3,756 research outputs found
Neutrino mass and magnetic moment in supersymmetry without R-parity in the light of recent data
We consider the generation of neutrino Majorana mass and transition magnetic
moment by the lepton-number violating and/or couplings in
R-parity-violating supersymmetric models. We update (and improve) the existing
upper limits on the relevant couplings using the most recent data on neutrino
masses and mixings, indicating also the possible improvement by the GENIUS
project. We study the implication of this update on the induced neutrino
magnetic moment.Comment: 7 pages, Latex, uses axodraw.sty; refs updated, to appear in PL
A simple and objective method for reproducible resting state network (RSN) detection in fMRI
Spatial Independent Component Analysis (ICA) decomposes the time by space
functional MRI (fMRI) matrix into a set of 1-D basis time courses and their
associated 3-D spatial maps that are optimized for mutual independence. When
applied to resting state fMRI (rsfMRI), ICA produces several spatial
independent components (ICs) that seem to have biological relevance - the
so-called resting state networks (RSNs). The ICA problem is well posed when the
true data generating process follows a linear mixture of ICs model in terms of
the identifiability of the mixing matrix. However, the contrast function used
for promoting mutual independence in ICA is dependent on the finite amount of
observed data and is potentially non-convex with multiple local minima. Hence,
each run of ICA could produce potentially different IC estimates even for the
same data. One technique to deal with this run-to-run variability of ICA was
proposed by Yang et al. (2008) in their algorithm RAICAR which allows for the
selection of only those ICs that have a high run-to-run reproducibility. We
propose an enhancement to the original RAICAR algorithm that enables us to
assign reproducibility p-values to each IC and allows for an objective
assessment of both within subject and across subjects reproducibility. We call
the resulting algorithm RAICAR-N (N stands for null hypothesis test), and we
have applied it to publicly available human rsfMRI data (http://www.nitrc.org).
Our reproducibility analyses indicated that many of the published RSNs in
rsfMRI literature are highly reproducible. However, we found several other RSNs
that are highly reproducible but not frequently listed in the literature.Comment: 54 pages, 13 figure
Neutrinos from Stellar Collapse: Comparison of signatures in water and heavy water detectors
Signatures of neutrino and antineutrino signals from stellar collapse in
heavy water detectors are contrasted with those in water detectors. The effects
of mixing, especially due to the highly dense matter in the supernova core, are
studied. The mixing parameters used are those sets allowed by current
understanding of available neutrino data: from solar, atmospheric and
laboratory neutrino experiments. Signals at a heavy water detector, especially
the dominant charged current reactions on deuteron, are very sensitive to some
of these sets of allowed mixing parameters. Theoretical uncertainties on
supernova neutrino spectra notwithstanding, a combination of supernova
measurements with water and heavy water detectors may be able to distinguish
many of these mixing possibilities and thus help in ruling out many of them.Comment: 36 pages Latex file, with 13 postscript figures; important
improvements in the analysis and more detailed presentation of results. To
appear in Phys. Rev.
Binary mixtures of condensates in generic confining potentials
We study a binary mixture of Bose-Einstein condensates, confined in a generic
potential, in the Thomas-Fermi approximation. We search for the
zero-temperature ground state of the system, both in the case of fixed numbers
of particles and fixed chemical potentials.Comment: 20 pages, 2 figure
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