Polarized DIS in N=4 SYM: Where is spin at strong coupling?

TL;DR

This paper uses AdS/CFT to compute polarized structure functions in strongly coupled N=4 SYM, revealing that spin is mainly from orbital angular momentum at strong coupling.

Contribution

It provides the first calculation of polarized structure functions at strong coupling in N=4 SYM, highlighting the dominance of orbital angular momentum in hadron spin.

Findings

Flavor singlet g_1 is negligible at strong coupling.

Flavor non-singlet g_1 exhibits Regge behavior with intercept less than 1.

Spin is primarily due to orbital angular momentum at strong coupling.

Abstract

Using the AdS/CFT correspondence, we calculate the polarized structure functions in strongly coupled N=4 supersymmetric Yang-Mills theory deformed in the infrared. We find that the flavor singlet contribution to the g_1 structure function is vanishingly small, while the flavor non-singlet contribution shows the Regge behavior at small-x with an intercept slightly less than 1. We explicitly check that the latter satisfies the moment sum rule. We discuss the `spin crisis' problem and suggest that at strong coupling the spin of a hadron entirely comes from the orbital angular momentum.