1,466 research outputs found
SU(3) Family Gauge Symmetry and the Axion
We analyze the structure of a recently proposed effective field theory (EFT)
for the generation of quark and lepton mass ratios and mixing angles, based on
the spontaneous breaking of an SU(3) family gauge symmetry at a high scale F.
We classify the Yukawa operators necessary to seed the masses, making use of
the continuous global symmetries that they preserve. One global U(1), in
addition to baryon number and electroweak hypercharge, remains unbroken after
the inclusion of all operators required by standard-model-fermion
phenomenology. An associated vacuum symmetry insures the vanishing of the
first-family quark and charged-lepton masses in the absence of the family gauge
interaction. If this U(1) symmetry is taken to be exact in the EFT, broken
explicitly by only the QCD-induced anomaly, and if the breaking scale F is
taken to lie in the range 10 to 9 - 10 to 12 GeV, then the associated
Nambu-Goldstone boson is a potential QCD axion.Comment: References added and clarifications in Vacuum Structure sectio
Neutrinos and SU(3) Family Gauge Symmetry
We include the standard-model (SM) leptons in a recently proposed framework
for the generation of quark mass ratios and Cabibbo-Kobayashi-Maskawa (CKM)
mixing angles from an SU(3) family gauge interaction. The set of SM-singlet
scalar fields describing the spontaneous breaking is the same as employed for
the quark sector. The imposition at tree-level of the experimentally correct
Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix, in the form of a tri-bi
maximal structure, fixes several of the otherwise free parameters and renders
the model predictive. The normal hierarchy among the neutrino masses emerges
from this scheme.Comment: 9 pages, 3 tables; a comment added to clarify the effects of
additional Yukawa operators; final version in PR
The effects of hemodynamic lag on functional connectivity and behavior after stroke
Stroke disrupts the brain's vascular supply, not only within but also outside areas of infarction. We investigated temporal delays (lag) in resting state functional magnetic resonance imaging signals in 130 stroke patients scanned two weeks, three months and 12 months post stroke onset. Thirty controls were scanned twice at an interval of three months. Hemodynamic lag was determined using cross-correlation with the global gray matter signal. Behavioral performance in multiple domains was assessed in all patients. Regional cerebral blood flow and carotid patency were assessed in subsets of the cohort using arterial spin labeling and carotid Doppler ultrasonography. Significant hemodynamic lag was observed in 30% of stroke patients sub-acutely. Approximately 10% of patients showed lag at one-year post-stroke. Hemodynamic lag corresponded to gross aberrancy in functional connectivity measures, performance deficits in multiple domains and local and global perfusion deficits. Correcting for lag partially normalized abnormalities in measured functional connectivity. Yet post-stroke FC-behavior relationships in the motor and attention systems persisted even after hemodynamic delays were corrected. Resting state fMRI can reliably identify areas of hemodynamic delay following stroke. Our data reveal that hemodynamic delay is common sub-acutely, alters functional connectivity, and may be of clinical importance
Wilson Loops in string duals of Walking and Flavored Systems
We consider the VEV of Wilson loop operators by studying the behavior of
string probes in solutions of Type IIB string theory generated by Nc D5 branes
wrapped on an internal manifold. In particular, we focus on solutions to the
background equations that are dual to field theories with a walking gauge
coupling as well as for flavored systems. We present in detail our walking
solution and emphasize various general aspects of the procedure to study Wilson
loops using string duals. We discuss the special features that the strings show
when probing the region associated with the walking of the field theory
coupling.Comment: 28 pages. Various figures. Version to be published
Breaking Discrete Symmetries in Broken Gauge Theories
We study the spontaneous breaking of discrete symmetries in theories with
broken gauge symmetry. The intended application is to CP breaking in theories
with gauged flavor symmetries, but the analysis described here is preliminary.
We dispense with matter fields and take the gauge theory to be weakly coupled
and broken spontaneously by unspecified, short-distance forces. We develop an
effective-field-theory description of the resultant low energy theory, and ask
whether this theory by itself can describe the subsequent breaking of discrete
symmetries. We conclude that this can happen depending on the parameters of the
effective theory, and that the intrinsic violation is naturally of order unity.Comment: 9 pages, 1 figure, corrected typos, added a referenc
O&M cost-based FMECA: Identification and ranking of the most critical components for 2-4 MW geared offshore wind turbines
To date, the focus of the research on offshore wind turbines (WTs) has been mainly on how to minimise their capital cost, but Operation and Maintenance (O&M) can represent up to a third of the lifetime costs of an offshore wind farm. The cost for the assets repair/replacement and for the logistics of the maintenance operations are two of the biggest contributors to O&M expenses. While the first is going to rise with the employment of bigger structures, the latter can significantly increase dependently on the reliability of the components, and thus the necessity to performed unscheduled maintenance operations. Using the reliability data for a population of offshore WTs (representing the configurations most employed offshore), first, the share of the components failures to the O&M cost, together with an estimation of their dependency on some O&M parameters has been derived. Then, by following a cost-based Failure Modes Effects and Criticality Analysis (FMECA), and ranking the components through O&M cost priority number, the most critical components for O&M unplanned operations are identified
Continuous Ordinal Regression for Analysis of Visual Analogue Scales: The R Package ordinalCont
This paper introduces the R package ordinalCont, which implements an ordinal regression framework for response variables which are recorded on a visual analogue scale (VAS). This scale is used when recording subjects' perception of an intangible quantity such as pain, anxiety or quality of life, and consists of a mark made on a linear scale. We implement continuous ordinal regression models for VAS as the appropriate method of analysis for such responses, and introduce smoothing terms and random effects in the linear predictor. The model parameters are estimated using constrained optimization of the penalized likelihood and the penalty parameters are automatically selected via maximization of their marginal likelihood. The estimation algorithm is shown to perform well, in a simulation study. Two examples of application are given: the first involves the analysis of pain outcomes in a clinical trial for laser treatment for chronic neck pain; the second is an analysis of quality of life outcomes in a clinical trial for chemotherapy for the treatment of breast cancer
Electronic structure investigation of the cubic inverse perovskite Sc3AlN
The electronic structure and chemical bonding of the recently discovered
inverse perovskite Sc3AlN, in comparison to ScN and Sc metal have been
investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured
Sc L, N K, Al L1, and Al L2,3 emission spectra are compared with calculated
spectra using first principle density-functional theory including dipole
transition matrix elements. The main Sc 3d - N 2p and Sc 3d - Al 3p chemical
bond regions are identified at -4 eV and -1.4 eV below the Fermi level,
respectively. A strongly modified spectral shape of 3s states in the Al L2,3
emission from Sc3AlN in comparison to pure Al metal is found, which reflects
the Sc 3d - Al 3p hybridization observed in the Al L1 emission. The differences
between the electronic structure of Sc3AlN, ScN, and Sc metal are discussed in
relation to the change of the conductivity and elastic properties.Comment: 11 pages, 5 picture
Coexistence of amplitude and frequency modulations in intracellular calcium dynamics
The complex dynamics of intracellular calcium regulates cellular responses to
information encoded in extracellular signals. Here, we study the encoding of
these external signals in the context of the Li-Rinzel model. We show that by
control of biophysical parameters the information can be encoded in amplitude
modulation, frequency modulation or mixed (AM and FM) modulation. We briefly
discuss the possible implications of this new role of information encoding for
astrocytes.Comment: 4 pages, 4 figure
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