Axel Grzesik

Physikalisches Institut der Universität Bonn
Nußallee 12
D-53115 Bonn
Federal Republic of Germany

Office:	AVZ-I, Room 104
Phone:	+49-228-73-3727
Fax:	+49-228-73-3223
Email:	axel@th.physik.uni-bonn.de

Research project

I am currently working on strong-coupling linked-cluster expansions for various t-J models as well as the Kondo lattice model. The linked-cluster expansion method is based on Rayleigh-Schrödinger perturbation theory. It's home turf is the computation of ground-state properties. Recent developments, however, have extended the method to computing effective Hamiltonians of degenerate excited states, which in turn yield experimentally accessible quantities, such as excitation spectra or spectral weights.
One particularly appealing feature of the linked-cluster method is its numerical exactness in the sense that all quantities are automatically obtained in the thermodynamic limit. This makes it a complementary tool to the more widely known DMRG or exact-diagonalization methods.
Furthermore, unlike quantum Monte Carlo techniques, it does not suffer from any fermion sign problems (the student implementing it may suffer, but the method prevails).

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Last modified: Mon Jul 26 10:04:01 MET DST 1999