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Keldysh diagram technique with non-Gaussian initial correlations.

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Title: Keldysh diagram technique with non-Gaussian initial correlations.
Authors: Mikhaylenko, A. G.1,2 (AUTHOR) mikhajlenko.ag@phystech.edu, Semenov, A. G.1 (AUTHOR)
Source: Theoretical & Mathematical Physics. Apr2026, Vol. 227 Issue 1, p680-704. 25p.
Subjects: Cumulants, Wigner distribution, Quantum field theory, Nonequilibrium statistical mechanics, Scalar field theory
Abstract: We modify the nonequilibrium Keldysh diagram technique to systematically account for non-Gaussian initial correlations. We represent information about the initial state of the system as an additional term in the Keldysh action, which is expressed in terms of the cumulants of the initial Wigner functional. This additional term leads to the appearance of additional vertices in the diagram technique. We study the role of non-Gaussian initial correlations in the further evolution of correlation functions. In particular, we show that the presence of non-Gaussian correlations of odd order leads to the generation of a mean field. We obtain Dyson equations with partially resummed self-energies and prove that diagrams with a finite number of loops contain a finite number of non-Gaussian cumulants of the initial Wigner functional. We apply the modified diagram technique to the description of the evolution of a scalar field after a quench and show that in the limit of short interaction times this technique leads to exact results. [ABSTRACT FROM AUTHOR]
Copyright of Theoretical & Mathematical Physics is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: <searchLink fieldCode="JN" term="%22Theoretical+%26+Mathematical+Physics%22">Theoretical & Mathematical Physics</searchLink>. Apr2026, Vol. 227 Issue 1, p680-704. 25p.
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  Data: We modify the nonequilibrium Keldysh diagram technique to systematically account for non-Gaussian initial correlations. We represent information about the initial state of the system as an additional term in the Keldysh action, which is expressed in terms of the cumulants of the initial Wigner functional. This additional term leads to the appearance of additional vertices in the diagram technique. We study the role of non-Gaussian initial correlations in the further evolution of correlation functions. In particular, we show that the presence of non-Gaussian correlations of odd order leads to the generation of a mean field. We obtain Dyson equations with partially resummed self-energies and prove that diagrams with a finite number of loops contain a finite number of non-Gaussian cumulants of the initial Wigner functional. We apply the modified diagram technique to the description of the evolution of a scalar field after a quench and show that in the limit of short interaction times this technique leads to exact results. [ABSTRACT FROM AUTHOR]
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  Data: <i>Copyright of Theoretical & Mathematical Physics is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1134/S0040577926040094
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        Text: English
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      – SubjectFull: Wigner distribution
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      – SubjectFull: Quantum field theory
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      – SubjectFull: Nonequilibrium statistical mechanics
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      – SubjectFull: Scalar field theory
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      – TitleFull: Keldysh diagram technique with non-Gaussian initial correlations.
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              Text: Apr2026
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