Torsion Theories for Finite Von Neumann Algebras
نویسنده
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.
منابع مشابه
Torsion Theories for Algebras of Affiliated Operators of Finite Von Neumann Algebras
The dimension of any module over an algebra of affiliated operators U of a finite von Neumann algebra A is defined using a trace on A. All zero-dimensional U-modules constitute the torsion class of torsion theory (T,P). We show that every finitely generated U-module splits as the direct sum of torsion and torsion-free part. Moreover, we prove that the theory (T, P) coincides with the theory of ...
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