BOUNDED PERTURBATIONS OF THE HEISENBERG COMMUTATION RELATION VIA DILATION THEORY

Abstract

We extend the notion of dilation distance to strongly continuous one-parameter unitary groups. If the dilation distance between two such groups is _nite, then these groups can be represented on the same space in such a way that their generators have the same domain and are in fact a bounded perturbation of one another. This result extends to d-tuples of one-parameter unitary groups. We apply our results to the Weyl canonical commutation relations, and as a special case we recover the result of Haagerup and R_rdam that the in_nite ampliation of the canonical position and momentum operators satisfying the Heisenberg commutation relation are a bounded perturbation of a pair of strongly commuting selfadjoint operators. We also recover Gao’s higher-dimensional generalization of Haagerup and R_rdam’s result, and in typical cases we signi_cantly improve control of the bound when the dimension grows.