Large-n limit of SU(n) quantum "spin" chains.

TL;DR: The first rigorous example of an isotropic model in such a phase is presented in this paper, where the Hamiltonian has an exactSO(3) symmetry and is translationally invariant, but the model has a unique ground state and exponential decay of the correlation functions in the ground state.

TL;DR: A valence-bond solid is presented, which is simply constructed out of valence bonds, is nondegenerate, and breaks no symmetries, and there is an energy gap and an exponentially decaying correlation function.

TL;DR: The Heisenberg-Hubbard model is solved in the large-n limit to gain insight into its relevance to the coppper-oxide materials and a gapless disordered ground state is found.

TL;DR: In this article, the effect of weak three-dimensional antiferromagnetic coupling and the role of an antisymmetric term, introduced to explain a hidden ferromagnetic behavior of the uniform susceptibility was discussed.

TL;DR: In this article, the authors give a brief description of a family of models which generalize the non-linear σ-model, and possess a local gauge invariance without containing explicitly a gauge field.