Definition 44.2.6 (Convolvers).label Let $(M, \tau)$ be a tracial von Neumann algebra and $\xi \in L^{2}(M, \tau)$, then $\xi$ is a left convolver if $L_{\xi}$ is bounded, and $\xi$ is a right convolver if $R_{\xi}$ is bounded. The sets of left and right convolvers are denoted $LC(M)$ and $RC(M)$, respectively.