James Hughes

Soliton quantization and internal symmetry.

We apply the method of collective coordinate quantization to a model of solitons in two spacetime dimensions with a global U(1) symmetry. In particular we consider the dynamics of the charged states associated with rotational excitations of the soliton in the internal space and their interactions with the quanta of the background field (mesons). By solving a system of coupled saddle-point equations we effectively sum all tree graphs contributing to the one-point Greens function of the meson field in the background of a rotating soliton. We find that the resulting one-point function evaluated between soliton states of definite U(1) charge exhibits a pole on the meson mass shell and we extract the corresponding

Solvability, consistency, and the renormalization group in large-Nc models of hadrons.

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Chiral divergent properties of hadrons in the large Nc limit

-matrix element for the decay of an excited state via the emission of a single meson using the standard Lehmann-Symanzik-Zimmermann reduction formula. This

Spherical wave expansion for any spin

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Next-to-leading order parton model calculations in the massless Schwinger model

-matrix element has a natural interpretation in terms of an effective Lagrangian for the charged soliton states with an explicit Yukawa coupling to the meson field. We calculate the leading-order semiclassical decay width of the excited soliton states and discuss the consequences of these results for the hadronic decay of the

Skyrmion quantization and the decay of the Delta

\ensuremath{\Delta}

Particle-hole induced intruder bands in ¹¹⁷Sb and ¹¹⁹Sb

resonance in the Skyrme model.

Superdeformation in Po198

We study meson-baryon Lagrangians in the large-[ital N][sub [ital c]] limit, and show the following. (a) To leading order in 1/[ital N][sub [ital c]], the dressed 1-meson--2-baryon Greens functions (an infinite class of divergent Feynman graphs) are obtained exactly by solving coupled classical field equations with a UV cutoff. (b) The only effect of this graph resummation is to renormalize---consistent with large-[ital N][sub [ital c]] selection rules---the bare Yukawa couplings, baryon masses and hyperfine baryon mass splittings. (c) The exact large-[ital N][sub [ital c]] renormalization group equations for these quantities are derived. Skyrme-type models are conjectured to be UV fixed points of such flows.

Smooth termination of intruder bands in 109 51Sb

Abstract We compute the leading non-analytic correction to the baryon mass in the combined limits mπ → 0, Nc → ∞ with mπNc held fixed. We reproduce the results of Cohen and Broniowski using semiclassical methods rather than heavy-baryon chiral perturbation theory. The calculation is organized to demonstrate: 1 the model independence of our results; and 2 the crucial role played by (iso)rotations of the hedgehog pion cloud surrounding the baryon. Our rotationally improved large-Nc calculation yields results that naturally interpolate between ordinary chiral perturbation theory on the one hand, and large-Nc physics on the other.

Superdeformation in ¹⁹⁸Po

The spherical wave expansion is derived for fields of particles of arbitrary spin and mass, and for arbitrary helicity, massless particles (such as the electromagnetic vector potential corresponding to photons). The starting point is Weinberg’s characterization of relativistic, higher spin fields that transform according to general irreducible representations of the homogeneous Lorentz group. The expansion is a relativistic generalization of the familiar tensor and spinor spherical harmonics. It is useful for central force problems that arise, for example, in scattering processes off spherically symmetric solitonic backgrounds such as monopoles or skyrmions.