Results 1 
3 of
3
Trichotomies for ideals of compact sets
 J. SYMBOLIC LOGIC
"... We prove several trichotomy results for ideals of compact sets. Typically, we show that a “sufficiently rich” universally Baire ideal is either Π 0 3hard, or Σ 0 3hard, or else a σideal. ..."
Abstract

Cited by 5 (3 self)
 Add to MetaCart
(Show Context)
We prove several trichotomy results for ideals of compact sets. Typically, we show that a “sufficiently rich” universally Baire ideal is either Π 0 3hard, or Σ 0 3hard, or else a σideal.
Classical and Effective Descriptive Complexities of ωPowers
, 2009
"... Université de Picardie, I.U.T. de l’Oise, site de Creil, ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
(Show Context)
Université de Picardie, I.U.T. de l’Oise, site de Creil,
SUCH THAT X × X IS A GROUP
"... Abstract. We provide an example of a zerodimensional (separable metric) absolute Borel set X which is not homogeneous, but whose square X × X admits the structure of a topological group. We also construct a zerodimensional absolute Borel set Y such that Y is a homogeneous nongroup but Y × Y is a ..."
Abstract
 Add to MetaCart
(Show Context)
Abstract. We provide an example of a zerodimensional (separable metric) absolute Borel set X which is not homogeneous, but whose square X × X admits the structure of a topological group. We also construct a zerodimensional absolute Borel set Y such that Y is a homogeneous nongroup but Y × Y is a group. This answers questions of Arhangel’skiĭandZhou. 1.