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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Strongly correlated electron systems are generally described by tight bindinglattice Hamiltonians with strong local (on site) interactions, the most popularbeing the Hubbard model. Although the half filled Hubbard model can besimulated by Monte Carlo(MC), physically more interesting cases beyond halffilling are plagued by the sign problem. One therefore should resort to othermethods. It was demonstrated recently that a systematic truncation of the setof Dyson-Schwinger equations for correlators of the Hubbard, supplemented by a\textquotedblleft covariant" calculation of correlators leads to a convergentseries of approximants. The covariance preserves all the Ward identities amongcorrelators describing various condensed matter probes. While first order(classical), second (Hartree-Fock or gaussian) and third (Cubic) covariantapproximation were worked out, the fourth (quartic) seems too complicated to beeffectively calculable in fermionic systems. It turns out that the complexityof the quartic calculation\ in local interaction models,is manageablecomputationally. The quartic (Bethe - Salpeter type) approximation isespecially important in 1D and 2D models in which the symmetry broken statedoes not exists (the Mermin - Wagner theorem), although strong fluctuationsdominate the physics at strong coupling. Unlike the lower order approximations,it respects the Mermin - Wagner theorem. The scheme is tested and exemplifiedon the single band 1D and 2D Hubbard model.

Covariant Bethe-Salpeter approximation in strongly correlated electron systems model