We investigate melting of stripe phases in the overdoped regime x > 0.3 of the two-dimensional t-t-U Hubbard model, using a spin rotation invariant form of the slave boson representation. We show that the spin and charge order disappear simultaneously, and discuss a mechanism stabilizing bond-centered and site-centered stripe structures.

The interplay between impurities and interactions is studied in the gapless phase of two-chain Hubbard model in order to see how the screening of impurity potentials due to repulsive interactions in single-chain model will be changed by increasing the number of channels. Renormalization group calculations show that charge stiffness, and hence persistent current, of the two-chain model are less ...

The use of technology has become increasingly important in language teaching and learning. The successful use of technology, however, requires that language teachers have the necessary technical competence and pedagogical knowledge. The volume Teacher Education in CALL, edited by Philip Hubbard and Mike Levy, appears at a critical time when the issue of how to prepare current and future languag...

We propose the two-leg fermion-ladder models for SU(2|2) and SU(4) cases. The former is exactly the extended Hubbard model proposed by Essler, Korepin and Schoutens. The later is a new model also with η-pairing symmetry which is important for superconductivity. This new extension of the Hubbard model can be solved exactly. PACS: 75.10.Jm, 71.10.Fd, 05.30.Fk. Since the discovery of high-temperat...

We propose the two-leg fermion-ladder models for SU(2|2) and SU(4) cases. The former is exactly the extended Hubbard model proposed by Essler, Korepin and Schoutens. The later is a new model also with η-pairing symmetry which is important for superconductivity. This new extension of the Hubbard model can be solved exactly. PACS: 75.10.Jm, 71.10.Fd, 05.30.Fk. Since the discovery of high-temperat...

Cold atom optical lattices typically simulate zero-range Hubbard models. We discuss the theoretical possibility of using excited states of optical lattices to generate extended range Hubbard models. We find that bosons confined to higher bands of optical lattices allow for a rich phase diagram, including the supersolid phase. Using Gutzwiller, mean-field theory we establish the parameter regime...

We review the superfluid to Mott-insulator transition of cold atoms in optical lattices. The experimental signatures of the transition are discussed and the RPA theory of the Bose-Hubbard model briefly described. We point out that the critical behavior at the transition, as well as the prediction by the RPA theory of a gapped mode (besides the Bogoliubov sound mode) in the superfluid phase, are...

In the framework of an approach to bosonization based on the use of fermionic composites as fundamental variables, a quadratic action in even Grassmann variables with the quantum numbers of the pions has been constructed. It includes the σ-field in order to be invariant under [SU(2)]L ⊗ [SU(2)]R transformations over the quarks. This action exhibits the Goldstone phenomenon reducing its symmetry...

We study the superfluid to Mott-insulator transition of bosons in an optical anizotropic lattice by employing the Bose-Hubbard model living on a two-dimensional lattice with anizotropy parameter κ. The compressible superfluid state and incompressible Mott-insulator (MI) lobes are efficiently described analytically, using the quantum U(1) rotor approach. The ground state phase diagram showing th...