35,544 research outputs found
Duality between Topologically Massive and Self-Dual models
We show that, with the help of a general BRST symmetry, different theories in
3 dimensions can be connected through a fundamental topological field theory
related to the classical limit of the Chern-Simons model.Comment: 13 pages, LaTe
First Disk-Resolved Millimeter Observations Of Io's Surface And SO2 Atmosphere
Aims. In spite of considerable progress in the last two decades, Io's atmosphere remains poorly understood. The goal of this work is to improve our understanding of its spatial distribution, temperature and dynamics. Methods. We present millimeter observations of Io's surface and SO2 atmosphere at 1.4 mm obtained with the IRAM Plateau de Bure Interferometer in January-February 2005. With a synthesized beam of 0.5 x 1.5 '', these observations resolve Io's similar to 1.0 '' disk in the longitudinal/local time direction, and sample the leading and trailing hemispheres of Io. Results. The measured continuum total flux and visibilities show that continuum radiation originates from a depth of at least 1 cm in Io's subsurface. On both the leading and trailing sides, emission in the SO2 216.643 GHz line appears spatially narrower than the continuum, and suggests that the atmosphere covers similar to 80% of the surface on the leading side and similar to 60% on the trailing. On the leading side, disk-resolved spectra yield Doppler shift measurements, indicating a beam-integrated limb-to-limb velocity difference of 330 +/-3 100 m/s in the prograde direction. Such a flow allows an improved fit of disk-averaged SO2 spectra, but its origin remains to be understood. Mean gas temperatures are in the range 130-180 K, in agreement with estimates from IR measurements, and with a tendency for higher trailing vs leading side gas temperatures. On the basis of realistic plume models, we find that the contribution of isolated volcanic plumes to the SO2 emission is small.Astronom
Thermodynamic fluctuations in solar photospheric three-dimensional convection simulations and observations
Numerical 3D radiative (M)HD simulations of solar convection are used to
understand the physical properties of the solar photosphere. To validate this
approach, it is important to check that no excessive thermodynamic fluctuations
arise as a consequence of the partially incomplete treatment of radiative
transfer. We investigate the realism of 3D convection simulations carried out
with the Stagger code. We compared the characteristic properties of several
spectral lines in solar disc centre observations with spectra synthesized from
the simulations. We degraded the synthetic spectra to the spatial resolution of
the observations using the continuum intensity distribution. We estimated the
necessary spectral degradation by comparing atlas spectra with averaged
observed spectra. In addition to deriving a set of line parameters directly, we
used the SIR code to invert the spectra. Most of the line parameters from the
observational data are matched well by the degraded simulation spectra. The
inversions predict a macroturbulent velocity below 10 m/s for the simulation at
full spatial resolution, whereas they yield ~< 1000 m/s at a spatial resolution
of 0.3". The temperature fluctuations in the inversion of the degraded
simulation do not exceed those from the observational data (of the order of
100-200 K rms for -2<log tau<-0.5). The comparison of line parameters in
spatially averaged profiles with the averaged values of line parameters in
spatially resolved profiles indicates a significant change of (average) line
properties at a spatial scale between 0.13" and 0.3". Up to a spatial
resolution of 0.3", we find no indications of the presence of excessive
thermodynamic fluctuations in the 3D HD simulation. To definitely confirm that
simulations without spatial degradation contain fully realistic thermodynamic
fluctuations requires observations at even better spatial resolution.Comment: 21 pages, 15 figures + 2 pages Appendix, accepted for publication in
A&A; v2 version: corrected for an error in the calculation of stray-light
estimates, for details see the Corrigendum to A&A, 2013, 557, 109 (DOI:
10.1051/0004-6361/201321596). Corrected text and numbers are in bold font.
Apart from the stray-light estimates, nothing in the rest of the paper was
affected by the erro
Una comparación de algoritmos basados en trayectoria granular para el problema de localización y ruteo con flota heterogénea (LRPH)
IndexaciĂłn: Scopus.We consider the Location-Routing Problem with Heterogeneous Fleet (LRPH) in which the goal is to determine the depots to be opened, the customers to be assigned to each open depot, and the corresponding routes fulfilling the demand of the customers and by considering a heterogeneous fleet. We propose a comparison of granular approaches of Simulated Annealing (GSA), of Variable Neighborhood Search (GVNS) and of a probabilistic Tabu Search (pGTS) for the LRPH. Thus, the proposed approaches consider a subset of the search space in which non-favorable movements are discarded regarding a granularity factor. The proposed algorithms are experimentally compared for the solution of the LRPH, by taking into account the CPU time and the quality of the solutions obtained on the instances adapted from the literature. The computational results show that algorithm GSA is able to obtain high quality solutions within short CPU times, improving the results obtained by the other proposed approaches.https://revistas.unal.edu.co/index.php/dyna/article/view/55533/5896
Mechanism of the anti-tumour effect of glucans and fructosans: a comparison with C. parvum.
The anti-tumour activity induced by glucans (lentinan, yeast cell walls, pseudonigeran, dextran, DEAE-dextran and dextran sulphate) and fructosans (levan and carboxymethyl-levan) was compared with the activity of C. parvum. The following effects on tumour systems in CBA mice were assayed: (a) adjuvant activity on the immune response against tumour-specific transplantation antigens (TSTA) with a methylcholanthrene-induced fibrosarcoma; (b) cytostatic activity of peritoneal macrophages against radiation-induced leukaemia cells; and (c) inhibition of tumour nodule formation in the lungs following i.v. injection of fibrosarcoma cells. All the polysaccharides induced cytostatic macrophages, but the dextrans and levans did so only after i.p. and not i.v. injection. Only lentinan, yeast cell walls and pseudonigeran were active in the lung-nodule inhibition test; and only lentinan and dextran sulphate showed slight adjuvant activity for TSTA. It is concluded that the anti-tumour activity induced by these polysaccharides is predominantly non-specific macrophage-mediated and much weaker than that found with C. parvum
Phase Space Reduction for Star-Products: An Explicit Construction for CP^n
We derive a closed formula for a star-product on complex projective space and
on the domain using a completely elementary
construction: Starting from the standard star-product of Wick type on and performing a quantum analogue of Marsden-Weinstein
reduction, we can give an easy algebraic description of this star-product.
Moreover, going over to a modified star-product on ,
obtained by an equivalence transformation, this description can be even further
simplified, allowing the explicit computation of a closed formula for the
star-product on \CP^n which can easily transferred to the domain
.Comment: LaTeX, 17 page
Errors on the inverse problem solution for a noisy spherical gravitational wave antenna
A single spherical antenna is capable of measuring the direction and
polarization of a gravitational wave. It is possible to solve the inverse
problem using only linear algebra even in the presence of noise. The simplicity
of this solution enables one to explore the error on the solution using
standard techniques. In this paper we derive the error on the direction and
polarization measurements of a gravitational wave. We show that the solid angle
error and the uncertainty on the wave amplitude are direction independent. We
also discuss the possibility of determining the polarization amplitudes with
isotropic sensitivity for any given gravitational wave source.Comment: 13 pages, 4 figures, LaTeX2e, IOP style, submitted to CQ
Synchronizability determined by coupling strengths and topology on Complex Networks
We investigate in depth the synchronization of coupled oscillators on top of
complex networks with different degrees of heterogeneity within the context of
the Kuramoto model. In a previous paper [Phys. Rev. Lett. 98, 034101 (2007)],
we unveiled how for fixed coupling strengths local patterns of synchronization
emerge differently in homogeneous and heterogeneous complex networks. Here, we
provide more evidence on this phenomenon extending the previous work to
networks that interpolate between homogeneous and heterogeneous topologies. We
also present new details on the path towards synchronization for the evolution
of clustering in the synchronized patterns. Finally, we investigate the
synchronization of networks with modular structure and conclude that, in these
cases, local synchronization is first attained at the most internal level of
organization of modules, progressively evolving to the outer levels as the
coupling constant is increased. The present work introduces new parameters that
are proved to be useful for the characterization of synchronization phenomena
in complex networks.Comment: 11 pages, 10 figures and 1 table. APS forma
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