Physical and unphysical regimes of self-consistent many-body perturbation theory

Kris Van Houcke, Evgeny Kozik, Riccardo Rossi, Youjin Deng, Felix Werner

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

In the standard framework of self-consistent many-body perturbation theory, the skeleton series for the self-energy is truncated at a finite order N and plugged into the Dyson equation, which is then solved for the propagator GN. We consider two examples of fermionic models, the Hubbard atom at half filling and its zero space-time dimensional simplified version. First, we show that GN converges when N → ∞ to a limit G , which coincides with the exact physical propagator Gexact at small enough coupling, while G ≠ Gexact at strong coupling. This follows from the findings of [1] and an additional subtle mathematical mechanism elucidated here. Second, we demonstrate that it is possible to discriminate between the G = Gexact and G ≠ Gexact regimes thanks to a criterion which does not require the knowledge of Gexact , as proposed in [2].

Original languageEnglish
Article number133
Pages (from-to)133
JournalSciPost Physics
Volume16
Issue number5
DOIs
Publication statusPublished - 27 May 2024

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