Exploring Baryon Chiral Multiplets

The full QCD chiral symmetry algebra has predictive consequences at low energies. I discuss the ground-state chiral multiplet involving the light baryons and emphasize the special role of the Roper resonance.Comment: 10 pages. Invited plenary talk at NSTAR 2002, Pittsburgh, PA, 9-12 October 200

Nucleon-Nucleon Scattering in the 1/N Expansion

The nucleon-nucleon 3S1-3D1 coupled-channel problem is solved analytically to leading order in a joint expansion in the quark masses and in 1/N. An approximate expression is derived for the 3S1 scattering length in the large-N limit, and the large-N behavior of the deuteron is discussed.Comment: 10 pages, Invited talk, The Phenomenology of Large-N_c QCD, to be published Proceedings of the Institute of Nuclear Theor

Ground state energy of the interacting Bose gas in two dimensions: an explicit construction

The isotropic scattering phase shift is calculated for non-relativistic bosons interacting at low energies via an arbitrary finite-range potential in d spacetime dimensions. Scattering on a (d-1)-dimensional torus is then considered, and the eigenvalue equation relating the energy levels on the torus to the scattering phase shift is derived. With this technology in hand, and focusing on the case of two spatial dimensions, a perturbative expansion is developed for the ground-state energy of N identical bosons which interact via an arbitrary finite-range potential in a finite area. The leading non-universal effects due to range corrections and three-body forces are included. It is then shown that the thermodynamic limit of the ground-state energy in a finite area can be taken in closed form to obtain the energy-per-particle in the low-density expansion, by explicitly summing the parts of the finite-area energy that diverge with powers of N. The leading and subleading finite-size corrections to the thermodynamic limit equation-of-state are also computed. Closed-form results --some well-known, others perhaps not-- for two-dimensional lattice sums are included in an appendix.Comment: 24 pages, 2 figure

Status of Effective Field Theory of NN Scattering

I review recent progress in developing a systematic power counting scheme for scattering processes involving more than one nucleon.Comment: 9 pages LaTeX and appb.sty, 2 figures (uses epsf); Talk given at the Workshop on 'The Structure of Mesons, Baryons and Nuclei', Cracow, May 1998, in honor of J. Speth's 60th birthday, to be published in Acta Physica Polonica

Elusive Neutrons from Nuclei in Effective Field Theory

We review recent computations of neutral pion photoproduction and Compton scattering on the deuteron in baryon chiral perturbation theory. Progress in extracting the neutron electric dipole amplitude, which is relevant in neutral pion photoproduction, and the neutron polarizabilities, which are relevant in Compton scattering, is discussed.Comment: 8 pages LaTeX and aipproc.sty, 3 figures (uses epsf). Corrected typos and references. Talk given at 11th International Light-Cone Workshop: New Directions in Quantum Chromodynamics, Seoul, Korea, June 199