Evolutionary search algorithms have become an essential asset in the algorithmic toolbox for solving high-dimensional optimization problems in across a broad range of bioinformatics problems. Genetic… (More)

Let M = M0 × R be a pp–wave type spacetime endowed with the metric 〈·, ·〉z = 〈·, ·〉x + 2 du dv + H(x, u) du, where (M0, 〈·, ·〉x) is any Riemannian manifold and H(x, u) an arbitrary function. We show… (More)

We present a new development of the causal boundary of spacetimes, originally introduced by Geroch, Kronheimer and Penrose. Given a strongly causal spacetime (or, more generally, a chronological… (More)

In order to apply variational methods to the action functional for geodesics of a stationary spacetime, some hypotheses, useful to obtain classical Palais–Smale condition, are commonly used:… (More)

Given two points of a Generalized Robertson-Walker spacetime, the existence, multiplicity and causal character of geodesics connecting them is characterized. Conjugate points of such geodesics are… (More)

A classical nonlinear equation Ds ’ x þrxVðx; sÞ 1⁄4 0 on a complete Riemannian manifoldM is considered. The existence of solutions connecting any two points x0; x1AM is studied, i.e., for T40 the… (More)

A new technique for the study of geodesic connectedness in a class of Lorentzian manifolds is introduced. It is based on arguments of Brouwer’s topological degree for the solution of functional… (More)

A complete and systematic approach to compute the causal boundary of wave-type spacetimes is carried out. The case of a 1-dimensional boundary is specially analyzed and its critical appearance in… (More)