factor groupoid
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Equivalence relation — In mathematics, an equivalence relation is a binary relation between two elements of a set which groups them together as being equivalent in some way. Let a , b , and c be arbitrary elements of some set X . Then a b or a ≡ b denotes that a is… … Wikipedia
Group action — This article is about the mathematical concept. For the sociology term, see group action (sociology). Given an equilateral triangle, the counterclockwise rotation by 120° around the center of the triangle acts on the set of vertices of the… … Wikipedia
Von Neumann algebra — In mathematics, a von Neumann algebra or W* algebra is a * algebra of bounded operators on a Hilbert space that is closed in the weak operator topology and contains the identity operator. They were originally introduced by John von Neumann,… … Wikipedia
Group (mathematics) — This article covers basic notions. For advanced topics, see Group theory. The possible manipulations of this Rubik s Cube form a group. In mathematics, a group is an algebraic structure consisting of a set together with an operation that combines … Wikipedia
Inverse semigroup — In mathematics, an inverse semigroup S is a semigroup in which every element x in S has a unique inverse y in S in the sense that x = xyx and y = yxy. Inverse semigroups appear in a range of contexts; for example, they can be employed in the… … Wikipedia
Semigroup — This article is about the algebraic structure. For applications to differential equations, see C0 semigroup. In mathematics, a semigroup is an algebraic structure consisting of a set together with an associative binary operation. A semigroup… … Wikipedia
Group theory — is a mathematical discipline, the part of abstract algebra that studies the algebraic structures known as groups. The development of group theory sprang from three main sources: number theory, theory of algebraic equations, and geometry. The… … Wikipedia
Ring (mathematics) — This article is about algebraic structures. For geometric rings, see Annulus (mathematics). For the set theory concept, see Ring of sets. Polynomials, represented here by curves, form a ring under addition and multiplication. In mathematics, a… … Wikipedia
Alain Connes — in 2004 Born 1 April 1947 (1947 04 01 … Wikipedia
George Mackey — George Whitelaw Mackey (February 1, 1916 in St. Louis, Missouri – March 15, 2006 in Belmont, Massachusetts) was an American mathematician. Mackey obtained his Ph.D. at Harvard University in 1942 under the direction of Marshall H. Stone. He joined … Wikipedia
