Various situations are described where the construction of exact solutions of nonlinear
ordinary and partial differential equations leads to overdetermined systems
of ODEs with parameters that are not included in the original differential equations.
A non-classical problem for ordinary differential equations with parameters
is formulated and the concept of the conditional capacity of an exact solution is
introduced. The method for investigating overdetermined systems of two ODEs
of any order on consistency, which eventually leads to algebraic equations with
parameters, is presented. A general description of the method of differential constraints
with respect to ordinary differential equations is given and many specific
examples of applying this method for obtaining exact solutions are considered. It
is shown that the use of the splitting method (and also the method based on the
use of invariant subspaces of nonlinear operators) for constructing exact generalized
separable solutions of nonlinear PDEs can lead to overdetermined systems of
ODEs with parameters. Several nonlinear partial differential equations (including
a delay PDE) of higher orders are considered, and their exact solutions are found
by analyzing the corresponding overdetermined ODE systems.
nonlinear equations, ordinary differential equations, partial differential equations, overdetermined systems of ODEs, exact solutions, differential constraints