Autohomeomorphism groups of spaces with unique non-isolated point
Automata, Borel functions and real numbers in Pisot base
This note is about functions ƒ : Aω → Bω whose graph is recognized by a Büchi finite automaton on the product alphabet A x B. These functions are Baire class 2 in the Baire hierarchy of Borel functions and it is decidable whether such function are continuous or not. In 1920 W. Sierpinski showed that a function is Baire class 1 if and only if both the overgraph and the undergraph of f are Fσ. We show that such characterization is also true for functions on infinite words if we replace the real...
Automorphism groups of complements of points
Automorphism invariants for semigroups.
Automorphisms and subsystems of the shift.
Averages of quasi-continuous functions
The goal of this paper is to characterize the family of averages of comparable (Darboux) quasi-continuous functions.
Axiom systems for Lipschitz structures
Axiom and the Simmons sublocale theorem
More precisely, we are analyzing some of H. Simmons, S. B. Niefield and K. I. Rosenthal results concerning sublocales induced by subspaces. H. Simmons was concerned with the question when the coframe of sublocales is Boolean; he recognized the role of the axiom for the relation of certain degrees of scatteredness but did not emphasize its role in the relation between sublocales and subspaces. S. B. Niefield and K. I. Rosenthal just mention this axiom in a remark about Simmons’ result. In this...
Axioms weaker then
on spaces of homogeneous type: a density result on - spaces.
Bad Wadge-like reducibilities on the Baire space
We consider various collections of functions from the Baire space into itself naturally arising in (effective) descriptive set theory and general topology, including computable (equivalently, recursive) functions, contraction mappings, and functions which are nonexpansive or Lipschitz with respect to suitable complete ultrametrics on (compatible with its standard topology). We analyze the degree-structures induced by such sets of functions when used as reducibility notions between subsets of...
Baire category from an abstract viewpoint
Baire category in spaces of probability measures
Baire category in spaces of probability measures, II
Baire category results for quasi–copulas
The aim of this manuscript is to determine the relative size of several functions (copulas, quasi– copulas) that are commonly used in stochastic modeling. It is shown that the class of all quasi–copulas that are (locally) associated to a doubly stochastic signed measure is a set of first category in the class of all quasi– copulas. Moreover, it is proved that copulas are nowhere dense in the class of quasi-copulas. The results are obtained via a checkerboard approximation of quasi–copulas.
Baire class of completely additive systems of Baire sets
Baire classes of affine vector-valued functions
We investigate Baire classes of strongly affine mappings with values in Fréchet spaces. We show, in particular, that the validity of the vector-valued Mokobodzki result on affine functions of the first Baire class is related to the approximation property of the range space. We further extend several results known for scalar functions on Choquet simplices or on dual balls of L₁-preduals to the vector-valued case. This concerns, in particular, affine classes of strongly affine Baire mappings, the...
Baire classification and infinite perceptrons
Baire functions and classes bounded by filters
Baire outer kernels of sets.