We study five dimensional thin-shell wormholes in Einstein-Maxwell theory with a GaussBonnet term. The linearized stability under radial perturbations and the amount of exotic matter are analyzed as a function of the parameters of the model. We find that the inclusion of the quadratic correction substantially widens the range of possible stable configurations, and besides it allows for a reduction of the exotic matter required to construct the wormholes.
Because of its apparent complexity, the discussion of Wigner rotation is usually reduced to the study of Thomas precession, which is too specific a case to allow a deep understanding of boost composition. However, by using simple arguments and linear algebra, the result for the Wigner rotation is obtaines straightforwardly, leading to a formula written in a manageable form. The result is exemplified in the context of the aberration of light.
We investigate divergence-type theories describing the disipative interaction betwen a field and a fluid. We look for theories which, under equilibrium conditions, reduce to the theory of a Klein-Gordon scalar field and a perfect fluid. We show that the requirements of causality and positivity of entropy production put non-trivial constraints to the structure of the interaction terms. These theories provide a basis for the phenomonological study of the reheating period.
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