Full title: "A field theoretical approach to non-equilibrium many-body dynamics: perturbative calulation of post-quench overlaps"

The history of realizing non-equilibrium quantum many-body dynamics in experiments spans almost two decades by now. The aim to understand these revolutionary experiments called for a renewed and fruitful effort on the theoretical side in setting up and solving models of quantum systems far from equilibrium. A particularly successful paradigm of this field is the quantum quench that describes a setup where the initial state is not an eigenstate of the Hamiltonian generating the time evolution. This setup can be studied in several ways, in a recent work [1] we took a field theoretical approach to obtain perturbatively the post-quench overlaps that are necessary ingredients to characterize the time evolution after a quantum quench. After briefly introducing the broader context of quantum quenches, I am going to present the results of this work in the seminar talk. In the paper we derive an expression for the overlaps assuming that either the model before or after the quench is integrable. Our calculations distinguish between the two approaches, showing serious constraints in the former case, while the latter calculation yields precise results. We illustrate this in a specific integrable model: the Ising Field Theory in a magnetic field where we contrast the perturbative expressions against numerical data using obtained using the Truncated Conformal Space Approach.

[1] K. Hódsági, M. Kormos, G. Takács: Perturbative post-quench overlaps in Quantum Field Theory, J. High Energ. Phys. (2019) 2019:47 [1905.05623]