We study the degeneracy of the ground-state energy E of the two-component Bose-Hubbard model and of the perturbative correction E(1). We show that the degeneracy properties of E and E(1) are closely related to the connectivity properties of the lattice. We determine general conditions under which E is nondegenerate. This analysis is then extended to investigate the degeneracy of E(1). In this c...

We propose a new method that by using the lattice Schrödinger functional allows to investigate the effective action for external background fields in lattice gauge theories. We show that this method gives sensible results for the case of four-dimensional U(1) gauge theory in an external constant magnetic field.

This review concentrates on progress in lattice QCD during the last two years and, particularly, its impact on phenomenology. The two main technical developments have been successful implementations of lattice actions with exact chiral symmetry, and results from simulations with two light dynamical flavours which provide quantitative estimates of quenching effects for some quantities. Results a...

In this note we prove several duality theorems in lattice theory. We also discuss the connection between spectral spaces and Priestley spaces, and interpret Priestley duality in terms of spectral spaces. The organization of this note is as follows. In the first section we collect appropriate definitions and basic results common to many of the various topics. The next four sections consider Birk...

We review efforts to study, using the methods of lattice field theory, the phenomenon of diquark condensation via BCS pairing at a Fermi surface, which has been proposed as a mechanism for color superconductivity in dense quark matter. The particular models studied are the Gross-Neveu model and SU(2) lattice gauge theory; in both cases evidence for superfluidity at high density is presented. Th...

In this paper, we present a detailed analysis of first-order perturbations the Kerr metric in slow-rotation limit. We perform calculation by perturbing Schwarzschild plus up to second-order corrections spin Regge-Wheeler gauge. The apparent coupling between different angular momentum axial-led and polar-led modes can be removed suitably combining perturbation equations projecting them onto spin...

We synthesized different Fe/TiO2 catalysts and studied the influence of Fe on the structure and performance of Fe/TiO2 as a photocatalyst to remove gaseous NO in air under visible light. The electron paramagnetic resonance results revealed that Fe ions substituted the Ti ions of TiO2 prepared by coprecipitation and homogeneous precipitation method. More Fe ions were incorporated into the crysta...