Calculus of Variations I

The book explores classical variational calculus, appealing to analysts, geometers, and physicists. Volume 1 focuses on the formal framework and nonparametric field theory, while Volume 2 covers parametric variational problems, Hamilton-Jacobi theory, and first-order partial differential equations. It emphasizes inner variations, revealing insights like monotonicity formulas and conservation laws, particularly through Emmy Noether's principles. Additionally, it examines Legendre-Jacobi theory, one-dimensional field theory, and the role of convexity in variational calculus, highlighting the concept of null Lagrangians.