Thermal out-of-time-order correlators, KMS relations, and spectral functions
- Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Physics and Astronomy
- International Centre for Theoretical Sciences (ICTS-TIFR), Bengahuru (India)
- Univ. of California, Davis, CA (United States). Center for Quantum Mathematics and Physics (QMAP)
We describe general features of thermal correlation functions in quantum systems, with specific focus on the fluctuation-dissipation type relations implied by the KMS condition. These end up relating correlation functions with different time ordering and thus should naturally be viewed in the larger context of out-of-time-ordered (OTO) observables. In particular, eschewing the standard formulation of KMS relations where thermal periodicity is combined with time-reversal to stay within the purview of Schwinger-Keldysh functional integrals, we show that there is a natural way to phrase them directly in terms of OTO correlators. We use these observations to construct a natural causal basis for thermal n-point functions in terms of fully nested commutators. We provide several general results which can be inferred from cyclic orbits of permutations, and exemplify the abstract results using a quantum oscillator as an explicit example.
- Research Organization:
- Univ. of California, Davis, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- SC0009999
- OSTI ID:
- 1502422
- Journal Information:
- Journal of High Energy Physics (Online), Vol. 2017, Issue 12; ISSN 1029-8479
- Publisher:
- Springer BerlinCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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