This study 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. 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 a supplementary text for postgraduate students.
1 Gradient Systems in a Lie Algebra.- 1.1 Preliminaries.- 1.2 Gradient systems in Fn and Der (Rn).- 1.3 Gradient Systems Determined by a Lie Algebra.- 2 Representation of a Gradient System.- 2.1 Finite-Dimensional Lie Algebra.- 2.2 The Maximal Rank Lie Algebra.- 2.3 Integral Manifolds.- 2.4 Some applications.- 3 F. G. O. Lie Algebras.- 3.1 Lie algebras finitely generated over orbits.- 3.2 Nonsingularity of the gradient system.- 3.3 Some Applications.- 4 Applications.- 4.1 Systems of Semiliniar Equations.- 4.2 Stochastic Differential Equations.- 4.3 Systems of Hyperbolic equations.- 4.4 Finite-Dimensional Nonlinear Filters.- 4.5 Affine Control Systems.- 4.6 Integral Representation of Solutions.- 4.7 Decomposition of affine control systems.- 5 Stabilization and Related Problems.- 5.1 Equivalent Controllable Systems.- 5.2 Approximations, Small Controls.- 5.3 Nonlinear Control Systems.- 5.4 Stabilization of Affine Control Systems.- 5.5 Controlled Invariant Lie Algebras.- 5.6 Stochastic differential equations.