On the continuity properties of the L_p balls.

Abstract

In this paper the right upper semicontinuity at p = 1 and continuity at p = ∞ of the set-valued map p → B_{Ω,X,p}(r), p ∈ [1, ∞], are studied where B_{Ω,X,p}(r) is the closed ball of the space L_p(Ω, Σ, μ; X) centered at the origin with radius r, (Ω, Σ, μ) is a finite and positive measure space, X is a separable Banach space. It is proved that the considered set-valued map is right upper semicontinuous at p = 1 and continuous at p = ∞. An application of the obtained results to the set of integrable outputs of the input-output system described by the Urysohn-type integral operator is discussed.