Higher-Order Differential Operators on a Lie Group and Quantization

This talk is devoted mainly to the concept of higher-order polarization on a group, which is introduced in the framework of a Group Approach to Quantization, as a powerful tool to guarantee the irreducibility of quantizations and/or representations of Lie groups in those anomalous cases where the Kostant-Kirilov co-adjoint method or the Borel-Weyl-Bott representation algorithm do not succeed.Comment: 9 pages, latex, no figures, uses IJMPB.sty (included). New version partially rewritten (title changed!), presented to the II Int. Workshop on Class. and Quant. Integrable Systems, Dubna (Rusia) 1996, and published in Int. J. Mod. Phys.

Hermite Coherent States for Quadratic Refractive Index Optical Media

Producción CientíficaLadder and shift operators are determined for the set of Hermite–Gaussian modes associated with an optical medium with quadratic refractive index profile. These operators allow to establish irreducible representations of the su(1, 1) and su(2) algebras. Glauber coherent states, as well as su(1, 1) and su(2) generalized coherent states, were constructed as solutions of differential equations admitting separation of variables. The dynamics of these coherent states along the optical axis is also evaluated.MINECO grant MTM2014-57129-C2-1-P and Junta de Castilla y Leon grant VA057U16

Hidden IR structures in NGC 40: signpost of an ancient born-again event

We present the analysis of infrared (IR) observations of the planetary nebula NGC 40 together with spectral analysis of its [WC]-type central star HD 826. Spitzer IRS observations were used to produce spectral maps centred at polycyclic aromatic hydrocarbons (PAH) bands and ionic transitions to compare their spatial distribution. The ionic lines show a clumpy distribution of material around the main cavity of NGC 40, with the emission from [Ar II] being the most extended, whilst the PAHs show a rather smooth spatial distribution. Analysis of ratio maps shows the presence of a toroidal structure mainly seen in PAH emission, but also detected in a Herschel PACS 70 mic image. We argue that the toroidal structure absorbs the UV flux from HD 826, preventing the nebula to exhibit lines of high-excitation levels as suggested by previous authors. We discuss the origin of this structure and the results from the spectral analysis of HD 826 under the scenario of a late thermal pulse.Comment: 10 pages, 10 figures; Accepted to MNRA

WISE morphological study of Wolf-Rayet nebulae

We present a morphological study of nebulae around Wolf-Rayet (WR) stars using archival narrow-band optical and Wide-field Infrared Survey Explorer (WISE) infrared images. The comparison among WISE images in different bands and optical images proves to be a very efficient procedure to identify the nebular emission from WR nebulae, and to disentangle it from that of the ISM material along the line of sight. In particular, WR nebulae are clearly detected in the WISE W4 band at 22 $\mu$m. Analysis of available mid-IR Spitzer spectra shows that the emission in this band is dominated by thermal emission from dust spatially coincident with the thin nebular shell or most likely with the leading edge of the nebula. The WR nebulae in our sample present different morphologies that we classified into well defined WR bubbles (bubble ${\cal B}$-type nebulae), clumpy and/or disrupted shells (clumpy/disrupted ${\cal C}$-type nebulae), and material mixed with the diffuse medium (mixed ${\cal M}$-type nebulae). The variety of morphologies presented by WR nebulae shows a loose correlation with the central star spectral type, implying that the nebular and stellar evolutions are not simple and may proceed according to different sequences and time-lapses. We report the discovery of an obscured shell around WR35 only detected in the infrared.Comment: 11 pages, 6 figures, plus 23 appendix figures; to appear in Astronomy and Astrophysic

Rings and arcs around evolved stars. II. The Carbon Star AFGL 3068 and the Planetary Nebulae NGC 6543, NGC 7009 and NGC 7027

We present a detailed comparative study of the arcs and fragmented ring-like features in the haloes of the planetary nebulae (PNe) NGC 6543, NGC 7009, and NGC 7027 and the spiral pattern around the carbon star AFGL 3068 using high-quality multi-epoch HST images. This comparison allows us to investigate the connection and possible evolution between the regular patterns surrounding AGB stars and the irregular concentric patterns around PNe. The radial proper motion of these features, ~15 km/s, are found to be consistent with the AGB wind and their linear sizes and inter-lapse times (500-1900 yr) also agree with those found around AGB stars, suggesting a common origin. We find evidence using radiative-hydrodynamic simulations that regular patterns produced at the end of the AGB phase become highly distorted by their interactions with the expanding PN and the anisotropic illumination and ionization patterns caused by shadow instabilities. These processes will disrupt the regular (mostly spiral) patterns around AGB stars, plausibly becoming the arcs and fragmented rings observed in the haloes of PNe.Comment: 13 pages, 9 figures, accepted for publication in MNRA

La vegetación de zonas erosionadas en la depresión media del Ebro y en el Prepirineo: influencia de factores climáticos, topográficos y geomorfológicos en la composición florística de las comunidades vegetales

[Resumen] Se han analizado 732 inventarios de vegetación en zonas sometidas a procesos erosivo-sedimentarios de un área del NE de la Península Ibérica, muy diversa climática y litológicamente (yesos, arcillas, margas y flysch). El objetivo del estudio es determinar cómo afectan dichos procesos a la composición florística de las comunidades vegetales de los diferentes sustratos. El tipo de sustrato ejerció una gran influencia sobre los procesos estudiados, siendo la cobertura de las fanerógamas el parámetro que mejor se asoció con el grado de erosión. En las zonas más secas con bajas tasas de erosión (yesos), las características topográficas controlaron la distribución de las comunidades vegetales, mientras que en las zonas más húmedas, sometidas a procesos erosivos más dinámicos (margas), la composición florística fué más homogénea y menos dependiente de la topografía y del grado de erosión. Los procesos erosivosedimentarios explicaron mejor la composición florística cuanto menor era la escala espacial de análisis.[Abstract] We have analysed 732 releves of plant communities taken from eroded lands in the NE Iberian Peninsula. This diverse area has very different climates and substrata: gypsum, clays, marls and flysch. The aim of the study was to explore how erosion and sedimentation processes affect floristic composition of plant communities in such different substrata. Substratum had a high influence on the studied processes, the cover of fanerogams being the best correlated parameter with erosion grade. In the driest lands, with low erosion rates (gypsum), plant community distribution was mostly affected by topography, but in the wettest areas, with strong and more dynamic erosional processes (marls), the floristic composition was more homogeneus and depended less on the topography and the erosion grade. The erosionsedimentation processes better explained the floristic composition when the scale of analysis was reduced

Nature of the f_0(600) from its N_c dependence at two loops in unitarized Chiral Perturbation Theory

By using unitarized two-loop Chiral Perturbation Theory partial waves to describe pion-pion scattering we find that the dominant component of the lightest scalar meson does not follow the q-qbar dependence on the number of colors that, in contrast, is obeyed by the lightest vectors. The method suggests that a subdominant q-qbar component of the f_0(600) possibly originates around 1 GeV.Comment: 4 pages, 1 Figure. To appear in Phys. Rev. Let

Self-Averaging in the Three Dimensional Site Diluted Heisenberg Model at the critical point

We study the self-averaging properties of the three dimensional site diluted Heisenberg model. The Harris criterion \cite{critharris} states that disorder is irrelevant since the specific heat critical exponent of the pure model is negative. According with some analytical approaches \cite{harris}, this implies that the susceptibility should be self-averaging at the critical temperature ($R_\chi=0$). We have checked this theoretical prediction for a large range of dilution (including strong dilution) at critically and we have found that the introduction of scaling corrections is crucial in order to obtain self-averageness in this model. Finally we have computed critical exponents and cumulants which compare very well with those of the pure model supporting the Universality predicted by the Harris criterion.Comment: 11 pages, 11 figures, 14 tables. New analysis (scaling corrections in the g2=0 scenario) and new numerical simulations. Title and conclusions chang