Inhomogeneous phases in the 3+1-dimensional Nambu-Jona-Lasinio model and their dependence on the regularization scheme

TL;DR

This study investigates the inhomogeneous phases of the 3+1-dimensional NJL model using various regularization schemes, revealing that these phases are likely artifacts of regularization rather than intrinsic features of the model.

Contribution

It systematically compares five regularization schemes in the NJL model, showing how inhomogeneous phases depend heavily on the regularization method used.

Findings

Inhomogeneous phases appear across all schemes at specific chemical potentials.

Wave numbers of condensates are comparable to or larger than regulators.

Inhomogeneous phases are likely artifacts of the regularization scheme.

Abstract

In this work we study the $3+1$-dimensional Nambu-Jona-Lasinio (NJL) model in the mean field-approximation. We carry out calculations using five different regularization schemes (two continuum and three lattice regularization schemes) with particular focus on inhomogeneous phases and condensates. The regularization schemes lead to drastically different inhomogeneous regions. We provide evidence that inhomogeneous condensates appear for all regularization schemes almost exclusively at values of the chemical potential and with wave numbers, which are of the order of or even larger than the corresponding regulators. This can be interpreted as indication that inhomogeneous phases in the $3+1$-dimensional NJL model are rather artifacts of the regularization and not a consequence of the NJL Lagrangian and its symmetries.