## Analyticity for singular sums of squares of degenerate vector fields

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- by David S. Tartakoff
- Proc. Amer. Math. Soc.
**134**(2006), 3343-3352 - DOI: https://doi.org/10.1090/S0002-9939-06-08419-X
- Published electronically: May 12, 2006
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## 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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## Bibliographic 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