Israel Journal of Mathematics

, Volume 111, Issue 1, pp 221–261 | Cite as

Orbit cardinals: On the effective cardinalities arising as quotient spaces of the formX/G whereG acts on a Polish spaceX



We prove an Ulm-type classification theorem for actions inL(ℝ), thereby answering a question of Becker and Kechris, and investigate the effective cardinalities which can be induced by various classes of Polish groups.


Equivalence Relation Polish Group Polish Space Generic Extension Force Notion 
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Copyright information

©  0 1999

Authors and Affiliations

  1. 1.Department of MathematicsUniversity of CaliforniaLos AngelesUSA

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