Unusual metallic phase in a chain of strongly interacting particles

We consider a one-dimensional lattice model with the nearest-neighbor interaction $V_1$ and the next-nearest neighbor interaction $V_2$ with filling factor 1/2 at zero temperature. The particles are assumed to be spinless fermions or hard-core bosons. Using very simple assumptions we are able to predict the basic structure of the insulator-metal phase diagram for this model. Computations of the flux sensitivity support the main features of the proposed diagram and show that the system maintains metallic properties at arbitrarily large values of $V_1$ and $V_2$ along the line $V_1-2V_2=\gamma J$, where $J$ is the hopping amplitude, and $\gamma\approx1.2$. We think that close to this line the system is a ``weak'' metal in a sense that the flux sensitivity decreases with the size of the system not exponentially but as $1/L^\alpha$ with $\alpha>1$.Comment: To appear in J. Phys. C; 9 revtex preprint pages + 4 ps figures, uuencode

Analytic Coulomb matrix elements in the lowest Landau level in disk geometry

Using Darling's theorem on products of generalized hypergeometric series an analytic expression is obtained for the Coulomb matrix elements in the lowest Landau level in the representation of angular momentum. The result is important in the studies of Fractional Quantum Hall effect (FQHE) in disk geometry. Matrix elements are expressed as simple finite sums of positive terms, eliminating the need to approximate these quantities with slowly-convergent series. As a by-product, an analytic representation for certain integals of products of Laguerre polynomials is obtained.Comment: Accepted to J. Math. Phys.; 3 pages revtex, no figure

Rules for Minimal Atomic Multipole Expansion of Molecular Fields

A non-empirical minimal atomic multipole expansion (MAME) defines atomic charges or higher multipoles that reproduce electrostatic potential outside molecules. MAME eliminates problems associated with redundancy and with statistical sampling, and produces atomic multipoles in line with chemical intuition.Comment: 3.5 pages, 3 color PS figures embedde

Disorder-induced enhancement of the persistent current for strongly interacting electrons in one-dimensional rings

We show that disorder increases the persistent current of a half-filled one-dimensional Hubbard-Anderson ring at strong interaction. This unexpected effect results from a perturbative expansion starting from the strongly interacting Mott insulator ground state. The analytical result is confirmed and extended by numerical calculations.Comment: 7 pages, 2 figures, LaTeX, using epl.cls (included), considerably revised final versio