On the propagation of flatness for second order hypoelliptic operators

Abstract

For a class of hypoelliptic operators with real-analytic coefficients, we provide a criterion ensuring a partial analyticity result. As a consequence, even when the “elliptic” strong unique continuation (i.e. a solution of the homogeneous equation which vanishes of infinite order at a point is zero near such a point) fails, a weaker form of “propagation” of zeroes still holds.