It is challenging to quantify chaos of QCD, because non-perturbative QCD accompanies non-local observables. By using holography, we find that QCD strings at large Nc and strong coupling limit exhibit chaos, and measure their Lyapunov exponent at zero temperature. A pair of a quark and an antiquark separated by Lq in the large Nc QCD is dual to a Nambu-Goto string hanging from the spatial boundary of the D4-soliton geometry. We numerically solve the motion of the string after putting a pulse force on its boundaries. The chaos is observed for the amplitude of the force larger than a certain lower bound. The bound increases as Lq grows, and its dependence is well approximated by a hypothesis that the chaos originates in the endpoints of the QCD string.
@article{arxiv.1903.04718,
title = {Chaos of QCD string from holography},
author = {Tetsuya Akutagawa and Koji Hashimoto and Keiju Murata and Toshihiro Ota},
journal= {arXiv preprint arXiv:1903.04718},
year = {2019}
}