Spontaneous BRST symmetry breaking in infrared QCD

TL;DR

This paper proposes a novel effective Lagrangian for low-energy Yang--Mills theory that exhibits spontaneous BRST symmetry breaking, leading to gluon and ghost mass generation and connecting to the Curci--Ferrari model.

Contribution

It introduces a new effective Lagrangian with spontaneous BRST symmetry breaking, incorporating Fujikawa fields and extended-BRST symmetry, unifying various models in low-energy QCD.

Findings

Reproduces the Curci--Ferrari model as a special case.

Predicts the emergence of gluon and ghost masses due to symmetry breaking.

Establishes a link between spontaneous BRST breaking and effective low-energy QCD dynamics.

Abstract

We present a novel proposal for the effective Lagrangian of the low-energy Yang--Mills quantum field theory. The proposed effective Lagrangian exhibits the spontaneous BRST symmetry breaking. We built the Fujikawa model that we couple to the Yang--Mills elementary field sector, motivated by the analogy with Chiral Quark Model. We interpret the Fujikawa fields as effective fields composite of the elementary gluon and ghost fields. In order to justify the existence of two massless Nambu--Goldstone modes among the Fujikawa fields, we require not only the BRST but also the anti-BRST invariance of the effective Lagrangian, both to be spontaneously broken. The most striking consequence of that is the emergence of the effective gluon and ghost masses. We reproduce the Curci--Ferrari model as a special case of our effective model upon the spontaneous BRST symmetry breaking. In order to reproduce also the non-nilpotent modified BRST symmetry, characteristic for the Curci--Ferrari model, we modify our effective Lagrangian to be invariant with respect to the extended-BRST symmetry, which mixes the elementary and Fujikawa field sectors, and which is nilpotent. The Curci--Ferrari is reproduced by the elementary field sector of the resulting Lagrangian. The remaining Fujikawa's field dependent terms guarantee the underlying nilpotent extended-BRST symmetry, which is now hidden in the sense of the spontaneous symmetry breaking.