Published online by Cambridge University Press: 20 November 2018
1. Introduction. Let (X, , m) be a σ-finite measure space and let T be a positive linear operator on L1 = L1(X, , m). T is called Markovian if
(1.1)
T is called sub-Markovian if
(1.2)
All sets and functions are assumed measurable; all relations and statements are assumed to hold modulo sets of measure zero.
For a sequence of L1+ functions (ƒ0, ƒ1, ƒ2, …), let
(ƒn) is called a super additive sequence or process, and (sn) a super additive sum relative to a positive linear operator T on L1 if
(1.3)
and
(1.4)