245 research outputs found
A low-absorption disk zone at low Galactic latitude in Centaurus
We investigate the properties of two stellar concentrations in a
low-absorption disk zone in Centaurus, located respectively at
, , and , . The present analysis is based mostly on 2MASS photometry, as well as
optical photometry. Based on colour-magnitude diagrams and stellar radial
density profiles, we show that these concentrations are not open star clusters.
Instead, they appear to be field stars seen through a differentially-reddened
window. We estimate that the bulk of the stars in both stellar concentrations
is located at kpc from the Sun, a distance consistent with that of
the Sgr-Car arm in that direction. This low-absorption window allows one to
probe into distant parts of the disk besides the Sgr-Car arm, probably the
tangent part of the Sct-Cru arm, and/or the far side of the Sgr-Car arm in that
direction. The main sequence associated to the Sgr-Car arm is reddened by
\ebv\sim0.5, so that this window through the disk is comparable in reddening
to Baade's window to the bulge. We also investigate the nature of the open
cluster candidate Ru 166. The presently available data do not allow us to
conclude whether Ru 166 is an actual open cluster or field stars seen through a
small-scale low-absorption window
Fermion localization on degenerate and critical branes
In this work we analyze the localization of fermions on degenerate and
critical Bloch branes. This is done directly on physical coordinates, in
constrast to some works that has been using conformal coordinates. We find the
range of coupling constants of the interaction of fermions with the scalar
fields that allow us to have normalizable fermion zero-mode localized on the
brane on both, critical and degenerate Bloch branes. In the case of critical
branes our results agree with those found in [Class. Quantum Grav. \textbf{27}
(2010) 185001]. The results on fermion localization on degenerate Bloch branes
are new. We also propose a coupling of fermions to the scalar fields which
leads to localization of massless fermion on both sides of a double-brane.Comment: 16 pages, 6 figure
Micropropagação de batata 'BRS Ana': produção de material básico com alta sanidade.
bitstream/item/60642/1/CIRCULAR-118.pd
Fermion localization on asymmetric two-field thick branes
In this paper we investigate the localization of fermions on asymmetric thick
branes generated by two scalars and . In order to trap fermions on
the asymmetric branes with kink-like warp factors, the couplings with the
background scalars are introduced, where
is a function of and . We find that the coupling
do not support the localization of 4-dimensional
fermions on the branes. While, for the case
, which is the kink-fermion
coupling corresponding to one-scalar-generated brane scenarios, the zero mode
of left-handed fermions could be trapped on the branes under some conditions.Comment: v2: 11 pages, 4 figures, accepted by CQ
Cold Fermi atomic gases in a pumped optical resonator
We study systems of fully polarized ultracold atomic gases obeying Fermi
statistics. The atomic transition interacts dispersively with a mode of a
standing-wave cavity, which is coherently pumped by a laser. In this setup, the
intensity of the intracavity field is determined by the refractive index of the
atomic medium, and thus by the atomic density distribution. Vice versa, the
density distribution of the atom is determined by the cavity field potential,
whose depth is proportional to the intracavity field amplitude. In this work we
show that this nonlinearity leads to an instability in the intracavity
intensity that differs substantially from dispersive optical bistability, as
this effect is already present in the regime, where the atomic dipole is
proportional to the cavity field. Such instability is driven by the matter
waves fluctuations and exhibits a peculiar dependence on the fluctuations in
the atomic density distribution.Comment: Two column, three figures. Replaced with final versio
New remarks on the linear constraint self-dual boson and Wess-Zumino terms
In this work we prove in a precise way that the soldering formalism can be
applied to the Srivastava chiral boson (SCB), in contradiction with some
results appearing in the literature. We have promoted a canonical
transformation that shows directly that the SCB is composed of two
Floreanini-Jackiw's particles with the same chirality which spectrum is a
vacuum-like one. As another conflictive result we have proved that a
Wess-Zumino term used in the literature consists of the scalar field, once
again denying the assertion that the WZ term adds a new degree of freedom to
the SCB theory in order to modify the physics of the system.Comment: 6 pages, Revtex. Final version to appear in Physical Review
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