Functional Space Consisted by Continuous Functions on Topological Space

Summary In this article, using the Mizar system [1], [2], first we give a definition of a functional space which is constructed from all continuous functions defined on a compact topological space [5]. We prove that this functional space is a Banach space [3]. Next, we give a definition of a function space which is constructed from all continuous functions with bounded support. We also prove that this function space is a normed space.

Ordinal compactness

We introduce a new covering property, defined in terms of order types of sequences of open sets, rather than in terms of cardinalities. The most general form depends on two ordinal parameters. Ordinal compactness turns out to be a much more varied notion than cardinal compactness. We prove many nontrivial results of the form ?every [?,?]-compact topological space is [?',?']-compact?, for ordinals ?,?, ?'and ?' while only trivial results of the above form hold, if we restrict to regular cardinals. Counterexamples are provided showing that many results are optimal. Many spaces satisfy the very same cardinal compactness properties, but have a broad range of distinct behaviors, as far as ordinal compactness is concerned. A much more refined theory is obtained for T1 spaces, in comparison with arbitrary topological spaces. The notion of ordinal compactness becomes partly trivial for spaces of small cardinality.

On the problem of condensation onto compacta

The paper proves (assuming the continuum hypothesis CH) that there exists a perfectly normal compact topological space Z and a countable set E ⊂ Z, such that Z\E is not condensed onto a compact. The existence of such a space answers (in CH) negatively to the question of V.I. Ponomareva: Is every perfectly normal compact an α-space? It is proved that in the class of ordered compacts the property of being an α-space is not multiplicative.

The flat topology on the minimal and maximal prime spectrum of a commutative ring

In this paper, we investigate connections between some algebraic properties of commutative rings and topological properties of their minimal and maximal prime spectrum with respect to the flat topology. We show that for a commutative ring [Formula: see text], the ascending chain condition on principal annihilator ideals of [Formula: see text] holds if and only if [Formula: see text] is a Noetherian topological space as a subspace of [Formula: see text] with respect to the flat topology and we give a characterization for a topological space [Formula: see text] for which [Formula: see text] is a Noetherian topological space as a subspace of [Formula: see text] with respect to the flat topology. Also, we give a characterization for rings whose maximal prime spectrum is a compact topological space with respect to the flat topology. Some other results are obtained too.

Pareto Optimality on Compact Spaces in a Preference-Based Setting under Incompleteness

We characterize the existence of Pareto optimal elements for a family of not necessarily total preorders on a compact topological space. We identify a rather general semi-continuity assumption, called weak upper semicontinuity, under which there exist Pareto optimal elements. We also show that weak upper semicontinuity of each individual preorder is a necessary and sufficient condition for determining the Pareto optimal elements by solving the classical multi-objective optimization problem in case that each function is upper semicontinuous and order-preserving for the respective preorder, and each preorder satisfies a condition of weak separability.

On the Maksa-Volkmann functional inequality |f (x + y)| ≥ |f (x) + f (y)| when the range of f is a space of functions

P. Volkmann functional inequality |f (x + y)| ≥ |f (x) + f (y)| is extended to functions f : G → F (X, E) where G is an additive group and F (X, E) is the space of functions from a set X to a linear normed space E. As a corollary one proves that an operator T : C (X, K) → C (X, K) which satisfies the functional inequality |T (f + g)| ≥ |T (f) + T (g)| , f, g ∈ C (X, K) is additive. Here we denoted by X a compact topological space, K is R or C and C (X, K) is the linear space of continuous functions defined on X with values in K.

Functional Space C(ω), C0(ω)

Functional Space C(ω), C0(ω) In this article, first we give a definition of a functional space which is constructed from all complex-valued continuous functions defined on a compact topological space. We prove that this functional space is a Banach algebra. Next, we give a definition of a function space which is constructed from all complex-valued continuous functions with bounded support. We also prove that this function space is a complex normed space.

On the Fuzzy Number Space with the Level Convergence Topology

We characterize compact sets of𝔼1endowed with the level convergence topologyτℓ. We also describe the completion(𝔼1̂,𝒰̂)of𝔼1with respect to its natural uniformity, that is, the pointwise uniformity𝒰, and show other topological properties of𝔼1̂, as separability. We apply these results to give an Arzela-Ascoli theorem for the space of(𝔼1,τℓ)-valued continuous functions on a locally compact topological space equipped with the compact-open topology.

ON HAUSDORFF DIMENSION AND TOPOLOGICAL ENTROPY

Let f: X → X be a continuous map of a compact topological space. If there exists a metric function on X and it satisfies some restricted conditions, we obtain some relationships between Hausdorff dimension and topological entropy for any Z ⊆ X. Using those results, we also obtain a variational principle of dimensions, generalize some known results and give some examples.