Large eigenvalues of the Connes-Moscovici operator

Abstract

We prove the logarithmic Weyl law predicted by Connes and Moscovici for large positive eigenvalues of the distinguished self-adjoint extension of the operator $P=-\partial_x(x^2-1)\partial_x-4\pi^2x^2$ on the real line. More precisely, we use the WKB method and show a Bohr-Sommerfeld quantization rule characterizing sufficiently large eigenvalues. A particular difficulty is that the associated $h$-dependent Lagrangian submanifolds are non-compact, which requires a renormalization of the action integral. Furthermore, to deal with the degeneracy of the coefficients at $x =\pm 1$, we use a quasimode matching argument based on radial estimates and Lagrangian regularity.