Let X,Y be normed spaces. The set of bounded linear operators is noted as L(X,Y ). Let now D = D(A) ⊂ X be a linear subspace, and A : D −→ Y a linear (not necessarily bounded!) operator. Notation: (A,D(A)) : X −→ Y Definition: G(A) := {(x,Ax) |x ∈ D} is called the graph of A. Obviously, G(A) is a linear subspace of X × Y . The linear operator A is called closed if G(A) is closed in X × Y . The ...

For suitable Banach spaces $X$ and $Y$ with Schauder decompositions and‎ ‎a suitable closed subspace $mathcal{M}$ of some compact operator space from $X$ to $Y$‎, ‎it is shown that the strong Banach-Saks-ness of all evaluation‎ ‎operators on ${mathcal M}$ is a sufficient condition for the weak‎ ‎Banach-Saks property of ${mathcal M}$, where for each $xin X$ and $y^*in‎ ‎Y^*$‎, ‎the evaluation op...

Covering-based rough set theory is a useful tool to deal with inexact, uncertain or vague knowledge in information systems. Topology, one of the most important subjects in mathematics, provides mathematical tools and interesting topics in studying information systems and rough sets. In this paper, we present the topological characterizations to three types of covering approximation operators. F...

in this paper‎, ‎we consider a general integral operator $g_n(z).$ the main object of the present paper is to study some properties of this integral operator on the classes $mathcal{s}^{*}(alpha),$ $mathcal{k}(alpha),$ $mathcal{m}(beta),$ $mathcal{n}(beta)$ and $mathcal{kd}(mu,beta).$‎

Uncertainty is an inherent property of all living systems. Curiously enough, computational models inspired by biological systems do not take, in general, under consideration this essential aspect of living systems. In this paper, after introducing the notion of a multi-fuzzy set (i.e. an orthogonal approach to the fuzzification of multisets), we introduce two variants of P systems with fuzzy co...

Exercise 13 of Chapter 2 is to show that a binary relation R ⊆ A × B induces a pair of closure operators, described as follows. For X ⊆ A, let σ(X) = {b ∈ B : x R b for all x ∈ X}. Similarly, for Y ⊆ B, let π(Y) = {a ∈ A : a R y for all y ∈ Y }. Then the composition πσ : P(A) → P(A) is a closure operator on A, given by πσ(X) = {a ∈ A : a R b whenever x R b for all x ∈ X}. Likewise, σπ is a clos...

The algebra Ψ(M) of order zero pseudodifferential operators on a compact manifold M defines a well-known C∗-extension of the algebra C(S∗M) of continuous functions on the cospherical bundle S∗M ⊂ T ∗M by the algebra K of compact operators. In his proof of the index theorem, Higson defined and used an asymptotic homomorphism T from C0(T ∗M) to K, which plays the role of a deformation for the com...