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Banach space, normed vector spaces which are complete with respect to the metric induced by the norm; Banach–Mazur compactum – Concept in functional analysis; Finsler manifold, where the length of each tangent vector is determined by a norm; Inner product space, normed vector spaces where the norm is given by an inner product
In mathematics, more specifically in functional analysis, a Banach space (/ ˈ b ɑː. n ʌ x /, Polish pronunciation:) 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 ...
The -normed space is studied in functional analysis, probability theory, and harmonic analysis. Another function was called the ℓ 0 {\displaystyle \ell _{0}} "norm" by David Donoho —whose quotation marks warn that this function is not a proper norm—is the number of non-zero entries of the vector x . {\displaystyle x.} [ citation needed ...
In the area of mathematics known as functional analysis, a reflexive space is a locally convex topological vector space for which the canonical evaluation map from into its bidual (which is the strong dual of the strong dual of ) is a homeomorphism (or equivalently, a TVS isomorphism).
Uniform Boundedness Principle — Let be a Banach space, a normed vector space and (,) the space of all continuous linear operators from into . Suppose that F {\displaystyle F} is a collection of continuous linear operators from X {\displaystyle X} to Y . {\displaystyle Y.}
The basic and historically first class of spaces studied in functional analysis are complete normed vector spaces over the real or complex numbers. Such spaces are called Banach spaces . An important example is a Hilbert space , where the norm arises from an inner product.
However, every finite dimensional normed space is a reflexive Banach space, so Riesz’s lemma does holds for = when the normed space is finite-dimensional, as will now be shown. When the dimension of X {\displaystyle X} is finite then the closed unit ball B ⊆ X {\displaystyle B\subseteq X} is compact.
The Frobenius norm defined by ‖ ‖ = = = | | = = = {,} is self-dual, i.e., its dual norm is ‖ ‖ ′ = ‖ ‖.. The spectral norm, a special case of the induced norm when =, is defined by the maximum singular values of a matrix, that is, ‖ ‖ = (), has the nuclear norm as its dual norm, which is defined by ‖ ‖ ′ = (), for any matrix where () denote the singular values ...