Théorie spectrale inverse pour les opérateurs de Toeplitz 1D
In this thesis, we prove some direct and inverse spectral results, in the semiclassical limit, for self-adjoint Toeplitz operators on surfaces. For pseudodifferential operators, these results are already known, and it is natural to expect their extension to the Toeplitz setting. The usual Bohr-Sommerfeld conditions, characterizing the eigenvalues close to a regular value of the principal symbol, have been obtained a few years ago for Toeplitz operators. Our contribution consists in extending these conditions near nondegenerate critical values. We handle the case of an elliptic value thanks to a normal form technique; the model operator is the realization of the harmonic oscillator in the Bargmann space, whose spectrum is well-known. In the case of a hyperbolic value, the normal form is no longer sufficient and we conclude by using additional arguments due to Colin de Verdière and Parisse, who derived the analogous result for pseudodifferential operators. Finally, we write an inverse spectral result for self-adjoint Toeplitz operators on surfaces; more precisely, we show that under some generic hypotheses, the knowledge of the spectrum up to order two in the semiclassical limit allows to recover the principal symbol up to symplectomorphism. This result essentially relies on Bohr-Sommerfeld rules.