Archive for Mathematical Logic

, Volume 54, Issue 5–6, pp 659–683 | Cite as

A Wadge hierarchy for second countable spaces

  • Yann Pequignot


We define a notion of reducibility for subsets of a second countable T 0 topological space based on relatively continuous relations and admissible representations. This notion of reducibility induces a hierarchy that refines the Baire classes and the Hausdorff–Kuratowski classes of differences. It coincides with Wadge reducibility on zero dimensional spaces. However in virtually every second countable T 0 space, it yields a hierarchy on Borel sets, namely it is well founded and antichains are of length at most 2. It thus differs from the Wadge reducibility in many important cases, for example on the real line \({\mathbb{R}}\) or the Scott Domain \({\mathcal{P}\omega}\) .


Wadge reducibility Wadge hierarchy Relatively continuous relation Admissible representation 

Mathematics Subject Classification

03E15 03D55 03F60 


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© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Institut des systèmes d’informationUniversité de LausanneLausanneSwitzerland
  2. 2.LIAFAUniversité Paris Diderot - Paris 7ParisFrance

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