On matrices over -algebras.
The aim of this paper is to characterize a class of subspectra for which the geometric spectral radius is the same and depends only upon a commuting -tuple of elements of a complex Banach algebra. We prove also that all these subspectra have the same capacity.
2000 Mathematics Subject Classification: 45A05, 45B05, 45E05,45P05, 46E30We obtain a criterion of Fredholmness and formula for the Fredholm index of a certain class of one-dimensional integral operators M with a weak singularity in the kernel, from the variable exponent Lebesgue space L^p(·) ([a, b], ?) to the Sobolev type space L^α,p(·) ([a, b], ?) of fractional smoothness. We also give formulas of closed form solutions ϕ ∈ L^p(·) of the 1st kind integral equation M0ϕ = f, known as the generalized...
Let be a continuous map of the closure of the open unit disc of into a unital associative Banach algebra , whose restriction to is holomorphic, and which satisfies the condition whereby for all and whenever (where is the spectrum of any ). One of the basic results of the present paper is that is , that is to say, is then a compact subset of that does not depend on for all . This fact will be applied to holomorphic self-maps of the open unit ball of some -algebra...