Lecture 2 (framework of QFT in Curved Space)
We discussed the framework of quantum field theory in curved spacetime. This is an approximation where we take the background spacetime to be fixed, and then consider fluctuations of fields on this background. An important difference with QFT in flat space is the fact that the mode functions may not be plane waves. Moreover, not all observers agree on the vacuum.
We also defined Bogoliubov coefficients and calculated what the vacuum state for one quantization looks like in terms of excited states in another quantization.
