Which field extensively applies Variational Perturbation Theory?

Variational Perturbation Theory finds extensive application in theoretical physics, particularly in areas such as quantum mechanics, quantum field theory, and condensed matter physics. It provides a powerful framework for studying the behavior of quantum systems and making predictions about their properties and interactions. In theoretical physics, Variational Perturbation Theory is used to address a wide range of problems, from understanding the behavior of atoms and molecules to describing the properties of materials and complex quantum systems.