Lecture
This lecture covers the Gelfand-Yaglom formula and time-ordered products in the context of the path integral representation of the propagator for a time-dependent harmonic oscillator. The instructor discusses the operator and matrix elements from the path integral, focusing on the classical limit. The lecture also explores the differential equations and initial conditions related to the harmonic oscillator, providing a detailed analysis of the propagator for both the free particle and the harmonic oscillator. The presentation concludes with exercises using the Gelfand-Yaglom formula to derive the propagators for different scenarios.