Exhaustion by compact sets
In mathematics, especially general topology and analysis, an exhaustion by compact sets of a topological space X {\displaystyle X} is a nested sequence of compact subsets K i {\displaystyle K_{i}} of X {\displaystyle X} (i.e. K 1 ⊆ K 2 ⊆ K 3 ⊆ ⋯ {\displaystyle K_{1}\subseteq K_{2}\subseteq K_{3}\subseteq \cdots } ), such that each K i {\displaystyle K_{i}} is contained in the interior of K i + 1 {\displaystyle K_{i+1}} , i.e.
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