Covariant canonical formalism for four-dimensional BF theory

The covariant canonical formalism for four-dimensional BF theory is performed. The aim of the paper is to understand in the context of the covariant canonical formalism both the reducibility that some first class constraints have in Dirac's canonical analysis and also the role that topological terms play. The analysis includes also the cases when both a cosmological constant and the second Chern character are added to the pure BF action. In the case of the BF theory supplemented with the second Chern character, the presymplectic 3-form is different to the one of the BF theory in spite of the fact both theories have the same equations of motion while on the space of solutions they both agree to each other. Moreover, the analysis of the degenerate directions shows some differences between diffeomorphisms and internal gauge symmetries.Comment: Latex file, 22 pages (due to the macro). Revised version to match published versio

Berry Phase of a Resonant State

We derive closed analytical expressions for the complex Berry phase of an open quantum system in a state which is a superposition of resonant states and evolves irreversibly due to the spontaneous decay of the metastable states. The codimension of an accidental degeneracy of resonances and the geometry of the energy hypersurfaces close to a crossing of resonances differ significantly from those of bound states. We discuss some of the consequences of these differences for the geometric phase factors, such as: Instead of a diabolical point singularity there is a continuous closed line of singularities formally equivalent to a continuous distribution of `magnetic' charge on a diabolical circle; different classes of topologically inequivalent non-trivial closed paths in parameter space, the topological invariant associated to the sum of the geometric phases, dilations of the wave function due to the imaginary part of the Berry phase and others.Comment: 28 pages Latex, three uuencoded postcript figure

Random Networks with given Rich-club Coefficient

In complex networks it is common to model a network or generate a surrogate network based on the conservation of the network's degree distribution. We provide an alternative network model based on the conservation of connection density within a set of nodes. This density is measure by the rich-club coefficient. We present a method to generate surrogates networks with a given rich-club coefficient. We show that by choosing a suitable local linking term, the generated random networks can reproduce the degree distribution and the mixing pattern of real networks. The method is easy to implement and produces good models of real networks.Comment: revised version, new figure

Contribution of the Residual Body in the Spatial Organization of Toxoplasma gondii Tachyzoites within the Parasitophorous Vacuole

Toxoplasma gondii proliferates and organizes within a parasitophorous vacuole in rosettes around a residual body and is surrounded by a membranous nanotubular network whose function remains unclear. Here, we characterized structure and function of the residual body in intracellular tachyzoites of the RH strain. Our data showed the residual body as a body limited by a membrane formed during proliferation of tachyzoites probably through the secretion of components and a pinching event of the membrane at the posterior end. It contributes in the intravacuolar parasite organization by the membrane connection between the tachyzoites posterior end and the residual body membrane to give place to the rosette conformation. Radial distribution of parasites in rosettes favors an efficient exteriorization. Absence of the network and presence of atypical residual bodies in a ΔGRA2-HXGPRT knock-out mutant affected the intravacuolar organization of tachyzoites and their exteriorization

Alternative symplectic structures for SO(3,1) and SO(4) four-dimensional BF theories

The most general action, quadratic in the B fields as well as in the curvature F, having SO(3,1) or SO(4) as the internal gauge group for a four-dimensional BF theory is presented and its symplectic geometry is displayed. It is shown that the space of solutions to the equations of motion for the BF theory can be endowed with symplectic structures alternative to the usual one. The analysis also includes topological terms and cosmological constant. The implications of this fact for gravity are briefly discussed.Comment: 13 pages, LaTeX file, no figure

Accidental Degeneracy and Berry Phase of Resonant States

We study the complex geometric phase acquired by the resonant states of an open quantum system which evolves irreversibly in a slowly time dependent environment. In analogy with the case of bound states, the Berry phase factors of resonant states are holonomy group elements of a complex line bundle with structure group C*. In sharp contrast with bound states, accidental degeneracies of resonances produce a continuous closed line of singularities formally equivalent to a continuous distribution of "magnetic" charge on a "diabolical" circle, in consequence, we find different classes of topologically inequivalent non-trivial closed paths in parameter space.Comment: 23 pages, 2 Postscript figures, LaTex, to be published in: Group 21: Symposium on Semigroups and Quantum Irreversibility (Proc. of the XXI Int. Colloquium on Group Theoretical Methods in Physics

Optical scalar beam propagation in nontrivial spacetime backgrounds

We study the propagation of structured optical scalar beams in a spacetime background parameterized by a second-rank symmetric tensor. An analytic expression for the Green's function in a cylindrical coordinate system is obtained for particular choices of such a tensor. This facilitates the numerical exploration of the propagation of apertured Gaussian beams in this nontrivial background. Unusual focusing properties are found along with a decrease in the Gouy phase compared to that in standard vacuum. In the case of apertured Bessel beams, the medium allows to overcome finite aperture effects so that the corresponding diffraction length is increased; besides, the central spot of a zero order Bessel concentrates an increased fraction of the energy of the beam. Multiple scenarios beyond an electromagnetic field in the presence of an anisotropic medium could support the results reported here. They include a bosonic field in a weak gravitational field or a nontrivial spacetime background arising from Lorentz symmetry breaking. In particular, our results could illustrate how optically transparent multiferroic materials offer unprecedented opportunities to tailor structured beam propagation, as well as to simulate nontrivial spacetime backgrounds.Comment: 15 pages, 24 figure

Weight bias internalization among adolescents in Spain: psychological correlates across gender diversity and weight status

Weight bias internalization refers to the negative weight-related attributions applied to oneself, but it does not just occur in the highest weight statuses, but rather exists across the entire weight spectrum. There is a negative impact associated to increase psychological problems in adults, however, it has been less studied among the adolescent Spanish population. In this study, we assess the relationship between the internalization of weight bias, social attitudes towards appearance, body appreciation and self-esteem, and potential differences regarding gender and weight status. A community sample of 1258 Spanish adolescents between 12 and 18 years old (46.3% male gender; Mage = 15.58; SD = 1.59; 49.5% female gender; Mage = 15.59; SD = 1.67; and 4.1% non-binary gender; Mage = 14.86; SD = 2.86) participated in the study. The Modified Weight Bias Internalization Scale (WBIS-M), the Rosenberg Self-Esteem Scale (RSES), and the Sociocultural Attitudes Towards Appearance Questionnaire (SATAQ-4) were used. ANOVA’s test and bivariate correlations were performed. The results suggest that females (t = -.55; p ≤ .001) and non-binary adolescents (t = .64; p ≤ .01) have higher levels of WBI-M compared to males. Regarding weight status, the group with obesity (t = 1.39; p ≤ .001) and the group with overweight (t = -.81; p ≤ .001) have higher levels of WBI-M compared to the normal weight group. Significant correlations between WBI-M and the assessed psychological variables were found in the total sample, and across all-gender and weight categories, except for the underweight group. These results are a first approximation to the internalization of weight bias in a Spanish adolescent sample and highlight the need to introduce this concept in prevention and psychological interventions in school context.La internalización de los prejuicios de peso entre los y las adolescentes en España: correlatos psicológicos en función del género y el estatus de peso. La internalización de los prejuicios de peso hace referencia a las atribuciones negativas relacionadas con el peso aplicadas a uno mismo/a, lo cual no ocurre únicamente en las personas con un estatus de peso elevado, sino en todo el rango de pesos. En adultos, existe evidencia de su impacto negativo asociados a incrementar problemas psicológicos; aunque se ha estudiado en menor medida en la población adolescente. El objetivo de este estudio fue examinar la relación entre la internalización de prejuicios de peso, las actitudes socioculturales hacia la apariencia, la apreciación corporal y el nivel de autoestima, y analizar las posibles diferencias en función del género y del estatus de peso. Participaron 1.258 adolescentes españoles de una muestra comunitaria entre 12 y 18 años (46.3% género masculino; Medad = 15.58; DT = 1.59; 49,5% género femenino; Medad = 15.59; DT = 1.67; y 4.1% género no binario; Medad = 14.86; DT = 2.86). Se utilizaron la escala de internalización de prejuicios de peso modificado (WBIS-M), la escala de autoestima de Rosenberg (RSES) y el cuestionario de actitudes socioculturales hacia la apariencia (SATAQ-4). Se realizó la prueba ANOVA y correlaciones bivariadas. Los resultados sugieren que el grupo identificado con el género femenino (t = -.55; p ≤ .001) y con el no binario (t = .64; p ≤ .01) muestran niveles más altos de internalización del sesgo de peso en comparación con el género masculino. En cuanto al estado ponderal, el grupo con obesidad (t = 1.39; p ≤ .001) y el grupo con sobrepeso (t = -.81; p ≤ .001) presentan niveles más altos de internalización de prejuicios de peso en comparación con el grupo con normopeso. Se encontraron correlaciones significativas entre las puntuaciones del WBIS-M y las variables psicológicas evaluadas en la muestra total y en todas las categorías de género y peso, con la excepción del grupo de bajo peso. Estos resultados son una primera aproximación a la interiorización del estigma del peso en una muestra adolescente española y resalta la necesidad de incluir esta dimensión en la prevención de las alteraciones de la imagen corporal y los problemas psicológicos relacionados con la autoestima entre adolescentes en el contexto escolar

S_3-flavour symmetry as realized in lepton flavour violating processes

A variety of lepton flavour violating effects related to the recent discovery of neutrino oscillations and mixings is here systematically discussed in terms of an S_3-flavour permutational symmetry. After a brief review of some relevant results on lepton masses and mixings, that had been derived in the framework of a Minimal S_3-Invariant Extension of the Standard Model, we derive explicit analytical expressions for the matrices of the Yukawa couplings and compute the branching ratios of some selected flavour changing neutral current (FCNC) processes, as well as, the contribution of the exchange of neutral flavour changing scalars to the anomaly of the muon's magnetic moment as functions of the masses of the charged leptons and the neutral Higgs bosons. We find that the S_3 x Z_2 flavour symmetry and the strong mass hierarchy of the charged leptons strongly suppress the FCNC processes in the leptonic sector well below the present experimental upper bounds by many orders of magnitude. The contribution of FCNC to the anomaly of the muon's magnetic moment is small but non-negligible.Comment: 23 pages, one figure. To appear in J. Phys A: Mathematical and Theoretical (SPE QTS5