arXiv subjects

Nick Dorey

Publications and source records attributed to Nick Dorey.

57 records · Page 4Linked to original sources

arXiv2000

Softly-Broken {\cal N} = 4 Supersymmetry in the Large-N Limit

We calculate the exact values of the holomorphic observables of {\cal N}=4 supersymmetric SU(N) Yang-Mills theory deformed by mass terms which preserve {\cal N}=1 SUSY. These include the chiral condensates in each massive vacuum of the theory as well as the central charge which determines the tension of BPS saturated domain walls interpolating between these vacua. Several unexpected features emerge in the large-N limit, including anomalous modular properties under an SL(2,Z) duality group which acts on a complexification of the 't Hooft coupling λ=g^{2}N/4π. We discuss our results in the context of the AdS/CFT correspondence.

hep-th↗

arXiv1995

The Large-N_c Renormalization Group

In this talk we review how effective theories of mesons and baryons become exactly soluble in the large-N_c limit. We start with a generic hadron Lagrangian constrained only by certain well-known large-N_c selection rules. The bare vertices of the theory are dressed by an infinite class of UV divergent Feynman diagrams at leading order in 1/N_c. We show how all these leading-order diagrams can be summed exactly using semiclassical techniques. The saddle-point field configuration is reminiscent of the chiral bag: hedgehog pions outside a sphere of radius Λ^{-1} (Λbeing the UV cutoff of the effective theory) matched onto nucleon degrees of freedom for r < Λ^{-1}. The effect of this pion cloud is to renormalize the bare nucleon mass, nucleon-Δhyperfine mass splitting, and Yukawa couplings of the theory. The corresponding large-N_c renormalization group equations for these parameters are presented, and solved explicitly in a series of simple models. We explain under what conditions the Skyrmion emerges as a UV fixed-point of the RG flow as Λ--> \infty.

hep-ph↗

arXiv1995

The Rotationally Improved Skyrmion, or ``RISKY''

The perceived inability of the Skyrme model to reproduce pseudovector pion-baryon coupling has come to be known as the ``Yukawa problem.'' In this talk, we review the complete solution to this problem. The solution involves a new configuration known as the rotationally improved Skyrmion, or ``RISKY,'' in which the hedgehog structure is modified by a small quadrupole distortion. We illustrate our ideas both in the Skyrme model and in a simpler model with a global U(1) symmetry.

hep-ph↗