English

type III representations and modular spectral triples for the noncommutative torus

Operator Algebras 2018-06-22 v1

Abstract

It is well known that for any irrational rotation number \a\a, the noncommutative torus \ba\a\ba_\a must have representations π\pi such that the generated von Neumann algebra π(\ba\a)"\pi(\ba_\a)" is of type \tyIII\ty{III}. Therefore, it could be of interest to exhibit and investigate such kind of representations, together with the associated spectral triples whose twist of the Dirac operator and the corresponding derivation arises from the Tomita modular operator. In the present paper, we show that this program can be carried out, at least when \a\a is a Liouville number satisfying a faster approximation property by rationals. In this case, we exhibit several type \tyII\ty{II_\infty} and \tyIII\l\ty{III_\l}, \l[0,1]\l\in[0,1], factor representations and modular spectral triples. The method developed in the present paper can be generalised to CCR algebras based on a locally compact abelian group equipped with a symplectic form.

Keywords

Cite

@article{arxiv.1806.08253,
  title  = {type III representations and modular spectral triples for the noncommutative torus},
  author = {Francesco Fidaleo and Luca Suriano},
  journal= {arXiv preprint arXiv:1806.08253},
  year   = {2018}
}

Comments

Journal of Functional Analysis, to appear

R2 v1 2026-06-23T02:37:21.185Z