07.01 Green's functions for independent electrons скачать в хорошем качестве

07.01 Green's functions for independent electrons

In Chapter 7 we will discuss Green's functions. Green's functions can be used to represent in an efficient way the properties of a many body quantum system. This video introduces Green's functions and gives their definitions. Later videos will explain why we define the Green's functions in this way. The Green's functions are defined as the expectation value of the operator that creates or annihilates a particle in a state with quantum number τ' and a time t later annihilates or creates a particle in a state with quantum number τ. We can Fourier transform the Green's functions in the time domain to obtain Green's functions in the frequency domain.