Abstract:
We obtain some new bifurcation criteria for solutions of general boundary value problems for nonlinear elliptic systems of partial differential equations. The results are of different nature from the ones that can be obtained via the traditional Lyapunov-Schmidt reduction. Our sufficient conditions for bifurcation are derived from the Atiyah-Singer family index theorem and therefore they depend only on the coefficients of derivatives of leading order of the linearized differential operators. They are computed explicitly from the coefficients without the need of solving the linearized equations. Moreover, they are stable under lower order perturbations.

Abstract:
We associate to a parametrized family $f$ of nonlinear Fredholm maps possessing a trivial branch of zeroes an {\it index of bifurcation} $\beta(f)$ which provides an algebraic measure for the number of bifurcation points from the trivial branch. The index $\beta(f)$ is derived from the index bundle of the linearization of the family along the trivial branch by means of the generalized $J$-homomorphism. Using the Agranovich reduction and a cohomological form of the Atiyah-Singer family index theorem, due to Fedosov, we compute the bifurcation index of a multiparameter family of nonlinear elliptic boundary value problems from the principal symbol of the linearization along the trivial branch. In this way we obtain criteria for bifurcation of solutions of nonlinear elliptic equations which cannot be achieved using the classical Lyapunov-Schmidt method.

Abstract:
We obtain an estimate for the covering dimension of the set of bifurcation points for solutions of nonlinear elliptic boundary value problems from the principal symbol of the linearization of the problem along the trivial branch of solutions.

Abstract:
We prove the existence of an unbounded connected branch of nontrivial homoclinic trajectories of a family of discrete nonautonomous asymptotically hyperbolic systems parametrized by a circle under assumptions involving the topological properties of the asymptotic stable bundles.

Abstract:
We show that nontrivial homoclinic trajectories of a family of discrete, nonautonomous, asymptotically hyperbolic systems parametrized by a circle bifurcate from a stationary solution if the asymptotic stable bundles Es(+{\infty}) and Es(-{\infty}) of the linearization at the stationary branch are twisted in different ways.

Abstract:
Given a continuous family of C^2 functionals of Fredholm type, we show that the non-vanishing of the spectral flow for the family of Hessians along a known (trivial) branch of critical points not only entails bifurcation of nontrivial critical points but also allows to estimate the number of bifurcation points along the branch. We use this result for several parameter bifurcation, estimating the number of connected components of the complement of the set of bifurcation points and apply our results to bifurcation of periodic orbits of Hamiltonian systems. By means of a comparison principle for the spectral flow, we obtain lower bounds for the number of bifurcation points of periodic orbits on a given interval in terms of the coefficients of the linearization.

Abstract:
Perturbed geodesics are trajectories of particles moving on a semi-Riemannian manifold in the presence of a potential. Our purpose here is to extend to perturbed geodesics on semi-Riemannian manifolds the well known Morse Index Theorem. When the metric is indefinite, the Morse index of the energy functional becomes infinite and hence, in order to obtain a meaningful statement, we substitute the Morse index by its relative form, given by the spectral flow of an associated family of index forms. We also introduce a new counting for conjugate points, which need not to be isolated in this context, and prove that the relative Morse index equals the total number of conjugate points. Finally we study the relation with the Maslov index of the flow induced on the Lagrangian Grassmannian.

Abstract:
This is the first article that attempts to trace a panoramic view of Sephardi/Mizrahi literature in Latin America. It starts by giving basic information about the migration of these Jewish groups at the end of the 19th and beginning of the 20th century. Later, it identifies more than twenty writers, and establishes two ways to approach Sephardi/- Mizrahi identity: 1) Reflection and study of the splendor of the Golden Age of Medieval Jewish culture in the Iberian Peninsula; and 2) representations of contemporary Sephardim and Mizrahim. Finally, the article proposes Isaac Chocrón's novel, Rómpase en caso de incendio, as the foundational text for contemporary Sephardi/- Mizrahi literature in Latin America. Este es el primer artículo que intenta trazar un panorama de la literatura sefardí/-mizrahi en América Latina. Tras una información básica sobre la migración de esos grupos judíos a finales del siglo XIX y principios del XX, se identifica a más de veinte escritores y se plantean dos modos de acercamiento a la identidad sefardí/mizrahi: 1) la reflexión y estudio del esplendor de la edad dorada de la cultura judía medieval; y 2) vivencias de los sefardíes y mizrahis contemporáneos. Finalmente, se considera la novela Rómpase en caso de incendio, de Isaac Chocrón, como el texto fundacional de la literatura sefardí/mizrahi contemporánea en América Latina.