# SKM 2023 – wissenschaftliches Programm

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# DY: Fachverband Dynamik und Statistische Physik

## DY 23: Statistical Physics: General II

### DY 23.4: Vortrag

### Dienstag, 28. März 2023, 14:45–15:00, ZEU 250

**Perturbative and Semiclassical Expansions in Quantum Thermodynamics Using a Modified Keldysh Contour** — •Sadeq S. Kadijani, Vasco Cavina, Massimiliano Esposito, and Thomas L. Schmidt — Department of Physics and Materials Science, University of Luxembourg, L-1511 Luxembourg, Luxembourg

Modified Keldysh contours are a versatile tool for calculating moment generating functions (MGFs) in the context of quantum thermodynamics and quantum transport theory, and are the backbone of both Green's functions (GFs) and path integral approaches to open quantum systems. By using a different modification of the Keldysh contour, we will construct a perturbation expansion of the MGFs and discuss its semi-classical expansion. Using the symmetry property of the modified contour, we prove that the perturbative expansion obtained in this way satisfies the fluctuation theorem (FT) in every order of perturbation theory. We show that the contribution of the different diagrams can be added to obtain a general expression of the work statistics in terms of a sum of independent Poisson processes.

To further investigate the work MGF we apply the Feynman path integral techniques to the modified contour. In this way, the MGF can be written in terms of the action, which depends on the fields running on the modified contour. The action can be used to obtain a semiclassical expansion of the MGF, which is then used to compute explicitly the zeroth (classical) and the first quantum correction to the work MGF.