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13 results on '"Majcher-Iwanow, Barbara"'

1. Polish G-spaces and continuous logic

Author

Ivanov, Aleksander and Majcher-Iwanow, Barbara

Subjects
Mathematics - Logic, 03E15, 03C07, 03C57
Abstract

We analyse logic actions of Polish groups which arise in continuous logic. We extend the generalised model theory of H.Becker to the case of Polish G-spaces when G is an arbitrary Polish group., Comment: 54 pages, Section 3 is corrected

Published
2013

2. Polish group actions and effectivity

Author

Majcher-Iwanow, Barbara

Subjects
Mathematics - Logic, 03E15, 03C70
Abstract

We extend the result of Nadel describing the relationship between approximations of canonical Scott sentences and admissible sets to the general case of orbit equivalence relations induced on an arbitrary Polish space by a Polish group action., Comment: 10 pages

Published
2011

3. Local operations and eventually open actions

Author

Majcher-Iwanow, Barbara

Subjects
Mathematics - Logic, 03E15
Abstract

We study continuous actions of Polish groups on Polish spaces. We develop Scott analysis introduced by Hjorth for studying orbit equivalence relations. We define eventually open actions and prove that this property characterizes the actions endowed with a complete system of hereditarily countable invariant structures., Comment: 24 pages

Published
2010

4. Polish group actions and computability

Author

Ivanov, Aleksander and Majcher-Iwanow, Barbara

Subjects
Mathematics - Logic, 03E15, 03D45
Abstract

Let G be a closed subgroup of the group of all permutations of a countably infinite set. Let X be a Polish G-space with a countable basis A of clopen sets. Each x from X defines a characteristic function f on A by f(U)=1 iff x belongs to U (where U is from A). We consider computable complexity of f and some related questions., Comment: AMS LaTeX file, Section 2.2 is corrected, there are some minor changes in other places

Published
2009

9. Subgroups of $$SF(\omega )$$ and the relation of almost containedness.

Author

Majcher-Iwanow, Barbara

Subjects
PERMUTATIONS, LATTICE theory, CARDINAL numbers, RAMSEY numbers, ORTHOGONALIZATION
Abstract

The relations of almost containedness and orthogonality in the lattice of groups of finitary permutations are studied in the paper. We define six cardinal numbers naturally corresponding to these relations by the standard scheme of $$P(\omega )$$ . We obtain some consistency results concerning these numbers and some versions of the Ramsey theorem. [ABSTRACT FROM AUTHOR]

Published
2016
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13. Gδ-pieces of canonical partitions of G-spaces.

Author

Majcher-Iwanow, Barbara

Subjects
*G-spaces, *METRIC spaces, *SET theory, *GENERALIZED spaces, *DIFFERENTIAL geometry, *MATHEMATICS
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 Gδ-set. We describe companions of some typical G-spaces. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Published
2005
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