Variational Analysis: Critical Extremals and Sturmian Extensions (Dover Books on Mathematics)

This text presents extended separation, comparison, and oscillation theorems that replace classical analysis of Legendre, Jacobi, and Hilbert. Its analysis of related quadratic functionals shows how critical extremals can substitute for minimizing extremals. Additional topics include focal conditions and Sturm-like theorems, general boundary conditions, and root theory prestructures. 1973 edition.