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Ideal Banach category theorems and functions

Zbigniew Piotrowski (1997)

Mathematica Bohemica

Based on some earlier findings on Banach Category Theorem for some “nice” σ -ideals by J. Kaniewski, D. Rose and myself I introduce the h operator ( h stands for “heavy points”) to refine and generalize kernel constructions of A. H. Stone. Having obtained in this way a generalized Kuratowski’s decomposition theorem I prove some characterizations of the domains of functions having “many” points of h -continuity. Results of this type lead, in the case of the σ -ideal of meager sets, to important statements...

Invariant Borel liftings for category algebras of Baire groups

Maxim R. Burke (2007)

Fundamenta Mathematicae

R. A. Johnson showed that there is no translation-invariant Borel lifting for the measure algebra of ℝ/ℤ equipped with Haar measure, a result which was generalized by M. Talagrand to non-discrete locally compact abelian groups and by J. Kupka and K. Prikry to arbitrary non-discrete locally compact groups. In this paper we study analogs of these results for category algebras (the Borel σ-algebra modulo the ideal of first category sets) of topological groups. Our main results are for the class of...

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