The Propagator Matrix Reloaded

For quantum fields in curved spacetimes there isn't a unique notion of vacuum state and the in and out vacua might be different, therefore, to perform calculations with interacting theories we require the use of the Schwinger-Keldysh formulation, very similar to undergraduate quantum mechanics. However, the usual assumption that the theory is free at past infinity isn't necessarily true and there is a need to modify the usual formalism to take this into account, resulting in a 3x3 matrix of propagators instead of the more familiar 2x2. In my talk I will describe this new formalism and test it in flat spacetime with the surprising conclusion that even in Minkowski spacetime it seems like the theory isn't free at past infinity at finite temperature as is commonly assumed.

Zoom link: https://zoom.us/j/91390797603?pwd=bWdEdUJNYkhZQWZQRFdsTjlSQXk0Zz09