3,403 research outputs found

    Boson-boson effective nonrelativistic potential for higher-derivative electromagnetic theories in D dimensions

    Full text link
    The problem of computing the effective nonrelativistic potential UDU_{D} for the interaction of charged scalar bosons within the context of D-dimensional electromagnetism with a cutoff, is reduced to quadratures. It is shown that U3U_3 cannot bind a pair of identical charged scalar bosons; nevertheless, numerical calculations indicate that boson-boson bound states do exist in the framework of three-dimensional higher-derivative electromagnetism augmented by a topological Chern-Simons term.Comment: 6 page

    Is it Physically Sound to Add a Topologically Massive Term to Three-Dimensional Massive Electromagnetic or Gravitational Models ?

    Full text link
    The addition of a topologically massive term to an admittedly non-unitary three-dimensional massive model, be it an electromagnetic system or a gravitational one, does not cure its non-unitarity. What about the enlargement of avowedly unitary massive models by way of a topologically massive term? The electromagnetic models remain unitary after the topological augmentation but, surprisingly enough, the gravitational ones have their unitarity spoiled. Here we analyze these issues and present the explanation why unitary massive gravitational models, unlike unitary massive electromagnetic ones, cannot coexist from the viewpoint of unitarity with topologically massive terms. We also discuss the novel features of the three-term effective field models that are gauge-invariant

    Unavoidable Conflict Between Massive Gravity Models and Massive Topological Terms

    Full text link
    Massive gravity models in 2+1 dimensions, such as those obtained by adding to Einstein's gravity the usual Fierz-Pauli, or the more complicated Ricci scalar squared (R2R^2), terms, are tree level unitary. Interesting enough these seemingly harmless systems have their unitarity spoiled when they are augmented by a Chern-Simons term. Furthermore, if the massive topological term is added to R+RőľőĹ2R + R_{\mu\nu}^2 gravity, or to R+RőľőĹ2+R2R + R_{\mu\nu}^2 + R^2 gravity (higher-derivative gravity), which are nonunitary at the tree level, the resulting models remain nonunitary. Therefore, unlike the common belief, as well as the claims in the literature, the coexistence between three-dimensional massive gravity models and massive topological terms is conflicting.Comment: 13 pages, no figure

    Assessment of e-government maturity in Portuguese municipalities using regression and clustering approaches

    Get PDF
    In order to evaluate the development of websites of the 308 Por- tuguese municipalities in this work it was performed an analysis using regression models and clustering techniques. That analysis allowed recognizing a group of socioeconomic variables that are significant to characterize homogenous groups of municipalities in what concerns e-government maturity

    Perspectiva social del e-learning en la universidad

    Get PDF
    En la actual sociedad del conocimiento, los progresos en ciencia y tecnolog√≠a conviven con una amplia problem√°tica social que es necesario abordar para analizar los problemas relacionados con la educaci√≥n. En los √ļltimos a√Īos, la presencia del Estado ha disminuido en todos los √°mbitos. El modelo estadounidense de privatizaci√≥n y comercializaci√≥n ha creado nuevas realidades, como la necesidad de los pa√≠ses ricos de controlar, entre otras cosas, los servicios, el conocimiento y las nuevas tecnolog√≠as. En este contexto, y ante la creciente comercializaci√≥n de la educaci√≥n como servicio, incluso desde los organismos internacionales, los pa√≠ses en desarrollo necesitan m√°s que nunca acceder a instituciones de educaci√≥n superior y de investigaci√≥n que les permitan avanzar hacia un desarrollo sostenible. Asistimos a un proceso de elitizaci√≥n en el que la educaci√≥n deja de ser un bien p√ļblico y pasa a convertirse en un bien privado, lo que se refleja en los sistemas educativos de distintos pa√≠ses. Son varios los procesos de reforma de los sistemas educativos de pa√≠ses en desarrollo que tienen como objetivo facilitar el acceso al conocimiento. Muchas de las medidas que deben aplicarse pasan por la utilizaci√≥n de las nuevas tecnolog√≠as y el intercambio de conocimientos mediante una cooperaci√≥n internacional que se aleje de la comercializaci√≥n y permita el acceso de todas las personas a la sociedad del conocimiento

    O vício de não incorporação da cláusula contratual nos contratos de adesão

    Get PDF
    Disserta√ß√£o de mestrado em Direito dos Contratos e da EmpresaOs deveres de informa√ß√£o assumem-se como um fator essencial de prote√ß√£o, no √Ęmbito dos contratos de ades√£o, mas as consequ√™ncias da sua viola√ß√£o n√£o se mostram claras, dada a ambiguidade da express√£o utilizada no artigo 8¬ļ do D.L. n¬ļ 446/85, de 25 de Outubro. Procurase, neste estudo, encontrar a consequ√™ncia para a referida viola√ß√£o, tendo em conta os objetivos da lei. Procede-se √† an√°lise do controlo da incorpora√ß√£o das cl√°usulas, controlo, este, onde se incluem os deveres de informa√ß√£o. Estudam-se os princ√≠pios subjacentes ao mesmo, apurandose o seu objetivo e verificando-se como devem ser aplicados os deveres de informa√ß√£o. Desta analise resulta que o controlo da incorpora√ß√£o deve permanecer separado do controlo do conte√ļdo, que os deveres de informa√ß√£o est√£o enquadrados pelo princ√≠pio da transpar√™ncia, que, por sua vez, √© express√£o do princ√≠pio da boa f√©; e que o objetivo destes deveres √© permitir que a parte que se limita a aderir, possa, por um lado, ponderar, de modo devidamente informado, se deve concluir o contrato ou n√£o e, por outro lado, esteja devidamente preparada para a execu√ß√£o do contrato. Com isto em mente faz-se o estudo das diferentes possibilidades, apreciando-se as vantagens e desvantagens das mesmas e a sua adequa√ß√£o ao regime legal. Da compara√ß√£o das diferentes possibilidades √© poss√≠vel concluir qual o regime a que est√° sujeita a san√ß√£o da viola√ß√£o dos deveres de informa√ß√£o, em termos de quem pode invocar a san√ß√£o, o respetivo prazo, a possibilidade de sana√ß√£o e a possibilidade de conhecimento oficioso. Daqui tamb√©m resulta a resposta ao problema que se p√īs inicialmente, ou seja, qual √© o v√≠cio que resulta da viola√ß√£o dos deveres de informa√ß√£o. N√£o se conclui sem antes de referir qual o efeito, no contrato, da n√£o incorpora√ß√£o da cl√°usula afetada.The information requirements are an essential factor of protection, regarding standard contracts and unfair contract terms, but the consequences of their violation are not clear, considering the ambiguity of the expression used in article 8¬ļ of the D.L. n¬ļ 446/85, of October 25th. Here we try to ascertain the consequence of that violation, bearing in mind the goals of the law. We analyze the incorporation control of the contract terms, in which are included the information requirements. We study its underlying principles, finding its goal and describing how the information requirements should be observed. From this analysis we find that the incorporation control should remain separated from the content control, that the information requirements are under the principle of transparency, which, itself, is an expression of the principle of good faith; and that the goal of these requirements is to allow the party, that is restricted to the option of accepting or not the contract, on one hand, to consider, with enough information, should he accept the contract or not, and, on the other hand, to be prepared for the execution of the contract. Keeping this in mind, we do the study of the different possibilities, considering their advantages and disadvantages, and their suitability to the law. From the comparison of the different possibilities it is possible to ascertain which regime regulates the sanction resulting from the non-compliance of information requirements; defining who can argue the non-compliance, its deadline, possibility of ratification and the possibility of being assessed on the court¬īs own motion. From this it is possible to answer our initial problem, that is, which sanction is the consequence of non-compliance regarding the information requirements. Finally, we study the consequences, on the contract, of the non-incorporation of the contractual term
    • ‚Ķ
    corecore