Appliies variational methods and critical point theory on infinite dimenstional manifolds to some problems in Lorentzian geometry which have a variational nature, such as existence and multiplicity results on geodesics and relations between such geodesics and the topology of the manifold.

The aim of this work is to apply variational methods and critical point theory on infinite dimensional manifolds, to some problems in Lorentzian Geometry which have a variational nature, such as existence and multiplicity results on geodesics and Relations between such geodesics and the topology of the manifold (in the spirit of Morse Theory). In particular Ljusternik-Schnirelmann critical point theory and Morse theory are exploited. Moreover, the results for general Lorentzian manifolds should be applied to physically relevant space-times of General Relativity, like Schwarzschild and Kerr space-times.