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projective hierarchy

См. также в других словарях:

  • Projective hierarchy — In the mathematical field of descriptive set theory, a subset A of a Polish space X is projective if it is oldsymbol{Sigma}^1 n for some positive integer n. Here A is * oldsymbol{Sigma}^1 1 if A is analytic * oldsymbol{Pi}^1 n if the… …   Wikipedia

  • Projective geometry — is a non metrical form of geometry, notable for its principle of duality. Projective geometry grew out of the principles of perspective art established during the Renaissance period, and was first systematically developed by Desargues in the 17th …   Wikipedia

  • Analytical hierarchy — In mathematical logic and descriptive set theory, the analytical hierarchy is a higher type analogue of the arithmetical hierarchy. It thus continues the classification of sets by the formulas that define them. The analytical hierarchy of… …   Wikipedia

  • Difference hierarchy — In set theory, the difference hierarchy over a pointclass is a hierarchy of larger pointclasses generated by taking differences of sets. If Γ is a pointclass, then the set of differences in Γ is . In usual notation, this set is denoted by 2 Γ.… …   Wikipedia

  • Descriptive set theory — In mathematical logic, descriptive set theory is the study of certain classes of well behaved subsets of the real line and other Polish spaces. As well as being one of the primary areas of research in set theory, it has applications to other… …   Wikipedia

  • Determinacy — Determined redirects here. For the 2005 heavy metal song, see Determined (song). For other uses, see Indeterminacy (disambiguation). In set theory, a branch of mathematics, determinacy is the study of under what circumstances one or the other… …   Wikipedia

  • Pointclass — In the mathematical field of descriptive set theory, a pointclass is a collection of sets of points, where a point is ordinarily understood to be an element of some perfect Polish space. In practice, a pointclass is usually characterized by some… …   Wikipedia

  • List of mathematics articles (P) — NOTOC P P = NP problem P adic analysis P adic number P adic order P compact group P group P² irreducible P Laplacian P matrix P rep P value P vector P y method Pacific Journal of Mathematics Package merge algorithm Packed storage matrix Packing… …   Wikipedia

  • Analytic set — This article is about analytic sets as defined in descriptive set theory. There is another notion in the context of analytic varieties. In descriptive set theory, a subset of a Polish space X is an analytic set if it is a continuous image of a… …   Wikipedia

  • Set theory — This article is about the branch of mathematics. For musical set theory, see Set theory (music). A Venn diagram illustrating the intersection of two sets. Set theory is the branch of mathematics that studies sets, which are collections of objects …   Wikipedia

  • Арифметическое множество — В теории множеств и математической логике, множество натуральных чисел называется арифметическим, если оно может быть определено формулой в языке арифметики первого порядка, то есть если существует такая формула с одной свободной переменной что… …   Википедия

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