6,239 research outputs found
The Topological Theory of the Milnor Invariant
We study a topological Abelian gauge theory that generalizes the Abelian
Chern-Simons one, and that leads in a natural way to the Milnor's link
invariant when the classical action on-shell is calculated.Comment: 4 pages; corrected equatio
Spatially resolved physical and chemical properties of the planetary nebula NGC 3242
Optical integral-field spectroscopy was used to investigate the planetary
nebula NGC 3242. We analysed the main morphological components of this source,
including its knots, but not the halo. In addition to revealing the properties
ofthe physical and chemical nature of this nebula, we also provided reliable
spatially resolved constraints that can be used for future photoionisation
modelling of the nebula. The latter is ultimately necessary to obtain a fully
self-consistent 3D picture of the physical and chemical properties of the
object. The observations were obtained with the VIMOS instrument attached to
VLT-UT3. Maps and values for specific morphological zones for the detected
emission-lines were obtained and analysed with routines developed by the
authors to derive physical and chemical conditions of the ionised gas in a 2D
fashion. We obtained spatially resolved maps and mean values of the electron
densities, temperatures, and chemical abundances, for specific morphological
structures in NGC 3242. These results show the pixel-to-pixel variations of the
the small- and large-scale structures of the source. These diagnostic maps
provide information free from the biases introduced by traditional single
long-slit observations. In general, our results are consistent with a uniform
abundance distribution for the object, whether we look at abundance maps or
integrated fluxes from specified morphological structures. The results indicate
that special care should be taken with the calibration of the data and that
only data with extremely good signal-to-noise ratio and spectral coverage
should be used to ensure the detection of possible spatial variations.Comment: 11 pages, 8 figures accepted for publication in Astronomy &
Astrophysic
Aspects of CPT-even Lorentz-symmetry violating physics in a supersymmetric scenario
Background fermion condensates in a landscape dominated by global SUSY are
reassessed in connection with a scenario where Lorentz symmetry is violated in
the bosonic sector (actually, the photon sector) by a -even -term. An
effective photonic action is discussed that originates from the supersymmetric
background fermion condensates. Also, the photino mass emerges in terms of a
particular condensate contrary to what happens in the -violation.
Finally, the interparticle potential induced by the effective photonic action
is investigated and a confining profile is identified.Comment: 14 pages. arXiv admin note: text overlap with arXiv:1102.3777 by
other author
Lattice-Boltzmann Method for Non-Newtonian Fluid Flows
We study an ad hoc extension of the Lattice-Boltzmann method that allows the
simulation of non-Newtonian fluids described by generalized Newtonian models.
We extensively test the accuracy of the method for the case of shear-thinning
and shear-thickening truncated power-law fluids in the parallel plate geometry,
and show that the relative error compared to analytical solutions decays
approximately linear with the lattice resolution. Finally, we also tested the
method in the reentrant-flow geometry, in which the shear-rate is no-longer a
scalar and the presence of two singular points requires high accuracy in order
to obtain satisfactory resolution in the local stress near these points. In
this geometry, we also found excellent agreement with the solutions obtained by
standard finite-element methods, and the agreement improves with higher lattice
resolution
Surface-Invariants in 2D Classical Yang-Mills Theory
We study a method to obtain invariants under area-preserving diffeomorphisms
associated to closed curves in the plane from classical Yang-Mills theory in
two dimensions. Taking as starting point the Yang-Mills field coupled to non
dynamical particles carrying chromo-electric charge, and by means of a
perturbative scheme, we obtain the first two contributions to the on shell
action, which are area-invariants. A geometrical interpretation of these
invariants is given.Comment: 17 pages, 2 figure
Caracterização agronômica de genótipos clonais de abacaxizeiro resistentes à fusariose.
O abacaxi tem destaque no mercado internacional de frutos tropicais, pois é o terceiro fruto tropical mais comercializado no mundo. O Brasil é um dos três maiores produtores mundiais, mas na produção brasileira há predomÃnio de poucas cultivares e é destinada basicamente ao mercado interno
Evaluating recommended audiometric changes to candidacy using the speech intelligibility index
INTRODUCTION: The National Institute of Health and Care Excellence (NICE) has derived candidacy guidelines for cochlear implants in the UK based on audiometric thresholds (90 dB HL or above at 2 and 4 kHz; hereafter referred to as the 90 dB HL criteria). Recent research has proposed that these criteria should be changed to 80 dB HL at 2 and 4 kHz (hereafter referred to as the 80 dB HL criteria) in the ear to be implanted. METHODS: In this study, we analysed aided SII scores derived for different hearing loss profiles falling within the current 90 dB HL criteria and equivalent profiles falling within the new 80 dB HL criteria. RESULTS: The aided SII scores demonstrated that the majority of potential hearing configurations falling within the new proposed 80 dB HL criteria have aided SII values of less than 0.65 (a recommended cut-off point below which there is not sufficient audibility to receive adequate benefit through hearing aids). CONCLUSIONS: This supports the proposed change to the 80 dB HL criterion level and also highlights the additional value of the SII score in supporting candidacy decisions for CI, especially for borderline candidates
- …