26,705 research outputs found
Cognitive Disease, Metabolic Disease, and Inflammation in the Honolulu Asia Aging Study: Connnecting the Dots between Insulin Resistance, Type 2 Diabetes, Alzheimer's Disease, Dementia, and Fibrinogen.
Ph.D. Thesis. University of HawaiÊ»i at MÄnoa 2017
Finite-volume Hamiltonian method for coupled channel interactions in lattice QCD
Within a multi-channel formulation of scattering, we investigate the
use of the finite-volume Hamiltonian approach to resolve scattering observables
from lattice QCD spectra. The asymptotic matching of the well-known L\"uscher
formalism encodes a unique finite-volume spectrum. Nevertheless, in many
practical situations, such as coupled-channel systems, it is advantageous to
interpolate isolated lattice spectra in order to extract physical scattering
parameters. Here we study the use of the Hamiltonian framework as a
parameterisation that can be fit directly to lattice spectra. We find that with
a modest amount of lattice data, the scattering parameters can be reproduced
rather well, with only a minor degree of model dependence.Comment: 25 pages, 16 figure
Unitary coupled-channels model for three-mesons decays of heavy mesons
A unitary coupled-channels model is presented for investigating the decays of
heavy mesons and excited meson states into three light pseudoscalar mesons. The
model accounts for the three-mesons final state interactions in the decay
processes, as required by both the three-body and two-body unitarity
conditions. In the absence of the Z-diagram mechanisms that are necessary
consequences of the three-body unitarity, our decay amplitudes are reduced to a
form similar to those used in the so-called isobar-model analysis. We apply our
coupled-channels model to the three-pions decays of a1(1260), pi2(1670),
pi2(2100), and D0 mesons, and show that the Z-diagram mechanisms can contribute
to the calculated Dalitz plot distributions by as much as 30% in magnitudes in
the regions where f0(600), rho(770), and f2(1270) dominate the distributions.
Also, by fitting to the same Dalitz plot distributions, we demonstrate that the
decay amplitudes obtained with the unitary model and the isobar model can be
rather different, particularly in the phase that plays a crucial role in
extracting the CKM CP-violating phase from the data of B meson decays. Our
results indicate that the commonly used isobar model analysis must be extended
to account for the final state interactions required by the three-body
unitarity to reanalyze the three-mesons decays of heavy mesons, thereby
exploring hybrid or exotic mesons, and signatures of physics beyond the
standard model.Comment: 32 pages, 10 figures. Version to appear in PR
Quartification with T' Flavor
In the simplest (non-quiver) unified theories, fermion families are often
treated sequentially and a flavor symmetry may act similarly. As an alternative
with non-sequential flavor symmetry, we consider a model based on the group
(T'*Z_2)_global * [SU(3)^4]_local which combines the predictions of T' flavor
symmetry with the features of a unified quiver gauge theory. The model
accommodates the relationships between mixing angles separately for neutrinos,
and for quarks, which have been previously predicted with T'. This quiver
unification theory makes predictions of several additional gauge bosons and
bifundamental fermions at the TeV scale.Comment: 8 pages, LaTex; added references and clarifie
Regge approach to charged-pion photoproduction at invariant energies above 2 GeV
A Regge model with absorptive corrections is employed in a global analysis of
the world data on positive and negative pion photoproduction for photon
energies from 3 to 8 GeV. In this region resonance contributions are expected
to be negligible so that the available experimental information on differential
cross sections and single polarization observables at -t \leq 2 GeV^2 allows us
to determine the non-resonant part of the reaction amplitude reliably. The
model amplitude is then used to predict observables for photon energies below 3
GeV. Differences between our predictions and data in this energy region are
systematically examined as possible signals for the presence of excited
baryons. We find that the data available for the polarized photon asymmetry
show promising resonance signatures at invariant energies around 2 GeV. With
regard to differential cross sections the analysis of negative pion
photoproduction data, obtained recently at JLab, indicates likewise the
presence of resonance structures around 2 GeVComment: misprint in Table 3 corrected; reference adde
Vacuum phenomenology of the chiral partner of the nucleon in a linear sigma model with vector mesons
We investigate a linear sigma model with global chiral symmetry. The mesonic degrees of freedom are the standard scalar and
pseudoscalar mesons and the vector and axial-vector mesons. The baryonic
degrees of freedom are the nucleon, , and its chiral partner, , which
is usually identified with N(1535). The chiral partner is incorporated in the
so-called mirror assignment, where the nucleon mass is not solely generated by
the chiral condensate but also by a chirally invariant mass term, . The
presence of (axial-) vector fields modifies the expressions for the axial
coupling constants of the nucleon, , and its partner,
. Using experimental data for the decays and
, as well as lattice results for we infer
MeV, i.e., an appreciable amount of the nucleon mass originates
from sources other than the chiral condensate. We test our model by evaluating
the decay and the s-wave nucleon-pion scattering lengths
.Comment: 16 pages, 2 figures. To appear in Phys. Rev.
Quark-Hadron Duality and Parity Violating Asymmetry of Electroweak Reactions in the Delta Region
A dynamical model of electroweak pion production reactions in the Delta(1232)
region has been extended to include the neutral current contributions for
examining the local Quark-Hadron Duality in neutrino-induced reactions and for
investigating how the axial N-Delta form factor can be determined by the parity
violating asymmetry of N(\vec{e},e') reactions. We first show that the recent
data of (e,e') structure functions F_1 and F_2, which exhibit the Quark-Hadron
Duality, are in good agreement with our predictions. For possible future
experimental tests, we then predict that the structure functions F_1, F_2, and
F_3 for (\nu,e) and (\nu,\nu') processes also show the similar Quark-Hadron
Duality. The spin dependent structure functions g_1 and g_2 of (e,e') have also
been calculated from our model. It is found that the local Quark-Hadron Duality
is not seen in the calculated g_1 and g_2, while our results for g_1 and some
polarization observables associated with the exclusive p(\vec{e},e' pi) and
\vec{p}(\vec{e},e' pi) reactions are in reasonably good agreement with the
recent data. In the investigation of parity violating asymmetry A of
N(\vec{e},e') reactions, it is found that the non-resonant contribution is
small at the Delta peak and a measurement of A can be used to distinguish two
previously determined axial N-Delta transition form factors. The predicted
asymmetry A are also compared with the Parton Model predictions for future
experimental investigations of Quark-Hadron Duality.Comment: 28 pages, 19 figures v2; figures and references adde
A path integral approach to the dynamics of a random chain with rigid constraints
In this work the dynamics of a freely jointed random chain which fluctuates
at constant temperature in some viscous medium is studied. The chain is
regarded as a system of small particles which perform a brownian motion and are
subjected to rigid constraints which forbid the breaking of the chain. For
simplicity, all interactions among the particles have been switched off and the
number of dimensions has been limited to two. The problem of describing the
fluctuations of the chain in the limit in which it becomes a continuous system
is solved using a path integral approach, in which the constraints are imposed
with the insertion in the path integral of suitable Dirac delta functions. It
is shown that the probability distribution of the possible conformations in
which the fluctuating chain can be found during its evolution in time coincides
with the partition function of a field theory which is a generalization of the
nonlinear sigma model in two dimensions. Both the probability distribution and
the generating functional of the correlation functions of the positions of the
beads are computed explicitly in a semiclassical approximation for a
ring-shaped chain.Comment: 36 pages, 2 figures, LaTeX + REVTeX4 + graphicx, minor changes in the
text, reference adde
A longitudinal study of muscle rehabilitation in the lower leg after cast removal using Magnetic Resonance Imaging and strength assessment
Acknowledgements We thank the A&E nurses and plaster technicians for identifying suitable patients, the MRI radiographers for performing the scanning, Dr Scott Semple for invaluable help in some of the pilot studies and Mr E. C. Stevenson for constructing the footrest used in the scanner. We are very grateful to the dedicated patients themselves who gave considerable amounts of time to come in for scanning, exercise and assessment during the course of this study.Peer reviewedPublisher PD
Cavity-enabled high-dimensional quantum key distribution
High-dimensional quantum key distribution (QKD) offers the possibility of encoding multiple bits of key on a single entangled photon pair. An experimentally promising approach to realizing this is to use energyâtime entanglement. Currently, however, the control of very high-dimensional entangled photons is challenging. We present a simple and experimentally compact approach, which is based on a cavity that allows one to measure two different bases: the time of arrival and another that is approximately mutually unbiased to the arrival time. We quantify the errors in the setup, due both to the approximate nature of the mutually unbiased measurement and as a result of experimental errors. It is shown that the protocol can be adapted using a cut-off so that it is robust against the considered errors, even within the regime of up to 10 bits per photon pair
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