# Proceedings of the American Mathematical Society

Published by the American Mathematical Society since 1950, Proceedings of the American Mathematical Society is devoted to shorter research articles in all areas of pure and applied mathematics.

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## Analyticity for singular sums of squares of degenerate vector fieldsHTML articles powered by AMS MathViewer

by David S. Tartakoff
Proc. Amer. Math. Soc. 134 (2006), 3343-3352 Request permission

## Abstract:

Recently J. J. Kohn (2005) proved $C^\infty$ hypoellipticity for $P_k=L\overline {L} + \overline {L}|z|^{2k}L =-\overline {L}^*\overline {L} - (\overline {z}^kL)^*\overline {z}^kL\mathrm { \quad with \quad } L={\partial \over \partial z} + i\overline {z}{\partial \over \partial t},$ (the negative of) a singular sum of squares of complex vector fields on the complex Heisenberg group, an operator which exhibits a loss of ${k-1}$ derivatives. Subsequently, M. Derridj and D. S. Tartakoff proved analytic hypoellipticity for this operator using rather different methods going back to earlier methods of Tartakoff. Those methods also provide an alternate proof of the hypoellipticity given by Kohn. In this paper, we consider the equation $P_{m,k}=L_m\overline {L_m} + \overline {L_m} |z|^{2k}L_m \mathrm { \; with \;} L_m={\partial \over \partial z} + i\overline {z}|z|^{2m}{\partial \over \partial t},$ for which the underlying manifold is only of finite type, and prove analytic hypoellipticity using methods of Derridj and Tartakoff. This operator is also subelliptic with large loss of derivatives, but the exact loss plays no role for analytic hypoellipticity. Nonetheless, these methods give a proof of $C^\infty$ hypoellipticity with precise loss as well, which is to appear in a forthcoming paper by A. Bove, M. Derridj, J. J. Kohn and the author.
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Additional Information
• David S. Tartakoff
• Affiliation: Department of Mathematics, University of Illinois at Chicago, m/c 249, 851 S. Morgan Street, Chicago, Illinois 60607
• Email: dst@uic.edu
• Received by editor(s): June 1, 2005
• Published electronically: May 12, 2006
• Communicated by: Eric Bedford
• © Copyright 2006 American Mathematical Society
The copyright for this article reverts to public domain 28 years after publication.
• Journal: Proc. Amer. Math. Soc. 134 (2006), 3343-3352
• MSC (2000): Primary 35H10; Secondary 35N15
• DOI: https://doi.org/10.1090/S0002-9939-06-08419-X
• MathSciNet review: 2231919