3,172 research outputs found
Quarks and Leptons between Branes and Bulk
We study a supersymmetric SO(10) gauge theory in six dimensions compactified
on an orbifold. Three sequential quark-lepton families are localized at the
three fixpoints where SO(10) is broken to its three GUT subgroups. Split bulk
multiplets yield the Higgs doublets of the standard model and as additional
states lepton doublets and down-quark singlets. The physical quarks and leptons
are mixtures of brane and bulk states. The model naturally explains small quark
mixings together with large lepton mixings in the charged current. A small
hierarchy of neutrino masses is obtained due to the different down-quark and
up-quark mass hierarchies. None of the usual GUT relations between fermion
masses holds exactly.Comment: 12 pages, 1 figur
Hadronic Axion Model in Gauge-Mediated Supersymmetry Breaking
A simple hadronic axion model is proposed in the framework of gauge-mediated
supersymmetry breaking. Dynamics of Peccei-Quinn symmetry breaking is governed
by supersymmetry breaking effects and the Peccei-Quinn breaking scale
is inversely proportional to the gravitino mass. The gravitino mass range which
corresponds to the axion window GeV -- GeV
lies in the region predicted by gauge-mediated supersymmetry breaking models.
The model is also shown to be cosmologically viable.Comment: 20 pages including seven postscript figures, reviced version to be
published in Physics Letters
Non-perturbative Corrections to Particle Production from Coherent Oscillation
We investigate particle production from coherent oscillation by using the
method based on the Bogolyubov transformation. Especially, we study the case
when the amplitude of the oscillation and also the coupling constants with the
oscillating field are small in order to avoid the non-perturbative corrections
from the broad parametric resonance. We derive the expressions for the
distribution functions and the number densities of produced particles at the
leading order of coupling constant. It is, however, found that these results
fail to describe the exact particle production eventually due to the
non-perturbative effects even if the coupling constants are small. We then
introduce a simple method to handle with such corrections, i.e., the time
averaging method. It is shown that this method successfully provides the
evolution of the occupation numbers of the growing mode. Further, we point out
that the approximate results by this method satisfy the exact scaling
properties coming from the periodicity of the coherent oscillation.Comment: 24 pages, 8 figure
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