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 sort of definability property; for example, the collection of all open sets in some fixed collection of Polish spaces is a pointclass. (An open set may be seen as in some sense definable because it cannot be a purely arbitrary collection of points; for any point in the set, all points sufficiently close to that point must also be in the set.)
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Adequate pointclassAnalytical hierarchyArithmetical hierarchyBoldface (disambiguation)Boldface (mathematics)Boldface hierarchyBoldface pointclassDescriptive set theoryDeterminacyDifference hierarchyEffective descriptive set theoryGlossary of areas of mathematicsGlossary of set theoryInductive setLightfaceLightface hierarchyLightface pointclassMoschovakis coding lemmaPoint classPointclassesPrewellorderingScale (descriptive set theory)Set theoryUniformization (set theory)Wadge hierarchyYiannis N. MoschovakisΠ01 classΩ-logic
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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 sort of definability property; for example, the collection of all open sets in some fixed collection of Polish spaces is a pointclass. (An open set may be seen as in some sense definable because it cannot be a purely arbitrary collection of points; for any point in the set, all points sufficiently close to that point must also be in the set.)
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In the mathematical field of d ...... and the perfect set property.
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In the mathematical field of d ...... oint must also be in the set.)
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Pointclass
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