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In mathematics, more specifically in functional analysis, a Banach space (pronounced ) is a complete normed vector space.Thus, a Banach space is a vector space with a metric that allows the computation of vector length and distance between vectors and is complete in the sense that a Cauchy sequence of vectors always converges to a well-defined limit that is within the space.
Joseph Diestel (January 27, 1943 – August 17, 2017) was an American mathematician and Professor of Mathematics at Kent State University.In addition to his contribution to functional analysis, particularly Banach space theory and the theory of vector measures, Diestel was known for a number of highly influential textbooks: in 1975 he published "Lecture Notes Geometry of Banach Spaces ...
Tsirelson space, a reflexive Banach space in which neither nor can be embedded. W.T. Gowers construction of a space X {\displaystyle X} that is isomorphic to X ⊕ X ⊕ X {\displaystyle X\oplus X\oplus X} but not X ⊕ X {\displaystyle X\oplus X} serves as a counterexample for weakening the premises of the Schroeder–Bernstein theorem [ 1 ]
A bounded disk in a topological vector space such that (,) is a Banach space is called a Banach disk, infracomplete, or a bounded completant in . If its shown that ( span D , p D ) {\displaystyle \left(\operatorname {span} D,p_{D}\right)} is a Banach space then D {\displaystyle D} will be a Banach disk in any TVS that contains D ...
In functional analysis, the open mapping theorem, also known as the Banach–Schauder theorem or the Banach theorem [1] (named after Stefan Banach and Juliusz Schauder), is a fundamental result that states that if a bounded or continuous linear operator between Banach spaces is surjective then it is an open map.
Together with the Hahn–Banach theorem and the open mapping theorem, it is considered one of the cornerstones of the field. In its basic form, it asserts that for a family of continuous linear operators (and thus bounded operators) whose domain is a Banach space, pointwise boundedness is equivalent to uniform boundedness in operator norm.
In mathematics, the Besov space (named after Oleg Vladimirovich Besov) , is a complete quasinormed space which is a Banach space when 1 ≤ p, q ≤ ∞.These spaces, as well as the similarly defined Triebel–Lizorkin spaces, serve to generalize more elementary function spaces such as Sobolev spaces and are effective at measuring regularity properties of functions.
The theorem is named for the mathematicians Hans Hahn and Stefan Banach, who proved it independently in the late 1920s.The special case of the theorem for the space [,] of continuous functions on an interval was proved earlier (in 1912) by Eduard Helly, [1] and a more general extension theorem, the M. Riesz extension theorem, from which the Hahn–Banach theorem can be derived, was proved in ...