21,838 research outputs found
A Minimal See-Saw Model for Hierarchical Neutrino Masses with Large Mixing
The atmospheric and solar neutrino oscillation data suggest hierarchical
neutrino masses with at least one large mixing. The simplest see-saw models for
reconciling the two features are U(1) extensions of the SM with flavour
dependent gauge charges. I discuss a minimal model of this type containing two
heavy right-handed neutrinos, which have normal Dirac couplings to
and but suppressed ones to . It can naturally account for the
large (small) mixing solutions to the atmospheric (solar) neutrino oscillation
data.Comment: 6 pages, Latex, Invited Talk at the 6th San Miniato Topical Seminar
on `Neutrino and Astroparticle Physics', to appear in Nuclear Physics B
(Proc. Suppl.
The Strategic Impact of China\u27s Artificial Islands in the South China Sea and their Influence on U.S. and China Relations
This is an integrative literature review of various perspectives of different authors of previous scholarly articles discussing the impact of China’s artificial Islands in the South China Sea and how it affects U.S. China relations in the region. This research covers a range of parameters surrounding how the artificial islands were made and how they affect the overall security of naval operations and will also discuss international waterway rights within the South China Sea, one of the World’s biggest trading routes. A review of current events in the region is discussed highlighting the potential powder keg that could explode and how it can provide a starting point to summarize and identify the seriousness of the current fluid situation that is changing daily and how it potentially impacts the region. By conducting this integrative literature review the author aims to present a wholesome picture to educate the public about events that are shaping the region in the South China Sea. The results of this study will add clarity and awareness to the events in the region and how they impact the United States and China relations. The hope is that this research creates a dialogue that addresses the strategic impact these artificial islands are having on the United States and China relations in the region of the South China Sea
Terahertz quantum cascade laser with an X-valley-based injector
We present a novel terahertz (THz) quantum cascade laser (QCL) design where Γ-valley states are used for lasing transition and X-valley states—in particular, Xz-states—are used as injector subbands. Since the lasing states in our proposed structure are populated and depopulated mainly through the interface roughness assisted Γ-Xz electron scattering, we present a model to describe this intervalley carrier transport. In the injector region of the proposed THz QCL, we use quaternary AlGaAsP material to introduce tensile strain, which plays a crucial role in increasing the gain. To compensate the strain per period, we propose to grow the periodic heterostructure on a GaAs.94P.06 virtual substrate. To simulate the carrier transport, and hence calculate the gain and lasing performance of the proposed THz QCL, we use a simplified density matrix formalism that considers resonant tunneling, dephasing, and the important intersubband scattering mechanisms. Since electron temperature significantly varies from lattice temperature for QCLs, we take their difference into account using the kinetic energy balance (KEB) method. We show that the proposed structure is capable of lasing up to a maximum lattice temperature of ∼119 K at 4.8 THz. For future improvements of the device, we identify major performance-degrading factors of the proposed design
Local and global persistence exponents of two quenched continuous lattice spin models
Local and global persistence exponents associated with zero temperature
quenched dynamics of two dimensional XY model and three dimensional Heisenberg
model have been estimated using numerical simulations. We have used the method
of block persistence to find both global and local exponents simultaneously (in
a single simulation). Temperature universality of both the exponents for three
dimensional Heisenberg model has been confirmed by simulating the stochastic
(with noise) version of the equation of motion. The noise amplitudes added were
small enough to retain the dynamics below criticality. In the second part of
our work we have studied scaling associated with correlated persistence sites
in the three dimensional Heisenberg model in the later stages of the dynamics.
The relevant length scale associated with correlated persistent sites was found
to behave in a manner similar to the dynamic length scale associated with the
phase ordering dynamics.Comment: 20 pages, 7 figure
Model of Four Light Neutrinos in the Light of All Present Data
Motivated by existing and recent data on possible neutrino oscillations, we
propose a model of four light neutrinos (, and a
singlet ) with a pattern of masses and mixing derivable from a
discrete symmetry and the seesaw mechanism. Atmospheric neutrino oscillations
occur between and as pseudo-Dirac partners; whereas solar
neutrino oscillations occur between and , a linear combination
of which is massless. Additional oscillations may occur between and
to account for the recent observation of the LSND (Liquid
Scintillator Neutrino Detector) experiment.Comment: Title changed, new (penultimate) paragraph added, Ref.[7] expanded,
12 pages, no figur
3DQ: Compact Quantized Neural Networks for Volumetric Whole Brain Segmentation
Model architectures have been dramatically increasing in size, improving
performance at the cost of resource requirements. In this paper we propose 3DQ,
a ternary quantization method, applied for the first time to 3D Fully
Convolutional Neural Networks (F-CNNs), enabling 16x model compression while
maintaining performance on par with full precision models. We extensively
evaluate 3DQ on two datasets for the challenging task of whole brain
segmentation. Additionally, we showcase our method's ability to generalize on
two common 3D architectures, namely 3D U-Net and V-Net. Outperforming a variety
of baselines, the proposed method is capable of compressing large 3D models to
a few MBytes, alleviating the storage needs in space critical applications.Comment: Accepted to MICCAI 201
Heavy Triplet Leptons and New Gauge Boson
A heavy triplet of leptons per family is
proposed as the possible anchor of a small seesaw neutrino mass. A new U(1)
gauge symmetry is then also possible, and the associated gauge boson may be
discovered at or below the TeV scale. We discuss the phenomenology of this
proposal, with and without possible constraints from the NuTeV and atomic
parity violation experiments, which appear to show small discrepancies from the
predictions of the standard model.Comment: 20 pages including 4 figure
SUSY Contributions to and Top Decay
I report on a systematic analysis of the MSSM parameter space to obtain the
best SUSY solution to the anomaly within the constraint of top quark
decay. Phenomenological implications for top decay and direct stop production
at the Tevatron collider are discussed.Comment: Latex file (3 pages)+ 2 ps files containing figures. Invited talk at
SUSY96, Maryland, May 199
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