Scattering Amplitude and Optical Theorem

This lecture covers the introduction of scattering amplitude, optical theorem, relation between scattering cross-section and scattering amplitude, and the use of unitary operators in quantum mechanics. The instructor explains the conditions for the unitarity of the Smatrix and its implications on the potential. The lecture also delves into the concept of bound and unbound states in quantum mechanics, emphasizing the importance of choosing eigenstates as a basis set. Furthermore, the instructor introduces the concept of Green's functions and their role in quantum mechanics.