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# Borel set

Any of the members of a Borel σ-algebra.

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• Borel set — In mathematics, a Borel set is any set in a topological space that can be formed from open sets (or, equivalently, from closed sets) through the operations of countable union, countable intersection, and relative complement. Borel sets are named… …   Wikipedia

• Non-Borel set — In mathematics, a non Borel set is a set that cannot be obtained from simple sets by taking complements and at most countable unions and intersections. (For the definition see Borel set.) Only sets of real numbers are considered in this article.… …   Wikipedia

• Infinity-Borel set — In set theory, a subset of a Polish space X is infin; Borel if itcan be obtained by starting with the open subsets of X, and transfinitely iterating the operations of complementation and wellordered union (but see the caveat below). Formal… …   Wikipedia

• Borel hierarchy — In mathematical logic, the Borel hierarchy is a stratification of the Borel algebra generated by the open subsets of a Polish space; elements of this algebra are called Borel sets. Each Borel set is assigned a unique countable ordinal number… …   Wikipedia

• Borel determinacy theorem — In descriptive set theory, the Borel determinacy theorem shows that any Gale Stewart game whose winning set is a Borel set is determined, meaning that one of the two players will have a winning strategy for the game. It was proved by Donald A.… …   Wikipedia

• Borel algebra — In mathematics, the Borel algebra (or Borel sigma; algebra) on a topological space X is a sigma; algebra of subsets of X associated with the topology of X . In the mathematics literature, there are at least two nonequivalent definitions of this… …   Wikipedia

• Borel measure — In mathematics, the Borel algebra is the smallest sigma; algebra on the real numbers R containing the intervals, and the Borel measure is the measure on this sigma; algebra which gives to the interval [ a , b ] the measure b − a (where a < b… …   Wikipedia

• Borel regular measure — In mathematics, an outer measure mu; on n dimensional Euclidean space R n is called Borel regular if the following two conditions hold:* Every Borel set B sube; R n is mu; measurable in the sense of Carathéodory s criterion: for every A sube; R n …   Wikipedia

• Borel measurable — adjective Said of a function: that the inverse image of any open set in its codomain is a Borel set of its domain. See Also: Borel function …   Wiktionary

• Borel subgroup — In the theory of algebraic groups, a Borel subgroup of an algebraic group G is a maximal Zariski closed and connected solvable algebraic subgroup. For example, in the group GLn (n x n invertible matrices), the subgroup of invertible upper… …   Wikipedia