Regensburg 2025 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 20: Many-body Quantum Dynamics II (joint session DY/TT)

DY 20.3: Vortrag

Mittwoch, 19. März 2025, 10:00–10:15, H37

Scrutinizing the Mori memory function for transport scenarios — •Scott Daniel Linz, Jiaozi Wang, Robin Steinigeweg, and Jochen Gemmer — Department of Mathematics/Computer Science/Physics, University of Osnabrück, D-49076 Osnabrück, Germany

Diffusion is a phenomenological hydrodynamic transport behavior that holds over a wide range of materials. Within condensed matter physics there is the opinion that as long as the area under the current-current correlation function converges in time, one has a criterion for diffusive behavior of the corresponding spatiotemporal density dynamics. Attempts to derive this statement are notoriously challenging. We will first demonstrate that it is possible to construct correlation functions of some local density, where the area under a current-current correlation function converges, but the system is not diffusive. After this is demonstrated, we shall introduce a method based on the recursion method and the Mori memory formalism, that yields insight into whether or not a process is truly diffusive. The only disadvantage of this strategy is that one would have to know the behavior infinitely many Lanczos coefficients, whereas in practice one can only calculate a finite number of them in most cases. In the cases examined in this talk, however, the convergence or lack thereof becomes apparent to the naked eye with the finite amount of coefficients that were calculated.

Keywords: Diffusion; Correlation function; Recursion method; Mori memory formalism; Spin chain