Banach space

[′bä‚näk ‚spās]

(mathematics)

A real or complex vector space in which each vector has a non-negative length, or norm, and in which every Cauchy sequence converges to a point of the space. Also known as complete normed linear space.

Banach space

(mathematics)

A complete normed vector space. Metric is induced by the norm: d(x,y) = ||x-y||. Completeness means that every Cauchy sequence converges to an element of the space. All finite-dimensional real and complex normed vector spaces are complete and thus are Banach spaces.

Using absolute value for the norm, the real numbers are a Banach space whereas the rationals are not. This is because there are sequences of rationals that converges to irrationals.

Several theorems hold only in Banach spaces, e.g. the Banach inverse mapping theorem. All finite-dimensional real and complex vector spaces are Banach spaces. Hilbert spaces, spaces of integrable functions, and spaces of absolutely convergent series are examples of infinite-dimensional Banach spaces. Applications include wavelets, signal processing, and radar.

[Robert E. Megginson, "An Introduction to Banach Space Theory", Graduate Texts in Mathematics, 183, Springer Verlag, September 1998].

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Banach Space

(named after S. Banach), a complete normed linear space.

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References in periodicals archive

Let ([OMEGA], [SIGMA], [mu]) be a complete probability measure space and Y a nonemptysubset of a separable Banach space E.

On the Equivalence of Stochastic Fixed Point Iterations for Generalized [phi]-Contractive-Like Operators

The results about the BVP with multiple point boundary conditions of impulsive p-Laplacian operator fractional differential equations are few, especially in Banach space.

Impulsive Fractional Differential Equations with p-Laplacian Operator in Banach Spaces

E is a nonreflexive Banach space, [sup.c][D.sup.[alpha].sub.0+] denotes the fractional Caputo derivative, [mathematical expression not reproducible] are given functions satisfying some assumptions that will be specified later, the integral is understood to be the Henstock-Kurzweil-Pettis, and solutions to (5) will be sought in E = C(I, [E.sub.[omega]]).

Existence of Weak Solutions for Fractional Integrodifferential Equations with Multipoint Boundary Conditions

Certain deficiencies of the descriptions (established in [1]) of the Carleman classes of vectors, in particular the Gevrey classes, of a scalar type spectral operator in a complex Banach space inadvertently overlooked by the author when proving the results of the three papers [2-4] are observed not to affect the validity of the latter due to more recent findings of [5].

Comment on "On the Carleman Classes of Vectors of a Scalar Type Spectral Operator"

A [C.sub.0]-quasisemigroup R(t, s) on Banach space X is said to be uniformly exponentially stable if there exist constants [alpha] > 0 and N [greater than or equal to] 1 such that

Exact Null Controllability, Stabilizability, and Detectability of Linear Nonautonomous Control Systems: A Quasisemigroup Approach

Throughout X denotes a real Banach space, X*, the dual of X, [B.sub.X] = {x [member of] X : [parallel]x[parallel] [less than or equal to] 1} and [S.sub.X] = {x [member of] X : [parallel]x[parallel] = 1}, the unit sphere of X.

Best approximative properties of exposed faces of [l.sub.1]

Recall that the right-hand quotient Ao[B.sup.-1] of two operator ideals A and B is the operator ideal that consists of all operators T [member of] L(X,Y) such that TS [member of] A ([X.sub.0],Y) whenever S [member of] B([X.SUB.0],X) for some Banach space [X.sub.0] (see [6,3.1.1]).

Representing the Banach operator ideal of completely continuous operators

Suppose X is a Banach space equipped with the norm topology (denoted by ||*||) as well as the weak topology (denoted by [T.sub.w]).

AN EXTREME POINT THEOREM ON HYPERSPACE

In this article we present a fractional quantitative Korovkin type approximation theory for linear operators involving Banach space valued functions.

VECTOR FRACTIONAL KOROVKIN TYPE APPROXIMATIONS

Where [mathematical expression not reproducible] and f : J x E x E x [OMEGA] [right arrow] E are given continuous functions, ([OMEGA], A, v) is a measurable space, and E is a real (or complex) Banach space with norm [[parallel] * [parallel].sub.e] and dual [E.sup.*], such that E is the dual of a weakly compactly generated Banach space [mathematical expression not reproducible], is the left-sided mixed Hadamard integral of order r, and [mathematical expression not reproducible] is a given continuous and measurable function such that

Weak Solutions for Partial Random Hadamard Fractional Integral Equations with Multiple Delays