4,976 research outputs found
Mass generation for non-Abelian antisymmetric tensor fields in a three-dimensional space-time
Starting from a recently proposed Abelian topological model in (2+1)
dimensions, which involve the Kalb-Ramond two form field, we study a
non-Abelian generalization of the model. An obstruction for generalization is
detected. However we show that the goal is achieved if we introduce a vectorial
auxiliary field. Consequently, a model is proposed, exhibiting a non-Abelian
topological mass generation mechanism in D=3, that provides mass for the
Kalb-Ramond field. The covariant quantization of this model requires ghosts for
ghosts. Therefore in order to quantize the theory we construct a complete set
of BRST and anti-BRST equations using the horizontality condition.Comment: 8 pages. To appear in Physical Review
Lithium and magnetic fields in giants. HD 232862 : a magnetic and lithium-rich giant star
We report the detection of an unusually high lithium content in HD 232862, a
field giant classified as a G8II star, and hosting a magnetic field. With the
spectropolarimeters ESPaDOnS at CFHT and NARVAL at TBL, we have collected high
resolution and high signal-to-noise spectra of three giants : HD 232862, KU Peg
and HD 21018. From spectral synthesis we have inferred stellar parameters and
measured lithium abundances that we have compared to predictions from
evolutionary models. We have also analysed Stokes V signatures, looking for a
magnetic field on these giants. HD 232862, presents a very high abundance of
lithium (ALi = 2.45 +/- 0.25 dex), far in excess of the theoretically value
expected at this spectral type and for this luminosity class (i.e, G8II). The
evolutionary stage of HD 232862 has been precised, and it suggests a mass in
the lower part of the [1.0 Msun ; 3.5 Msun ] mass interval, likely 1.5 to 2.0
solar mass, at the bottom of the Red Giant Branch. Besides, a time variable
Stokes V signature has been detected in the data of HD 232862 and KU Peg,
pointing to the presence of a magnetic field at the surface of these two
rapidly rotating active stars.Comment: 11 pages, 9 figures ; accepted by Astronomy and Astrophysic
Functional Bosonization of Non-Relativistic Fermions in Dimensions
We analyze the universality of the bosonization rules in non-relativistic
fermionic systems in . We show that, in the case of linear fermionic
dispersion relations, a general fermionic theory can be mapped into a gauge
theory in such a way that the fermionic density maps into a magnetic flux and
the fermionic current maps into a transverse electric field. These are
universal rules in the sense that they remain valid whatever the interaction
considered. We also show that these rules are universal in the case of
non-linear dispersion relations provided we consider only density-density
interactions. We apply the functional bosonization formalism to a
non-relativistic and non-local massive Thirring-like model and evaluate the
spectrum of collective excitations in several limits. In the large mass limit,
we are able to exactly calculate this spectrum for arbitrary density-density
and current-current interactions. We also analyze the massless case and show
that it has no collective excitations for any density-density potential in the
Gaussian approximation. Moreover, the presence of current interactions may
induce a gapless mode with a linear dispersion relation.Comment: 26 Pages, LaTeX, Final version to appear in International Journal of
Modern Physics
Observational constraints for Lithium depletion before the RGB
Precise Li abundances are determined for 54 giant stars mostly evolving
across the Hertzsprung gap. We combine these data with rotational velocity and
with information related to the deepening of the convective zone of the stars
to analyse their link to Li dilution in the referred spectral region. A sudden
decline in Li abundance paralleling the one already established in rotation is
quite clear. Following similar results for other stellar luminosity classes and
spectral regions, there is no linear relation between Li abundance and
rotation, in spite of the fact that most of the fast rotators present high Li
content. The effects of convection in driving the Li dilution is also quite
clear. Stars with high Li content are mostly those with an undeveloped
convective zone, whereas stars with a developed convective zone present clear
sign of Li dilution.Comment: 5 pages, 4 figures. accepted for publicatio
The Visual Orbit and Evolutionary State of 12 Bootes
We report on the determination of the visual orbit of the double-lined
spectroscopic binary system 12 Bootes with data obtained by the Palomar Testbed
Interferometer in 1998 and 1999. 12 Boo is a nearly equal-mass double-lined
binary system whose spectroscopic orbit is well known. We have estimated the
visual orbit of 12 Boo from our interferometric visibility data fit both
separately and in conjunction with archival radial velocity data. Our 12 Boo
orbit is in good agreement with the spectroscopic results, and the physical
parameters implied by a combined fit to our visibility data and radial velocity
data result in precise component masses. In particular, the orbital parallax of
the system is determined to be 27.09 0.41 mas, and masses of the two
components are determined to be 1.435 0.023 M_{\sun} and 1.409
0.020 M_{\sun}, respectively.
Somewhat remarkably, even though the two components are nearly equal mass,
the system exhibits a significant brightness difference between the components
in the near infrared and visible. We attribute this brightness difference to
evolutionary differences between the two components in their transition between
main sequence and giant evolutionary phases, and based on theoretical
isochrones we can estimate a system age. Further, because the atmospheres of
the two components are becoming more convective, we project the system
components are currently at or near synchronous rotation, and the system orbit
is in the process of circularizing.Comment: 32 pages, 7 figures + 2 data tables, ApJ in pres
Eficiência da irrigação e produtividade de feijão-caupi no cerrado Roraimense.
Suplemento. Edição dos Anais do 53 Congresso Brasileiro de Olericultura, jul. 2014
On the relation between local and geometric Lagrangians for higher spins
Equations of motion for free higher-spin gauge fields of any symmetry can be
formulated in terms of linearised curvatures. On the other hand, gauge
invariance alone does not fix the form of the corresponding actions which, in
addition, either contain higher derivatives or involve inverse powers of the
d'Alembertian operator, thus introducing possible subtleties in degrees of
freedom count. We suggest a path to avoid ambiguities, starting from local,
unconstrained Lagrangians previously proposed, and integrating out the
auxiliary fields from the functional integral, thus generating a unique
non-local theory expressed in terms of curvatures.Comment: 14 pages. Contribution to the proceedings of the 1st Mediterranean
Conference on Classical and Quantum Gravity, Kolymbary (Crete, Greece)
September 14-18 200
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