Applications of Lie Algebras to Hyperbolic and Stochastic Differential Equations (Mathematics and Its Applications)

The main part of the book is based on a one semester graduate course for students in mathematics. I have attempted to develop the theory of hyperbolic systems of differen­ tial equations in a systematic way, making as much use as possible ofgradient systems and their algebraic representation. However, despite the strong sim­ ilarities between the development of ideas here and that found in a Lie alge­ bras course this is not a book on Lie algebras. The order of presentation has been determined mainly by taking into account that algebraic representation and homomorphism correspondence with a full rank Lie algebra are the basic tools which require a detailed presentation. I am aware that the inclusion of the material on algebraic and homomorphism correspondence with a full rank Lie algebra is not standard in courses on the application of Lie algebras to hyperbolic equations. I think it should be. Moreover, the Lie algebraic structure plays an important role in integral representation for solutions of nonlinear control systems and stochastic differential equations yelding results that look quite different in their original setting. Finite-dimensional nonlin­ ear filters for stochastic differential equations and, say, decomposability of a nonlinear control system receive a common understanding in this framework. This book deals mainly with the relevance of integral manifolds associated with a Lie algebra with singularities for studying systems of first order partial differential equations, stochastic differential equations and nonlinear control systems. The analysis is based on the algebraic representation of gradient systems in a Lie algebra, allowing the recovery of the original vector fields and the associated Lie algebra as well. Special attention is paid to nonlinear control systems encompassing specific problems of this theory and their significance for stochastic differential equations. The work is written in a self-contained manner, presupposing only some basic knowledge of algebra, geometry and differential equations. Audience: This volume will be of interest to mathematicians and engineers working in the field of applied geometric and algebraic methods in differential equations. It can also be recommended as a supplementary text for postgraduate students.