NONCOMMUTATIVE MAXIMAL INEQUALITIES ASSOCIATED WITH CONVEX FUNCTIONS.

We prove several noncommutative maximal inequalities associated with convex functions, including a Doob type inequality for a convex function of maximal operators on noncommutative martingales, and noncommutative Dunford-Schwartz and Stein maximal ergodic inequalities for a convex function of positive and symmetric positive contractions. The key ingredient in our proofs is a Marcinkiewicz type interpolation theorem for a convex function of maximal operators in the noncommutative setting, which we establish in this paper. These generalize the results of Junge and Xu in the L_p case to the case of convex functions. [ABSTRACT FROM AUTHOR]