Hilbert transform associated with finite maximal subdiagonal algebras

Abstract

Let $M$ be a von Neumann algebra with a faithful normal finite trace $t$, and $H^{\infty }$ be a finite, maximal, subdiagonal of $M$. Fundamental theorems on conjugate functions for weak* Dirichlet algebras are shown to be a bounded linear map from $L^p(M,t)$ into $L^p(M,t)$ for $1<p<\infty$, and to be a continuous linear map from $L^1(M,t)$ into $L^{1,\infty }(M,t)$. We also obtain that if a positive operator $a$ is such that $a{\log }^{+}a\in L^1(M,t)$, then its conjugate belongs to $L^1(M,t)$.