Ergodicity and differences of functions on semigroups

Journal of the Australian Mathematical Society

Bolis Basit¹ 

[1] A. J. Pryde

关键词: primary 43A60;    secondary 47A10;    47D03;    28B05;   

DOI  :  10.1017/S1446788700001749

学科分类：数学（综合）

来源: Cambridge University Press

【 摘 要 】

Iseki [11] defined a general notion of ergodicity suitable for functions ϕ: J → X where J is an arbitrary abelian semigroup and X is a Banach space. In this paper we develop the theory of such functions, showing in particular that it fits the general framework established by Eberlein [9] for ergodicity of semigroups of operators acting on X. Moreover, let A be a translation invariant closed subspace of the space of all bounded functions from J to X. We prove that if A contains the constant functions and ϕ is an ergodic function whose differences lie in A then ϕ ∈ A. This result has applications to spaces of sequences facilitating new proofs of theorems of Gelfand and Katznelson-Tzafriri [12]. We also obtain a decomposition for the space of ergodic vectors of a representation T: J → L(X) generalizing results known for the case J = Z+. Finally, when J is a subsemigroup of a locally compact abelian group G, we compare the Iseki integrals with the better known Cesàro integrals.

【 授权许可】

Unknown