We give a simple argument to show that if α is an affine isometric action of a product G ×H of topological groups on a reflexive Banach space X with linear part π, then either π(H) fixes a unit vector or α|G almost fixes a point on X . It follows that if π is an isometric linear representation of a topological group G on a reflexive space X such that π(Z(G)) has no fixed unit vectors, then the ...

It is shown that a series of positive terms that converges on all sets of null density should be convergent. Using this result we construct examples of complete topological vector spaces that are proper subspaces of a Banach space, but whose dual spaces coincide with the dual space of the Banach space.

Let X be a completely regular Hausdorff space, let V be a system of weights on X and let T be a locally convex Hausdorff topological vector space. Then CVb(X, T) is a locally convex space of vector-valued continuous functions with a topology generated by seminorms which are weighted analogues of the supremum norm. In the present paper we characterize multiplication operators on the space CVb(X,...

Let X be a completely regular Hausdorff space, E a Hausdorff topological vector space, CL(E) the algebra of continuous operators on E, V a Nachbin family on X and F ⊆ CVb(X,E) a topological vector space (for a given topology). If π : X → CL(E) is a mapping, consider the induced multiplication operator Mπ : F → F given by Mπ(f)(x) := π(x)f(x), f ∈ G, x ∈ coz(F). In this paper we give necessary a...

We discuss the concept of the bisector of a segment in a Minkowski normed n-space. We prove that all bisectors are topological images of a plane of the embedding Euclidean 3-space iff the shadow boundaries of the unit ball K are topological circles. To a conjectured proving strategy for dimensions n, we introduce the concept of general parameter sphere of the unit ballK, corresponding to a dire...

Two topological spaces X and Y are said to be l-equivalent if there is a linear homeomorphism between Cp(X) and Cp(Y ), the spaces of continuous functions on X and Y endowed with the pointwise convergence topology. We prove a necessary condition on a topological space to be lequivalent to the n-dimensional cube. This, in particular, combined with a recent result of R. Górak, characterizes the t...

We present a measure-theoretic condition for a property to hold “almost everywhere” on an infinite-dimensional vector space, with particular emphasis on function spaces such as C and L. Like the concept of “Lebesgue almost every” on finite-dimensional spaces, our notion of “prevalence” is translation invariant. Instead of using a specific measure on the entire space, we define prevalence in ter...

Introduction. In his monograph [l], Császár introduced the notion of a syntopogenous space, which generalized the notions of a topological space, a proximity space, and a uniform space. Although Császár was able to obtain many of the usual theorems of general topology in this more general setting, the basic topological notion of connectedness was not introduced at all. Mrówka and Pervin [2] hav...

Bogdan and Kolumbán [3] gave sufficient conditions for closedness of the solution map defined on the set of parameters. They considered the parametric equilibrium problems governed by topological pseudomonotone maps depending on a parameter. In this paper we generalize this result for parametric vector equilibrium problems with trifunctions. Let X and Y be Hausdorff topological spaces and P , t...

‎for any archimedean$f$-ring $a$ with unit in whichbreak$awedge‎‎(1-a)leq 0$ for all $ain a$‎, ‎the following are shown to be‎‎equivalent‎:‎‎1‎. ‎$a$ is isomorphic to the $l$-ring ${mathfrak z}l$ of all‎‎integer-valued continuous functions on some frame $l$‎. 2‎. ‎$a$ is a homomorphic image of the $l$-ring $c_{bbb z}(x)$‎‎of all integer-valued continuous functions‎, ‎in the usual sense‎,‎on som...