Solid-fluid phase transition in multicomponent hard sphere systems: Interference amongst the watermelons

Appropriately weighted multicomponent small watermelon diagrams and their elementary derivatives are approximately summed and found to effect the solid-fluid phase transition.     

Solid-fluid phase transition in multicomponent hard sphere systems: Interference amongst the watermelons

Appropriately weighted multicomponent small watermelon diagrams and their elementary derivatives are approximately summed and found to effect the solid-fluid phase transition.     

Order-disorder transition in one-dimensional system with disorder in composition

The influence of structural inhomogeneity onto order-disorder transitions in 1D systems is considered in the scope of the Potts-like model with many-particle interactions. The helix-coil transition in DNAs, heterogeneous by hydrogen bonding energy, is considered as an example. The microcanonical method is employed to evaluate the free energy. The secular equation for the heteropolymer is constructed. Both the melting temperature and interval of DNA melting are obtained. In the limit of small difference between inverse melting temperatures of poly(A-T) and poly(G-C), the coincidence with classical results is obtained.     

New scenario to chaos transition in the mappings with discontinuities

We consider a many-parametric piecewise mapping with discontinuity. That is a one-dimensional model of singular dynamic system. The stability boundary are calculated analytically and numerically. New typical features of stable cycle structures and scenario to chaos transition provoked by discontinuity are found.     

Unitarity and the isobar model: Two-body discontinuities

In the isobar model the fact that the final-state isobar channels overlap calls for an investigation in which unitarity provides constraints on the construction. The discontinuities in all the physical two-body subenergies are treated, allowing for two-body intermediate states. The process KN → KπN is used for illustration throughout. The discontinuity formulas are applied to the isobar expansion of the amplitude; rather explicit attention is given to the details of spin in order to show how the recoupling problems can be unraveled. The resulting subenergy discontinuities take the form of integrations across the Dalitz plot. An example is given in conclusion in which s-waves dominate in the final state, so that a modest number of coupled isobar amplitudes enter in the constraint relations.     

Localization-delocalization transition in one-dimensional system with long-range correlated diagonal disorder

We show that the electronic states in a one-dimensional (1D) Anderson model of diagonal disorder with long-range correlation proposed by de Moura and Lyra exhibit localization-delocalization phase transition in varying the energy of electrons. Using transfer matrix method, we calculate the average resistivity and investigate how it changes with the size of the system N. For given value of α (> 2) we find critical energies E_c1 and E_c2 such that the resistivity decreases with N as a power law ∝ N ^{- γ} for electron energies within the range of [E _c1, E _c2], and exponentially grows with N outside this range. Such behaviors persist in approaching the transition points and the exponent γ is in the range from 0.92 to 0.96. The origin of the delocalization in this 1D model is discussed. Received 18 December 2001 / Received in final form 2 May 2002 Published online 14 October 2002 RID="a" ID="a"e-mail: sjxiong@nju.edu.cn     

Phase transition of the symmetric Ashkin-Teller model near the decoupling limit

The Ashkin-Teller model can be viewed as two ferromagnetic Ising models interacting via a four-spin coupling ε. We investigate the phase transition of the symmetric AT-model near the decoupling limit ε=0 and compare it with the 8-Vertex model phase transition. The expansion of the free energy is derived to second order in ε. From this the specific heat exponent is determined to the same order with the result: $$\alpha (\varepsilon ) = \frac{8}{\pi }.\varepsilon + \frac{{16}}{\pi }\left( {1 - \frac{4}{\pi }} \right)\varepsilon ^2 + O(\varepsilon ^3 ).$$      

A new representation for the supercurrent in He-A and its zero temperature limit

A new representation for the thermal Green's function of ³He-A and its zero the corresponding supercurrent at an arbitrary temperature. Expansion of this general expression in the orbital vector gradients is considered at zero temperature; the widely accepted first-order contribution with the anomalous part and the second-order corrections to it are obtained, thus confirming the existence of the anomalous current at zero temperature.     

Phase transition in a system of one-dimensional bosons with strong disorder

We study one-dimensional disordered bosons at large commensurate filling. Using a real space renormalization group approach, we find a new random fixed point which controls a phase transition from a superfluid to an incompressible Mott glass. The transition can be tuned by changing the disorder distribution even with vanishing interactions. We derive the properties of the transition, which suggest that it is in the Kosterlitz-Thouless universality class.     

Dissipation of quantum turbulence in the zero temperature limit

Turbulence, produced by an impulsive spin down from angular velocity Omega to rest of a cube-shaped container, is investigated in superfluid 4He at temperatures 0.08 K-1.6 K. The density of quantized vortex lines L is measured by scattering negative ions. Homogeneous turbulence develops after time t approximately 20/Omega and decays as L proportional, t-3/2. The corresponding energy flux =nu'(kappaL)2 proportional, t-3 is characteristic of quasiclassical turbulence at high Re with a saturated energy-containing length. The effective kinematic viscosity in T=0 limit is nu'=0.003kappa, where kappa=10(-3) cm2 s(-1) is the circulation quantum.     

A computer model of the interaction of acoustic surface waves with discontinuities

Surface acoustic waves are under active investigation in three fields of study: geophysics, electronics and non-destructive testing. While the mathematical features are the same for all three fields, the wavelengths, as well as the dimensions of the features, range over at least ten orders of magnitude.In this paper a brief review of available numerical techniques is presented and this is followed by discussion of a series of models which use finite difference methods to predict the reflected and transmitted signals from wide band pulses of ultrasonic Rayleigh waves incident on various surface-breaking features. The paper concludes with a comparison of analytical, numerical and experimental results.     

A model for phase transitions in a system of rod-like colloidal suspensions

The present paper describes an extension of the Maier-Saupe theory of liquid crystals to a system of charged interacting rods and shows that nematic to isotropic transitions can also be induced by increasing the charge on the rods. The effects of length of rod, concentration of salt and the volume fraction on the phase diagram are described. The concept of the charge-induced isotropic phase is described, and it is argued that the structure is expected to be glassy. Evidence to support these conclusions from the existing literature is presented.     

Phase transition in the 2D random Potts model in the large-q limit

Phase transition in the two-dimensional q-state Potts model with random ferromagnetic couplings is studied in the large-q limit by a combinatorial optimization algorithm and by approximate mappings. We conjecture that the critical behavior of the model is controlled by the isotropic version of the infinite randomness fixed point of the random transverse-field Ising spin chain and the critical exponents are exactly given by beta=(3-sqrt[5])/4, beta(s)=1/2, and nu=1. The specific heat has a logarithmic singularity, but at the transition point there are very strong sample-to-sample fluctuations. Discretized randomness results in discontinuities in the internal energy.     

Superfluid-insulator transition in a commensurate one-dimensional bosonic system with off-diagonal disorder

We study the nature of the superfluid-insulator quantum phase transition in a one-dimensional system of lattice bosons with off-diagonal disorder in the limit of a large integer filling factor. Monte Carlo simulations of two strongly disordered models show that the universality class of the transition in question is the same as that of the superfluid-Mott-insulator transition in a pure system. This result can be explained by disorder self-averaging in the superfluid phase and the applicability of the standard quantum hydrodynamic action. We also formulate the necessary conditions which should be satisfied by the stong-randomness universality class, if one exists.     

Vortex glass transition in a frustrated 3D XY model with disorder

The anisotropic frustrated three-dimensional (3D) XY model with disorder in the coupling constants is simulated as a model of a point disordered superconductor in an applied magnetic field. A finite size scaling analysis of the helicity modulus gives strong evidence for a finite temperature transition with isotropic scaling and the correlation length exponent nu=1.5+/-0.3, consistent with 3D gauge glass universality.     

Spin depolarization and a metal-insulator transition in a two-dimensional system in zero magnetic field

The conditions for spontaneous spin polarization in a two-dimensional system in a zero magnetic field are considered in the case of a partial filling of the lower quantum-well subbands when the energy of exchange interaction of charge carriers exceeds their kinetic energy. The critical density above which the two-dimensional gas of charge carriers undergoes complete spin depolarization is determined in the Hartree-Fock approximation. It is assumed that this process can be due to a transition of the two-dimensional gas to a metallic state.