English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Most currently used approximations for the one-particle Green's function G inthe framework of many-body perturbation theory, such as Hedin's GWapproximation or the cumulant GW+C approach, are based on a linear responseapproximation for the screened interaction W. The extent to which such ahypothesis is valid and ways to go beyond have been explored only very little.Here we show how to derive a cumulant Green's function beyond linear-responsefrom the equation of motion of the Green's function in a functional derivativeformulation. The results can be written in a compact form, which opens thepossibility to calculate the corrections in a first principles framework usingtime-dependent density functional theory. In order to illustrate the potentialimportance of the corrections, numerical results are presented for a modelsystem with a core level and two valence orbitals.

Non-linear response in the cumulant expansion for core hole photoemission