41 research outputs found
Diabatic and Adiabatic Collective Motion in a Model Pairing System
Large amplitude collective motion is investigated for a model pairing
Hamiltonian containing an avoided level crossing. A classical theory of
collective motion for the adiabatic limit is applied utilising either a
time-dependent mean-field theory or a direct parametrisation of the
time-dependent Schr\"odinger equation. A modified local harmonic equation is
formulated to take account of the Nambu-Goldstone mode. It turns out that in
some cases the system selects a diabatic path. Requantizing the collective
Hamiltonian, a reasonable agreement with an exact calculation for the low-lying
levels are obtained for both weak and strong pairing force. This improves on
results of the conventional Born-Oppenheimer approximation.Comment: 23 pages, 7 ps figures. Latex, uses revtex and graphic
A Coupled-Cluster Formulation of Hamiltonian Lattice Field Theory: The Non-Linear Sigma Model
We apply the coupled cluster method (CCM) to the Hamiltonian version of the
latticised O(4) non-linear sigma model. The method, which was initially
developed for the accurate description of quantum many-body systems, gives rise
to two distinct approximation schemes. These approaches are compared with each
other as well as with some other Hamiltonian approaches. Our study of both the
ground state and collective excitations leads to indications of a possible
chiral phase transition as the lattice spacing is varied.Comment: 44 Pages, 14 figures. Uses Latex2e, graphicx, amstex and geometry
package
Instanton vibrations of the 3-Skyrmion
The Atiyah-Drinfeld-Hitchin-Manin matrix corresponding to a tetrahedrally
symmetric 3-instanton is calculated. Some small variations of the matrix
correspond to vibrations of the instanton-generated 3-Skyrmion. These
vibrations are decomposed under tetrahedral symmetry and this decomposition is
compared to previous knowledge of the 3-Skyrmion vibration spectrum.Comment: 10 pages, LaTeX, no figures, PRD version with longer introduction and
minor change
Coherent state formulation of pion radiation from nucleon antinucleon annihilation
We assume that nucleon antinucleon annihilation is a fast process leading to
a classical coherent pion pulse. We develop the quantum description of such
pion waves based on the method of coherent states. We study the consequences of
such a description for averages of charge types and moments of distributions of
pion momenta with iso-spin and four-momentum conservation taken into account.
We briefly discuss the applicability of our method to annihilation at rest,
where we find agreement with experiment, and suggest other avenues for its use.Comment: 24 pages, 3 figures, 1 table, PSI-preprin
Translationally invariant treatment of pair correlations in nuclei: II. Tensor correlations
We study the extension of our translationally invariant treatment of few-body
nuclear systems to include tensor forces and correlations. It is shown that a
direct application of our method is not as successful for realistic V6
interactions as our previous results for V4 potentials suggested. We
investigate the cause in detail for the case of He, and show that a
combination of our method with that of Jastrow-correlated wave functions seems
to be a lot more powerful, thereby suggesting that for mildly to strongly
repulsive forces such a hybrid procedure may be an appropriate description.Comment: 19 pages, 3 ps figures. uses elsart, graphicx, amssym
A study of the SU(3)* limit of IBM-2
In this paper the SU(3)* limit of IBM-2 is studied. It is shown that the complete dynamical symmetry group of IBM-2 contains a U(6) subgroup (called U(6)*) of which SU(3)* is a subgroup. The explicit form of the U(6) Casimir operator is given, and the complete reduction from U(6)* to SU(3)* is tabulated. The SU(3)* limit is applied to the nucleus 192Os. After introduction of appropriate symmetry breaking terms the description is as good as that obtained through a phenomenological fit