On the Stability of Randall-Sundrum Braneworlds with Conformal Bulk Fields

In the Randall-Sundrum scenario we consider exact 5-dimensional solutions with localized gravity which are associated with a well defined class of conformal bulk fields. We analyze their behaviour under radion field perturbations. We show that if the Randall-Sundrum exponential warp is the localizing metric function and the equation of state of the conformal fields is not changed by the radion perturbation then the 5-dimensional solutions are unstable. We present new stable solutions which describe on the brane the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytopic matter.Comment: 10 pages, latex, no figures. Contribution to the special issue of Vestnik of Tomsk State Pedagogical University in the field QFT/Cosmology/Gravity/Strings, edited by Sergei D. Odintso

Braneworlds, Conformal Fields and Dark Energy

In the Randall-Sundrum scenario we analize the dynamics of a spherically symmetric 3-brane when matter fields propagate in the bulk. For a well defined class of conformal fields of weight -4 we determine a new set of exact 5-dimensional solutions which localize gravity in the vicinity of the brane and are stable under radion field perturbations. Geometries which describe the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy are shown to belong to this set.Comment: 7 pages, latex, no figures. Talk given at the Fifth International Workshop on New Worlds in Astroparticle Physics, University of Algarve, Faro, 8-10 January 2005. To be published in the workshop proceeding

Inhomogeneous Dark Radiation Dynamics on a de Sitter Brane

Assuming spherical symmetry we analyse the dynamics of an inhomogeneous dark radiation vaccum on a Randall and Sundrum 3-brane world. Under certain natural conditions we show that the effective Einstein equations on the brane form a closed system. On a de Sitter brane and for negative dark energy density we determine exact dynamical and inhomogeneous solutions which depend on the brane cosmological constant, on the dark radiation tidal charge and on its initial configuration. We also identify the conditions leading to the formation of a singularity or of regular bounces inside the dark radiation vaccum.Comment: 6 pages, LaTeX, 1 EPS figure. Talk given at the Workshop The Cosmology of Extra Dimensions and Varying Fundamental Constants of the Conference JENAM 2002, The Unsolved Universe: Challenges for the Future, 2-7 September 2002, Porto, Portuga

Implications of anomalous gauge boson interactions to the fermion electromagnetic moments

We calculate the electromagnetic fermion form-factors induced by the anomalous gauge boson interactions contained in the operators ODW and ODB. Other results regarding anomalous triple gauge boson interactions are briefly overviewed. We study the interplay between vertex corrections and gauge boson self-energies extended to the longitudinal degrees of freedom. The physical couplings to an external electromagnetic field are then derived.Comment: 14 pages, LATeX, to appear in Modern Physics Letters A, some literary changes, a few notation correction

Dark Radiation and Localization of Gravity on the Brane

We discuss the dynamics of a spherically symmetric dark radiation vaccum in the Randall-Sundrum brane world scenario. Under certain natural assumptions we show that the Einstein equations on the brane form a closed system. For a de Sitter brane we determine exact dynamical and inhomogeneous solutions which depend on the brane cosmological constant, on the dark radiation tidal charge and on its initial configuration. We define the conditions leading to singular or globally regular solutions. We also analyse the localization of gravity near the brane and show that a phase transition to a regime where gravity propagates away from the brane may occur at short distances during the collapse of positive dark energy density.Comment: 7 pages, latex with 2 eps figures. Talk given by Rui Neves, Fourth International Workshop on New Worlds in Astroparticle Physics, Algarve University, Faro, 5-7 September, 2002. To be published in the corresponding proceedings, World Scientifi

Polchinski ERG equation and 2D scalar field theory

We investigate a $Z_2$-symmetric scalar field theory in two dimensions using the Polchinski exact renormalization group equation expanded to second order in the derivative expansion. We find preliminary evidence that the Polchinski equation is able to describe the non-perturbative infinite set of fixed points in the theory space, corresponding to the minimal unitary series of 2D conformal field theories. We compute the anomalous scaling dimension $\eta$ and the correlation length critical exponent $\nu$ showing that an accurate fit to conformal field theory selects particular regulating functions.Comment: 9 pages, latex with 2 figures, uses sprocl.sty. To be published in the Proceedings of the Workshop on the Exact Renormalization Group held in Faro, Portugal, in September 10-12 1998, World Scientifi

Polchinski ERG Equation in O(N) Scalar Field Theory

We investigate the Polchinski ERG equation for d-dimensional O(N) scalar field theory. In the context of the non-perturbative derivative expansion we find families of regular solutions and establish their relation with the physical fixed points of the theory. Special emphasis is given to the large N limit for which many properties can be studied analytically.Comment: 7 pages, 4 figures, uses latex sprocl style. Two references added. To be published in the proceedings of the Second Conference on the Exact Renormalization Group (Rome, September 18-22, 2000), World Scientifi

Da lógica do mosaico à lógica do projecto: as actividades de enriquecimento curricular na escola do 1º CEB

Resumo indisponível

Braneworlds, Conformal Fields and the Gravitons

We investigate the dynamics of Randall-Sundrum AdS5 braneworlds with 5-dimensional conformal matter fields. In the scenario with a compact fifth dimension the class of conformal fields with weight -4 is associated with exact 5-dimensional warped geometries which are stable under radion field perturbations and describe on the brane the dynamics of inhomogeneous dust, generalized dark radiation and homogeneous polytropic dark energy. We analyse the graviton mode flutuations around this class of background solutions and determine their mass eigenvalues and wavefunctions from a Sturm-Liouville problem. We show that the localization of gravity is not sharp enough for large mass hierarchies to be generated. We also discuss the physical bounds imposed by experiments in particle physics, in astrophysics and in precise measurements of the low energy gravitational interaction.Comment: LaTeX, 9 pages, 2 figures. Based on talk given in the Second International Conference on Quantum Theories and the Renormalization Group in Gravity and Cosmology, CSIC and University of Barcelona, Barcelona, Spain, 11-15 July 2006. Submitted to be published in the Conference Proceedings, J. Phys. A: Math. Ge

Actividades de enriquecimento curricular no 1º Ciclo do Ensino Básico: um olhar sobre a avaliação

Este texto centrado sobre as Actividades de Enriquecimento Curricular (AEC) na escola do 1º Ciclo do Ensino Básico (CEB) pretende reflectir sobre os desafios da avaliação nesta componente educativa em generalização neste nível de ensino. Para isso, são previamente enquadradas questões conceptuais das AEC no actual contexto da realidade das escolas e equacionadas a natureza, o papel e características da sua avaliação contextualizada. Tendo como ponto de partida o enquadramento legislativo das AEC, são utilizados dados identificados em vários relatórios nacionais e internacionais, bem como relatos de realidades locais que ilustram as suas práticas educativas. Decorrente destas reflexões, são enunciados princípios e propostas de equacionar e operacionalizar a avaliação nas e das AEC na escola do 1º CEB.The present text, focussing on Curricular Enrichment Activities (CEA) in primary education, aims at reflecting about the assessment challenges of this educational component that is under generalisation in this level of teaching. For that purpose we first discuss the conceptual issues of CEA within the present context of the reality of schools and equate the nature, role and characteristics of their contextualised assessment. Taking the legislative background of CEA as a starting point we will use data identified in various national and international reports as well as local reality testimonies that illustrate CEA educational practices. From these reflections we offer principles and proposals with a view to equating and performing assessment in and of CEA in primary education schools.Cet article a pour but de réfléchir sur l’évaluation des Activités Extra-Curriculaires (AEC) dans le cadre de l’enseignement primaire. On analyse, du point de vue théorique, le rôle joué par les AEC dans ce niveau d’enseignement, ainsi que la nature et les caractéristiques spécifiques de son évaluation dans ce contexte. Les données analysées sont issues de rapports nationaux et internationaux (ayant pour base les lois qui soutiennent les AEC) et des rapports locaux traitant plus directement de pratiques éducatives courantes. L’analyse débouche sur un ensemble de recommandations concernant les pratiques et l’évaluation attachées aux AEC dans les écoles primaires portugaises