The index of a pseudo B-Fredholm operator will be defined and generalize the usual operator. This concept used to extend some known results in Fredholm’s theory. Among other results, nullity, deficiency, ascent descent extended for pseudo-Fredholm

A Banach space operator T ∈ B(X ) is polaroid if points λ ∈ isoσσ(T ) are poles of the resolvent of T . Let σa(T ), σw(T ), σaw(T ), σSF+(T ) and σSF−(T ) denote, respectively, the approximate point, the Weyl, the Weyl essential approximate, the upper semi–Fredholm and lower semi–Fredholm spectrum of T . For A, B and C ∈ B(X ), let MC denote the operator matrix (

Consider a selfadjoint unbounded operator D on a Hilbert space H and a one parameter norm continuous family of selfadjoint bounded operators {A(t) | t ∈ R} that converges in norm to asymptotes A± at ±∞. Then under certain conditions [RoSa95] that include the assumption that the operators {D(t) = D + A(t), t ∈ R} all have discrete spectrum then the spectral flow along the path {D(t)} can be show...

We prove that the operator G, the closure of the first-order differential operator −d/dt + D(t) on L2(R, X), is Fredholm if and only if the not well-posed equation u′(t) = D(t)u(t), t ∈ R, has exponential dichotomies on R+ and R− and the ranges of the dichotomy projections form a Fredholm pair; moreover, the index of this pair is equal to the Fredholm index of G. Here X is a Hilbert space, D(t)...

We define a notion of topological degree for a class of maps (called orientable), defined between real Banach spaces, which are Fredholm of index zero. We introduce first a notion of orientation for any linear Fredholm operator of index zero between two real vector spaces. This notion (which does not require any topological structure) allows to define a concept of orientability for nonlinear Fr...

It is shown that the inverse scattering problem for the three-dimensional SchrSdinger equation with a potential having no spherical symmetry can be solved using a Fredholm integral equation. The integral operator studied here is shown to be compact and self-adjoint with its spectrum in [-1, 1]. The relationship between solutions of this Fredholm equation and of a related RiemannHilbert problem ...

For A ? L(X), B L(Y) and C L(Y,X) we denote by MC the operator matrix defined on X Y = (A 0 B). In this paper, prove that ?qF(A) ?qF(B) [ C?L(Y,X) ?qF(MC) ?p(B) ?p(A?), where ?qF(.) (resp. ?p(.)) denotes quasi-Fredholm spectrum point spectrum). Furthermore, consider some sufficient conditions for to be have ?qF(MC).