A light-front coupled-cluster method for quantum field theories

TL;DR

This paper introduces a novel light-front coupled-cluster method for quantum field theories that avoids Fock-space truncation by using an exponential-operator approximation, enabling more accurate bound state calculations.

Contribution

It develops a new coupled-cluster approach in light-front coordinates that formulates the Hamiltonian eigenvalue problem without Fock-space truncation, using nonlinear integral equations.

Findings

Eliminates the need for Fock-space truncation in bound state calculations.

Provides a framework for calculating matrix elements using coupled-cluster techniques.

Formulates a set of nonlinear integral equations for the exponential operator.

Abstract

The Hamiltonian eigenvalue problem for bound states of a quantum field theory is formulated in terms of Dirac's light-front coordinates and then approximated by the exponential-operator technique of the standard coupled-cluster method. This approximation eliminates any need for the usual approximation of Fock-space truncation. Instead, the exponential operator is truncated and the terms retained are determined by a set of nonlinear integral equations. These equations are solved simultaneously with an effective eigenvalue problem in the valence sector, where the number of constituents is small. Matrix elements can be calculated, with extensions of techniques from standard coupled-cluster theory.