EN
Let X and Y be Banach spaces. A subset M of 𝓚(X,Y) (the vector space of all compact operators from X into Y endowed with the operator norm) is said to be equicompact if every bounded sequence (xₙ) in X has a subsequence $(x_{k(n)})ₙ$ such that $(Tx_{k(n)})ₙ$ is uniformly convergent for T ∈ M. We study the relationship between this concept and the notion of uniformly completely continuous set and give some applications. Among other results, we obtain a generalization of the classical Ascoli theorem and a compactness criterion in $ℳ_{c}(ℱ,X)$, the Banach space of all (finitely additive) vector measures (with compact range) from a field ℱ of sets into X endowed with the semivariation norm.