bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Dimensional Chiral Chromodynamics with Faddeevian Anomaly
Authors: Rahaman Anisur , Mukhopadhyay Subir
Published: October 2003

We consider the non-Abelian generalization of chiral electrodynamics with Faddeevian anomaly and show that despite the lack of manifest Lorentz invariance in the action, it has a consistent and Poincaré invariant phase space structure. We also discuss a modification of this system by imposing a constraint that removes the non-interacting chirality sector.
Random Lattice Strings Versus Type IIB Matrix Models
Authors: Soloviev Oleg A.
Published: October 2003

We comment on a curious relation between Siegel's model of random lattice strings and type IIB matrix model. The comparison of the two theories suggests that there may exist extra terms in the latter which are overlooked in the weak string coupling limit.
A Model of Magnetic Monopoles
Authors: Kühne Rainer W.
Published: October 2003

The possibility of the existence of magnetic charges is one of the greatest unsolved issues of the physics of this century. The concept of magnetic monopoles has at least two attractive features: (i) Electric and magnetic fields can be described equivalently. (ii) In contrast to quantum electrodynamics, models of monopoles are able to explain the quantization of electric charge. We suggest a quantum field theoretical model of the electromagnetic interaction that describes electricity and magnetism as equivalent as possible. This model requires the cross-section of Salam's "magnetic photon" to depend on the absolute motion of the electric charge with which it interacts. We suggest a tabletop experiment to verify this magnetic photon. Its discovery by the predicted effect would have far-reaching consequences: (i) Evidence for a new gauge boson and a new kind of radiation which may find applications in medicine. (ii) Evidence for symmetrized Maxwell equations. (iii) Evidence for an absolute rest frame that gives rise to local physical effects and violation of Einstein's relativity principle.
On Classical String Configurations
Authors: Konopelchenko B. G. , Landolfi G.
Published: October 2003

Equations which define classical configurations of strings in R3 are presented in a simple form. General properties as well as particular classes of solutions of these equations are considered.
Self-Dual Chern–Simons Solitons in the Planar CP(1) Model
Authors: Kim Yoonbai , Oh Phillial , Rim Chaiho
Published: October 2003

We consider a nonrelativistic CP (1) system coupled minimally to an Abelian Chern–Simons gauge field and study the self-dual solitons which saturate the Bogomol'nyi bound. We find a rich structure of rotationally symmetric static soliton solutions for various uniform background charge densities. Possible application to spin system is mentioned.
Lorentz Multiplet Structure of Baryon Spectra and Relativistic Description
Authors: Kirchbach M.
Published: October 2003

The pole positions of the various baryon resonances are known to reveal well-pronounced clustering, so-called Höhler clusters. For nonstrange baryons, the Höhler clusters are shown to be identical to Lorentz multiplets of the type {j,j}⊗[{1/2,0} ⊕ {0,1/2}] with j being a half-integer. For the Λ hyperons below 1,800 MeV, these clusters are shown to be of the type {1,0} ⊕ {0,1} ⊗ [{1/2,0} ⊕ {0,1/2}] while above 1,800 MeV they are parity duplicated {J,0} ⊕ {0,J} higher-spin (Weinberg–Ahluwalia) states. Therefore, for Λ hyperons the restoration of chiral symmetry takes place above 1,800 MeV. Finally, it is demonstrated that the description of spin-3/2 particles in terms of a second rank antisymmetric Lorentz tensor with Dirac spinor components does not contain any off-shell parameters and avoids the main difficulties of the Rarita–Schwinger description based on a four-vector with Dirac spinor components.
Superconducting Phase Transitions in (2+1)-Dimensional Quantum Field Theories Modeling Generalized Polaronic Interactions I.
Authors: Tscheuschner Ralf D.
Published: October 2003

We review the fundamentals of Jahn–Teller interactions and their field theoretical modelings and show that a (2+1)-dimensional gauge theory where the gauge field couples to "flavored fermions" arises in a natural way from a two-band model describing the dynamical Jahn–Teller effect. The theory exhibits a second order phase transition to novel finite-temperature superconductivity.
Wave Propagation Through a Coherently Amplifying Random Medium
Authors: Joshi Sandeep K. , Jayannavar A. M.
Published: October 2003

We report a detailed and systematic numerical study of wave propagation through a coherently amplifying random one-dimensional medium. The coherent amplification is modeled by introducing a uniform imaginary part in the site energies of the disordered single-band tight binding Hamiltonian. Several distinct length scales (regimes), most of them new, are identified from the behavior of transmittance and reflectance as a function of the material parameters. We show that the transmittance is a non-self-averaging quantity with a well defined mean value. The stationary distribution of the super reflection differs qualitatively from the analytical results obtained within the random phase approximation in strong disorder and amplification regime. The study of the stationary distribution of the phase of the reflected wave reveals the reason for this discrepancy. The applicability of random phase approximation is discussed. We emphasize the dual role played by the lasing medium, as an amplifier as well as a reflector.
Evidence of Tricritical Behavior at the Nematic Isotropic Transition
Authors: Mukherjee Prabir K.
Published: October 2003

Tricritical behavior at the nematic–isotropic phase transition is discussed by means of Landau–de Gennes phenomenological theory. The temperature difference TNI-T*is obtained near the tricritical point. We also obtained the value of the ratio (Q*-QNI)/QNI, where Q*is the order parameter at the temperature T*of the absolute stability limit of the isotropic phase and QNIis the order parameter at the nematic–isotropic transition temperature TNI. As a definite improvement over the earlier attempts utilizing Landau–de Gennes scheme the present work can reproduce low values of (Q*-QNI)/QNIand that of TNI-T*as demanded by experimental observations. The tricritical exponents are calculated from the scaling theory and compared with observed values. Using the Ginzburg criterion, we also determine the critical region of the nematic–isotropic phase transition.
The Study on the Filling of Atoms in a Carbon Nanotube
Authors: Wu Jian , Wang Ming-Liang , Lü Rong , Duan Wenhui
Published: October 2003

The filling of Pb, C, Al and S atoms into Carbon nanotubes is studied by use of the discrete variational method within the local density functional theory. It is found that Lead atom inclines to enter into tubes, while Carbon atom rather stays at the mouth of nanotubes, which is in good agreement with experiments. The effect of nanotube length and diameter on the filling is discussed.
Ground State Geometries and Vibrational Spectra of Small Hydrogenated Silicon Clusters using Nonorthogonal Tight-Binding Molecular Dynamics
Authors: Gupte Girish R. , Prasad R.
Published: October 2003

We report a systematic study of ground state structures, vibrational spectra cohesive energies and HOMO-LUMO gaps of small Si n H m clusters (n=1, 2 and m=1–6) and their deuterated derivatives based on the nonorthogonal tight-binding molecular dynamics scheme. The ground state structures have been obtained by using simulated annealing. The bond lengths, bond angles and the frequencies of normal modes are found to be in good agreement with available experimental data and ab initio calculations. Our calculation of cohesive energies indicate SiH 2 to be more stable than SiH 3 or SiH and Si 2 H 4, more stable than Si 2 H 3 or Si 2 H 5.
Phase Separation in Binary Mixtures with Chemical Reactions
Authors: Puri Sanjay , Frisch Harry L.
Published: October 2003

This paper is the second in a two-stage exposition on phase separation in binary (AB) mixtures with simple chemical reactions, which involve only the components A and B of the mixture. In this paper, we present details of our modelling, which employs the master equation formalism, for a number of different reactions. We also present detailed numerical results which supplement those in our previous paper (S. Puri and H. L. Frisch, J. Phys.A27, 6027 (1994)).
Electron–Intramolecular Vibration Coupling in Charge-Transfer Salts Studied by Infrared Spectroscopy
Authors: Yartsev V. M. , Graja A.
Published: October 2003

A short discussion of theoretical calculations of the optical properties of quasi-one and quasi-bidimensional molecular crystals is presented. Special attention is devoted to the electron–molecular vibration coupling which is analyzed in charge-transfer salts with tetrathiafulvalene (TTF) derivatives (including giant analoges of TTF) as donor components.
Vertex Corrections in Gauge Theories for Two-dimensional Condensed Matter Systems
Authors: Kopietz Peter
Published: October 2003

We calculate the self-energy of two-dimensional fermions that are coupled to transverse gauge fields, taking two-loop corrections into account. Given a bare gauge field propagator that diverges for small momentum transfers q as 1/qη, 1<η≤ 2, the fermionic self-energy without vertex corrections vanishes for small frequencies ω as Σ(ω)∝ ωγ with γ=2/(1+η)<1. We show that inclusion of the leading radiative correction to the fermion-gauge field vertex leads to Σ(ω)∝ωγ [1-aη ln (ω0/ω)], where aη is a positive numerical constant and ω0 is some finite energy scale. The negative logarithmic correction is consistent with the scenario that higher order vertex corrections push the exponent γ to larger values.
Ab Initio Electronic Band Structure Calculations for Calcium Monochalcogenides
Authors: Shameem Banu I. B. , Kalpana G. , Palanivel B. , Shenbagaraman P. , Rajagopalan M. , Yousuf Mohammed
Published: October 2003

The first principles tight-binding linear muffin-tin orbital method within the local density approximation was used to calculate the electronic band structures and the total energies of CaS, CaSe and CaTe in NaCl-type and CsCl-type structures. The total energies were used to calculate the ground state properties such as lattice parameter, bulk modulus and the structural phase stability of these compounds. The transition pressure at which these compounds undergo the structural phase transition from NaCl-type to CsCl-type structure were calculated. The ground state properties, the transition pressures and the transition volumes are found to agree with the experimental and other theoretical results. The energy band gap at ambient condition in the NaCl-type structure were calculated and compared with the experimental results available for CaS and CaSe. For CaTe the experimental values of energy gap are not available. The valence-band width and the pressure coefficient of energy gap were also calculated. The closure of band gap at transition in CsCl structure for CaSe, and CaTe were explained by comparing the band structures of BaSe and SrSe in this phase.
Scattering Rates in a Semiconductor Heterostructure: The Electron–Phonon Coupling
Authors: Comas F. , Castro F. , Gondar J. L.
Published: October 2003

We investigate Scattering-Rates due to the electron–phonon interaction in a Semiconductor Heterostructure (SH) on the basis of a phenomenological theory for Polar Optical Phonons (POP) in semiconductor nanostructures which was proposed in the latter times. The applied theory has led to a plausible description of POP in Quantum-Wells, Quantum-Wires and Quantum-Dots. Using this theory we find an explicit expression for the electron–phonon Hamiltonian with direct application to a SH. Scattering Rates are calculated by applying this Hamiltonian and also a realistic wave-function for the electron states (using Airy functions) is considered. The obtained results are discussed in detail and compared with previous works on the subject.
Phase Evolution of an Aharonov–Bohm Ring with an Embedded Quantum Dot
Authors: Chen Hao
Published: October 2003

We demonstrate there are two phase shifts, which a quantum dot caused, in a modified Aharonov–Bohm (AB) ring. On two sides of the conductance resonance peaks the AB oscillations have different functional forms as a function of the bias voltage on the QD, that is similar to the recent experiment. We find that several special incident energies of electrons may drive the AB ring system into a resonant state (T=1) or antiresonant state (T=0), respectively.
Geometries and Vibrational Spectra of Small Hydrogenated Silicon Clusters
Authors: Gupte Girish R. , Prasad R.
Published: October 2003

We report a systematic study of ground state structures, vibrational spectra, cohesive energies and HOMO-LUMO gaps of small Si n H clusters (n=3, 10) based on the nonorthogonal tight-binding molecular dynamics scheme. The ground state structures have been obtained by using simulated annealing. In particular, we focus on how the addition of a hydrogen atom affects the ground state geometry and the stability of a Si n cluster. We find that hydrogen either enters into the surface of the cluster or occupies a position outside the cluster. In the first case, it drastically distorts the cluster, while in the latter, there is very little distortion. We find that in some cases Si n H cluster has some resemblance with Si n+1 cluster. We also find that hydrogen can form bonds with more than one silicon atom. Our calculation indicates that SiH, Si3H and Si5H will be more stable and Si4H , Si6H , Si7H , Si9H and Si10H will be less stable clusters.
Linear Laws in Physics
Authors: Wang Liqiu
Published: October 2003

The empirical laws in physics, relating two frame-indifferent spatial vectors linearly, are shown to be both necessary and sufficient condition for a general linear relation between two vectors to satisfy the principle of material frame indifference, a more universal law in physics.
Superconductivity of SrxCuO2-δ Film in YBCO/SrxCuO2-δ/YBCO System
Authors: Koba S. , Nagata R. , Onishi M. , Ozono Y. , Shibata K. , Higo S. , Kawano I. , Kushida T. , Kim Y. W. , Ogushi T.
Published: October 2003

The zero resistance behavior of a Sr x CuO 2-δ film (x=0.05 ~ 1.0) sandwiched between YBa 2 Cu 3 O 7-z film was examined. The highest transition temperatures of the sandwiched-type- Sr x CuO 2-δ, which was deposited optimally at x=0.1 and with a thickness ≈2200 Å, was T c-end = 93.8 K and T c-onset = 99.0 K. In the region of x=0.05 ~ 1.0, the scattering order of T c tended to decrease with increase of x, and the resistivity in a normal state had a minimum value at x=0.1. XRD exhibited a phase transformation of a infinite layer type (at x=1.0)-to-NaCl type like C/2c (at x=0.1). It was determined by XPS that Sr -3d5/2,3/2 core lines were the same value for both concentrations of x=1.0 and 0.1 in Sr x CuO 2-δ.
Structure and Magnetoresistance of Pr0.7(Sr0.3-yCay) MnO3
Authors: Lin J. G. , Liu R. S. , Chang C. Y. , Huang C. Y.
Published: October 2003

We have investigated the structural and magnetoresitive properties for a series of Pr 0.7( Sr 0.3-y) Ca y MnO 3 with y=0 to 0.3. A systematic decrease in a- ad c-lattice parameter was observed, while b-lattice parameter remains as a constant with y increasing from 0 to 0.3. A significant reduction in the planar Mn-O-Mn bond angle is accompanied by an enhancement of magnetoresistance. Our results can be explained based on the model of spin-disorder scattering, in which the electronic bandwidth plays an important role on determining the relation between resistivity and magnetization.
Breakdown of the Spin-1 Haldane Phase Via Quantum Fluctuations
Authors: Yamamoto Shoji
Published: October 2003

Investigating quantum fluctuations in the ground states of S=1 quantum antiferromagnetic spin chains described by the bilinear-biquadratic Hamiltonian ℋ=∑i [Si·Si+1+β (Si·Si+1)2], we study a mechanism of the breakdown of the Haldane phase. Based on the valence-bond-solid structure, but replacing two links of them by triplet bonds (crackions), we construct a trial wave function which is singlet and translationally invariant, where the crackion-crackion distance is regarded as a variational parameter. At β < 1/3, the minimization of the variational energy results in a bound state of crackions, while at β > 1/3, crackions come to be set free from their bound state with increase of β and the chain length. We point out that the breakdown of the Haldane phase with β approaching 1 can be attributed to the collapse of the bound state and the growth of a short-range repulsive interaction between crackions.
Interplay of Magnetic Field and Disorder: Magnetic Subbands and Bound States
Authors: Valente Loredana , Ramaglia Vincenzo Marigliano
Published: October 2003

The effect of an impurity on the spectrum of a Bloch electron in a uniform magnetic field is studied. Rational values of the magnetic flux parameter, defined as the ratio between the magnetic flux through a unit cell and the flux quantum, have been considered, corresponding to a subband spectrum for the electron energy.

The impurity levels are determined through an extension of the Koster–Slater method, using the magnetic Wannier functions, a generalization of the usual Wannier functions in the presence of a magnetic field.
The Derivation of 1/N Energy-Solutions to the harper-Equation and Related Magnetizations
Authors: Micu C. , Papp E.
Published: October 2003

Proofs are given for the first time that the energy-spectrum of the Harper-equation can be derived in a closed implicit form by using the one-dimensional limit of the 1/N-description. Explicitly solvable cases are discussed in some more detail for Δ=1. Here Δ expresses the Harper-parameter discriminating between metallic (Δ<1) and insulator (Δ>1) phases. Related magnetizations have been established by applying both Dingle- and quantum-gas approaches, now for a fixed value of the Fermi-level. The first description leads to large paramagnetic-like magnetizations oscillating with nearly field-independent amplitudes increasing with the temperature. In the second case one deals with magnetization-oscillations centered around the zero-value, such that the amplitudes decrease both with the field and the temperature.
Computer Simulation Study of Classical Spin Models in Two Dimensions with Long-Range Ferromagnetic Interactions Anisotropic in Spin Space
Authors: Romano S. , Zagrebnov Valentin A.
Published: October 2003

We have considered a classical spin system, consisting of 3-component unit vectors, associated with a two-dimensional lattice {uk, k ∈ Z2}, and interacting via a translationally invariant pair potential, of the long-range ferromagnetic form, anisotropic in spin space [Formula: see text] here a ≥ 0, b ≥ 0, σ > 2, ∊ is a positive constant setting energy and temperature scales (i.e. T*=kBT/∊), xj denotes dimensionless coordinates of lattice sites, and uj,α cartesian spin components; our discussion has been specialized to the extreme, O(2)-symmetric, case 0=a < b. When 2 < σ < 4, the potential model can be proven to support an ordering transition taking place at finite temperature; on the other hand, when σ ≥ 4 a Berezinskiǐ–Kosterlitz–Thouless-like transition takes place. Two potential models defined by σ=3 and σ=4, respectively, have been characterized quantitatively by Monte Carlo simulation. For σ=3, comparison is also reported with other theoretical treatments, such as Molecular Field and Two Site Cluster approximations.
Irreversible Deposition of Line Segment Mixtures on a Square Lattice: Monte Carlo Study
Authors: Lee Jae Woo
Published: October 2003

We have studied kinetics of random sequential adsorption of mixtures on a square lattice using Monte Carlo method. Mixtures of linear short segments and long segments were deposited with the probability p and 1-p, respectively. For fixed lengths of each segment in the mixture, the jamming limits decrease when p increases. The jamming limits of mixtures always are greater than those of the pure short- or long-segment deposition. For fixed p and fixed length of the short segments, the jamming limits have a maximum when the length of the long segment increases. We conjectured a kinetic equation for the jamming coverage based on the data fitting.
Hubbard Models as Fusion Products of Free Fermions
Authors: Maassarani Z.
Published: October 2003

A class of recently introduced su (n) "free-fermion" models has recently been used to construct generalized Hubbard models. I derive an algebra defining the "free-fermion" models and give new classes of solutions. I then introduce a conjugation matrix and give a new and simple proof of the corresponding decorated Yang–Baxter equation. This provides the algebraic tools required to couple in an integrable way two copies of free-fermion models. Complete integrability of the resulting Hubbard-like models is shown by exhibiting their L and R matrices. Local symmetries of the models are discussed. The diagonalization of the free-fermion models is carried out using the algebraic Bethe Ansatz.
Bound States in Two-dimensional Crossed or Bent Quantum Wires
Authors: Razavy M.
Published: October 2003

The method of conformal transformation is applied to solve the bound state problem for two-dimensional crossed wires with sharp and with smooth circular corners, for T-shaped and L-shaped wires and a number of other geometries. It is shown that in this method the wave equation with Dirichlet boundary condition on the boundaries of these wires can be transformed to a Schrödinger equation with a unique two-dimensional energy-dependent noneseparable potential. The results for various geometries indicate that sharp corners are essential in generating the bound states.
Kinetic Roughening by Linear Growth Mechanism with Correlated Noise
Authors: Pang Ning-Ning
Published: October 2003

We give the detailed calculation of various correlation functions of the system described by the Edwards–Wilkinson (EW) equation with long-range noise correlation of the power-law form for arbitrary substrate dimensionality. The obtained information can be employed for comparison with experimental data directly, permitting extraction of various phenomenological parameters. Furthermore, we explicitly evaluate the large-distance asymptotic form of the equal-time correlation function. The result shows that it goes as a power-law form of distance, instead of the exponential decaying form as the case with white noise. This distinct behavior can be used to experimentally distinguish whether the roughening of a system is caused by white noise or correlated noise.
The Anomalous Diffusion of the Self-Interacting Passive Scalar in the Turbulent Environment
Authors: Antonov N. , Hnatich M. , Horváth D. , Nalimov M.
Published: October 2003

Two variants of the statistical model of diffusing self-interacting passive scalar θ(x, t) driven by the incompressible Navier–Stokes turbulence were studied by means of the field-theoretical renormalization group technique and ∊-expansion scheme, where ∊ denotes the parameter of the forcing spectrum. Dual ∫ ddxdt[θ(x, t)]2 and triple ∫ ddxdt[θ(x, t)]3 interaction terms of the action represent two different mechanisms of the self-interaction matching two alternative values of the critical dimension: d c =4 and d c =6. The major part of the calculations was carried out in the one loop order, nevertheless, the inclusion of the specific two loop contributions represents the important step of the analysis of some renormalization group functions.

In the basic model variant the effective action is renormalizable for the supercritical dimensions d > d c . This theory exhibits the presence of the asymptotical regime, which is stable for the inertial-conductive range of wave numbers. It was also shown that stability of this regime remains preserved for a variety of the parametric paths connecting domain ∊>0, d>d c with ∊<2, d=3. In the second model variant, the effective action is constructed to be renormalizable at dimensions d≥d c and to justify the realizability of the continuation from ∊>0, d>d c to ∊< 2, d=3. This variant of the model was analyzed using "double expansion" method with the expansion parameters (d-d c )/2 and ∊. The negative correction ζ(ζ≃0.039 for d=3) to the universal Richardson exponent 4/3 is the physical consequence stemming from the calculations.
Ab initio Electronic Band Structure Calculations for Beryllium Chalcogenides
Authors: Kalpana G. , Pari G. , Mookerjee A. , Bhattacharyya A. K.
Published: October 2003

The first principles tight-binding linear muffin-tin orbital method within the local density approximation (LDA) has been used to calculate the ground state properties structural phase transition and pressure dependence of the band gap of BeS, BeSe and BeTe. We have calculated the energy-volume relations for these compounds in the B3 and B8 phases. The calculated lattice parameters, bulk modulus and the pressure-volume relation were found to be in good agreement with the recent experimental results. We have also calculated the cohesive energy for them and they are consistent with the bulk modulus. The calculated B3 to B8 structural transition pressure for BeS, BeS and BeTe agree well with the experimental results. Our calculations show that these compounds are indirect band gap (Γ-X) semiconductors at ambient conditions. The calculated band gap values are found to be underestimated by 20–30% which is due to the usage of LDA. After the structural transition to the B8 phase BeS continues to be indirect band gap semiconductor and ultimately it becomes metallic above 100 GPa. BeSe and BeTe are metallic at B3 to B8 structural transition.
Effects of the Tangentially Directed C-σ Orbital on the Conduction-Band Electronic Structure of the Simple-Cubic Na2CsC60
Authors: Lu Jing , Zhang Xinwei , Zhao Xiangeng , Zhang Liyuan
Published: October 2003

The conduction-band electronic structure of the simple-cubic (sc) Na 2 CsC 60 in different molecular orientational states is studied with a tight-binding model in which both the radially directed C-pπ orbital and tangentially directed C-σ orbital are considered. The obtained results are basically in agreement with the previous ones induced by the radially directed C-pπ orbital approximation. This implies that the conduction-band electronic structure of Na 2 CsC 60 is dominated by the radially directed C-pπ orbital. Both the valence and conduction band of the body-centered-cubic (bcc) K 6 C 60 obtained from this tight-binding model are also comparable to the existing ab initio ones.
The Grassmann Representation of Ising Model
Authors: Nojima K.
Published: October 2003

The integral representations for the partition functions of Ising models are surveyed. The connection with the underlying fermion field in the two-dimensional case is discussed. The relation between the low and the high-temperature expansions is examined.
On the Fundamental Equation of Nonequilibrium Statistical Physics
Authors: Xing Xiu-San
Published: October 2003

In this paper we proposed a new fundamental equation of statistical physics in place of the Liouville equation. That is the anomalous Langevin equation in Γ space or its equivalent Liouville diffusion equation of time-reversal asymmetry. This equation reflects that the form of motion of particles in statistical thermodynamic systems has the drift-diffusion duality and the law of motion of statistical thermodynamics is stochastic in essence, but not completely deterministic. Starting from this equation the BBGKY diffusion equation hierarchy, the law of entropy increase, the theorem of minimum entropy production, the balance equations of Gibbs and Boltzmann nonequilibrium entropy are derived and presented here. Furthermore we have derived a nonlinear evolution equation of Gibbs and Boltzmann nonequilibrium entropy density. To our knowledge, this is the first treatise on them. The evolution equation shows that the change of nonequilibrium entropy density originates together from drift, typical diffusion and complicated inherent source production. Contrary to conventional viewpoint, the entropy production density σ≥0 everywhere for any systems cannot be proved universally. Conversely, σ may be negative in some local space of some inhomogeneous systems far from equilibrium. The hydrodynamic equations, such as the generalized Navier–Stokes equation, the mass drift-diffusion equation and the thermal conductivity equation have been derived succinctly from the BBGKY diffusion equation hierarchy. The Liouville diffusion equation has the same equilibrium solution as that of the Liouville equation. All these derivations and results are unified and rigorous from the new fundamental equation without adding any extra assumption.
Ferromagnetism, Dimerization, Charge and Spin Density Waves in Quasi-One-Dimensional Organic Polymers: Self-Consistent Mean Field Theory
Authors: Liang Shi-Dong , Wang Qianghua , Wang Z. D. , Shen Shun-Qing
Published: October 2003

We address the low temperature properties of quasi-one-dimensional organic polymers, which may be described by a modified Anderson lattice-Su–Schrieffer–Heeger Hamiltonian. The condition and nature of various orders, such as, the ferromagnetic order, the dimerization order, the charge density wave order and the spin density wave order, are analyzed by a self-consistent mean field theory. Analytical results are obtained for a specific case. The topological structure of the chain leads to a flatband structure of the energy band, which gives rise to a ferromagnetic order in the case of half filling at low temperatures. The on-site Coulomb repulsion enhances the ferromagnetic order, while the nearest-neighbor interaction (V) suppresses both the ferromagnetic order and the dimerization, and leads to the charge density wave. The π–d hybridization (td) suppresses the dimerization, and does not affect the magnetization. The ferromagnetic order and dimerization order coexist for weak td.
Finite Size Scaling of Metastability in First Order Transitions
Authors: Ota Smita , Ota S. B.
Published: October 2003

Microcanonical Monte Carlo simulations have been carried out for the extended 2d XY-model and the 2d q=10 state Potts model undergoing first order transitions. It has been found that the temperature dependence of the physical quantities exhibit "S"-shaped nature at the first order transition. The excursion into the metastable branch is found to increase by reducing the system size. The metastability is found to scale with the linear dimension of the system.
New Phonon Echo-Signals Due to the Two-Level Systems in Glasses
Authors: Busiello G. , Saburova R. , Vagapova F.
Published: October 2003

A theory of the microwave tunnel phonon echo excited by long acoustic pulses in glass is developed. We take into account a large broadening of the two-level system (TLS) energy levels, a broad distribution of glassy parameters through their averaging with some distribution functions, TLS potential asymmetry as well as a tunneling parameter, dipole–dipole interaction between TLS and echo decay. For the first time new subsidiary phonon echo signals excited by long acoustic pulses are found. New echoes appear due to the asymmetry of the TLS potential. These signals are less intensive than basic echo. They have unusual orientational dependence. The intensities, form and moments of generation of echo signals are calculated. It is shown that the broad distribution of glassy parameters results in the change of echo amplitude, echo form and echo decay character. The amplitude and form of echoes in glass depend on the amplitude and length of external exciting pulses. The delay effects in time moments of echo generation are found. The estimations shown a possibility for the experimental display of the basic and subsidiary echo signals. A corresponding experiment relative to observing of the new echoes is proposed.
Concentration Dependence of Polarization for the AC* Phase Transition in a Binary Mixture of Liquid Crystals
Authors: Salihoğlu S , Yurtseven H. , Bumin B.
Published: October 2003

Using mean-field theory with P2θ2 coupling term in the free energy expansion, we calculate the polarization as a function of concentration for the AC* phase transition in a binary mixture of C7 and 10.O.4 liquid crystalline material. Our calculated values of polarization are in good agreement with the experimental data.
Directional Dependence of Spin Currents Induced by Aharonov–Casher Phase
Authors: Choi Taeseung , Ryu Chang-Mo , Jayannavar A. M.
Published: October 2003

We have calculated the persistent spin current of an open ring induced by the Aharonov–Casher phase. For unpolarized electrons there exist no persistent charge currents, but persistent spin currents. We show that, in general, the magnitude of the persistent spin current in a ring depends on the direction of the direct current flow from one reservoir to another. The persistent spin current is modulated by the cosine function of the spin precession angle. The nonadiabatic Aharonov–Casher phase gives anomalous behaviors. The Aharonov–Anandan phase is determined by the solid angle of spin precession. When the nonadiabatic Aharonov–Anandan phase approaches a constant value with the increase of the electric field, the periodic behavior of the spin persistent current occurs in an adiabatic limit. In this limit the periodic behavior of the persistent spin current could be understood by the effective spin-dependent Aharonov–Bohm flux.
Effective Field Theory Approach to Bose–Einstein Condensation
Authors: Liu W. Vincent
Published: October 2003

We consider the low-energy collective excitations at finite temperature of Bose–Einstein condensed gases (and liquids as well). A most general model-independent effective Lagrangian is written down according to a prescription obtained from the breakdown of the global symmetry U(1). To show how the theory predicts easily, we derive the momentum and temperature dependence of the damping of excitations by means of power counting as an example.
Liquid 4He: Equation of State, Compressibility and Velocity of First Sound
Authors: Skjetne B. , Østgaard E.
Published: October 2003

In calculations for liquid 4 He , an investigation is made to check the accuracy of a lowest-order constrained variational (LOCV) method, using modified "healing" conditions on the two-body Jastrow wave function. Results obtained for the ground-state energy for four different interaction models are fitted by a polynomial expression, whereby the pressure, compressibility and velocity of first sound are obtained. The theoretical results are found to be in fair agreement with experimental results.
Ground-State Properties of Bosons in Three- and Two-Dimensional Traps
Authors: Gonzalez Augusto , Perez Aurora
Published: October 2003

We study trapped systems of bosons at zero temperature in three and two dimensions. Conditions are fulfilled for the application of Gross–Pitaevskii theory with a positive scattering length. Series expansions for ground-state properties are obtained in both the noninteracting and the strong-coupling (Thomas–Fermi) limits. From these expansions, analytic estimates are presented in the form of two-point Padé approximants. We explicitly show the approximants for the total energy per particle and the chemical potential.
Quantum Statistics of Cooper Pairs; Superconducting Temperature
Authors: Fujita Shigeji , Morabito David L.
Published: October 2003

We show that the eigenvalues of the number operator [Formula: see text] in the pair state (k1, k2), where c's and c†'s are fermion operators, are limited to 0 or 1, while the eigenvalues of the pair-number operator with the net momentum q≡ k1+k2 fixed, [Formula: see text], are 0, 1, 2,…. Both fermionic and bosonic natures of the Cooper pairs (pairons) must be used in the superconductivity theory. The Bose–Einstein condensation (BEC) of the pairons moving with a linear energy–momentum relation occurs at [Formula: see text] (3D), [Formula: see text] (2D), where n0 is the pairon density and v F the Fermi velocity. The connection between this [Formula: see text] and the BCS superconducting temperature is discussed.
The Microscopic Theory of Superfluidity and Superconductivity Driven by Single Particle and Pair Condensation of Attracting Bosons
Authors: Dzhumanov S.
Published: October 2003

A original microscopic theory of superfluidity and superconductivity driven by the single particle (SPC) and pair condensation (PC) of attracting bosons both in Fermi and in Bose systems is developed. This theory (as distinct from the existing theories) for Fermi systems contains two order parameters Δ F and Δ B characterizing the attracting fermion pairs and boson pairs, respectively. In such systems superconducting (SC) phase transition is accompanied, as a rule, by the formation of k-space composite bosons (e.g. Cooper pairs and bipolarons) with their subsequent transition to the superfluid (SF) state by attractive SPC and PC. A novel Fermi-liquid and SF Bose-liquid theories are elaborated for description this two-stage Fermi–Bose-liquid (FBL) scenario of SC (or SF) transition. The crossover from k- to real (r)-space pairing regime for BCS-like coupling constants γ F ≃ 0.7-0.9 and the irrelevance of r-space pairs to the superconductivity are shown. The developed SF Bose-liquid theory predicts the first-order phase transition SPC ↔ PC of attracting 3d-bosons with the kink-like behaviors of all SC (SF) parameters near [Formula: see text] in accordance with the observations in 4 He , 3 He and superconductors. It is argued that the coexistence of the order parameters Δ F and Δ B leads to the superconductivity by two FBL scenarios. One of these scenarios is realized in the so-called fermion (type I, II and III) superconductors (FSC) (where formation of k-space composite bosons and their condensation occur at the same temperature) and the other in the boson (type II and III) superconductors (BSC) (where BCS-like pairing take place in the normal state with manifesting of the second-order phase transition and opening of the pseudogap at T=T F > T c ). There the gapless superfluidity (superconductivity) is caused by the gapless excitation spectrum of bosons at [Formula: see text] and not by the presence of point or line nodes of the BCS-like gap Δ F assumed in some s-, p- and d-pairing models. The 3D- and 2D-insulator–metal–superconductor phase diagrams are presented. The necessary and sufficient microscopic criterions for superfluidity is formulated. The theory proposed are in close agreement with the observations in 4 He , 3 He , superconductors, nuclear and neutron star matter, cosmology, etc.
Properties of the Squeezed Polarons in One Dimension
Authors: Su Xiyu , Zheng Hang
Published: October 2003

An electron related squeezed phonon transformation is employed to investigate the ground state properties of the strongly coupled electron–phonon system in one dimension. It has been shown that the binding energy of the polaron and the interaction between the polarons are renormalized together with the energy reducement of the electron subsystem resulted from the squeeze state of the phonon subsystem. Some relevance with the earlier variational treatments has been discussed as well.
Electrical and Elastic Behavior of In and Al Substituted Mg-Mn Ferrites
Authors: Purushotham Y. , Singh Mahavir , Sud S. P. , Reddy P. Venugopal
Published: October 2003

Thermopower and electrical conductivity studies of polycrytslline In 3+ and Al 3+ substituted Mg-Mn ferrites having different compositions were undertaken in the temperature range 300–700 K, using differential and two-probe methods respectively. It has been observed that all the ferrites are found to exhibit clear and well-defined transtions near their respective Curie temperatures in both Seebeck coefficient and electrical conductivity versus temperature behavior. The elastic behavior of these ferrites has also been studied as a function of composition at room temperature using ultrasonic pulse transmission technique and it has been found that the elastic moduli decrease continuously with increasing Indium concentration and increase with increasing Aluminium dopants. Suitable explanation for the observed phenomena are given.
Electron Diffraction Study of α-AlMnSi Crystals Along Non-Crystallographic Zone Axes
Authors: Song G. L. , Bursill L. A.
Published: October 2003

The structure of crystalline α-AlMnSi is examined by electron diffraction. Six distinct zone axes are examined, including both normal crystallographic and non-crystallographic zone axes, allowing the space group symmetry of α-AlMnSi to be studied. A method for indexing the non-crystallographic zone axis diffraction patterns, which involve reflections from several nearby crystallographic zone axes, is described and applied to electron diffraction patterns of the quasi-5-fold, 3-fold and 2-fold axes of the icosahedral building units of cubic α-AlMnSi. These are compared with electron diffraction patterns from the corresponding 5-fold, 3-fold and 2-fold axes of the quasicrystalline phase i-AlMnSi, from which we may make some conclusions concerning the occupancies of the icosahedral units in i-AlMnSi.

Electron diffraction patterns characteristic of [Formula: see text] were obtained for thicker specimens. However, for thin specimens, as used for HRTEM imaging, the electron diffraction patterns were characteristic of [Formula: see text] space group symmetry. This unusual behaviour arises because the structural basis for the [Formula: see text] to [Formula: see text] phase transition is a weak effect, involving changes in occupancy of the icosahedral structural elements located at the corners (double-MacKay icosahedra) and body-centers (MacKay icosahedra) of the cubic unit cell. The effects of changing the occupancies of the outer shells of the MI and DMI structural units on the diffraction intensities of the weak reflections were examined. Thus, calculation of the dynamical diffraction amplitudes shows that in fact the weak reflections characteristic of [Formula: see text] only develop sufficient intensity if two conditions are satisfied: namely (1) the crystal thickness exceeds approx. 50 nm and (2) if a significant proportion of [Formula: see text] occupancies are included in the structural model. By fitting the observed thickness variation of the diffraction intensities we propose a new set of occupancies for α-AlMnSi, which is consistent with the electron, X-ray and neutron diffraction data.
Elastic Constants and Pair Potentials for Nematogenic Lattice Models
Authors: Romano S.
Published: October 2003

Director configurations in nematic Liquid Crystals can be determined by minimizing their elastic free-energy density, on the basis of elastic constants and of specific boundary conditions; in some published cases, this has been obtained by numerical procedures where the elastic free-energy density plays the same role as the overall potential energy in a standard Monte Carlo simulation. The "potentials" used in these papers are short-ranged but, in general, not pairwise additive, unless the three elastic constants are set to a common value, thus reducing the potential to the well-known Lebwohl–Lasher lattice model.

On the other hand, one can construct, possibly in different ways, a lattice model with pairwise additive interactions, approximately reproducing the elastic free-energy density, where parameters defining the pair potential are expressed as linear combinations of elastic constants; a nematogenic pair interaction of this kind, originally proposed by Gruhn and Hess (T. Gruhn and S. Hess, Z. Naturforsch.A51, 1 (1996)), has been investigated here by Monte Carlo simulation with periodic boundary conditions, i.e. aimed at the resulting bulk behavior.
Finitely Correlated Generalized Spin Ladders
Authors: Kolezhuk A. K. , Mikeska H.-J.
Published: October 2003

We study two-leg S=1/2 ladders with general isotropic exchange interactions between spins on neighboring rungs, whose ground state can be found exactly in a form of finitely correlated (matrix product) wave function. Two families of models admitting an exact solution are found: one yields translationally invariant ground states and the other describes spontaneously dimerized models with twofold degenerate ground state. Several known models with exact ground states (Majumdar–Ghosh and Shastry–Sutherland spin-1/2 chains, Affleck–Kennedy–Lieb–Tasaki spin-1 chain, Δ-chain, Bose–Gayen ladder model) can be obtained as particular cases from the general solution of the first family, which includes also a set of models with only bilinear interactions. Those two families of models have nonzero intersection, which enables us to determine exactly the phase boundary of the second-order transition into the dimerized phase and to study the properties of this transition. The structure of elementary excitations in the dimerized phase is discussed on the basis of a variational ansatz. For a particular class of models, we present exact wave functions of the elementary excitations becoming gapless at second-order transition lines. We also propose a generalization of the Bose–Gayen model which has a rich phase diagram with all phase boundaries being exact.
Correlation Functions of the Ising Model with Multisite Interaction on the Husimi Lattice
Authors: Ananikian N. S. , Ghulghazaryan R. G. , Izmailian N. Sh.
Published: October 2003

We consider a general spin-1/2 Ising model with multisite interaction on the Husimi lattice with the coordination number q and derive an analytical expression of correlation functions for stable fixed points of the corresponding recurrence relation. We show that for q=2 our model transforms to the two-state vertex model on the Bethe lattice with q=3 and for the case q=3, with only nearest neighbor interactions, we transform our model to the corresponding model on the Bethe lattice with q=3, using the Yang–Baxter equations.
A Modified Quantum Renormalization Group for XXZ Spin Chain
Authors: Langari A. , Karimipour V.
Published: October 2003

A simple modification of the standard Renormalization Group (RG) technique for the study of quantum spin systems is introduced. Our method which takes into account the effect of boundary conditions by employing the concept of superblock, may be regarded as a simple way for obtaining first estimates of many properties of spin systems. By applying this method to the XXZ spin-[Formula: see text] Heisenberg chain, we obtain the ground state energy with much higher accuracy than the standard RG. We have also obtained the staggered magnetization and the z-component of spin–spin correlation function which confirms the absence of long-range order in the massless region of the 1D XXZ model.
The Coupled Cluster Method Applied to the Spin-Half XXZ Model on the Honeycomb Lattice
Authors: Bishop R. F. , Rosenfeld J.
Published: October 2003

The coupled cluster method (CCM) is applied to the spin-half XXZ model on the honeycomb lattice. Hierarchical CCM approximation schemes are applied in order to obtain the ground-state properties. The possible critical behavior of this model is also examined. Reasonably good results for the ground-state energy and the staggered magnetization are obtained, in comparison to the results from Monte Carlo simulations, spin-wave techniques, series expansions, and finite lattice diagonalizations, that have already been performed on this model.
Competing Glauber and Kawasaki Dynamics
Authors: Artz Simone , Trimper Steffen
Published: October 2003

Using a quantum formulation of the master equation we study a kinetic Ising model with competing stochastic processes: the Glauber dynamics with probability p and the Kawasaki dynamics with probability 1-p. Introducing explicitly the coupling to a heat bath and the mutual static interaction of the spins the model can be traced back exactly to a Ginzburg–Landau functional when the interaction is of long range order. The dependence of the correlation length on the temperature and on the probability p is calculated. In case that the spins are subject to flip processes the correlation length disappears for each finite temperature. In the exchange dominated case the system is strongly correlated for each temperature.