a combination of two baselines
turns out to be very important in resolving degeneracies.Comment: 19 pages, 14 figures, uses epsfi
Gauged Dimension Bubbles
Some of the peculiar electrodynamical effects associated with gauged
``dimension bubbles'' are presented. Such bubbles, which effectively enclose a
region of 5d spacetime, can arise from a 5d theory with a compact extra
dimension. Bubbles with thin domain walls can be stabilized against total
collapse by the entrapment of light charged scalar bosons inside the bubble,
extending the idea of a neutral dimension bubble to accommodate the case of a
gauged U(1) symmetry. Using a dielectric approach to the 4d dilaton-Maxwell
theory, it is seen that the bubble wall is almost totally opaque to photons,
leading to a new stabilization mechanism due to trapped photons. Photon
dominated bubbles very slowly shrink, resulting in a temperature increase
inside the bubble. At some critical temperature, however, these bubbles
explode, with a release of radiation.Comment: 14 pages, no figures; to appear in Phys.Rev.
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