Abstract:
General symmetric hypoelliptic systems of differential operators in $R^n$ with discrete spectrum are considered. Two-sided estimates, as $t\to\infty$, are found for $N(t)$, the number of eigenvalues in the interval $[0,t]$. Under a regularity assumption on the behavior of the spectrum of the Weyl matrix symbol of the system, these estimates reduce to the asymptotics of $N(t)$ with an estimate of the remainder term. In part the results are also new for the scalar case.
Bibliography: 9 titles.