Local derivations on subalgebras of $\tau$-measurable operators with respect to semi-finite von Neumann algebras

TL;DR

This paper proves that under certain conditions, local derivations on subalgebras of $ au$-measurable operators affiliated with semi-finite von Neumann algebras are actually derivations, extending known results to new algebra classes.

Contribution

It establishes that local derivations on specific subalgebras of $ au$-measurable operators are derivations, even in cases not previously covered, such as standard subalgebras of $B(H)$.

Findings

Every local derivation on the algebra $ ext{solid}^*$-subalgebra is a derivation.

The result applies to the algebra of $ au$-compact operators.

The theorem extends to subalgebras without abelian summands.

Abstract

This paper is devoted to local derivations on subalgebras on the algebra $S(M, \tau)$ of all $\tau$-measurable operators affiliated with a von Neumann algebra $M$ without abelian summands and with a faithful normal semi-finite trace $\tau.$ We prove that if $\mathcal{A}$ is a solid $\ast$-subalgebra in $S(M, \tau)$ such that $p\in \mathcal{A}$ for all projection $p\in M$ with finite trace, then every local derivation on the algebra $\mathcal{A}$ is a derivation. This result is new even in the case standard subalgebras on the algebra $B(H)$ of all bounded linear operators on a Hilbert space $H.$ We also apply our main theorem to the algebra $S_0(M, \tau)$ of all $\tau$-compact operators affiliated with a semi-finite von Neumann algebra $M$ and with a faithful normal semi-finite trace $\tau.$