Long-distance properties of baryons in the Sakai–Sugimoto model

Abstract

We reconsider the realization of baryons in the Sakai--Sugimoto model. It has previously been shown that, at least with the standard approach to calculations of baryon properties in the theory, one does not reproduce some model-independent predictions for the behavior of baryon electromagnetic form factors that are connected with long-range pion physics. In the standard approach, considerations involving the consequences of the ${\ensuremath{\alpha}}^{\ensuremath{'}}$ expansion motivated the use of a linearized approximation. This made it appear that the long-range pion physics of baryons may be hidden in (intractable) ${\ensuremath{\alpha}}^{\ensuremath{'}}$ corrections in the gravity dual. In this paper, we study the long-range properties of baryons in the Sakai--Sugimoto model without relying on the standard linearization approximations that we suspect appeared to drop pion contributions to baryon properties. The baryon solution we obtain gives the correct result for the model-independent ratio of form factors, implying that the model captures the expected infrared properties of baryons without the need to go beyond the leading order in the ${\ensuremath{\alpha}}^{\ensuremath{'}}$ expansion.