33,955 research outputs found
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
Deformed self-dual magnetic monopoles
We develop a deformation method for attaining new magnetic monopole
analytical solutions consistent with generalized Yang-Mills-Higgs model
introduced recently. The new solutions fulfill the usual radially symmetric
ansatz and the boundary conditions suitable to assure finite energy
configurations. We verify our prescription by studying some particular cases
involving both exactly and partially analytical initial configurations whose
deformation leads to new analytic BPS monopoles. The results show consistency
among the models, the deformation procedure and the profile of the new
solutions.Comment: 7 pages, 3 figure
Mean-field analysis of the majority-vote model broken-ergodicity steady state
We study analytically a variant of the one-dimensional majority-vote model in
which the individual retains its opinion in case there is a tie among the
neighbors' opinions. The individuals are fixed in the sites of a ring of size
and can interact with their nearest neighbors only. The interesting feature
of this model is that it exhibits an infinity of spatially heterogeneous
absorbing configurations for whose statistical properties we
probe analytically using a mean-field framework based on the decomposition of
the -site joint probability distribution into the -contiguous-site joint
distributions, the so-called -site approximation. To describe the
broken-ergodicity steady state of the model we solve analytically the
mean-field dynamic equations for arbitrary time in the cases n=3 and 4. The
asymptotic limit reveals the mapping between the statistical
properties of the random initial configurations and those of the final
absorbing configurations. For the pair approximation () we derive that
mapping using a trick that avoids solving the full dynamics. Most remarkably,
we find that the predictions of the 4-site approximation reduce to those of the
3-site in the case of expectations involving three contiguous sites. In
addition, those expectations fit the Monte Carlo data perfectly and so we
conjecture that they are in fact the exact expectations for the one-dimensional
majority-vote model
Supersymmetric Construction of W-Algebras from Super Toda and Wznw Theories
A systematic construction of super W-algebras in terms of the WZNW model
based on a super Lie algebra is presented. These are shown to be the symmetry
structure of the super Toda models, which can be obtained from the WZNW theory
by Hamiltonian reduction. A classification, according to the conformal spin
defined by an improved energy-momentum tensor, is dicussed in general terms for
all super Lie algebras whose simple roots are fermionic . A detailed discussion
employing the Dirac bracket structure and an explicit construction of
W-algebras for the cases of , , and are given. The and super conformal algebras are discussed
in the pertinent cases.Comment: 24 page
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