# Hecke von Neumann Algebra of Ergodic Discrete Measured Equivalence Relations

### Hisashi Aoi

Ritsumeikan University, Shiga, Japan### Takehiko Yamanouchi

Tokyo Gakugei University, Japan

## Abstract

We generalize the notion of a Hecke pair of groups to the case of an inclusion of ergodic discrete measured equivalence relations. A key ingredient in defining this new concept is a commensurability subrelation introduced and discussed in [3]. As in the group case, with each such Hecke pair, we associate a von Neumann algebra which we call the Hecke von Neumann algebra of the pair. It is shown that the Hecke von Neumann algebra thus defined is realized as one of the relative commutants of the tower of the corresponding inclusion of factors.

## Cite this article

Hisashi Aoi, Takehiko Yamanouchi, Hecke von Neumann Algebra of Ergodic Discrete Measured Equivalence Relations. Publ. Res. Inst. Math. Sci. 46 (2010), no. 3, pp. 607–667

DOI 10.2977/PRIMS/20