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The regular topology on C ( X )

Wolf Iberkleid, Ramiro Lafuente-Rodriguez, Warren Wm. McGovern (2011)

Commentationes Mathematicae Universitatis Carolinae

Hewitt [Rings of real-valued continuous functions. I., Trans. Amer. Math. Soc. 64 (1948), 45–99] defined the m -topology on C ( X ) , denoted C m ( X ) , and demonstrated that certain topological properties of X could be characterized by certain topological properties of C m ( X ) . For example, he showed that X is pseudocompact if and only if C m ( X ) is a metrizable space; in this case the m -topology is precisely the topology of uniform convergence. What is interesting with regards to the m -topology is that it is possible, with...

The Rothberger property on C p ( Ψ ( 𝒜 ) , 2 )

Daniel Bernal-Santos (2016)

Commentationes Mathematicae Universitatis Carolinae

A space X is said to have the Rothberger property (or simply X is Rothberger) if for every sequence 𝒰 n : n ω of open covers of X , there exists U n 𝒰 n for each n ω such that X = n ω U n . For any n ω , necessary and sufficient conditions are obtained for C p ( Ψ ( 𝒜 ) , 2 ) n to have the Rothberger property when 𝒜 is a Mrówka mad family and, assuming CH (the Continuum Hypothesis), we prove the existence of a maximal almost disjoint family 𝒜 for which the space C p ( Ψ ( 𝒜 ) , 2 ) n is Rothberger for all n ω .

The structure of atoms (hereditarily indecomposable continua)

R. Ball, J. Hagler, Yaki Sternfeld (1998)

Fundamenta Mathematicae

Let X be an atom (= hereditarily indecomposable continuum). Define a metric ϱ on X by letting ϱ ( x , y ) = W ( A x y ) where A x , y is the (unique) minimal subcontinuum of X which contains x and y and W is a Whitney map on the set of subcontinua of X with W(X) = 1. We prove that ϱ is an ultrametric and the topology of (X,ϱ) is stronger than the original topology of X. The ϱ-closed balls C(x,r) = y ∈ X:ϱ ( x,y) ≤ r coincide with the subcontinua of X. (C(x,r) is the unique subcontinuum of X which contains x and has Whitney value...

Topological structure of the space of lower semi-continuous functions

Katsuro Sakai, Shigenori Uehara (2006)

Commentationes Mathematicae Universitatis Carolinae

Let L ( X ) be the space of all lower semi-continuous extended real-valued functions on a Hausdorff space X , where, by identifying each f with the epi-graph epi ( f ) , L ( X ) is regarded the subspace of the space Cld F * ( X × ) of all closed sets in X × with the Fell topology. Let LSC ( X ) = { f L ( X ) f ( X ) , f ( X ) ( - , ] } and LSC B ( X ) = { f L ( X ) f ( X ) is a bounded subset of } . We show that L ( X ) is homeomorphic to the Hilbert cube Q = [ - 1 , 1 ] if and only if X is second countable, locally compact and infinite. In this case, it is proved that ( L ( X ) , LSC ( X ) , LSC B ( X ) ) is homeomorphic to ( Cone Q , Q × ( 0 , 1 ) , Σ × ( 0 , 1 ) ) (resp. ( Q , s , Σ ) ) if X is compact (resp. X is non-compact), where Cone Q = ( Q × 𝐈 ) / ( Q × { 1 } ) is the cone over...

Currently displaying 301 – 320 of 347