31964372
Three-body unitarity and the K-matrix analyses of dibaryon resonances.
We derive a K-matrix expression starting with three-body unitarity. This is then used to parametrize the results of a Faddeev ..pi..d..--> pi..d calculation whose poles are known. We find that the K-matrix method is unable to reproduce the known pole in the system when the width of that pole is greater than the width of the ..delta.. resonance. This is explainable in terms of the approximations used in deriving the K matrix.
42069854
Three-body unitarity, the cloudy bag model, and the Roper resonance.
We present the details and results of a Faddeev calculation of ..pi../ital N/scattering in the /ital P//sub 11/ channel in the region of the Roperresonance. Our equations respect two- and three-body unitarity, treat thenucleon and delta on an equal footing, and have a pole with correct residue atthe nucleon mass. The input is from the cloudy bag model. Resonance behavior isexhibited without the inclusion of a bare Roper bag, although not in detailedagreement with experiment. If a bare Roper bag is included, the phase shiftsvary far too rapidly in the resonance region, implying that identifying thelowest radial bag excitations with the Roper leads to a physical Roper that ismuch too narrow.
120965794
Resonance poles in three-body systems
15260939
$\rho - \omega$ mixing and the pion electromagnetic form-factor
Abstract The suggestion of momentum dependence in the amplitude for rho-omega mixing has generated concern over related implications for vector meson dominance and the photon-rho coupling. We discuss two established and formally equivalent representations of vector meson dominance and show that in one of these such a coupling is an automatic consequence of the model. We then apply it to a calculation of the pion electromagnetic form-factor. Our analysis leads to a revised value for the on-shell rho-omega mixing amplitude of −3800 ± 370 MeV 2 .
123416407
Meson-Meson Contributions to the Nucleon Sigma-Term and Electromagnetic form Factors
Our modern understanding of hadrons is of a core of valence quarks surrounded by a sea of \(\bar q\) pairs and gluons. For low energy processes (~ 1 GeV) there is good reason to assume (Witten, 1979; T’Hooft, 1974) that much of the detailed dynamics of the quarks can be neglected and the cloud can be approximated by the correlated, colour neutral \(\bar q\) states that we know as mesons. This is the basis of the success of the meson exchange models of medium energy nuclear physics whose degrees of freedom consist of nucleons, mesons and isobars.
123135909
A Relativistic meson exchange model of pion - nucleon scattering
Abstract A relativistic meson exchange approach to the pion-nucleon interaction is developed using a three-dimensional relativistic two-body propagator and the results using different propagators compared. The relativistic approach is able to describe low-energy scattering up to 400 MeV above threshold, while preserving the soft-pion theorems. The different propagators give similar results, as the form factors necessary to get a fit suppress much of the multiple scattering.
27460121
Finite-size corrections and scaling dimensions of solvable lattice models: An analytic method.
A general analytic method for calculating finite-size corrections, central charges, and scaling dimensions of solvable lattice models is presented. The approach is to solve the special functional equations or inversion identities satisfied by the commuting row transfer matrices of these lattice models at criticality. For purposes of illustration, the method is applied to calculate the central charge c=4/5 and leading magnetic scaling dimension x=2/15 of hard hexagons. These numbers are rational due to special values of Rogers dilogarithms.
31859363
Solvable hierarchy of cyclic solid-on-solid lattice models.