Quasideterminant solutions of noncommutative integrable systems

QC Physics;QA Mathematics

Macfarlane, Susan R. ; Gilson, Claire

University:University of Glasgow

Department:School of Mathematics and Statistics

关键词: Integrable systems, noncommutative, quasideterminants;   

Others  :  http://theses.gla.ac.uk/1887/1/2010macfarlanephd.pdf

来源: University of Glasgow

【 摘 要 】

Quasideterminants are a relatively new addition tothe field of integrable systems.Their simple structure disguises a wealth of interesting and useful properties, enabling solutions of noncommutative integrable equations to be expressed in a straightforward and aesthetically pleasing manner.This thesis investigates the derivation and quasideterminant solutions of two noncommutative integrable equations - the Davey-Stewartson (DS) andSasa-Satsuma nonlinear Schrodinger (SSNLS) equations.Chapter 1 provides a brief overview of the various conceptsto which we will refer during the course of the thesis.We begin by explaining the notion of an integrable system, although no concrete definition has ever been explicitly stated.We then move on to discuss Lax pairs, and also introduce the Hirota bilinear form of an integrable equation, looking at the Kadomtsev-Petviashvili (KP)equation as an example.Wronskian and Grammian determinants will play an important role in later chapters, albeit in a noncommutative setting, and, as such, we give an account of their widespread use in integrable systems.Chapter 2 provides further background information, now focusing on noncommutativity.We explain how noncommutativity can be defined and implemented, bothspecifically using a star product formalism, and also in a more general manner.It is this general definition to which we will allude in the remainder of the thesis.We then give the definition of a quasideterminant, introduced by Gel'fand and Retakh in 1991, and provide some examples and properties of these noncommutative determinantal analogues.We also explain how to calculate thederivative of a quasideterminant.The chapter concludes byoutlining the motivation for studying our particular choice of noncommutative integrable equations and their quasideterminant solutions.We begin with the DS equations in Chapter 3, and derive a noncommutative version of this integrable system usinga Lax pair approach.Quasideterminant solutions arise in a natural way by the implementation of Darboux and binary Darboux transformations, and, after describing these transformations in detail, we obtain two types of quasideterminant solution to our system of noncommutative DS equations - a quasi-Wronskian solution from the application of the ordinary Darboux transformation, and aquasi-Grammian solution by applying the binary transformation. After verification of these solutions, in Chapter 4 we select the quasi-Grammian solution to allow us to determine a particular class of solution to our noncommutative DS equations. These solutions, termed dromions, are lump-like objects decaying exponentially in all directions, and are found at the intersection of two perpendicular plane waves.We extend earlierwork of Gilson and Nimmo by obtaining plots of these dromionsolutions in a noncommutative setting.The work on thenoncommutative DS equations and their dromion solutions constitutes our paper published in 2009.Chapter 5 describes how the well-known Darboux andbinary Darboux transformations in (2+1)-dimensions discussed in the previous chapter can be dimensionally-reduced to enable their application to (1+1)-dimensional integrable equations.This reduction was discussed briefly by Gilson, Nimmo and Ohta in reference to the self-dual Yang-Mills (SDYM) equations, however we explain these results in more detail, using a reduction from the DS to the nonlinear Schrodinger (NLS) equation as a specificexample. Results stated here are utilised in Chapter 6, where we consider higher-order NLS equations in(1+1)-dimension.We choose to focus on one particular equation, the SSNLS equation, and, after deriving a noncommutative version of this equation in a similar manner to the derivation of our noncommutative DS system in Chapter 3, we apply the dimensionally-reduced Darboux transformation to the noncommutative SSNLS equation.We see that this ordinary Darboux transformation does not preserve the properties of the equation and its Lax pair,and we must therefore look to the dimensionally-reduced binary Darboux transformation to obtain a quasi-Grammian solution.After calculating some essential conditions on various terms appearing in our solution, we are then able to determine and obtain plots of soliton solutions in a noncommutative setting.Chapter 7 seeks to bring together the various results obtained in earlier chapters, and also discusses some open questions arising from our work.