Positively $p$-nuclear operators, positively $p$-integral operators and approximation properties

Abstract

In the present paper, we introduce and investigate a new class of positively $p$-nuclear operators that are positive analogues of right $p$-nuclear operators. One of our main results establishes an identification of the dual space of positively $p$-nuclear operators with the class of positive $p$-majorizing operators that is a dual notion of positive $p$-summing operators. As applications, we prove the duality relationships between latticially $p$-nuclear operators introduced by O. I. Zhukova and positively $p$-nuclear operators. We also introduce a new concept of positively $p$-integral operators via positively $p$-nuclear operators and prove that the inclusion map from $L_{p^{*}}(\mu)$ to $L_{1}(\mu)$($\mu$ finite) is positively $p$-integral. New characterizations of latticially $p$-integral operators by O. I. Zhukova and positively $p$-integral operators are presented and used to prove that an operator is latticially $p$-integral (resp. positively $p$-integral) precisely when its second adjoint is. Finally, we describe the space of positively $p^{*}$-integral operators as the dual of the $\|\cdot\|_{\Upsilon_{p}}$-closure of the subspace of finite rank operators in the space of positive $p$-majorizing operators. Approximation properties, even positive approximation properties, are needed in establishing main identifications.