Topological degree and atypical bifurcation results for a class of multivalued perturbations of Fredholm maps in Banach spaces

We obtain a global (atypical) bifurcation result for a semilinear inclusion problem in Banach spaces. The approach is topological, making use of a topological degree introduced by the second author for locally compact multivalued perturbations of nonlinerar Fredholm maps. We also study some specific aspects of the construction of this concept of degree.