Miscellaneous on Commutants mod Normed Ideals and Quasicentral Modulus I

We define commutants mod normed ideals associated with compact smooth manifolds with boundary. The results about the K-theory of these operator algebras include an exact sequence for the connected sum of manifolds, derived from the Mayer-Vietoris sequence. We also make a few remarks about bicommutants mod normed ideals and about the quasicentral modulus for the quasinormed p-Schatten-von Neumann classes 0 < p < 1.