Bosonic Monocluster Expansion

TL;DR

This paper introduces a minimal expansion method for Bosonic field theories that simplifies the computation of connected Green's functions, enabling direct construction of the thermodynamic limit and aligning Bosonic expansions with Fermionic and perturbative approaches.

Contribution

It presents a novel minimal expansion technique for Bosonic fields that unifies cluster, Mayer, and perturbative expansions into a single step.

Findings

Allows direct construction of the infinite volume limit.

Brings Bosonic expansions closer to Fermionic and perturbative methods.

Simplifies the computation of connected Green's functions.

Abstract

We compute connected Green's functions of a Bosonic field theory with cutoffs by means of a ``minimal'' expansion which in a single move, interpolating a generalized propagator, performs the usual tasks of the cluster and Mayer expansion. In this way it allows a direct construction of the infinite volume or thermodynamic limit and it brings constructive Bosonic expansions closer to constructive Fermionic expansions and to perturbation theory.