Quasi-periodic solutions of the Heisenberg hierarchy

The Heisenberg hierarchy and its Hamiltonian structure are derived respectively by virtue of the zero curvature equation and the trace identity. With the help of the Lax matrix we introduce an algebraic curve $\mathcal{K}_{n}$ of arithmetic genus $n$, from which we define meromorphic function $\phi$ and straighten out all of the flows associated with the Heisenberg hierarchy under the Abel-Jacobi coordinates. Finally, we achieve the explicit theta function representations of solutions for the whole Heisenberg hierarchy as a result of the asymptotic properties of $\phi$

Sistemas de Lie, simetrías de Lie y transformaciones recíprocas

[ES]En esta tesis, estamos interesados en sistemas de interés físico y matemático, descritos por medio de ecuaciones diferenciales ordinarias y en derivadas parciales. Como es bien sabido, gran parte de los fenómenos naturales pueden modelizarse a través de estas ecuaciones. Por ejemplo, las cuatro ecuaciones de la Electrodinámica de Maxwell, o las ecuaciones de Einstein son ecuaciones diferenciales. Vamos a centrar nuestra investigación en dos tipos de sistemas: los llamados sistemas de Lie, muy recurrentes en la literatura, dadas sus múltiples propiedades geométricas y las ecuaciones diferenciales en derivadas parciales que aparecen en modelos físicos como los pertenecientes a la Mecánica de Fluidos, Física del Plasma o la Neurociencia, entre otros. Dada la importancia de los métodos geométricos en el tratamiento de ecuaciones diferenciales, vamos a formular nuestra investigación desde el punto de vista de la geometría diferencial

Lie systems, Lie symmetries and reciprocal transformations

This work represents a PhD thesis concerning three main topics. The first one deals with the study and applications of Lie systems with compatible geometric structures, e.g. symplectic, Poisson, Dirac, Jacobi, among others. Many new Lie systems admitting Vessiot--Guldberg Lie algebras of Hamiltonian vector fields relative to the above mentioned geometric structures are analyzed and their importance is illustrated by their appearances in physical, biological and mathematical models. The second part details the study of Lie symmetries and reductions of relevant hierarchies of differential equations and their corresponding Lax pairs. For example, the Cammasa-Holm and Qiao hierarchies in 2+1 dimensions. The third and last part is dedicated to the study of reciprocal transformations and their application in differential equations appearing in mathematical physics, e.g. Qiao and Camassa-Holm equations equations appearing in the second part.Comment: PhD thesi

Periodic and almost periodic potentials in the inverse problems

We review basic ideas and basic examples of the theory of the inverse spectral problems.Comment: 36 pages, 5 figures, LaTe