- countably compact set
-
Math.a set for which every cover consisting of a countable number of sets has a subcover consisting of a finite number of sets.
* * *
Universalium. 2010.
* * *
Universalium. 2010.
countably compact set — Math. a set for which every cover consisting of a countable number of sets has a subcover consisting of a finite number of sets … Useful english dictionary
Countably compact space — In mathematics a topological space is countably compact if every countable open cover has a finite subcover. Examples and Properties A compact space is countably compact. Indeed, directly from the definitions, a space is compact if and only if it … Wikipedia
Compact space — Compactness redirects here. For the concept in first order logic, see compactness theorem. In mathematics, specifically general topology and metric topology, a compact space is an abstract mathematical space whose topology has the compactness… … Wikipedia
Compact operator — In functional analysis, a branch of mathematics, a compact operator is a linear operator L from a Banach space X to another Banach space Y, such that the image under L of any bounded subset of X is a relatively compact subset of Y. Such an… … Wikipedia
Compact operator on Hilbert space — In functional analysis, compact operators on Hilbert spaces are a direct extension of matrices: in the Hilbert spaces, they are precisely the closure of finite rank operators in the uniform operator topology. As such, results from matrix theory… … Wikipedia
Limit point compact — In mathematics, particularly topology, limit point compactness is a certain condition on a topological space which generalizes some features of compactness. In a metric space, limit point compactness, compactness, and sequential compactness are… … Wikipedia
Locally compact space — In topology and related branches of mathematics, a topological space is called locally compact if, roughly speaking, each small portion of the space looks like a small portion of a compact space.Formal definitionLet X be a topological space. The… … Wikipedia
Cantor set — In mathematics, the Cantor set, introduced by German mathematician Georg Cantor in 1883 [Georg Cantor (1883) Über unendliche, lineare Punktmannigfaltigkeiten V [On infinite, linear point manifolds (sets)] , Mathematische Annalen , vol. 21, pages… … Wikipedia
Closed set — This article is about the complement of an open set. For a set closed under an operation, see closure (mathematics). For other uses, see Closed (disambiguation). In geometry, topology, and related branches of mathematics, a closed set is a set… … Wikipedia
Corona set — In mathematics, the corona or corona set of a topological space X is the complement βXX of the space in its Stone–Čech compactification βX. A topological space is said to be σ compact if it is the union of countably many compact subspaces, and… … Wikipedia