Torsion Theories for Finite Von Neumann Algebras

نویسنده

  • LIA VAŠ
چکیده

The study of modules over a finite von Neumann algebra A can be advanced by the use of torsion theories. In this work, some torsion theories for A are presented, compared and studied. In particular, we prove that the torsion theory (T,P) (in which a module is torsion if it is zero-dimensional) is equal to both Lambek and Goldie torsion theories for A. Using torsion theories, we describe the injective envelope of a finitely generated projective A-module and the inverse of the isomorphism K0(A) → K0(U), where U is the algebra of affiliated operators of A. Then, the formula for computing the capacity of a finitely generated module is obtained. Lastly, we study the behavior of the torsion and torsion-free classes when passing from a subalgebra B of a finite von Neumann algebra A to A. With these results, we prove that the capacity is invariant under the induction of a B-module.

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تاریخ انتشار 2007