scholarly journals Pointwise measurable functions

2004 ◽  
Vol 95 (2) ◽  
pp. 305
Author(s):  
Herman Render ◽  
Lothar Rogge
Keyword(s):  
Large Class ◽  
Metric Space ◽  
Measurable Function ◽  
Polish Space ◽  
Topological Spaces ◽  
Range Space ◽  
Compact Metric Space ◽  
Delta Set ◽  
Measurable Functions ◽  
Borel Measurable

We introduce the new concept of pointwise measurability. It is shown in this paper that a measurable function is measurable at each point and that for a large class of topological spaces the converse also holds. Moreover it can be seen that a function which is continuous at a point is Borel-measurable at this point too. Furthermore the set of measurability points is considered. If the range space is a $\sigma$-compact metric space, then this set is a $G_{\delta}$-set; if the range space is only a Polish space this is in general not true any longer.

Additive Functionals on Lp Spaces

1966 ◽  
Vol 18 ◽  
pp. 1264-1271 ◽  
Author(s):  
N. Friedman ◽  
M. Katz
Keyword(s):  
Metric Space ◽  
Representation Theorem ◽  
Compact Metric Space ◽  
Lp Spaces ◽  
Additive Functionals ◽  
Measurable Functions ◽  
Present Purpose

In (1) a representation theorem was proved for a class of additive functionals defined on the continuous real-valued functions with domain S = [0, 1]. The theorem was extended to the case where S is an arbitrary compact metric space in (3). Our present purpose is to consider the corresponding class of additive functionals defined on Lp spaces, p > 0. In (4) Martin and Mizel have considered functionals defined on the class of bounded measurable functions which, however, satisfy a certain “stochastic” condition which we do not require.

Federer-Čech Couples

1969 ◽  
Vol 21 ◽  
pp. 842-864
Author(s):  
Micheal Dyer
Keyword(s):  
Simplicial Complex ◽  
Large Class ◽  
Metric Space ◽  
Topological Spaces ◽  
Compact Open Topology ◽  
Finite Dimensional ◽  
Cw Complexes

In (5),I considered two-term conditions in π-exact couples, of which the exact couple of Federer (7) is an example. Let M(X, Y)be the space of all maps from X to Y with the compact-open topology. Our aim in this paper is to construct a π-exact couple , where Xis a finite-dimensional (in the sense of Lebesgue) metric space and , a certain (rather large) class of spaces. Specifically, is the class of all topological spaces Xwhich possess the following property (P).(P) Let Y be a (possibly infinite) simplicial complex. There exists x0 ∈ X and y0 ∊ Y such that [X, x0]≃ [Y, y0].In § 5 it will be seen that contains all CW complexes and all metric absolute neighbourhood retracts (ANR)s.

Measurable distal and topological distal systems

1999 ◽  
Vol 19 (4) ◽  
pp. 1063-1076 ◽  
Author(s):  
ELON LINDENSTRAUSS
Keyword(s):  
Continuous Function ◽  
Compact Group ◽  
Metric Space ◽  
Measurable Function ◽  
Borel Measure ◽  
Base Space ◽  
Compact Metric Space ◽  
Full Support

In this paper we prove that any ergodic measurably distal system can be realized as a minimal topologically distal system with an invariant Borel measure of full support. The proof depends upon a theorem stating that every measurable function from a measurable system with its base space being a compact metric space to a connected compact group is cohomologous to a continuous function.

scholarly journals Fixed points for pairs of mappings indcomplete topological spaces

1993 ◽  
Vol 16 (2) ◽  
pp. 259-266 ◽  
Author(s):  
Troy L. Hicks ◽  
B. E. Rhoades
Keyword(s):  
Fixed Point ◽  
Fixed Points ◽  
Large Class ◽  
Distance Function ◽  
Metric Space ◽  
Fixed Point Theorems ◽  
Metric Spaces ◽  
Topological Spaces ◽  
Triangular Inequality

Several important metric space fixed point theorems are proved for a large class of non-metric spaces. In some cases the metric space proofs need only minor changes. This is surprising since the distance function used need not be symmetric and need not satisfy the triangular inequality.

scholarly journals On the uniform exponential stability of linear skew-product semiflows

2006 ◽  
Vol 4 (2) ◽  
pp. 145-161
Author(s):  
Ciprian Preda
Keyword(s):  
Exponential Stability ◽  
Large Class ◽  
Metric Space ◽  
Orlicz Spaces ◽  
Skew Product ◽  
Test Functions ◽  
Type Condition ◽  
Locally Compact ◽  
Compact Metric Space ◽  
Uniform Exponential Stability

The problem of uniform exponential stability of linear skew-product semiflows on locally compact metric space with Banach fibers, is discussed. It is established a connection between the uniform exponential stability of linear skewproduct semiflows and some admissibility-type condition. This approach is based on the method of “test functions”, using a very large class of function spaces, the so-called Orlicz spaces.

On stability of solutions of integral equations in the class of measurable functions

2021 ◽  
pp. 44-54
Author(s):  
Wassim Merchela
Keyword(s):  
Integral Equation ◽  
Uniform Convergence ◽  
Metric Space ◽  
Measurable Function ◽  
Sufficient Conditions ◽  
Stability Of Solutions ◽  
Lebesgue Measurable Function ◽  
Lipschitz Property ◽  
Measurable Functions ◽  
The Stability

Consider the equation G(x)=(y,) ̃ where the mapping G acts from a metric space X into a space Y, on which a distance is defined, y ̃ ∈ Y. The metric in X and the distance in Y can take on the value ∞, the distance satisfies only one property of a metric: the distance between y,z ∈Y is zero if and only if y= z. For mappings X → Y the notions of sets of covering, Lipschitz property, and closedness are defined. In these terms, the assertion is obtained about the stability in the metric space X of solutions of the considered equation to changes of the mapping G and the element y ̃. This assertion is applied to the study of the integral equation f(t,∫_0^1▒K (t,s)x(s)ds,x(t))= y ̃(t),t ∈[0,1], with respect to an unknown Lebesgue measurable function x: [0,1] ∈R. Sufficient conditions are obtained for the stability of solutions (in the space of measurable functions with the topology of uniform convergence) to changes of the functions f,K,(y.) ̃

scholarly journals Onp-Convergence in Measure of a Sequence of Measurable Functions

2011 ◽  
Vol 2011 ◽  
pp. 1-7
Author(s):  
A. Boccuto ◽  
Ch. Papachristodoulos ◽  
N. Papanastassiou
Keyword(s):  
Equivalence Relation ◽  
Metric Space ◽  
Quotient Space ◽  
Compact Metric Space ◽  
Convergence In Measure ◽  
Measurable Functions ◽  
Natural Way

In the study by Papanastassiou and Papachristodoulos, 2009 the notion ofp-convergence in measure was introduced. In a natural wayp-convergence in measure induces an equivalence relation on the spaceMof all sequences of measurable functions converging in measure to zero. We show that the quotient spaceℳis a complete but not compact metric space.

Weakly Confluent Mappings and Atriodic Suslinian Curves

1978 ◽  
Vol 30 (01) ◽  
pp. 32-44 ◽  
Author(s):  
H. Cook ◽  
A. Lelek
Keyword(s):  
Continuous Function ◽  
Branch Point ◽  
Metric Space ◽  
Related Result ◽  
Cantor Set ◽  
Topological Spaces ◽  
Compact Metric Space ◽  
Covering Theorem ◽  
The Given

There are theorems in which some classes of topological spaces are characterized by means of properties of mappings of these spaces into a single space. For example, it is well known that a compactum X is at most n-dimensional if and only if no mapping of X irto an (n + l)-cube has a stable value [5, Theorems VI. 1-2, pp. 75-77]. Also, a curve X is tree-like if and only if no mapping of X into a figure eight is homotopically essential [1, Theorem 1, pp. 74-75; 8, p. 91]. By a curve we mean any at most 1-dimensional continuum; a continuum is a connected compactum; a compactum is a compact metric space, and a mapping is a continuous function. The aim of the present paper is to prove another theorem of this type. We distinguish a class of curves and show that it is characterized by imposing the condition that no weakly confluent mapping [13] can transform the given curve onto a simple triod (see 2.4). A related result is applied to a generalized branch-point covering theorem (see 3.2). In addition, two results are obtained in which we establish some characterizations of weakly confluent images and preimages of the product of the Cantor set and an arc (see 1.1 and 2.2). Continua that are such images turn out to be identical with regular curves (see 1.3).

scholarly journals On a Lindenbaum Composition Theorem

2019 ◽  
Vol 74 (1) ◽  
pp. 145-158
Author(s):  
Jaroslav Šupina ◽  
Dávid Uhrik
Keyword(s):  
Topological Space ◽  
Real Line ◽  
Topological Spaces ◽  
The Real ◽  
Measurable Functions ◽  
Borel Measurable ◽  
Composition Theorem ◽  
Perfectly Normal

Abstract We discuss several questions about Borel measurable functions on a topological space. We show that two Lindenbaum composition theorems [Lindenbaum, A. Sur les superpositions des fonctions représentables analytiquement, Fund. Math. 23 (1934), 15–37] proved for the real line hold in perfectly normal topological space as well. As an application, we extend a characterization of a certain class of topological spaces with hereditary Jayne-Rogers property for perfectly normal topological space. Finally, we pose an interesting question about lower and upper Δ02-measurable functions.

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