On effective σ-boundedness and σ-compactness

نویسندگان

  • Vladimir Kanovei
  • Vassily A. Lyubetsky
چکیده

We prove several dichotomy theorems which extend some known results on σ -bounded and σ -compactpointsets. In particular we show that, given a finite number of Δ1 equivalence relations F1 , . . . , Fn , any Σ1 set A of the Baire space either is covered by compact Δ1 sets and lightface Δ1 equivalence classes of the relations Fi , or A contains a superperfect subset which is pairwise Fi -inequivalent for all i = 1, . . . , n . Further generalizations to Σ2 sets A are obtained.

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عنوان ژورنال:
  • Math. Log. Q.

دوره 59  شماره 

صفحات  -

تاریخ انتشار 2013