A note on finite codimensional linear isometries of into .
A note on noetherianity.
A note on pervasive algebras
A note on pervasive function algebras
A positivity result and normalization of positive convolution structures.
A remark on linear codimensions of function algebras
A remark on non-existence of an algebra norm for the algebra of continuous functions on a topological space admitting an unbounded continuous function
Let X be any topological space, and let C(X) be the algebra of all continuous complex-valued functions on X. We prove a conjecture of Yood (1994) to the effect that if there exists an unbounded element of C(X) then C(X) cannot be made into a normed algebra.
A remark on supra-additive and supra-multiplicative operators on
M. Radulescu proved the following result: Let be a compact Hausdorff topological space and a supra-additive and supra-multiplicative operator. Then is linear and multiplicative. We generalize this result to arbitrary topological spaces.
A theorem concerning Ditkin's condition
A uniform F-algebra with locally complete spectrum and with nonglobal peak points
Additively spectral-radius preserving surjections between unital semisimple commutative Banach algebras
Let A and B be unital, semisimple commutative Banach algebras with the maximal ideal spaces M A and M B, respectively, and let r(a) be the spectral radius of a. We show that if T: A → B is a surjective mapping, not assumed to be linear, satisfying r(T(a) + T(b)) = r(a + b) for all a; b ∈ A, then there exist a homeomorphism φ: M B → M A and a closed and open subset K of M B such that for all a ∈ A, where e is unit element of A. If, in addition, and on M B, then T is an algebra isomorphism.
Affine bijections of C(X,I)
Let 𝒳 be a compact Hausdorff space which satisfies the first axiom of countability, I = [0,1] and 𝓒(𝒳,I) the set of all continuous functions from 𝒳 to I. If φ: 𝓒(𝒳,I) → 𝓒(𝒳,I) is a bijective affine map then there exists a homeomorphism μ: 𝒳 → 𝒳 such that for every component C in 𝒳 we have either φ(f)(x) = f(μ(x)), f ∈ 𝓒(𝒳,I), x ∈ C, or φ(f)(x) = 1-f(μ(x)), f ∈ 𝓒(𝒳,I), x ∈ C.
Algebraic and essentially algebraic composition operators on C(X).
Algebras of Continuous Functions Invariant Under the Backward Shift.
Algebras of continuous functions over -spaces
Nella prima parte della nota sono studiate le proprietà di connessione dei sottospazi dello spettro di un anello. Con l’ausilio dei risultati ottenuti, si stabiliscono le condizioni necessarie e sufficienti affinchè un’algebra reale assolutamente piatta sia isomorfa ad un’algebra di funzioni continue a valori reali su un -spazio, del quale determini la topologia. Ulteriori condizioni sono necessarie e sufficienti affinché un’algebra reale assolutamente piatta sia isomorfa all’algebra di tutte le...
Algebras of real analytic functions: Homomorphisms and bounding sets
This article deals with bounding sets in real Banach spaces E with respect to the functions in A(E), the algebra of real analytic functions on E, as well as to various subalgebras of A(E). These bounding sets are shown to be relatively weakly compact and the question whether they are always relatively compact in the norm topology is reduced to the study of the action on the set of unit vectors in of the corresponding functions in . These results are achieved by studying the homomorphisms on the...
Algèbres de fonctions à orthogonal purement atomique
Algèbres duales uniformes d'opérateurs sur l'espace de Hilbert
Almost multiplicative functionals
A linear functional F on a Banach algebra A is almost multiplicative if |F(ab) - F(a)F(b)| ≤ δ∥a∥ · ∥b∥ for a,b ∈ A, for a small constant δ. An algebra is called functionally stable or f-stable if any almost multiplicative functional is close to a multiplicative one. The question whether an algebra is f-stable can be interpreted as a question whether A lacks an almost corona, that is, a set of almost multiplicative functionals far from the set of multiplicative functionals. In this paper we discuss...
Amenability and weak amenability of Lipschitz operators algebras.