SciPost Submission Page
Scaling of free cumulants in closed system-bath setups
by Merlin Füllgraf, Jochen Gemmer, Jiaozi Wang
Submission summary
| Authors (as registered SciPost users): | Merlin Füllgraf |
| Submission information | |
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| Preprint Link: | scipost_202512_00012v1 (pdf) |
| Date submitted: | Dec. 4, 2025, 10:24 a.m. |
| Submitted by: | Merlin Füllgraf |
| Submitted to: | SciPost Physics Core |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
The Eigenstate Thermalization Hypothesis (ETH) has been established as a cornerstone for understanding thermalization in quantum many-body systems. Recently, there has been growing interest in the full ETH, which extends the framework of the conventional ETH and postulates a smooth function to describe the multi-point correlations among matrix elements. Within this framework, free cumulants play a central role, and most previous studies have primarily focused on closed systems. In this paper, we extend the analysis to a system–bath setup, considering both an idealized case with a random- matrix bath and a more realistic scenario where the bath is modeled as a defect Ising chain. In both cases, we uncover a universal scaling of microcanonical free cumulants of system observables with respect to the interaction strength. Furthermore we estab- lish a connection between this scaling behavior and the thermalization dynamics of the thermal free cumulants of corresponding observables.