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The collision of pure electromagnetic plane waves with collinear polarization in N-dimensional (N = 2 + n) Einstein-Maxwell theory is considered. A class of exact solutions for the higher dimensional Bell-Szekeres metric is obtained and its singularity structure is examined. © 2003 The American Physical Society

We investigate the B → K * 0 (1430)l + l − transition in the Applequist-Cheng-Dobrescu model in the presence of a universal extra dimension. In particular, we calculate double lepton polarization asymmetries and branching ratio related to this channel and compare the obtained results with the predictions of the standard model. Our analysis of the considered observables in terms of radius R of the compactified extra-dimension as the new parameter of the model show a considerable discrepancy between the predictions of two models in low

A simple proof of the quantum virial theorem that can be used in undergraduate courses is given. The proof proceeds by first showing that the energy eigenvalues of a Hamiltonian remain invariant under a scale transformation. Then invoking the Hellmann–Feynman theorem produces the final statement of the virial theorem.

The partition function defined in the usual way is a gauge-dependent quantity. However, the ansatz of Bernard and Gross et al leaves it gauge invariant. We use this ansatz for the partition function to show that Lagrange multipliers (non-physical bosonic fields) are not restricted to satisfying any boundary conditions in the path integral at finite temperature. We take a quantum mechanical model to illustrate that boundary conditions satisfied by non-physical fields depend on the choice of `gauge'. Resumo. Pela definição usual da Função de Partição, esta é uma quantidade que depende da escolha de calibre. Entretanto, Bernard e Gross et al. propuseram um ansatz no qual a Função de Partição é independente do calibre. Utilizamos este ansatz para a Função de Partição, para mostrar que os multiplicadores de Lagrange (campos bosônicos não-físicos) não são obrigados a satisfazerem condições de contorno na integral funcional a temperatura finita. Consideramos um modelo em Mecânica Quântica para ilustrar, que as condições de contorno satisfeitas pelos campos não - físicos nas integrais funcionais a temperatura finita, representam uma escolha de calibre.