Onsager’s regression hypothesis adjusted to quantum systems: theory, applications and outlook

by Christian Eidecker-Dunkel

Thursday May 15, 2025, 2:15 PM → 3:00 PM Europe/Berlin

D5-153 (UHG)

Onsager’s regression hypothesis connects the temporal relaxation of close-to-equilibrium systems with their dynamical correlation functions at thermal equilibrium. While the hypothesis is provably correct in classical systems, it is known to fail in the quantum
regime. On the other hand, in [1] we have derived an adjusted version of Onsager’s regression hypothesis suitable for quantum systems.
In my presentation, I will introduce the formalism established in [1], together with analytical and numerical considerations regarding its validity. Furthermore, I will show the usefulness of this approach by applying it to selected spin-chain models to rigorously tackle the problem of (re-)thermalization after a local quantum quench in these systems [2]. I will conclude my talk with an outlook for a possible generalization together with a useful approximation of the adjusted version of Onsager's regression hypothesis.

[1] P. Reimann and C. Eidecker-Dunkel, Onsager’s regression hypothesis adjusted to quantum systems, Phys. Rev. B 110, 014306 (2024)
[2] P. Reimann and C. Eidecker-Dunkel, Thermalization in a simple spin-chain model, Phys. Rev. B 111, 054312 (2025)