The Heisenberg model is described. Some of the interesting behavior of Heisenberg antiferromagnets and its behavior as a function of dimension is described. One dimensional systems have no long range order, two dimensional systems order magnetically only at zero temperature, and three dimensional systems have a non-zero critical temperature. Assembling lower dimensional pieces into ladders and ...

A supersymmetric way of imposing the constraint of no double occupancy in models with strong on-site Coulomb repulsion is presented in this paper. In this formulation the physical operators in the constrainted Hilbert space are invariant under local unitary transformations mixing boson and fermion representations. To illustrate, the formulation is applied to the Heisenberg, t-J , and infinite-U...

We study the relationship among the XXZ Heisenberg model and three models obtained from it by various transformations. In particular, we emphasize the role of a non trivial central element t in the underlying algebra and its relationship with the twisted boundary conditions, S N+1 = t S 1 . Key-words: Quantum Groups; Quantum Spin Chains; Integrable Models.

It is shown that, with an appropriate scaling, the energy of low-lying excitations of the (1, 1,. .. , 1) interface in the d-dimensional quantum Heisenberg model are given by the spectrum of the d − 1-dimensional Lapla-cian on an suitable domain.

Recently a significant progress in matching the anomalous dimensions of certain class of operators in N=4 SYM and rotating strings was made. The correspondence was established mainly by using of Bethe ansatz technique applied to the spin s Heisenberg chain model. In a recent paper Kruczenski (hep-th/0311203) suggested to solve the Heisenberg model by using of sigma model approach. In this paper...

We compute the magnetic susceptibility and specific heat of the spin1 2 Heisenberg model on the kagome lattice with high-temperature expansions and exact diagonalizations. We compare the results with the experimental data on ZnCu3(OH)6Cl2 obtained by Helton et al. [Phys. Rev. Lett. 98, 107204 (2007)]. Down to kBT/J ' 0.2, our calculations reproduce accurately the experimental susceptibility, wi...

In this paper, we study the spin and energy dynamic correlations of the one dimensional spin 1/2 Heisenberg model, using mostly exact diagonalization numerical techniques. In particular, observing that the uniform spin and energy currents decay to finite values at long times, we argue for the absence of spin and energy diffusion in the easy plane anisotropic Heisenberg model.

The thermodynamical property of a small cluster including M Hubbard dimers, each of which is described by the two-site Hubbard model, has been discussed within the nonex-tensive statistics (NES). The temperature dependence of the energy, entropy, specific heat and susceptibility has been calculated for M = 1, 2, 3 and ∞ (corresponding to q = 1) with the use of the relation between the entropic ...

A criterion for ferromagnetism is presented suggesting a line of proof to rigorously establish the phase transition. Spectral information will be required in certain invariant subspaces of the Hamiltonian, hopefully the relatively crude estimates needed will be not too difficult to establish.