43,773 research outputs found
Neutrino-nucleus interactions in the T2K experiment
We present a study of neutrino-nucleus interactions at the T2K experiment
based on the GiBUU transport model. The aim of T2K is to measure
appearance and , but it will also be able to do a precise
measurement of disappearance. The former requires a good
understanding of production while the latter is closely connected with
a good understanding of quasielastic scattering. For both processes we
investigate the influence of nuclear effects and particular final-state
interactions on the expected event rates taking into account the T2K detector
setup.Comment: v3: matches version to be published in Phys. Rev.
Static and Dynamic Pressure Distributions in a Short Labyrinth Seal
As part of a study into turbine blade tip destabilizing forces, a seals test rig was built in which spin rate, circular whirl rate, direction and amplitude of inlet swirl angle, and eccentricity can all be controlled over wide ranges, and measurements can be made at gap Reynolds numbers up to about 2 x 10(exp 4). This facility is described and preliminary data is presented for a one cavity labyrinth seal with a flat, stator mounted land. The impact of different flow coefficients for the first and second knives on the rotordynamic coefficients was found. While this effect is dominant for the direct forces, it should also be incorporated into calculations of cross forces where it has an impact under many conditions
Cosmological perturbations from inhomogeneous preheating and multi-field trapping
We consider inhomogeneous preheating in a multi-field trapping model. The
curvature perturbation is generated by inhomogeneous preheating which induces
multi-field trapping at the enhanced symmetric point (ESP), and results in
fluctuation in the number of e-foldings. Instead of considering simple
reheating after preheating, we consider a scenario of shoulder inflation
induced by the trapping. The fluctuation in the number of e-foldings is
generated during this weak inflationary period, when the additional light
scalar field is trapped at the local maximum of its potential. The situation
may look similar to locked or thermal inflation or even to hybrid inflation,
but we will show that the present mechanism of generating the curvature
perturbation is very different from these others. Unlike the conventional
trapped inflationary scenario, we do not make the assumption that an ESP
appears at some unstable point on the inflaton potential. This assumption is
crucial in the original scenario, but it is not important in the multi-field
model. We also discuss inhomogeneous preheating at late-time oscillation, in
which the magnitude of the curvature fluctuation can be enhanced to accommodate
low inflationary scale.Comment: 18pages, 2 figures, to appear in JHE
Effects of Orientations, Aspect Ratios, Pavement Materials and Vegetation Elements on Thermal Stress inside Typical Urban Canyons
The analysis of local climate conditions to test artificial urban boundaries and related climate hazards through modelling tools should become a common practice to inform public authorities about the benefits of planning alternatives. Different finishing materials and sheltering objects within urban canyons (UCs) can be tested, predicted and compared through quantitative and qualitative understanding of the relationships between the microclimatic environment and subjective thermal assessment. This process can work as support planning instrument in the early design phases as has been done in this study that aims to analyze the thermal stress within typical UCs of Bilbao (Spain) in summertime through the evaluation of Physiologically Equivalent Temperature using ENVI-met. The UCs are characterized by different orientations, height-to-width aspect ratios, pavement materials, trees’ dimensions and planting pattern. Firstly, the current situation was analyzed; secondly, the effects of asphalt and red brick stones as streets’ pavement materials were compared; thirdly, the benefits of vegetation elements were tested. The analysis demonstrated that orientation and aspect ratio strongly affect the magnitude and duration of the thermal peaks at pedestrian level; while the vegetation elements improve the thermal comfort up to two thermophysiological assessment classes. The outcomes of this study, were transferred and visualized into green planning recommendations for new and consolidated urban areas in Bilbao.The work leading to these results has received funding from COST Action TU0902, the European Community’s Seventh Framework Programme under Grant Agreement No. 308497, Project RAMSES—Reconciling Adaptation, Mitigation and Sustainable Development for Cities (2012–2017) and Diputación Foral de Bizkaia Exp. 6-12-TK-2010-0027, Project SICURB-ITS- Desarrollo de Sistemas para el análisis de la Contaminación atmosférica en zonas URBanas integrados en ITS (2010–2011)
Baryon chemical potential and in-medium properties of BPS skyrmions
We continue the investigation of thermodynamical properties of the BPS Skyrme
model. In particular, we analytically compute the baryon chemical potential
both in the full field theory and in a mean-field approximation. In the full
field theory case, we find that the baryon chemical potential is always exactly
proportional to the baryon density, for arbitrary solutions. We further find
that, in the mean-field approximation, the BPS Skyrme model approaches the
Walecka model in the limit of high density - their thermodynamical functions as
well as the equation of state agree in this limit. This fact allows to read off
some properties of the -meson from the BPS Skyrme action, even though
the latter model is entirely based on the (pionic) Skyrme field. On the
other hand, at low densities, at the order of the usual nuclear matter density,
the equations of state of the two models are no longer universal, such that a
comparison depends on some model details. Still, also the BPS Skyrme model
gives rise to nuclear saturation in this regime, leading, in fact, to an exact
balance between repulsive and attractive forces. The perfect fluid aspects of
the BPS Skyrme model, which, together with its BPS properties, form the base of
our results, are shown to be in close formal analogy with the Eulerian
formulation of relativistic fluid dynamics. Within this analogy, the BPS Skyrme
model, in general, corresponds to a non-barotropic perfect fluid.Comment: Latex, 28 pages, 3 figure
Neutrino-induced coherent pion production off nuclei reexamined
It is pointed out that so far all theoretical estimates of coherent pion
production off nuclei induced by neutrinos rely on the 'local approximation'
well known in photonuclear physics. The effects of dropping this approximation
are discussed. It is found that in a plane wave approximation for the pion the
local approximation overestimates the coherent neutrino-induced pion production
on nuclei.Comment: v3: comments on pion FSI added, minor corrections; version as
published in Phys. Rev.
Hybrid Curvatons from Broken Symmetry
We present a new general mechanism for generating curvature perturbations
after inflation. Our model is based on the simple assumption that a field that
starts to oscillate after inflation has a potential characterized by an
underlying global symmetry that is slightly or badly broken. Inhomogeneous
preheating occurs due to the oscillation with the broken symmetry. Unlike the
traditional curvaton model, we will not identify the curvaton with the
oscillating field. The curvaton is identified with the preheat field that could
be either a scalar, vector, or fermionic field. We introduce an explicit mass
term for the curvaton, which is important for later evolution and the decay.
Our present model represents the simplest example of the hybrid of the
curvatons and inhomogeneous preheating.Comment: 21pages, 5 figures, accepted for publication in JHE
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