Comments on Non-Commutative Phenomenology

Abstract

It is natural to ask whether non-commutative geometry plays a role in four dimensional physics. By performing explicit computations in various toy models, we show that quantum effects lead to violations of Lorentz invariance at the level of operators of dimension three or four. The resulting constraints are very stringent.

Comments: Correction of an error in the U(1) and U(N) calculation leads to stronger limits than those given previously Clarifying comments and reference added