Ward identities and Chiral anomaly in the Luttinger liquid

TL;DR

This paper develops a Renormalization Group framework using Ward identities and Dyson equations to analyze Luttinger liquids, revealing non-universal critical behavior and constructing a related quantum field theory.

Contribution

It introduces a method to control flow of coupling constants in 1D fermionic systems using Ward identities despite anomalies, completing the Luttinger liquid theory without exact solutions.

Findings

Demonstrates non-universal critical indices in Luttinger liquids

Constructs a quantum field theory for the Thirring model

Shows ultraviolet cutoff can be removed in the analysis

Abstract

Systems of interacting non relativistic fermions in $d=1$, as well as spin chains or interacting bidimensional Ising models, verify an hidden approximate Gauge invariance which can be used to derive suitable Ward identities. Despite the presence of corrections and anomalies, such Ward identities can be implemented in a Renormalization Group approach and used to exploit nontrivial cancellations which allow to control the flow of the running coupling constants; in particular this is achieved combining Ward identities, Dyson equations and suitable correction identities for the extra terms appearing in the Ward identities, due to the presence of cutoffs breaking the local gauge symmetry. The correlations can be computed and show a Luttinger liquid behavior characterized by non universal critical indices, so that the general Luttinger liquid construction for one dimensional systems is completed without any use of exact solutions. The ultraviolet cutoff can be removed and a Quantum Field Theory corresponding to the Thirring model is also constructed.