International Journal of Modern Physics B

General relationship among the density matrix formalism, the double-space formulation and thermo field dynamics is discussed in non-equilibrium dissipative quantum systems. The concept of weakly equivalent operators in the double space formulation is introduced to review many well-known results and it is shown to be useful in mapping between the density matrix formalism and the double space formulation. A new non-equilibrium thermo field dynamics is formulated to discuss dissipative quantum systems. A simple example of damped harmonic oscillators is discussed in the present representation.

We review the recent theoretical developments in the study of domain structure dynamics through nucleation-and-growth processes of first-order phase transitions with non-conserved order parameters. We introduce the spatial and space-time correlation functions of the domain structures based on the model proposed by Kolmogorov, Johnson, Mehl and Avrami. Our main purpose is to show why and how the rigorous correlation functions can be derived from their model.

The energies involved in various surface atomic processes such as surface diffusion, the binding of small atomic clusters on the surface, the interaction between two adsorbed atoms, the dissociation of an atom from a small cluster or from a surface layer, the binding of kink site atoms or atoms at different adsorption sites to the surface etc., can be derived from an analysis of atomically resolved field ion microscope images and a kinetic energy measurement of low temperature field desorbed ions using the time-of-flight atom-probe field ion microscope. These energies can be used to compare with theories and to understand the transport of atoms on the surface in atomic reconstructions, epitaxial growth of surface layers and crystal growth, adsorption layer superstructure formation, and also why an atomic ordering or atomic reconstruction at the surface is energetically favored. Mechanisms of some of the surface atomic processes are also clarified from these quantitative, atomic resolution studies. Very recent work in this area is briefly reviewed.

A large number of tunneling measurements on ceramic monophasic Y₁Ba₂Cu₃O_7−x samples with different oxygen content using the point-contact geometry was performed. After a deconvolution procedure for removing the thermal broadening, experimental data were analyzed by means of a model of the total tunneling current which contains two terms: A background "normal" tunneling current and a quasi-particle tunneling one. The quasi-particle current was expressed in terms of the lifetime broadening model. The dependence of the energy gap Δ and of the lifetime broadening parameter Γ, as determined by the model, on the temperature of the sample is discussed. A linear behaviour in the dependence of the gap on the critical temperature of the sample has been found. The ratio 2Δ/kT_c varies between 4.3 and 7.2 depending on the value of T_c which can be attributed to the sample surface. The possible presence of proximity effect in our tunneling experiments is also discussed.

The two-variable perimeter and area generating functions derived recently by Brak and Guttmann for the staircase and row-convex polygons on the square lattice are generalized to the rectangular lattice. We consider the three-variable generating function where c_n,m,r is the number of appropriate polygons with 2n horizontal steps, 2m vertical steps and area r. Two generating functions G(x, y, z) for the staircase and row-convex polygons are derived. We also calculate the generating functions for the first and second area-weighted moments by the perturbation method of Lin.

Quasiperiodic patterns with eight- and twelvefold symmetry are presented which share the root lattice D₄, i.e., the 4-D face-centered hypercubic lattice, for their minimal embedding in four-space. We derive the patterns by means of the dualization method and investigate key properties like vertex configurations, local deflation/inflation symmetries and kinematic diffraction. The generalized point symmetries (and thus the Laue group) of these patterns are the dihedral groups d₈ and d₁₂, respectively, which share a common subgroup, d₄. We introduce a contiunous one-parameter rotation between the two phases which leaves this subgroup invariant. This should prove useful for modelling alloys like V₁₅Ni₁₀Si where quasicrystalline phases with eight- and twelvefold symmetry coexist.

In this paper, the relation of the nearest-neighbor majority vote model to the contact process by coupling is studied. Using this method, we obtain that if the parameter of the nearest-neighbor d-dimensional majority vote model is δ ∈ ((2d − 1)/4d, (2d + 1)/4d), then there is no phase transition for this model. It is an improvement of the result δ ∈ (d/(2d + 1), (2d + 1)/4d) in Ref. 1.