cone-saturated

{{Multiple issues|{{one source|date=June 2020}}{{inline|date=September 2020}}{{technical|date=June 2020}}}}

In mathematics, specifically in order theory and functional analysis, if C is a cone at 0 in a vector space X such that 0 \in C, then a subset S \subseteq X is said to be C-saturated if S = [S]_C, where [S]_C := (S + C) \cap (S - C).

Given a subset S \subseteq X, the C-saturated hull of S is the smallest C-saturated subset of X that contains S.{{sfn|Schaefer|Wolff|1999|pp=215–222}}

If \mathcal{F} is a collection of subsets of X then \left[ \mathcal{F} \right]_C := \left\{ [F]_C : F \in \mathcal{F} \right\}.

If \mathcal{T} is a collection of subsets of X and if \mathcal{F} is a subset of \mathcal{T} then \mathcal{F} is a fundamental subfamily of \mathcal{T} if every T \in \mathcal{T} is contained as a subset of some element of \mathcal{F}.

If \mathcal{G} is a family of subsets of a TVS X then a cone C in X is called a \mathcal{G}-cone if \left\{ \overline{[G]_C} : G \in \mathcal{G} \right\} is a fundamental subfamily of \mathcal{G} and C is a strict \mathcal{G}-cone if \left\{ [B]_C : B \in \mathcal{B} \right\} is a fundamental subfamily of \mathcal{B}.{{sfn|Schaefer|Wolff|1999|pp=215–222}}

C-saturated sets play an important role in the theory of ordered topological vector spaces and topological vector lattices.

Properties

If X is an ordered vector space with positive cone C then [S]_C = \bigcup \left\{ [x, y] : x, y \in S \right\}.{{sfn|Schaefer|Wolff|1999|pp=215–222}}

The map S \mapsto [S]_C is increasing; that is, if R \subseteq S then [R]_C \subseteq [S]_C.

If S is convex then so is [S]_C. When X is considered as a vector field over \R, then if S is balanced then so is [S]_C.{{sfn|Schaefer|Wolff|1999|pp=215–222}}

If \mathcal{F} is a filter base (resp. a filter) in X then the same is true of \left[ \mathcal{F} \right]_C := \left\{ [ F ]_C : F \in \mathcal{F} \right\}.

See also

  • {{annotated link|Banach lattice}}
  • {{annotated link|Fréchet lattice}}
  • {{annotated link|Locally convex vector lattice}}
  • {{annotated link|Vector lattice}}

References

{{reflist}}

Bibliography

  • {{Narici Beckenstein Topological Vector Spaces|edition=2}}
  • {{Schaefer Wolff Topological Vector Spaces|edition=2}}

{{Functional analysis}}

{{Ordered topological vector spaces}}

Category:Functional analysis