arXiv math/07025282007-02-18math.RAmath.OA

Torsion theories for algebras of affiliated operators of finite von Neumann algebras

Lia Vas

备注：: To appear in Rocky Mountain Journal of Mathematics
发表信息：: Rocky Mountain Journal of Mathematics, 37 (2007), no. 6, 2053 - 2075

英文摘要：

The dimension of any module over an algebra of affiliated operators ${\mathcal U}$ of a finite von Neumann algebra ${\mathcal A}$ is defined using a trace on ${\mathcal A}.$ All zero-dimensional ${\mathcal U}$-modules constitute the torsion class of torsion theory $(\mathrm{\bf T},\mathrm{\bf P})$. We show that every finitely generated ${\mathcal U}$-module splits as the direct sum of torsion and torsion-free part. Moreover, we prove that the theory $(\mathrm{\bf T},\mathrm{\bf P})$ coincides with the theory of bounded and unbounded modules and also with the Lambek and Goldie torsion theories. Lastly, we use the introduced torsion theories to give the necessary and sufficient conditions for ${\mathcal U}$ to be semisimple.

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