Dan-Virgil Voiculescu
University of California, Berkeley, USA

The quasicentral modulus plays a key role in normed ideal perturbations of Hilbert space operators, in the multivariable analogues of the Weyl - von Neumann - Kuroda and Kato - Rosenblum theorems. I will explain a non-commutative analogy with condenser capacity in nonlinear potential theory.