Molecular cluster perturbation theory. I. Formalism

8 Cluster Perturbation Theory

Cluster Perturbation Theory (CPT) is a simple approximation scheme that applies to lattice models with local interactions, like the Hubbard model, or models where the local interaction is predominant. It proceeds by tiling the lattice into identical, finite-size clusters, solving these clusters exactly and treating the inter-cluster hopping terms at first order in strong-coupling perturbation t...

Statistical Perturbation Theory of Cosmic Fields I: Basic Formalism and Second-order Theory

We formulate a general method for perturbative evaluations of statistics of smoothed cosmic fields, which we call as “Statistical Perturbation Theory”. The formalism is an extensive generalization of the method used by Matsubara (1994) who derived a weakly nonlinear formula of the genus statistic in a 3D density field. After describing the general method, we apply the formalism especially to an...

A New Formalism in Perturbation Theory Using Continued Fractions.

Analysis of a New Formalism in Perturbation Theory.

Many-polaron problem by cluster perturbation theory

The carrier-density dependence of the photoemission spectrum of the Holstein many-polaron model is studied using cluster perturbation theory combined with an improved cluster diagonalization by Chebychev expansion.