Complete spaces and tri-quotient maps

Generalized tri-quotient maps and Čech-completeness

For a topological space X let K(X) be the set of all compact subsets of X. The purpose of this paper is to characterize Lindelöf Čech-complete spaces X by means of the sets K(X). Similar characterizations also hold for Lindelöf locally compact X, as well as for countably K-determined spaces X. Our results extend a classical result of J. Christensen.

A Non-separable Christensen’s Theorem and Set Tri-quotient Maps

For every space X let K(X) be the set of all compact subsets of X . Christensen [6] proved that if X, Y are separable metrizable spaces and F : K(X) → K(Y ) is a monotone map such that any L ∈ K(Y ) is covered by F (K) for some K ∈ K(X), then Y is complete provided X is complete. It is well known [3] that this result is not true for non-separable spaces. In this paper we discuss some additional...

Superstability of $m$-additive maps on complete non--Archimedean spaces

The stability problem of the functional equation was conjectured by Ulam and was solved by Hyers in the case of additive mapping. Baker et al. investigated the superstability of the functional equation from a vector space to real numbers. In this paper, we exhibit the superstability of $m$-additive maps on complete non--Archimedean spaces via a fixed point method raised by Diaz and Margolis.

Relative Compactness and Product Stable Quotient Maps

Asymptotic Geometry of Banach Spaces and Uniform Quotient Maps

Recently, Lima and Randrianarivony pointed out the role of the property (β) of Rolewicz in nonlinear quotient problems, and answered a ten-year-old question of Bates, Johnson, Lindenstrauss, Preiss and Schechtman. In the present paper, we prove that the modulus of asymptotic uniform smoothness of the range space of a uniform quotient map can be compared with the modulus of (β) of the domain spa...