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Durham University

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Publication details for Paul Sutcliffe

Bolognesi, S. & Sutcliffe, P.M. (2014). The Sakai-Sugimoto soliton. Journal of High Energy Physics 2014(1): 78.

Author(s) from Durham


The Sakai-Sugimoto model is the preeminent example of a string theory de-
scription of holographic QCD, in which baryons correspond to topological solitons in the
bulk. Here we investigate the validity of various approximations of the Sakai-Sugimoto
soliton that are used widely to study the properties of holographic baryons. These ap-
proximations include the flat space self-dual instanton, a linear expansion in terms of
eigenfunctions in the holographic direction and an asymptotic power series at large radius.
These different approaches have produced contradictory results in the literature regarding
properties of the baryon, such as relations for the electromagnetic form factors. Here we
determine the regions of validity of these various approximations and show how to relate
different approximations in contiguous regions of applicability. This analysis clarifies the
source of the contradictory results in the literature and resolves some outstanding issues,
including the use of the flat space self-dual instanton, the detailed properties of the asymp-
totic soliton tail, and the role of the UV cutoff introduced in previous investigations. A
consequence of our analysis is the discovery of a new large scale, that grows logarithmically
with the ’t Hooft coupling, at which the soliton fields enter a nonlinear regime. Finally,
we provide the first numerical computation of the Sakai-Sugimoto soliton and demonstrate
that the numerical results support our analysis.