A note on singular and degenerate abstract equations
Si considera l’equazione astratta , dove
Si considera l’equazione astratta , dove
A connection between the Landesman-Lazer condition and the solvability of the equation Lx = N(x) in a cone with a noninvertible linear operator L is studied. The result is based on the abstract framework from [5], applied to the existence of periodic solutions of ordinary differential equations, and compared with theorems by Santanilla (see [7]).
The proofs of Theorems 2.1, 2.2 and 2.3 from [Olatinwo M.O., Some results on multi-valued weakly jungck mappings in b-metric space, Cent. Eur. J. Math., 2008, 6(4), 610–621] base on faulty evaluations. We give here correct but weaker versions of these theorems.
Let be a Banach space operator. In this paper we characterize -Browder’s theorem for by the localized single valued extension property. Also, we characterize -Weyl’s theorem under the condition where is the set of all eigenvalues of which are isolated in the approximate point spectrum and is the set of all left poles of Some applications are also given.
We investigate the Banach manifold consisting of complex functions on the unit disc having boundary values in a given one-dimensional submanifold of the plane. We show that ∂/∂λ̅ restricted to that submanifold is a Fredholm mapping. Moreover, for any such function we obtain a relation between its homotopy class and the Fredholm index.