On the Gevrey hypo-ellipticity of sums of squares of vector fields

@article{Bove2004OnTG,
  title={On the Gevrey hypo-ellipticity of sums of squares of vector fields},
  author={Antonio Bove and François Tr{\`e}ves},
  journal={Annales de l'Institut Fourier},
  year={2004},
  volume={54},
  pages={1443-1475}
}
On etudie un operateur differentiel du second ordre du type -L = X 2 1 + ... +X 2 r , ou les X i sont des champs vectoriels reels et analytiques. On decrit, en termes analytiques et geometriques simples, la stratification de Poisson de la variete caracteristique de L et on rappelle la conjecture selon laquelle une condition necessaire et suffisante pour l'hypo-ellipticite analytique de L serait que chaque strate de Poisson soit symplectique. Les auteurs formulent une conjecture nouvelle sur l… 
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