In mathematics, especially functional analysis, a bornology B {\displaystyle {\mathcal {B}}} on a vector space X {\displaystyle X} over a field K , {\displaystyle \mathbb {K} ,} where K {\displaystyle \mathbb {K} } has a bornology ℬ K {\displaystyle \mathbb {K} } , is called a vector bornology if B {\displaystyle {\mathcal {B}}} makes the vector space operations into bounded maps.
Definitions
Prerequisites
A bornology on a set X {\displaystyle X} is a collection B {\displaystyle {\mathcal {B}}} of subsets of X {\displaystyle X} that satisfy all the following conditions:
B {\displaystyle {\mathcal {B}}} covers X ; {\displaystyle X;} that is, X = ∪ B {\displaystyle X=\cup {\mathcal {B}}}
B {\displaystyle {\mathcal {B}}} is stable under inclusions; that is, if B ∈ B {\displaystyle B\in {\mathcal {B}}} and A ⊆ B , {\displaystyle A\subseteq B,} then A ∈ B {\displaystyle A\in {\mathcal {B}}}
B {\displaystyle {\mathcal {B}}} is stable under finite unions; that is, if B 1 , … , B n ∈ B {\displaystyle B_{1},\ldots ,B_{n}\in {\mathcal {B}}} then B 1 ∪ ⋯ ∪ B n ∈ B {\displaystyle B_{1}\cup \cdots \cup B_{n}\in {\mathcal {B}}}
Elements of the collection B {\displaystyle {\mathcal {B}}} are called B {\displaystyle {\mathcal {B}}} -bounded or simply bounded sets if B {\displaystyle {\mathcal {B}}} is understood. The pair ( X , B ) {\displaystyle (X,{\mathcal {B}})} is called a bounded structure or a bornological set. A base or fundamental system of a bornology B {\displaystyle {\mathcal {B}}} is a subset B 0 {\displaystyle {\mathcal {B}}_{0}} of B {\displaystyle {\mathcal {B}}} such that each element of B {\displaystyle {\mathcal {B}}} is a subset of some element of B 0 . {\displaystyle {\mathcal {B}}_{0}.} Given a collection S {\displaystyle {\mathcal {S}}} of subsets of X , {\displaystyle X,} the smallest bornology containing S {\displaystyle {\mathcal {S}}} is called the bornology generated by S . {\displaystyle {\mathcal {S}}.}
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