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G δ ‐pieces of canonical partitions of G ‐spaces
Author(s) -
MajcherIwanow Barbara
Publication year - 2005
Publication title -
mathematical logic quarterly
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.473
H-Index - 28
eISSN - 1521-3870
pISSN - 0942-5616
DOI - 10.1002/malq.200410041
Subject(s) - mathematics , orbit (dynamics) , set (abstract data type) , pure mathematics , algebra over a field , computer science , engineering , programming language , aerospace engineering
Abstract Generalizing model companions from model theory we define companions of pieces of canonical partitions of Polish G ‐spaces. This unifies several constructions from logic. The central problem of the paper is the existence of companions which form a G ‐orbit which is a G δ ‐set. We describe companions of some typical G ‐spaces. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)