paper

Global Hypoellipticity for First-Order Operators on Closed Smooth Manifolds

arXiv:1507.08880 · doi:10.1007/s11854-018-0039-6

Abstract

The main goal of this paper is to address global hypoellipticity issues for the following class of operators: , where , is the one-dimensional torus, is a closed manifold and is a first order pseudo-differential operator on , smoothly depending on the periodic variable . In the case of separation of variables, namely, , we give necessary and sufficient conditions for the global hypoellipticity of . In particular, we show that, under suitable conditions, the famous (P) condition of Niremberg-Treves is neither necessary nor sufficient to guarantee the global hypoellipticity of .

53 pages; updated version (fixed typos and new references, resized to fit on fewer pages) to appear in J. Anal. Math

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