Nuclear forces on the lattice

Recent studies by the NPLQCD collaboration of hadronic interactions using lattice QCD are reviewed, with an emphasis on a recent calculation of meson-baryon scattering lengths. Ongoing high-statistics calculations of baryon interactions are also reviewed. In particular, new insights into the signal/noise problems that plague correlation functions involving baryons are discussed.Comment: 12 pages, 12 figures, Talk given at 6th International Workshop on Chiral Dynamics, Bern, Switzerland, 6-10 Jul 200

New approach to NN with perturbative pions

The current status of effective field theory (EFT) descriptions of nucleon-nucleon (NN) interactions is briefly reviewed, and a new formulation of EFT which treats pion interactions perturbatively is presented. This approach differs from the Kaplan-Savage-Wise (KSW) expansion in that the singular short distance part of the pion tensor interaction is summed to all orders.Comment: 8 pages, 7 figures, Talk given at 6th International Workshop on Chiral Dynamics, Bern, Switzerland, 6-10 Jul 200

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