{ "id": "1511.05702", "version": "v1", "published": "2015-11-18T09:26:02.000Z", "updated": "2015-11-18T09:26:02.000Z", "title": "Algebras of singular integral operators with kernels controlled by multiple norms", "authors": [ "Alexander Nagel", "Fulvio Ricci", "Elias M. Stein", "Stephen Wainger" ], "categories": [ "math.FA" ], "abstract": "The purpose of this paper is to study algebras of singular integral operators on $\\mathbb{R}^{n}$ and nilpotent Lie groups that arise when one considers the composition of Calder\\'on-Zygmund operators with different homogeneities, such as operators that occur in sub-elliptic problems and those arising in elliptic problems. For example, one would like to describe the algebras containing the operators related to the Kohn-Laplacian for appropriate domains, or those related to inverses of H\\\"ormander sub-Laplacians, when these are composed with the more standard class of pseudo-differential operators. The algebras we study can be characterized in a number of different but equivalent ways, and consist of operators that are pseudo-local and bounded on $L^{p}$ for $1