My research interests lie in theoretical physics, at the interface between particle physics and statistical mechanics. Our group studies quantum lattice models, which may represent atomic spins in a magnet, electrons in a superconductor, or quarks confined within the proton. Various methods of treating such models are employed including series expansions, Monte Carlo simulations, exact diagonalization and the density matrix renormalization group (DMRG).
We are also interested in "effective field theories" for systems at a critical point.

We have recently published a book on series expansion techniques, ‘Series Expansion Methods for Strongly Interacting Lattice Models’, by Jaan Oitmaa, Chris Hamer and Weihong Zheng (Cambridge University Press, 2006). Much of our computational work in this area was carried out by our late friend and colleague, Dr Weihong Zheng, who collected many of his codes used in this field at his personal website.

Examples of current projects are:

1. We made the first application of DMRG techniques to a lattice gauge theory, and performed the most accurate study yet of the "lattice Schwinger model"(electrodynamics in one space dimension). It was shown that a background electric field can destroy charge confinement in this model, and create quantum "kinks" or solitons corresponding to single, unconfined quarks. It would be possible to apply similar methods to other gauge theories in low dimensions.
2. We have developed new series expansion methods to calculate dispersion relations for multiparticle excited states in quantum lattice models, which can give important information about the dynamics of the system. We are applying this approach to magnetic "spin liquid" systems, and to models of electrons hopping around a crystal lattice, which can represent high temperature superconductors.
3. We have worked on Monte Carlo methods to simulate "Hamiltonian" lattice gauge theories, and to calculate quantities such as the 'string tension' between quark-antiquark pairs, and glueball masses. It turns out that the standard Euclidean path integral Monte Carlo approach, extrapolated to the Hamiltonian limit, gives the best results.
4. There has been great interest recently in 'quantum wires' and 'quantum dots', e.g. the phenomenon of persistent currents in quantum rings induced by the Aharonov-Bohm effect. We have made a study of persistent currents in a Heisenberg spin ring with a 'weak link', representing a defect or constriction, and plan to extend the study to other models in the future.

Selected Publications

Other Interests

I have long been interested in the problem of arms control and the elimination of nuclear weapons, and have acted as Convenor of the General Studies course GENS4008: Nuclear Arms and the New World Order since its inception. I believe that global problems require global solutions, and to promote these ideas I have written a book on world federalism entitled “A Global Parliament”, and initiated in conjunction with A/Prof. Shirley Scott in international relations another General Education course GENT0708: International Governance in the 21^st Century. In 2004 I founded the World Citizens Association (Australia) to help in the campaign for better global governance.

School of Physics
The University of New South Wales
SYDNEY 2052
Australia

c.hamer@unsw.edu.au

61 2 9385 4590

61 2 9385 6060