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Hypoellipticity: Geometrization and Speculation

Michael Christ
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Abstract

To any finite collection of smooth real vector fields $X_j$ in $\reals^n$ we associate a metric in the phase space $T^*\reals^n$. The relation between the asymptotic behavior of this metric and hypoellipticity of $\sum X_j^2$, in the smooth, real analytic, and Gevrey categories, is explored.

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Michael Christ. 1998-01-13. Hypoellipticity: Geometrization and Speculation. https://arxiv.org/abs/math/9801142

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