Explore advanced concepts in cosmology through this lecture by renowned physicist Nima Arkani-Hamed, part of the Kavli Asian Winter School on Strings, Particles and Cosmology 2018. Delve into topics such as path integrals, harmonic oscillation, wave functions, and boundary conditions in cosmological contexts. Examine equations of motion, Bessel and Hankel functions, and their applications in theoretical physics. Gain insights into conformal field theory and its relevance to cosmological models. Conclude with a Q&A session to further clarify complex ideas presented throughout the 1 hour 40 minute lecture.