Causal optimization method for imaginary-time Green's functions in interacting electron systems

Mancheon Han, Hyoung Joon Choi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We develop a causal optimization method that ensures causality in numerical calculations of Green's functions in interacting electron systems. Our method removes noncausality of numerical data by finding causal functions closest to the data. By testing our method with an exactly calculable model and applying it to practical dynamical mean-field calculations, we find that intermediate-frequency behaviors of Green's functions are determined solely by causality, and noncausal statistical errors are removed very efficiently. Furthermore, we demonstrate that numerical calculations of the physical branch of the Luttinger-Ward functional can be stabilized by ensuring causality of the noninteracting Green's function. Our method and findings provide a basis for improving stability and efficiency of numerical simulations of quantum many-body systems.

Original languageEnglish
Article number115112
JournalPhysical Review B
Issue number11
Publication statusPublished - 2021 Sept 15

Bibliographical note

Funding Information:
This work was supported by NRF of Korea (Grant No. 2020R1A2C3013673), KISTI supercomputing center (Project No. KSC-2019-CRE-0195), and the Graduate School of Yonsei University Research Scholarship Grants in 2018.

Publisher Copyright:
© 2021 American Physical Society.

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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