The notion of monodromy was introduced by J. J. Duistermaat as the first obstruction to the existence of global action coordinates in integrable Hamiltonian systems. This invariant was extensively studied since then and was shown to be non-trivial in various concrete examples of finite-dimensional integrable systems. The goal of the present paper is to give a brief overview of monodromy and discuss some of its generalisations. In particular, we will discuss the monodromy around a focus-focus singularity and the notions of quantum, fractional and scattering monodromy. The exposition will be complemented with a number of examples and open problems.
We show that spheroidal wave functions viewed as the essential part of the joint eigenfunction of two commuting operators of $L_2(S^2)$ has a defect in the joint spectrum that makes a global labelling of the joint eigenfunctions by quantum numbers impossible. To our knowledge this is the first explicit demonstration that quantum monodromy exists in a class of classically known special functions. Using an analogue of the Laplace-Runge-Lenz vector we show that the corresponding classical Liouville integrable system is symplectically equivalent to the C. Neumann system. To prove the existence of …
Hamiltonian Monodromy is the simplest topological obstruction to the existence of global action-angle coordinates in a completely integrable system. We show that this property can be studied in a neighborhood of a focus-focus singularity by a spectral Lax pair approach. From the Lax pair, we derive a Riemann surface which allows us to compute in a straightforward way the corresponding Monodromy matrix. The general results are applied to the Jaynes-Cummings model and the spherical pendulum.
The 2d principal models without boundaries have $G\times G$ symmetry. The already known integrable boundaries have either $H\times H$ or $G_{D}$ symmetries, where $H$ is such a subgroup of $G$ for which $G/H$ is a symmetric space while $G_{D}$ is the diagonal subgroup of $G\times G$. These boundary conditions have a common feature: they do not contain free parameters. We have found new integrable boundary conditions for which the remaining symmetry groups are either $G\times H$ or $H\times G$ and they contain one free parameter. The related boundary monodromy matrices are also described.
We show that Hamiltonian monodromy of an integrable two degrees of freedom system with a global circle action can be computed by applying Morse theory to the Hamiltonian of the system. Our proof is based on Takens's index theorem, which specifies how the energy-h Chern number changes when h passes a non-degenerate critical value, and a choice of admissible cycles in Fomenko-Zieschang theory. Connections of our result to some of the existing approaches to monodromy are discussed.
The isotropic harmonic oscillator in dimension 3 separates in several different coordinate systems. Separating in a particular coordinate system defines a system of three commuting operators, one of which is the Hamiltonian. We show that the joint spectrum of the Hamilton operator, the $z$ component of the angular momentum, and a quartic integral obtained from separation in prolate spheroidal coordinates has quantum monodromy for sufficiently large energies. This means that one cannot globally assign quantum numbers to the joint spectrum. The effect can be classically explained by showing that…
An integrable Hamiltonian system presents monodromy if the action-angle variables cannot be defined globally. As a prototype of classical monodromy with azimuthal symmetry, we consider a linear molecule interacting with external fields and explore the topology structure of its phase space. Based on the behavior of closed orbits around singular points or regions of the energy-momentum plane, a semi-theoretical method is derived to detect classical monodromy. The validity of the monodromy test is numerically illustrated for several systems with azimuthal symmetry.
Hamiltonian Monodromy in a Tavis-Cummings System with an $A_2$ Singularity
Duke Kunshan University（杜克昆山大学）；École Normale Supérieure de Lyon（里昂高等师范学院）；Université Bourgogne Europe（勃艮第欧洲大学）；University of Zagreb（萨格勒布大学）；Instituto de Matemáticas Unidad Cuernavaca, Mexico（墨西哥库埃纳瓦卡数学研究所）；Laboratorio Internacional Solomon Lefschetz IRL 2001 CNRS-UNAM（CNRS-UNAM所罗门·列夫谢茨国际实验室）
Bohr-Sommerfeld conditions for Integrable Systems with critical manifolds of focus-focus type
我们提出了一个详细的研究，在半经典的制度$h \to 0$，两个交换的H-PDO的$P_1(h)$，$P_2(h)$系统的微局部性质，使联合主象征$p=(p_1,p_2)$有一种特殊的奇异性称为“焦点焦点”奇异性。典型的例子包括量子球摆或量子香槟瓶。本着Colin de Verdière和Parisse的精神，我们证明了这样的系统具有由Bohr-Sommerfeld型奇异量子化条件描述的普适行为。这些条件被用来给出一个精确的描述，这样的系统，包括量子monodromy现象和不同配方的联合本征值的计数函数接近奇点，其中出现的半经典常数$h$的对数的联合频谱。多亏了M.S.以香槟酒瓶为例，我们能够准确地说明我们的说法。
