In 1953 von Neumann has proved that every n × n doubly substochastic matrix A can be increased to a doubly stochastic matrix, i.e., there is an n × n doubly stochastic matrix D for which A ≤ D. In this paper, we will discuss this result for a class of I × I doubly substochastic matrices. In fact, by a constructive method, we find an equivalent condition for existence of a doubly stochastic matrix D which satisfies A ≤ D, for all A ∈ A, where A is assumed a class of (finite or infinite) doubly substochastic matrices. Such a matrix D is called a cover of A. The uniqueness of the cover will also be discussed. Then we obtain an application of this concept to a system of (infinite) linear equations and inequalities.
MSC(2020): 15B48, 15B51, 15A45, 47A50