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

Abstract

Using the AdS/CFT correspondence, we calculate the polarized structure functions in strongly coupled = 4 supersymmetric Yang-Mills theory deformed in the infrared. We find that the flavor singlet contribution to the g1 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.