On the hypoellipticity for infinitely degenerate semi-elliptic operators
On the hypoellipticity for infinitely degenerate semi-elliptic operators
In this paper we shall study hypoellipticity for a partial differential operator of the form $(0.1)$ $P=a(x, y, D_{x})+g(x)b(x, y, D_{y})$ in $R^{n}=R_{x^{1}}^{n}\times R_{y^{2}}^{n}$ , where $a(x, y, D_{x})$ and $b(x, y, D_{y})$ are strongly elliptic operators of order $2l$ and $2m$ with respect to $x$ and $y$ , respectively, …