A Coupled-Cluster Formulation of Hamiltonian Lattice Field Theory: The Nonlinear Sigma Model

✍ Scribed by N.E. Ligterink; N.R. Walet; R.F. Bishop

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 591 KB
• Volume: 267
• Category: Article
• ISSN: 0003-4916
• DOI: 10.1006/aphy.1998.5812

✦ Synopsis

We apply the coupled cluster method (CCM) to the Hamiltonian version of the latticised O(4) nonlinear 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. 1998 Academic Press Contents. 1. Introduction. 2. The O(4) nonlinear sigma model. 3. Elements of coupled cluster theory. 3.1. The standard form of the CCM. 3.2. The functional form of the CCM. 4. The operatorial form of the CCM for classical spin models. 4.1. The LSUB2 approximation. 4.2. The SUB2-n approximations. 4.3. Full SUB2 calculations. 4.4. Collective excitations. 5. The functional form of the CCM for classical spin models. 5.1. The LSUB2 approximation. 5.2. The SUB2-n-m approximations. 5.3. Collective excitations. 6. Solution and results. 6.1. Numerical methods. 6.2. LSUB2 results. 6.3. SUB2-n(-m) results. 6.4. Excitations. 6.5. Comparison with other work. 7. Conclusions and outlook. Appendix A. Quantisation.