12,122 research outputs found
Lorentz-violating Yang-Mills theory: discussing the Chern-Simons-like term generation
We analyze the Chern-Simons-like term generation in the CPT-odd
Lorentz-violating Yang-Mills theory interacting with fermions. Moreover, we
study the anomalies of this model as well as its quantum stability. The whole
analysis is performed within the algebraic renormalization theory, which is
independent of the renormalization scheme. In addition, all results are valid
to all orders in perturbation theory. We find that the Chern-Simons-like term
is not generated by radiative corrections, just like its Abelian version.
Additionally, the model is also free of gauge anomalies and quantum stable.Comment: 16 pages. No figures. Final version to appear in the Eur.Phys.J.
Quasar Microlensing: when compact masses mimic smooth matter
The magnification induced by gravitational microlensing is sensitive to the
size of a source relative to the Einstein radius, the natural microlensing
scale length. This paper investigates the effect of source size in the case
where the microlensing masses are distributed with a bimodal mass function,
with solar mass stars representing the normal stellar masses, and smaller
masses (down to M) representing a dark matter
component. It is found that there exists a critical regime where the dark
matter is initially seen as individual compact masses, but with an increasing
source size the compact dark matter acts as a smooth mass component. This study
reveals that interpretation of microlensing light curves, especially claims of
small mass dark matter lenses embedded in an overall stellar population, must
consider the important influence of the size of the source.Comment: 6 pages, to appear in ApJ. As ever, quality of figures reduce
Topological superconductivity in lead nanowires
Superconductors with an odd number of bands crossing the Fermi energy have
topologically protected Andreev states at interfaces, including Majorana states
in one dimensional geometries. Superconductivity, a low number of 1D channels,
large spin orbit coupling, and a sizeable Zeeman energy, are present in lead
nanowires produced by nanoindentation of a Pb tip on a Pb substrate, in
magnetic fields higher than the Pb bulk critical field. A number of such
devices have been analyzed. In some of them, the dependence of the critical
current on magnetic field, and the Multiple Andreev Reflections observed at
finite voltages, are compatible with the existence of topological
superconductivity
Seeing Star Formation Regions with Gravitational Microlensing
We qualitatively study the effects of gravitational microlensing on our view
of unresolved extragalactic star formation regions. Using a general
gravitational microlensing configuration, we perform a number of simulations
that reveal that specific imprints of the star forming region are imprinted,
both photometrically and spectroscopically, upon observations. Such
observations have the potential to reveal the nature and size of these star
forming regions, through the degree of variability observed in a monitoring
campaign, and hence resolve the star formation regions in distant galaxies
which are too small to be probed via more standard techniques.Comment: 7 pages, 8 figures, ApJ accepte
Modeling Hybrid Stars with an SU(3) non-linear sigma model
We study the behavior of hybrid stars using an extended hadronic and quark
SU(3) non-linear sigma model. The degrees of freedom change naturally, in this
model, from hadrons to quarks as the density/temperature increases. At zero
temperature, we reproduce massive neutron stars containing a core of hybrid
matter of 2 km for the non-rotating case and 1.18 km and 0.87 km, in the
equatorial and polar directions respectively, for stars rotating at the Kepler
frequency (physical cases lie in between). The cooling of such stars is also
analyzed.Comment: Revised version, references and figures added. Accepted for
publication in Physical Review
Spatio-temporal patterns of seasonal rainfall in Spain (1912-2000) using cluster and principal component analysis: comparison
In this work, cluster and principal component analysis are used to divide Spain in a limited number of climatically homogeneous zones, based on seasonal rainfall for 32 Spanish localities for the period 1912â2000. Using the hierarchical technique of clustering Ward's method, three clusters have been obtained in winter and spring, and four clusters have been obtained in summer and autumn. Results are similar to those obtained by applying principal component analysis. Centroid series of each cluster and principal component series of each EOF have been compared to analyze the temporal patterns. The comparison of both methods indicates that cluster analysis is suitable to establish spatio-temporal patterns of seasonal rainfall distribution in Spain.<br><br> <b>Key words.</b> Meteorology and atmospheric dynamics (climatology; precipitation; general or miscellaneous
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