Abstract:
As part of the report, before the new results themselves, the Keldysh Schwinger diagrammatic technique will be described and the procedure for isolating and analyzing secular contributions from loop corrections will be shown, using the simplest example – a state close to equilibrium in a flat Minkowski space. The main part of the report will be devoted to the study of the model of continuous infinite expansion of the Universe with a flat start. We use a conformally flat metric with an exponentially growing coefficient in conformal time as the gravitational background. We aim to clarify some properties of QFT against such a gravitational background. In particular, we calculate loop corrections to the Keldysh propagator in order to confirm the fact of a secular grow in the level population and anomalous quantum averages in scalar field theory with self-interaction. The main results are presented for cubic self-interaction. We also provide some results for the case of self-interaction of arbitrary integer degree.
