31,601 research outputs found
On the distribution of the total energy of a system on non-interacting fermions: random matrix and semiclassical estimates
We consider a single particle spectrum as given by the eigenvalues of the
Wigner-Dyson ensembles of random matrices, and fill consecutive single particle
levels with n fermions. Assuming that the fermions are non-interacting, we show
that the distribution of the total energy is Gaussian and its variance grows as
n^2 log n in the large-n limit. Next to leading order corrections are computed.
Some related quantities are discussed, in particular the nearest neighbor
spacing autocorrelation function. Canonical and gran canonical approaches are
considered and compared in detail. A semiclassical formula describing, as a
function of n, a non-universal behavior of the variance of the total energy
starting at a critical number of particles is also obtained. It is illustrated
with the particular case of single particle energies given by the imaginary
part of the zeros of the Riemann zeta function on the critical line.Comment: 28 pages in Latex format, 5 figures, submitted for publication to
Physica
SIDE, a fiber fed spectrograph for the 10.4 m Gran Telescopio Canarias (GTC)
SIDE (Super Ifu Deployable Experiment) will be a second-generation,
common-user instrument for the Grantecan (GTC) on La Palma (Canary Islands,
Spain). It is being proposed as a spectrograph of low and intermediate
resolution, highly efficient in multi-object spectroscopy and 3D spectroscopy.
SIDE features the unique possibility of performing simultaneous visible and NIR
observations for selected ranges. The SIDE project is leaded by the Instituto
de Astrofisica de Andalucia (IAA-CSIC) in Granada (Spain) and the SIDE
Consortium is formed by a total of 10 institutions from Spain, Mexico and USA.
The SIDE Feasibility Study has been completed and currently the project is
under revision by the GTC Project Office.Comment: 9 pages, 6 figures, to appear in "Ground-based and Airborne
Instrumentation for Astronomy II" SPIE conference Proc. 7014, Marseille,
23-28 June 200
Impact of internal bremsstrahlung on the detection of gamma-rays from neutralinos
We present a detailed study of the effect of internal bremsstrahlung photons
in the context of the minimal supersymmetric standard models and their impact
on gamma-ray dark matter annihilation searches. We find that although this
effect has to be included for the correct evaluation of fluxes of high energy
photons from neutralino annihilation, its contribution is relevant only in
models and at energies where the lines contribution is dominant over the
secondary photons. Therefore, we find that the most optimistic supersymmetric
scenarios for dark matter detection do not change significantly when including
the internal bremsstrahlung. As an example, we review the gamma-ray dark matter
detection prospects of the Draco dwarf spheroidal galaxy for the MAGIC
stereoscopic system and the CTA project. Though the flux of high energy photons
is enhanced by an order of magnitude in some regions of the parameter space,
the expected fluxes are still much below the sensitivity of the instruments.Comment: 5 pages, twocolumn format, 3 figures:3 references added, accepted as
Brief Report in PR
Prediction of force coefficients for labyrinth seals
The development of a linear model for the prediction of labyrinth seal forces and on its comparison to available stiffness data is presented. A discussion of the relevance of fluid damping forces and the preliminary stages of a program to obtain data on these forces are examined. Fluid-dynamic forces arising from nonuniform pressure patterns in labyrinth seal glands are known to be potentially destablizing in high power turbomachinery. A well documented case in point is that of the space Shuttle Main Engine turbopumps. Seal forces are also an important factor for the stability of shrouded turbines, acting in that case in conjunction with the effects of blade-tip clearance variations
Implications of the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) with Liquid Argon
The CENNS-10 experiment of the COHERENT collaboration has recently reported
the first detection of coherent-elastic neutrino-nucleus scattering (CEvNS) in
liquid Argon with more than significance. In this work, we exploit
the new data in order to probe various interesting parameters which are of key
importance to CEvNS within and beyond the Standard Model. A dedicated
statistical analysis of these data shows that the current constraints are
significantly improved in most cases. We derive a first measurement of the
neutron rms charge radius of Argon, and also an improved determination of the
weak mixing angle in the low energy regime. We also update the constraints on
neutrino non-standard interactions, electromagnetic properties and light
mediators with respect to those derived from the first COHERENT-CsI data.Comment: discussion expanded including light mediators and nuclear
uncertainties, figures added, references added. V3: Fig. 7 corrected,
conclusions unchange
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