Lectures related to Dilute Instanton Gas Approximation

Covers perturbation theory, variational principle, and systematic approaches to determining true energy levels.

Introduces quantum perturbation theory and its systematic approach to solving perturbed quantum systems.

Covers cross section, lifetime, quantum fluid, asymptotic states, discrete symmetries, and normal ordering in quantum field theory.

Covers time-dependent perturbation theory, focusing on Fermi's Golden Rule and spontaneous emission.