Spectrum of confining strings in SU(N) gauge theories

TL;DR

This paper investigates the spectrum of confining strings in SU(N) gauge theories using lattice simulations, confirming the sine formula for string tension ratios with high precision and discussing deviations from Casimir scaling.

Contribution

The study provides the first high-precision lattice measurements of string tensions in SU(4) and SU(6) gauge theories, confirming the sine formula for string ratios.

Findings

Results consistent with the sine formula for string tension ratios.

Approximate 1-2% accuracy in measurements.

Deviations from Casimir scaling observed.

Abstract

We study the spectrum of the confining strings in four-dimensional SU(N) gauge theories. We compute, for the SU(4) and SU(6) gauge theories formulated on a lattice, the string tensions sigma_k related to sources with Z_N charge k, using Monte Carlo simulations. Our results are consistent with the sine formula sigma_k/sigma = sin k pi/N / sin pi/N for the ratio between sigma_k and the standard string tension sigma. For the SU(4) and SU(6) cases the accuracy is approximately 1% and 2%, respectively. The sine formula is known to emerge in various realizations of supersymmetric SU(N) gauge theories. On the other hand, our results show deviations from Casimir scaling. We also discuss an analogous behavior exhibited by two-dimensional SU(N) x SU(N) chiral models.