Baire category from an abstract viewpoint
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 functions and classes bounded by filters
Baire sets and uniformities on complete metric spaces
Banach spaces of bounded Szlenk index
For a countable ordinal α we denote by the class of separable, reflexive Banach spaces whose Szlenk index and the Szlenk index of their dual are bounded by α. We show that each admits a separable, reflexive universal space. We also show that spaces in the class embed into spaces of the same class with a basis. As a consequence we deduce that each is analytic in the Effros-Borel structure of subspaces of C[0,1].
Banach spaces of bounded Szlenk index II
For every α < ω₁ we establish the existence of a separable Banach space whose Szlenk index is and which is universal for all separable Banach spaces whose Szlenk index does not exceed . In order to prove that result we provide an intrinsic characterization of which Banach spaces embed into a space admitting an FDD with Tsirelson type upper estimates.
Banach Spaces Over Topological Semifields and Common Fixed Points
Banach's Mappings And Some Generalizations
Base-base paracompactness and subsets of the Sorgenfrey line
A topological space is called base-base paracompact (John E. Porter) if it has an open base such that every base has a locally finite subcover . It is not known if every paracompact space is base-base paracompact. We study subspaces of the Sorgenfrey line (e.g. the irrationals, a Bernstein set) as a possible counterexample.
Beiträge zur Fixpunkttheorie nichtexpandierender Operatoren.
Bernstein sets with algebraic properties
We construct Bernstein sets in ℝ having some additional algebraic properties. In particular, solving a problem of Kraszewski, Rałowski, Szczepaniak and Żeberski, we construct a Bernstein set which is a < c-covering and improve some other results of Rałowski, Szczepaniak and Żeberski on nonmeasurable sets.
Best approximation and fixed points in strong -starshaped metric spaces.
Best approximation for nonconvex set in -normed space
Some existence results on best approximation are proved without starshaped subset and affine mapping in the set up of -normed space. First, we consider the closed subset and then weakly compact subsets for said purpose. Our results improve the result of Mukherjee and Som (Mukherjee, R. N., Som, T., A note on an application of a fixed point theorem in approximation theory, Indian J. Pure Appl. Math. 16(3) (1985), 243–244.) and Jungck and Sessa (Jungck, G., Sessa, S., Fixed point theorems in best...
Best approximation of coincidence points in metric trees
In this work we present results on fixed points, pairs of coincidence points and best approximation for ε-semicontinuous mappings in metric trees. It is a generalization of the similar properties of upper and almost lower semicontinuous mappings.
Best approximations theorem for a couple in cone Banach space.
Best proximity pairs theorems for continuous set-valued maps.
Best proximity point theorems for -cyclic Meir–Keeler contractions.
Best proximity points of cyclic -contractions on reflexive Banach spaces.
Best simultaneous approximations
In this paper we study simultaneous approximation of real-valued functions in and give a generalization of some related results.
Betti numbers of regions of attraction