# Chaos of QCD string from holography

## TL;DR

This paper investigates chaos in large N_c, strongly coupled QCD strings using holography, measuring Lyapunov exponents and identifying conditions under which chaos emerges.

## Contribution

It demonstrates that QCD strings exhibit chaos at strong coupling via holographic duality and quantifies this chaos through Lyapunov exponents.

## Key findings

- Chaos appears when boundary force exceeds a certain threshold.
- The chaos bound increases with quark-antiquark separation.
- Chaos originates from the endpoints of the QCD string.

## Abstract

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 $N_c$ and strong coupling limit exhibit chaos, and measure their Lyapunov exponent at zero temperature. A pair of a quark and an antiquark separated by $L_q$ in the large $N_c$ 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 $L_q$ grows, and its dependence is well approximated by a hypothesis that the chaos originates in the endpoints of the QCD string.