Abstract
Conditions are obtained under which the degenerate operator \(P(D)\) (polynomial \(P(\xi)\) ) will be hypoelliptic. In the case of two-layer degenerate polynomials these conditions are necessary and sufficient and for multilayered ones, these conditions are only sufficient. To impediment this, we first consider the case when polynomial \(P(\xi)\) is two-layer degenerate. It is further shown that in the multi-layer–degenerate case the question comes down to compering the powers of certain sub-polynomials of polynomial \(P(\xi)\) with polynomial \(P(\xi)\) . Therefore, we further study the question of comparing differential operators (polynomials).