3,738 research outputs found
Explicit SO(10) Supersymmetric Grand Unified Model for the Higgs and Yukawa Sectors
A complete set of fermion and Higgs superfields is introduced with
well-defined SO(10) properties and U(1) x Z_2 x Z_2 family charges from which
the Higgs and Yukawa superpotentials are constructed. The structures derived
for the four Dirac fermion and right-handed Majorana neutrino mass matrices
coincide with those previously obtained from an effective operator approach.
Ten mass matrix input parameters accurately yield the twenty masses and mixings
of the quarks and leptons with the bimaximal atmospheric and solar neutrino
vacuum solutions favored in this simplest version.Comment: Published version appearing in PRL in which small modifications to
original submission and a paragraph concerning proton decay appea
Resonant leptogenesis in a predictive SO(10) grand unified model
An SO(10) grand unified model considered previously by the authors featuring
lopsided down quark and charged lepton mass matrices is successfully predictive
and requires that the lightest two right-handed Majorana neutrinons be nearly
degenerate in order to obtain the LMA solar neutrino solution. Here we use this
model to test its predictions for baryogenesis through resonant-enhanced
leptogenesis. With the conventional type I seesaw mechanism, the best
predictions for baryogenesis appear to fall a factor of three short of the
observed value. However, with a proposed type III seesaw mechanism leading to
three pairs of massive pseudo-Dirac neutrinos, resonant leptogenesis is
decoupled from the neutrino mass and mixing issues with successful baryogenesis
easily obtained.Comment: 22 pages including 1 figure; published version with reference adde
Realization of the Large Mixing Angle Solar Neutrino Solution in an SO(10) Supersymmetric Grand Unified Model
An SO(10) supersymmetric grand unified model proposed earlier leading to the
solar solution involving ``just-so'' vacuum oscillations is reexamined to study
its ability to obtain the other possible solar solutions. It is found that all
four viable solar neutrino oscillation solutions can be achieved in the model
simply by modification of the right-handed Majorana neutrino mass matrix, M_R.
Whereas the small mixing and vacuum solutions are easily obtained with several
texture zeros in M_R, the currently-favored large mixing angle solution
requires a nearly geometric hierarchical form for M_R that leads by the seesaw
formula to a light neutrino mass matrix which has two or three texture zeros.
The form of the matrix which provides the ``fine-tuning'' necessary to achieve
the large mixing angle solution can be understood in terms of Froggatt-Nielsen
diagrams for the Dirac and right-handed Majorana neutrino mass matrices. The
solution fulfils several leptogenesis requirements which in turn can be
responsible for the baryon asymmetry in the universe.Comment: 14 pages including 2 figure
Lifting a Realistic SO(10) Grand Unified Model to Five Dimensions
It has been shown recently that the problem of rapid proton decay induced by
dimension five operators arising from the exchange of colored Higgsinos can be
simply avoided in grand unified models where a fifth spatial dimension is
compactified on an orbifold. Here we demonstrate that this idea can be used to
solve the Higgsino-mediated proton decay problem in any realistic SO(10) model
by lifting that model to five dimensions. A particular SO(10) model that has
been proposed to explain the pattern of quark and lepton masses and mixings is
used as an example. The idea is to break the SO(10) down to the Pati-Salam
symmetry by the orbifold boundary conditions. The entire four-dimensional
SO(10) model is placed on the physical SO(10) brane except for the gauge
fields, the 45 and a single 10 of Higgs fields, which are placed in the
five-dimensional bulk. The structure of the Higgs superpotential can be
somewhat simplified in doing so, while the Yukawa superpotential and mass
matrices derived from it remain essentially unaltered.Comment: 17 pages, version to be published in Phys. Rev. D with expanded
discussion of the suppression of dim-5 proton decay operator
On the Numerical Dispersion of Electromagnetic Particle-In-Cell Code : Finite Grid Instability
The Particle-In-Cell (PIC) method is widely used in relativistic particle
beam and laser plasma modeling. However, the PIC method exhibits numerical
instabilities that can render unphysical simulation results or even destroy the
simulation. For electromagnetic relativistic beam and plasma modeling, the most
relevant numerical instabilities are the finite grid instability and the
numerical Cherenkov instability. We review the numerical dispersion relation of
the electromagnetic PIC algorithm to analyze the origin of these instabilities.
We rigorously derive the faithful 3D numerical dispersion of the PIC algorithm,
and then specialize to the Yee FDTD scheme. In particular, we account for the
manner in which the PIC algorithm updates and samples the fields and
distribution function. Temporal and spatial phase factors from solving
Maxwell's equations on the Yee grid with the leapfrog scheme are also
explicitly accounted for. Numerical solutions to the electrostatic-like modes
in the 1D dispersion relation for a cold drifting plasma are obtained for
parameters of interest. In the succeeding analysis, we investigate how the
finite grid instability arises from the interaction of the numerical 1D modes
admitted in the system and their aliases. The most significant interaction is
due critically to the correct represenation of the operators in the dispersion
relation. We obtain a simple analytic expression for the peak growth rate due
to this interaction.Comment: 25 pages, 6 figure
Leptogenesis in the type III seesaw mechanism
It is shown that the type III seesaw mechanism proposed recently can have
certain advantages over the conventional (or type I) seesaw mechanism for
leptogenesis. In particular a resonant enhancement of leptogenesis via heavy
quasi-Dirac right-handed neutrino pairs can occur without a special flavor form
or "texture" of the mass matrices being assumed. Some of the requirements for
neutrino mixing and leptogenesis are effectively decoupled.Comment: 12 pages including one figure, several references adde
Lepton Flavor Violation in Supersymmetric SO(10) Grand Unified Models
The study for lepton flavor violation combined with the neutrino oscillation
may provide more information about the lepton flavor structure of the grand
unified theory. In this paper, we study two lepton flavor violation processes,
and , in the context of supersymmetric SO(10)
grand unified models. We find the two processes are both of phenomenological
interest. In particular the latter may be important in some supersymmetric
parameter space where the former is suppressed. Thus, Z-dacay may offer another
chance for looking for lepton flavor violation.Comment: 26 pages, 10 figure
Next Generation Differential GPS Architecture
The United States Coast Guard is engaged in a project to re-capitalize Reference Station (RS) and Integrity Monitor (IM) equipment used in the Nationwide Differential Global Position System (NDGPS). The Coast Guard in partnership with industry is developing a new software application to run on an open architecture platform as a replacement for legacy equipment. Present commercially available off-the-shelf Differential Global Positioning System (DGPS) RS and IM equipment lacks the open architecture required to support long term goals and future system improvements. The utility of the proposed new hardware architecture and software application is impressive - nearly every aspect of performance and supportability significantly exceeds that of the legacy architecture. The flexibility of the new hardware and software architectures complement each other to offer promising possibilities for the future. For example, the new hardware architecture uses Ethernet for internal and external site equipment communications. Each Local Area Network (LAN) will be equipped with a router and two 24 port switches. Various levels of password protection are provided to manage security both locally and remotely. While the new software application directly supports the legacy RS-232/422 interfaces to devices such as GPS receivers, a system design goal includes the ability to directly address each device from NCS. With the use of TCP/IP to RS-232/422 port server devices, the system can meet these forward reaching goals while supporting legacy equipment. New system capabilities include remote software management, remote hardware configuration management, and flexible options for management of licenses.
The new configurable RS and IM architecture is a PCbased emulation of legacy reference station and integrity monitor equipment. It supports fluid growth and exploitation of new signals, formats, and technology as they become available, while remaining backward compatible with legacy architecture and user equipment. Examples of new capabilities include enhanced data management & anomaly analysis, universal On Change Reference Station Integrity Monitor (RSIM) message scheduling, improved satellite clock handling, additional observation interval modes, and Range Rate Correction monitoring in the IM. Engineering initiatives under development such as implementation of pre-broadcast integrity are also presented.
This paper details challenges and goals that drove software and hardware design approaches destined to become the backbone of the Next Generation Differential GPS Architecture. Functional differences between legacy and next generation operation are explored. The new DGPS system architecture will allow the USCG radiobeacon system to continue to deliver and improve navigation and positioning services to our nation and its territories.
Reprinted with permission from The Institute of Navigation (http://ion.org/) and The Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, (pp. 816-826). Fairfax, VA: The Institute of Navigation
The Stark effect in linear potentials
We examine the Stark effect (the second-order shift in the energy spectrum
due to an external constant force) for two 1-dimensional model quantum
mechanical systems described by linear potentials, the so-called quantum
bouncer (defined by V(z) = Fz for z>0 and V(z) infinite for z<0) and the
symmetric linear potential (given by V(z) = F|z|). We show how straightforward
use of the most obvious properties of the Airy function solutions and simple
Taylor expansions give closed form results for the Stark shifts in both
systems. These exact results are then compared to other approximation
techniques, such as perturbation theory and WKB methods. These expressions add
to the small number of closed-form descriptions available for the Stark effect
in model quantum mechanical systems.Comment: 15 pages. To appear in Eur. J. Phys. Needs Institute of Physics
(iopart) style file
Horizontal symmetry in Higgs sector of GUT with U(1)_A symmetry
In a series of papers, we pointed out that an anomalous gauge
symmetry naturally solves various problems in grand unified theories (GUTs) and
that a horizontal gauge symmetry, or , not only realizes the
unification of three generation quarks and leptons in fewer multiplets but also
solves the supersymmetric flavor problem. In this paper, we examine the
possibility that the Higgs sectors of the GUT symmetry and of the horizontal
symmetry are unified, that is, there are some Higgs fields whose vacuum
expectation values (VEVs) break both the GUT gauge symmetry and the horizontal
symmetry at the same time. Although the scale of the VEVs become too large to
suppress the flavor changing neutral current processes sufficiently, the
unification is possible. In addition, for the models, the
gauge anomaly is cancelled in the unified models without introducing additional
fields in contrast with the previous models in which the Higgs sectors are not
unified.Comment: 35 page
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