Variedades semi-riemannianas con tensor de curvatura especial

The notion of curvature played a basic role in the development of geometry since the XIX century with the initial work of many mathematicians, among them Gauss and Riemann. Even though the curvature tensor of a semi-Riemannian manifold carries a lot of information, it is a di_cult object to deal with. Therefore, many attempts have been done in considering other kinds of objects which, being easier to handle, somehow reect the properties of the curvature tensor. Among those objects, curvature operators have received much attention for the last years. Indeed, motivated by a conjecture of Osserman in the 90's, spectral properties of Jacobi operators, generalized Jacobi operators, skew-symmetric curvature operators, Szabó operators, …have been considered.