On the deformation method for studies of performance functionals in systems with an infinite number of degrees of freedom

A tool is suggested for investigating the performance functionals of nonlinear infinitely-dimensional systems whereby the functional is deformed to become a functional with a minimum point. Theorems on the minimum of integral functional are found to be related to those on uniqueness of boundary value problems for differential equations. Some applications to stability analysis of systems with an infinite number of degrees of freedom are pointed up to.