On string solutions of Bethe equations in N=4 supersymmetric Yang-Mills theory

TL;DR

This paper analyzes the solutions of Bethe equations in N=4 supersymmetric Yang-Mills theory, proving string formation in the thermodynamic limit and exploring the vacuum structure influenced by exponential corrections.

Contribution

It demonstrates that roots of the deformed Bethe equations form strings in the thermodynamic limit and investigates the impact of exponential corrections on the vacuum structure.

Findings

Roots group into strings in the thermodynamic limit.

Energy decreases with increasing string length.

Non-analyticity affects the density and energy of even-length strings.

Abstract

The Bethe equations, arising in description of the spectrum of the dilatation operator for the su(2) sector of the N=4 supersymmetric Yang-Mills theory, are considered in the anti-ferromagnetic regime. These equations are deformation of those for the Heisenberg XXX magnet. It is proven that in the thermodynamic limit roots of the deformed equations group into strings. It is proven that the corresponding Yang's action is convex, which implies uniqueness of solution for centers of the strings. The state formed of strings of length (2n+1) is considered and the density of their distribution is found. It is shown that the energy of such a state decreases as n grows. It is observed that non-analyticity of the left hand side of the Bethe equations leads to an additional contribution to the density and energy of strings of even length. Whence it is concluded that the structure of the anti-ferromagnetic vacuum is determined by the behaviour of exponential corrections to string solutions in the thermodynamic limit and possibly involves strings of length 2.