Functions continuous in the fine topology for the heat equation
Functions Equivalent to Borel Measurable Ones
Let X and Y be two Polish spaces. Functions f,g: X → Y are called equivalent if there exists a bijection φ from X onto itself such that g∘φ = f. Using a theorem of J. Saint Raymond we characterize functions equivalent to Borel measurable ones. This characterization answers a question asked by M. Morayne and C. Ryll-Nardzewski.
Functions of Baire class one
Let K be a compact metric space. A real-valued function on K is said to be of Baire class one (Baire-1) if it is the pointwise limit of a sequence of continuous functions. We study two well known ordinal indices of Baire-1 functions, the oscillation index β and the convergence index γ. It is shown that these two indices are fully compatible in the following sense: a Baire-1 function f satisfies for some countable ordinals ξ₁ and ξ₂ if and only if there exists a sequence (fₙ) of Baire-1 functions...
Functions that map cozerosets to cozerosets
A function mapping the topological space to the space is called a z-open function if for every cozeroset neighborhood of a zeroset in , the image is a neighborhood of in . We say has the z-separation property if whenever , are cozerosets and is a zeroset of such that , there is a zeroset of such that . A surjective function is z-open if and only if it maps cozerosets to cozerosets and has the z-separation property. We investigate z-open functions and other functions...
Functions with continuous Wallman extensions
Functions with preclosed graphs.
Functor of extension in Hilbert cube and Hilbert space
It is shown that if Ω = Q or Ω = ℓ 2, then there exists a functor of extension of maps between Z-sets in Ω to mappings of Ω into itself. This functor transforms homeomorphisms into homeomorphisms, thus giving a functorial setting to a well-known theorem of Anderson [Anderson R.D., On topological infinite deficiency, Michigan Math. J., 1967, 14, 365–383]. It also preserves convergence of sequences of mappings, both pointwise and uniform on compact sets, and supremum distances as well as uniform continuity,...
Functor of extension of -isometric maps between central subsets of the unbounded Urysohn universal space
The aim of the paper is to prove that in the unbounded Urysohn universal space there is a functor of extension of -isometric maps (i.e. dilations) between central subsets of to -isometric maps acting on the whole space. Special properties of the functor are established. It is also shown that the multiplicative group acts continuously on by -isometries.
Fundamental groups of one-dimensional spaces
Let X be a metrizable one-dimensional continuum. We describe the fundamental group of X as a subgroup of its Čech homotopy group. In particular, the elements of the Čech homotopy group are represented by sequences of words. Among these sequences the elements of the fundamental group are characterized by a simple stabilization condition. This description of the fundamental group is used to give a new algebro-combinatorial proof of a result due to Eda on continuity properties of homomorphisms from...
Funzioni -convesse
We study a class of functions which differ essentially from those which are the sum of a convex function and a regular one and which have interesting properties related to -convergence and to problems with non-convex constraints. In particular some results are given for the associated evolution equations.
Funzioni reali continue e semicontinue
Furi–Pera fixed point theorems in Banach algebras with applications
In this work, we establish new Furi–Pera type fixed point theorems for the sum and the product of abstract nonlinear operators in Banach algebras; one of the operators is completely continuous and the other one is -Lipchitzian. The Kuratowski measure of noncompactness is used together with recent fixed point principles. Applications to solving nonlinear functional integral equations are given. Our results complement and improve recent ones in [10], [11], [17].
Furstenberg families and sensitivity.
Furstenberg’s theorem in topological dynamics
Further characterizations of boundedly UC spaces
Following the paper [BDC1], further relations between the classical topologies on function spaces and new ones induced by hyperspace topologies on graphs of functions are introduced and further characterizations of boundedly spaces are given.
Further new generalized topologies via mixed constructions due to Császár
The theory of generalized topologies was introduced by Á. Császár (2002). In the literature, some authors have introduced and studied generalized topologies and some generalized topologies via generalized topological spaces due to Á. Császár. Also, the notions of mixed constructions based on two generalized topologies were introduced and investigated by Á. Császár (2009). The main aim of this paper is to introduce and study further new generalized topologies called via mixed constructions based...
Further note on Fréchet spaces
Further properties of 1-sequence-covering maps
Some relationships between -sequence-covering maps and weak-open maps or sequence-covering -maps are discussed. These results are used to generalize a result from Lin S., Yan P., Sequence-covering maps of metric spaces, Topology Appl. 109 (2001), 301–314.
Further properties of an extremal set of uniqueness
Further Relationships between Decomposition Theories and Topologies