1,984 research outputs found
Restrictions over two-dimensional gauge models with Thirring-like interaction
Some years ago, it was shown how fermion self-interacting terms of the
Thirring-type impact the usual structure of massless two-dimensional gauge
theories [1]. In that work only the cases of pure vector and pure chiral gauge
couplings have been considered and the corresponding Thirring term was also
pure vector and pure chiral respectively, such that the vector (or chiral)
Schwinger model should not lose its chirality structure due to the addition of
the quartic interaction term. Here we extend this analysis to a generalized
vector and axial coupling both for the gauge interaction and the quartic
fermionic interactions. The idea is to perform quantization without losing the
original structure of the gauge coupling. In order to do that we make use of an
arbitrariness in the definition of the Thirring-like interaction.Comment: 9 pages, no figure
Discovery of new Milky Way star cluster candidates in the 2MASS point source catalog III. Follow-up observations of cluster candidates in the Galactic Center region
This paper is part of a project to search the inner Milky Way for hidden
massive clusters and to address the question of whether our Galaxy still forms
clusters similar to the progenitors of the present-day globular clusters.
We report high angular resolution deep near-infrared imaging of 21 cluster
candidates selected from the catalogues of Bica et al. (2003) and Dutra et
al.(2003) in a region around the Galactic Center. These catalogues were created
from visual inspection of the 2MASS images. Seven objects appear to be genuine
clusters, and for these objects we present estimates of extinction, distance
and in some cases age and mass.
Our estimated masses range from 1200 to 5500 solar masses. These clusters are
thus significantly smaller than any Galactic globular cluster, and indicate
that the formation of massive young clusters such as Arches and Quintuplet is
not common in the present-day Milky Way.
The remaining 14 objects are either not clusters or cannot be classified
based on our data.Comment: 8 pages, 19 figures, accepted for publication in A&
High Spatial Resolution of the Mid-Infrared Emission of Compton-Thick Seyfert 2 Galaxy Mrk3
Mid-infrared (MIR) spectra observed with Gemini/Michelle were used to study
the nuclear region of the Compton-thick Seyfert 2 (Sy 2) galaxy Mrk 3 at a
spatial resolution of 200 pc. No polycyclic aromatic hydrocarbons (PAHs)
emission bands were detected in the N-band spectrum of Mrk 3. However, intense
[Ar III] 8.99 m, [S IV] 10.5 m and [Ne II] 12.8 m ionic
emission-lines, as well as silicate absorption feature at 9.7m have been
found in the nuclear extraction (200 pc). We also present
subarcsecond-resolution Michelle N-band image of Mrk 3 which resolves its
circumnuclear region. This diffuse MIR emission shows up as a wings towards
East-West direction closely aligned with the S-shaped of the Narrow Line Region
(NLR) observed at optical [O III]5007\AA image with Hubble/FOC. The
nuclear continuum spectrum can be well represented by a theoretical torus
spectral energy distribution (SED), suggesting that the nucleus of Mrk 3 may
host a dusty toroidal structure predicted by the unified model of active
galactic nucleus (AGN). In addition, the hydrogen column density
(N cm) estimated with a torus
model for Mrk 3 is consistent with the value derived from X-ray spectroscopy.
The torus model geometry of Mrk 3 is similar to that of NGC 3281, both
Compton-thick galaxies, confirmed through fitting the 9.7m silicate band
profile. This results might provide further evidence that the silicate-rich
dust can be associated with the AGN torus and may also be responsible for the
absorption observed at X-ray wavelengths in those galaxies.Comment: 11 pages, 6 figure
Multiflavor Soldering
In two dimensions the simple addition of two chiral bosons of opposite
chiralities does not lead to a full massless scalar field. Similarly, in three
dimensions the addition of two Maxwell-Chern-Simons fields of opposite
helicities will not produce a parity invariant Maxwell-Proca theory. An
interference term between the opposite chiralities (helicities) states is
required in order to obtain the expected result. The so called soldering
procedure provides the missing interference Lagrangian in both 2D and 3D cases.
In two dimensions such interference term allows to fuse two chiral fermionic
determinants into a nonchiral one. In a recent work we have generalized this
procedure by allowing the appearance of an extra parameter which takes two
possible values and leads to two different soldered Lagrangians. Here we apply
this generalized soldering in a bosonic theory which has appeared in a partial
bosonization of the 3D gauged Thirring with flavors. The multiplicity of
flavors allow new types of solderings and help us to understand the connection
between different perturbative approaches to bosonization in 3D. In particular,
we obtain an interference term which takes us from a multiflavor
Maxwell-Chern-Simons theory to a pair of self-dual and anti-self-dual theories
when we combine together both fermionic determinants of +1/2 and -1/2 helicity
fermions. An important role is played by a set of pure non-interacting
Chern-Simons fields which amount to a normalization factor in the fermionic
determinants and act like spectators in the original theory but play an active
role in the soldering procedure. Our results suggest that the generalized
soldering could be used to provide dual theories in both 2D and 3D cases.Comment: 14 pages, no figure
Evaluation of entropy and JM-distance criterions as features selection methods using spectral and spatial features derived from LANDSAT images
A study area near Ribeirao Preto in Sao Paulo state was selected, with predominance in sugar cane. Eight features were extracted from the 4 original bands of LANDSAT image, using low-pass and high-pass filtering to obtain spatial features. There were 5 training sites in order to acquire the necessary parameters. Two groups of four channels were selected from 12 channels using JM-distance and entropy criterions. The number of selected channels was defined by physical restrictions of the image analyzer and computacional costs. The evaluation was performed by extracting the confusion matrix for training and tests areas, with a maximum likelihood classifier, and by defining performance indexes based on those matrixes for each group of channels. Results show that in spatial features and supervised classification, the entropy criterion is better in the sense that allows a more accurate and generalized definition of class signature. On the other hand, JM-distance criterion strongly reduces the misclassification within training areas
Vacuumless kinks systems from vacuum ones, an example
Some years ago, Cho and Vilenkin, introduced a model which presents
topological solutions, despite not having degenerate vacua as is usually
expected. Here we present a new model with topological defects, connecting
degenerate vacua but which in a certain limit recovers precisely the one
proposed originally by Cho and Vilenkin. In other words, we found a kind of
parent model for the so called vacuumless model. Then the idea is extended to a
model recently introduced by Bazeia et al. Finally, we trace some comments the
case of the Liouville model.Comment: 11 pages, 4 figure
Two field BPS solutions for generalized Lorentz breaking models
In this work we present nonlinear models in two-dimensional space-time of two
interacting scalar fields in the Lorentz and CPT violating scenarios. We
discuss the soliton solutions for these models as well as the question of
stability for them. This is done by generalizing a model recently published by
Barreto and collaborators and also by getting new solutions for the model
introduced by them.Comment: 12 pages, 2 figure
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