Dispersive estimates for principally normal pseudodifferential operators

In this article we construct parametrices and obtain dispersive estimates for a large class of principally normal pseudodifferential operators. The main motivation for this comes from unique continuation problems. Such estimates can be used to prove L^q Carleman inequalities, which in turn yield unique continuation results for various partial differential operators with rough potentials. © 2004 Wiley Periodicals, Inc.