Relative Commutant Pictures of Roe Algebras

Let X be a proper metric space, which has finite asymptotic dimension in the sense of Gromov (or more generally, straight finite decomposition complexity of Dranishnikov and Zarichnyi). New descriptions are provided of the Roe algebra of X : (i) it consists exactly of operators which essentially commute with diagonal operators coming from Higson functions (that is, functions on X whose oscillation tends to 0 at ∞ ), and (ii) it consists exactly of quasi-local operators, that is, ones which have finite ϵ -propogation (in the sense of Roe) for every ϵ > 0 . These descriptions hold both for the usual Roe algebra and for the uniform Roe algebra.