Lie groups and Bäcklund transformations: application to nonlinear physical models

A diversity of physical phenomena is modelled by systems of nonlinear differential equations not, in general, amenable to exact solution. However, in certain cases, exploitation of hidden symmetries in the nonlinear models can lead to solutions and reduction to canonical systems. Invariance under Lie groups and/or Bäcklund transformations are two pivotal methods in this regard. [Continues.]