Algebraic $K$-theory and a semi-finite Fuglede-Kadison determinant

TL;DR

This paper develops a new algebraic $K$-theory based construction of a Fuglede-Kadison determinant for semi-finite von Neumann algebras, extending previous methods and ensuring algebraic properties are automatic.

Contribution

It introduces a novel algebraic $K$-theoretic approach to define determinants in semi-finite von Neumann algebras, improving existing methods by using relative $K$-groups.

Findings

Constructed a Fuglede-Kadison type determinant for semi-finite von Neumann algebras.

Extended the approach to semi-finite cases where the topological $K$-group is trivial.

Ensured algebraic properties of the determinant are automatic within the $K$-theory framework.

Abstract

In this paper we apply algebraic $K$-theory techniques to construct a Fuglede-Kadison type determinant for a semi-finite von Neumann algebra equipped with a fixed trace. Our construction is based on the approach to determinants for Banach algebras developed by Skandalis and de la Harpe. This approach can be extended to the semi-finite case since the first topological $K$-group of the trace ideal in a semi-finite von Neumann algebra is trivial. On our way we also improve the methods of Skandalis and de la Harpe by considering relative $K$-groups with respect to an ideal instead of the usual absolute $K$-groups. Our construction recovers the determinant homomorphism introduced by Brown, but all the relevant algebraic properties are automatic due to the algebraic $K$-theory framework.