Band (order theory)
{{Multiple issues|{{one source|date=June 2020}}{{inline|date=September 2020}}{{technical|date=June 2020}}}}
{{Distinguish|Band (algebra)}}
In mathematics, specifically in order theory and functional analysis, a band in a vector lattice is a subspace of that is solid and such that for all such that exists in we have {{sfn|Narici|Beckenstein|2011|pp=204–214}}
The smallest band containing a subset of is called the band generated by in {{sfn|Narici|Beckenstein|2011|pp=204–214}}
A band generated by a singleton set is called a principal band.
Examples
For any subset of a vector lattice the set of all elements of disjoint from is a band in {{sfn|Narici|Beckenstein|2011|pp=204–214}}
If () is the usual space of real valued functions used to define Lp spaces then is countably order complete (that is, each subset that is bounded above has a supremum) but in general is not order complete.
If is the vector subspace of all -null functions then is a solid subset of that is {{em|not}} a band.{{sfn|Narici|Beckenstein|2011|pp=204–214}}
Properties
The intersection of an arbitrary family of bands in a vector lattice is a band in {{sfn | Schaefer |Wolff| 1999 | pp=204–214}}
See also
- {{annotated link|Solid set}}
- {{annotated link|Locally convex vector lattice}}
- {{annotated link|Vector lattice}}
References
{{reflist|group=note}}
{{reflist}}
- {{Narici Beckenstein Topological Vector Spaces|edition=2}}
- {{Schaefer Wolff Topological Vector Spaces|edition=2}}
{{Ordered topological vector spaces}}
{{Functional analysis}}