On the asymptotic eigenvalue distribution of a pseudo-differential operator.
A description of the number N(K) of eigenvalues less than K for a pseudo-differential operator with positive symbol is given in terms of the number of unit cubes canonically imbedded in the subset of phase space where the symbol is less than CK. This gives back in particular the order of magnitude of N(K) for elliptic symbols.
Fefferman
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Department of Mathematics, Princeton University, Princeton, New Jersey 08544.
Phong
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