17,454 research outputs found
A 4-neutrino model with a Higgs triplet
We take as a starting point the Gelmini -- Roncadelli model enlarged by a
term with explicit lepton number violation in the Higgs potential and add a
neutrino singlet field coupled via a scalar doublet to the usual leptons. This
scenario allows us to take into account all three present indications in favour
of neutrino oscillations provided by the solar, atmospheric and LSND neutrino
oscillation experiments. Furthermore, it suggests a model which reproduces
naturally one of the two 4-neutrino mass spectra favoured by the data. In this
model the solar neutrino problem is solved by large mixing MSW \nu_e\to\nu_\tau
transitions and the atmospheric neutrino problem by transitions of \nu_\mu into
a sterile neutrino.Comment: Latex, 14 pages, no figure
A socio-economic analysis of youth disconnectedness
According to our research, some 12% of young people in Germany between the ages of 17 and 19 are disconnected, i.e. not in school, unemployed, and not living with a partner. The percentage of disconnected youths has been on the rise since 2002. There is evidence that an adverse family environment is the most important variable for being disconnected. Early life adversity influences the development of cognitive and noncognitive skills as well as school and labour market outcomes. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by an increase in the number of disconnected youth. --Disconnected youth,unemployment,school failure,life adversity
A Socio-Economic Analysis of Youth Disconnectedness
Disconnectedness among youth can have several dimensions. From a socio-economic viewpoint, failure in school, unemployment and the lack of an intimate relationship are among the most important ones. In our samples from SOEP youth questionnaires, approximately 13% of young people in Germany between the ages of 17 and 19 are disconnected. The percentage of disconnected youths has been on the rise since 2001. There is evidence that an adverse family background is the most important variable for being disconnected in young adulthood. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by increases in the number of disconnected youth.Disconnected youth, unemployment, school failure, life adversity
A Socio-economic Analysis of Youth Disconnectedness
Disconnectedness among youth can have several dimensions. From a socio-economic viewpoint, failure in school, unemployment and the lack of an intimate relationship are among the most important ones. In our samples from SOEP youth questionnaires, approximately 13% of young people in Germany between the ages of 17 and 19 are disconnected. The percentage of disconnected youths has been on the rise since 2001. There is evidence that an adverse family background is the most important variable for being disconnected in young adulthood. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by increases in the number of disconnected youth.disconnected youth, unemployment, school failure, life adversity
Higher Gauge Theory and Gravity in (2+1) Dimensions
Non-abelian higher gauge theory has recently emerged as a generalization of
standard gauge theory to higher dimensional (2-dimensional in the present
context) connection forms, and as such, it has been successfully applied to the
non-abelian generalizations of the Yang-Mills theory and 2-form
electrodynamics. (2+1)-dimensional gravity, on the other hand, has been a
fertile testing ground for many concepts related to classical and quantum
gravity, and it is therefore only natural to investigate whether we can find an
application of higher gauge theory in this latter context. In the present paper
we investigate the possibility of applying the formalism of higher gauge theory
to gravity in (2+1) dimensions, and we show that a nontrivial model of
(2+1)-dimensional gravity coupled to scalar and tensorial matter fields - the
model - can be formulated both as a standard gauge theory and
as a higher gauge theory. Since the model has a very rich structure - it admits
as solutions black-hole BTZ-like geometries, particle-like geometries as well
as Robertson-Friedman-Walker cosmological-like expanding geometries - this
opens a wide perspective for higher gauge theory to be tested and understood in
a relevant gravitational context. Additionally, it offers the possibility of
studying gravity in (2+1) dimensions coupled to matter in an entirely new
framework.Comment: 22 page
Direct innervation of capillary endothelial cells in the lamina propria of the ferret stomach
Direct innervation of capillary endothelial cells in lamina propria of ferret stomac
IMEX evolution of scalar fields on curved backgrounds
Inspiral of binary black holes occurs over a time-scale of many orbits, far
longer than the dynamical time-scale of the individual black holes. Explicit
evolutions of a binary system therefore require excessively many time steps to
capture interesting dynamics. We present a strategy to overcome the
Courant-Friedrichs-Lewy condition in such evolutions, one relying on modern
implicit-explicit ODE solvers and multidomain spectral methods for elliptic
equations. Our analysis considers the model problem of a forced scalar field
propagating on a generic curved background. Nevertheless, we encounter and
address a number of issues pertinent to the binary black hole problem in full
general relativity. Specializing to the Schwarzschild geometry in Kerr-Schild
coordinates, we document the results of several numerical experiments testing
our strategy.Comment: 28 pages, uses revtex4. Revised in response to referee's report. One
numerical experiment added which incorporates perturbed initial data and
adaptive time-steppin
Degenerate states of narrow semiconductor rings in the presence of spin orbit coupling: Role of time-reversal and large gauge transformations
The electron Hamiltonian of narrow semiconductor rings with the Rashba and
Dresselhaus spin orbit terms is invariant under time-reversal operation
followed by a large gauge transformation. We find that all the eigenstates are
doubly degenerate when integer or half-integer quantum fluxes thread the
quantum ring. The wavefunctions of a degenerate pair are related to each other
by the symmetry operation. These results are valid even in the presence of a
disorder potential. When the Zeeman term is present only some of these
degenerate levels anticross
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