Constraints of cluster separability and covariance on current operators

TL;DR

This paper investigates the constraints imposed by cluster separability and covariance on current operators in light-front quantum mechanics, finding that corrections needed for cluster properties are negligible for nucleon-meson models.

Contribution

It analyzes the size of corrections needed to restore cluster properties in Bakamjian-Thomas models with light-front symmetry, showing they are too small to observe experimentally.

Findings

Corrections for cluster properties are negligible in nucleon-meson models.

Bakamjian-Thomas models can be adjusted to satisfy cluster conditions with minimal impact.

Restoring cluster properties involves computationally intensive methods, but the effects are small.

Abstract

Realistic models of hadronic systems should be defined by a dynamical unitary representation of the Poincare group that is also consistent with cluster properties and a spectral condition. All three of these requirements constrain the structure of the interactions. These conditions can be satisfied in light-front quantum mechanics, maintaining the advantage of having a kinematic subgroup of boosts and translations tangent to a light front. The most straightforward construction of dynamical unitary representations of the Poincare group due to Bakamjian and Thomas fails to satisfy the cluster condition for more than two particles. Cluster properties can be restored, at significant computational expense, using a recursive method due to Sokolov. In this work we report on an investigation of the size of the corrections needed to restore cluster properties in Bakamjian-Thomas models with a light-front kinematic symmetry. Our results suggest that for models based on nucleon and meson degrees of freedom these corrections are too small to be experimentally observed.