Weakly compact cardinal, an infinite cardinal number on which every binary relation has an equally large homogeneous subset
Weakly compact set, a compact set in a space with the weak topology
Weakly compact set, a set that has some but not all of the properties of compact sets, for example:
Sequentially compact space, a set in which every infinite sequence has a convergent subsequence
Limit point compact, a set in which every infinite subset of X has a limit point
Topics referred to by the same term
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Weaklycompact set, a compact set in a space with the weak topology Weaklycompact set, a set that has some but not all of the properties of compact sets...
In mathematics, a weaklycompact cardinal is a certain kind of cardinal number introduced by Erdős & Tarski (1961); weaklycompact cardinals are large...
vector space weakly closed (respectively, weaklycompact, etc.) if they are closed (respectively, compact, etc.) with respect to the weak topology. Likewise...
that compact subsets of Hausdorff spaces are closed, and closed subsets of compact spaces are compact. Spaces satisfying (1) are also called weakly locally...
{\displaystyle X} has a weakly convergent subsequence. A weaklycompact subset A {\displaystyle A} in ℓ 1 {\displaystyle \ell ^{1}} is norm-compact. Indeed, every...
{\displaystyle M} is sequentially weaklycompact. We say the family M {\displaystyle M} of probability measures is sequentially weaklycompact if for every sequence...
{\displaystyle Y} carry their weak topologies. If G ′ {\displaystyle {\mathcal {G}}'} was the set of all convex balanced weaklycompact equicontinuous subsets...
is a Mahlo cardinal. However, the first Woodin cardinal is not even weaklycompact. The hierarchy V α {\displaystyle V_{\alpha }} (known as the von Neumann...
to λ-compactness. A cardinal is weaklycompact if and only if it is κ-compact; this was the original definition of that concept. Strong compactness implies...
<\gamma } . An ordinal α {\displaystyle \alpha } is called recursively weaklycompact if it is Π 3 {\displaystyle \Pi _{3}} -reflecting, or equivalently,...
mathematics, a weak Hausdorff space or weakly Hausdorff space is a topological space where the image of every continuous map from a compact Hausdorff space...
also equivalent to compactness for first-countable uniform spaces). (X, d) is limit point compact (also called weakly countably compact); that is, every...
weaklycompact, that is, the image of a bounded subset of X {\displaystyle X} is a weaklycompact subset of Y . {\displaystyle Y.} for every weakly compactly...
κ is weaklycompact then no κ-Aronszajn trees exist. Conversely, if κ is inaccessible and no κ-Aronszajn trees exist, then κ is weaklycompact. An Aronszajn...
strength of Morse–Kelley set theory with the proper class ordinal a weaklycompact cardinal. The universal set is a proper set in this theory. The sets...
of H, the closed unit ball B is weaklycompact. Also, the compactness of T means (see above) that T : X with the weak topology → X with the norm topology...
topological space X {\displaystyle X} is said to be limit point compact or weakly countably compact if every infinite subset of X {\displaystyle X} has a limit...
are weakly closed, it follows from the third property that closed bounded convex subsets of a reflexive space X {\displaystyle X} are weaklycompact. Thus...
topology, the topology of uniform convergence on all absolutely convex weaklycompact subsets of X ′ {\displaystyle X'} . Given a dual pair ( X , X ′ ) {\displaystyle...
compact sets. X {\displaystyle X} is σ-compact and weakly locally compact. X {\displaystyle X} is Lindelöf and weakly locally compact. (where weakly locally...
\setminus X\in {\mathcal {F}}} . This is similar to a characterization of weaklycompact cardinals. More generally, κ {\displaystyle \kappa } is called n {\displaystyle...