Spectral monodromy of non selfadjoint operators

TL;DR

This paper introduces the spectral monodromy, a new combinatorial invariant derived from the spectrum of non-selfadjoint operators, extending concepts of quantum monodromy to more complex, perturbed systems in the semi-classical limit.

Contribution

It defines the spectral monodromy for non-selfadjoint operators and demonstrates its relation to classical monodromy, including in perturbed, non-integrable cases.

Findings

Spectral monodromy can be constructed from the spectrum of non-selfadjoint operators.

The spectral monodromy generalizes quantum monodromy to non-selfadjoint and perturbed systems.

The monodromy relates to classical monodromy, even with limited spectral information.

Abstract

We propose to build a combinatorial invariant, called the spectral monodromy, from the spectrum of a single non-selfadjoint h-pseudodifferential operator with two degrees of freedom in the semi-classical limit. Our inspiration comes from the quantum monodromy defined for the joint spectrum of an integrable system of n commuting selfadjoint h-pseudodifferential operators, given by S. Vu Ngoc. The first simple case that we treat in this work is a normal operator. In this case, the discrete spectrum can be identified with the joint spectrum of an integrable quantum system. The second more complex case we propose is a small perturbation of a selfadjoint operator with a classical integrability property. We show that the discrete spectrum (in a small band around the real axis) also has a combinatorial monodromy. The difficulty here is that we do not know the description of the spectrum everywhere, but only in a Cantor type set. In addition, we also show that the monodromy can be identified with the classical monodromy defined by J. Duistermaat.