High-frequency lower bound for an elliptic polynomial
= High-frequency lower bound for an elliptic polynomial
{title2=$|P(\xi)|\gtrsim\langle\xi\rangle^N$}
A scalar <elliptic differential operator> of order $N$ has a <principal symbol> nonzero on the unit <sphere>. Compactness gives a positive minimum there, and homogeneity makes that term dominate all lower-degree terms at sufficiently large real frequencies.