bluuebunny/crossref_metadata_2025 huggingface dataset:
PERIODIC AND QUASI-PERIODIC LAGUERRE TILINGS
Authors: SCHLOTTMANN MARTIN
Published: November 2004

The Laguerre construction extends and unifies the notions of Voronoi (or Dirichlet) and Delaunay complex. It is shown how the standard projection formalism for the generation of quasi-periodic tilings from higher-dimensional periodic “oblique” (or “klotz”) tilings associated to periodic Voronoi and Delaunay complexes also applies more generally to Laguerre complexes. It turns out that all quasi-periodic tilings obtained this way are Laguerre tilings themselves.
QUANTUM STATE CONTROL IN SEMICONDUCTOR p-n JUNCTIONS (I) — SQUEEZED STATE GENERATION IN SEMICONDUCTOR LASERS
Authors: YAMAMOTO Y. , INOUE S. , RICHARDSON W. , MACHIDA S.
Published: November 2004

Quantum statistical properties of laser light have been extensively studied for the last thirty years by using an operator Langevin equation, a density operator master equation, and a quantum mechanical Fokker-Planck equation. It has been generally accepted among physicists and quantum electronics engineers that an ideal laser operating at far above the threshold generates a coherent state of light. Various experimental facts such as the Poissonian photoelectron statistics, the shot noise limited photocurrent fluctuations, and the Gaussian distributions of optical homodyne detector output seem to support this. However, recent careful studies on a semiconductor laser have revealed that a semiconductor laser does not necessarily produce a coherent state of light, but generates a number-phase squeezed state, in which the photon-number noise is smaller than the standard quantum limit (shot noise limit or Poisson limit). This paper reviews the theoretical and experimental aspects of number-phase squeezed state generation by a semiconductor laser.
QUANTUM STATE CONTROL IN SEMICONDUCTOR pn-JUNCTIONS (II): CONTROLLED SPONTANEOUS EMISSION IN QUANTUM WELL MICROCAVITY LASERS
Authors: YAMAMOTO YOSHIHISA , BJÖRK GUNNAR , KARLSSON ANDERS , HEITMANN HENRICH , MATINAGA FRANKLIN M.
Published: November 2004

The principles and applications of controlled spontaneous emission in semiconductor microcavities are reviewed. The coupling efficiency of spontaneous emission into a lasing mode and the spontaneous emission rate can be modified by various microcavity structures. By increasing the coupling efficiency, semiconductor lasers with a very low threshold current, and semiconductors lasers and light emitting diodes with a high quantum efficiency, broad modulation bandwidth and low noise are expected.
SYNTHESIS AND DC CONDUCTIVITY OF PALLADIUM POLYACRYLATE
Authors: AKHTAR PARVEEN , PASHA M. , KHWAJA FARID A.
Published: November 2004

This papers reports the synthesis and the results of the measurements of dc conductivity of heat treated palladium polyacrylate. Infrared spectra and the scanning electron microscopy of the samples before and after heat treatments are compared in order to reveal their structural details. It is conjectured that at T>38° C molecular aggregates are formed or ion pairing takes place in the material due to the breakdown of the polymer chain in it. The semiconductor-like behavior of the electrical conductivity with the increase of temperature from room temperature to 38°C and thereafter, an exponential decrease in conductivity with further increase in temperature exhibiting a metal-like behaviour show that the material undergoes an insulator-metal transition at this temperature.
Molecular Dynamics Study of Cohesionless Granular Materials: Size Segregation by Shaking
Authors: OHTSUKI Toshiya , TAKEMOTO Yoshikazu , HATA Tatsuo , KAWAI Shigeki , HAYASHI Akihisa
Published: November 2004

The Molecular Dynamics technique is used to investigate size segregation by shaking in cohesionless granular materials. Temporal evolution of the height h of the tagged particle with different size and mass is measured for various values of the particle radius and specific gravity. It becomes evident that h approaches the steady state value h∞ independent of initial positions. There exists a threshold of the specific gravity of the particle. Below the threshold, h∞ is an increasing function of the particle size, whereas above it, h∞ decreases with increasing the particle radius. The relaxation time τ towards the steady state is calculated and its dependence on the particle radius and specific gravity is clarified. The pressure gradient of pure systems is also measured and turned out to be almost constant. This suggests that the buoyancy force due to the pressure gradient is not responsible to h∞.
A SURVEY OF MULTI-PHASE FLOWS
Authors: Morioka Shigeki
Published: November 2004

Features, methods of formulation and wave characteristics of multi-phase flows are mentioned. These matters should be useful to understand. explain and illustrate the properties of multi-phase flows. respectively.
SIMULATION OF GRANULAR PARTICLES IN FLOW BY THE STOKESIAN-DYNAMICS METHOD
Authors: ICHIKI KENGO , HAYAKAWA HISAO
Published: November 2004

We apply the Stokesian-dynamics method for colloidal particles to simulate motion of granular particles in uniform flow. Our preliminary result suggests that inhomogeneity of flow including the boundary condition of flow is important to get fluidized motion of granular particles.
Plugging of the Flow of Granular Materials during the Discharge from a Silo
Authors: SAKAGUCHI HIDE , OZAKI EIJI , IGARASHI TOHRU
Published: November 2004

Laboratory experiments and numerical simulations were performed to find the mechanism of the plugging during the gravitationally emptying a silo. Some interesting results were given by this investigation: 1) Two major slip lines can be seen symmetrically about a vertical midline in the continuous flow, but particles flow only on a one-side slip line was found at each moment; 2) At transition of the flow from one-side to the other, two-side flows collided each other on a vertical midline. And this collision possibly resulted in the formation of the arches of granular materials; 3) In the special case for 2) when arches were stable enough under certain geometrical condition the plugging of the flow occurred. For computer simulation on this issue, the Discrete Element Method specifically taking into account of rolling friction effect was used. Results of numerical simulations were in good agreement with the experimental measures not only in the flow pattern but also in the occurrence of the plugging.
PARAMETERS OF RADIATED SOUND AND STATE VARIABLES IN FLOWING PARTICLES
Authors: HIDAKA JUSUKE , SHIMOSAKA ATSUKO
Published: November 2004

The acoustic noise generated from flowing particles on an inclined plate was studied to measure simultaneously the flow rate and particle size. The pressure waveform of the flow noise was estimated on the basis of the generation mechanism of impact sound when two particles collide. The frequency spectrum of the calculated pressure waveform agrees well with the measured one. Correlation between the flow rate and the pressure of flow noise was obtained, and the frequency of flow noise was related closely to particle diameter. Further, the mean collision time and the mean distance between flowing particles was estimated by the frequency spectrum of the flow noise.
SMOOTHED PARTICLE SIMULATIONS OF THE PYROCLASTIC FLOW
Authors: NAGASAWA MIKIO , KUWAHARA KUNIO
Published: November 2004

We apply the Smoothed Particle Hydrodynamics (SPH) to the three-dimensional simulation of pyroclastic flow over the terrain in Unzen area. The actual flow was observed in June 1991. The comparison of the simulation with the observation tells us the proper parameter sets for this kind of particle simulation. The gas particle and the lava particle are approximated by the polytropic gas which has a hard adiabatic index, that is, the weak compressibility. Theoretical modeling of eruption, movement and emplacement of lava are in success. The covered area by the pyroclastic flow can be estimated in this simulation with a given volume of initial lava dome. Cohesion force modeled by two-point potential could be the source of surface tension, which halts the flow due to the bunching of fragments. Porous pressure and auto-suspension of transported sediment are reproduced by introducing the buoyancy of gaseous components in the flow.
MAGNETIZATION STUDIES OF Rb3C60 IN SUPERCONDUCTING STATE
Authors: POLITIS C. , BUNTAR V. , SEMINOZHENKO V.P.
Published: November 2004

We present the results of magnetic measurements in fields up to 50 kOe for superconducting Rb 3 C 60. The temperature dependence of upper H c 2 critical magnetic field is determined, from which the zero temperature value Hc2(0)=465±50 kOe is evaluated. The magnitudes of penetration depth and coherence length are calculated as ξ(0)=26.7±3 Å; λ L (0)=2150±100 Å at zero temperature. The temperature dependence of ξ(T) and λ L (T) for T≧23 K is in good agreement with the Ginzburg-Landau theory. The critical current densities for different temperatures are calculated, showing a strong decrease of Jc with increasing temperature for T≤7 K . Two regions of fading critical current density on a magnetic field dependence are found.
EFFECTS OF MACROSCOPIC QUANTUM TUNNELING OF CHARGE IN ULTRASMALL SET DOUBLE-JUNCTIONS WITH EXTERNAL ELECTROMAGNETIC ENVIRONMENT
Authors: KRECH W. , HÄDICKE A.
Published: November 2004

It is known that classical Coulomb blockade effects of SET devices are disturbed by the tunneling effects of higher order denoted as macroscopic quantum tunneling of charge (q-mqt) or co-tunneling. The influence of an external electromagnetic environment modelled by an additional impedance in the circuit on the mean q-mqt current is studied in the high-impedance limit. This is important especially for devices containing only two SET junctions, for instance the SET electrometer, where the influence of the environment on the Coulomb blockade is remarkable. It can be shown that the Coulomb blockade is only partly destroyed producing a new, lower “quantum” Coulomb blockade. This holds as well in the case of the incoherent as of the coherent q-mqt. Furthermore, a method is presented on how to regularize the logarithmic singularities in the q-mqt current using line width effects.
RANDOM-FIELD INDUCED ANTIFERROMAGNETIC, FERROELECTRIC AND STRUCTURAL DOMAIN STATES
Authors: KLEEMANN WOLFGANG
Published: November 2004

The occurrence of metastable or stable domain states on mesoscopic length scales seems to be a widespread property of many solids undergoing phase transitions in the presence of quenched random fields. A survey is given on the experimental evidence of domain states in various magnetic, ferroelectric and structural systems. In particular we discuss phenomena like the excess magnetization of field-cooled diluted uniaxial antiferromagnets and its relaxation. The domain state of the relaxor ferroelectric PbM g1/3 Nb 2/3O3 is due to the random distribution of B site cations, whereas dipolar quenched impurities give rise to mesoscopic disorder in K 1−x Li x TaO 3 and Sr 1−x Ca x TiO 3. Spontaneously relaxing quadrupolar domain states are observed in KTa 1−x Nb x O 3. They are probably caused by random strain fields due to ionic size mismatch. The same type of random fields determines the critical behavior of the Jahn-Teller compound DyAs x V 1−x O 4 but merely causes roughening of the natural ferroeleastic twin domain walls.
FERMI SURFACES OF ORGANIC SUPERCONDUCTORS
Authors: WOSNITZA J.
Published: November 2004

In this review an overview of the present-day knowledge of the Fermi surfaces of organic superconductors obtained by Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) experiments is given. Almost all measurements reported here were made on charge transfer salts of the type (ET)2X where ET stands for bis(ethelenedithio)-tetrathiafulvalene (or BEDT-TTF) and X is a monovalent anion. The ET-salts are characterized by their extremely two-dimensional properties. Some unique features resulting from this two-dimensionality, like gigantic SdH and dHvA oscillations, directly observable spin-splitting far from the quantum limit and a distinctive angular dependence of the dHvA amplitude will be discussed in detail. By comparison of the measured cyclotron effective mass with the bare band mass the electron-phonon coupling constant can be extracted and the validity of the BCS formula for the superconducting transition temperature can be checked.
EXACT PHASE DIAGRAMS FOR THE CONDENSATION OF A KAGOMÉ LATTICE GAS WITH THREE-PARTICLE INTERACTIONS
Authors: BARRY J.H. , SULLIVAN N.S.
Published: November 2004

The condensation of a two-dimensional kagomé lattice gas having purely three-particle interactions is first theoretically investigated. The Hamiltonian Hℓg=−∈3Σ ninjnk, where ∈3>0 is the strength. parameter of the short-range attractive triplet interaction, the sum is taken over all elementary triangles of the kagomé lattice, and nℓ=0, 1 is an idempotent site-occupation number. The method initially involves transforming the lattice-gas model into a generalized kagomé Ising model having both pair and triplet interactions as well as a magnetic field. Since the canonical partition function of a generalized kagomé Ising model is equivalent (aside from known prefactors) to the canonical partition function of a standard honeycomb Ising model in a magnetic field, one can deduce the exact liquid-vapor phase diagrams of the triplet-interaction kagomé lattice gas from its grand canonical partition function. As results, the liquid-vapor phase boundary (reduced chemical potential μ/∈3 vs reduced temperature T/Tc) is found to be curvilinear with a positive slope, originating at zero temperature with μ/∈3=−2/3 and analytic at its terminating critical point whose coordinates are T/Tc=1, μc/∈3=−0.64469…, where ∈3/kBTc=3.96992…. The companion coexistence curve (particle number density ρ vs. reduced temperature T/Tc) exhibits an asymmetric rounded shape with a positive-slope curvilinear diameter, and the value of the critical density ρc=0.58931…. At criticality, the expression for the coexistence curve superposes a pair of branch point singularities resulting in an infinite (vertical) slope at the critical point (T/Tc=ρ/ρc=1). The case of a kagomé lattice gas having mixed attractive pair interactions and very weak repulsive triplet interactions (Axilrod-Teller) is next considered. Perturbation analyses upon exact expressions relating to the phase diagrams reveal, over chosen ranges of reduced temperatures, that the phase boundary and the diameter of the two-phase coexistence region each have a negative slope due to the repulsive three-particle interactions.
INDUSTRIAL USES OF NEUTRON SCATTERING
Authors: PRIESMEYER HANS GEORG
Published: November 2004

Recent progress in neutron scattering for industrial purposes is reviewed. The relevant fields of interest are small-angle scattering, high-resolution diffraction, texture determination, reflectometry and radiography. Potential users are encouraged to address themselves to one of the neutron scattering centers given in the Appendix.
MAGNETIC EXCITATIONS AND POLARIZATION ANALYSIS METHOD
Authors: Kakurai K. , Steiner M. , Pynn R.
Published: November 2004

With the recent advances of efficient polarizing and flipping devices and with the increase of the absolute flux at modern neutron sources, polarized neutron inelastic scattering experiments using cold and thermal neutrons have become more commonplace. In this review paper we present experiments recently performed where this technique has been applied to obtain more detailed informations on magnetic excitations thus contributing to a deeper understanding of the spin dynamics in magnetic materials.
MODULATED MAGNETIC PHASES
Authors: CHATTOPADHYAY TAPAN
Published: November 2004

General aspects of modulated magnetic phases are reviewed. The present understanding of the microscopic origin of such phases is discussed. A few examples of modulated magnetic phases are treated in detail. Temperature, pressure and magnetic-field-induced transitions of the modulated magnetic phases are reviewed.
SINGLE SITE-OCCUPANCY CONSTRAINT FOR THE HUBBARD MODEL AT FINITE TEMPERATURE
Authors: STASIO M. DI , ERCOLESSI E. , MORANDI G. , TAGLIACOZZO A. , VENTRIGLIA F.
Published: November 2004

We show how it is possible to include the constraint of single site-occupancy in the large U limit of the Hubbard model at half-filling by means of a local chemical potential. The formalism which is in principle exact allows for finite temperature mean field results satisfying the constraint within 10%. The method is here applied to the dimerized phase and the commensurate flux phase which are still found as local saddle points of the action. The symmetry properties of these actions have been studied. One loop static corrections have been added to obtain an effective free energy and an estimate of the specific heat. In the limit of zero temperature our results reproduce those of the conventional mean field theory of these phases, because quantum fluctuations have not been included. We find that the temperature destabilizes the flux phase more than it does with the dimer phase, especially due to the constraint, which does not suppress phase fluctuating modes, provided the flux is conserved.
HOPPING TRANSPORT ALONG A POTENTIAL WALL: OSCILLATIONS OF THE MAGNETORESISTANCE IN A PARALLEL FIELD
Authors: RAIKH M.E. , SHAHBAZYAN T.V.
Published: November 2004

We study the variable-range-hopping magnetoresistance of a 2D system of localized electrons in the presence of a boundary parallel to the plane of the 2D electrons. In a magnetic field B parallel to the plane, the magnetoresistance oscillates with B if the distance between the plane and the boundary is not too large. These oscillations result from the interference of the amplitude of the in-plane tunneling path with the amplitude of the path reflected by the boundary. We show that the orbital shrinkage effect, altering differently both amplitudes, strongly enhances the interference. At the same time, the amplitude of oscillations appears to be small compared to the general increase in the resistance caused by the orbital shrinkage. The most pronounced effect of the interference can be seen in the differential magnetoresistance R−1(B)∂R(B)/∂B, which we analyze numerically.
STRUCTURAL RELATION BETWEEN SUPERCONDUCTING OXIDES, AURIVILLIUS PHASES ANDRUDDLESDEN-POPPER PHASES
Authors: HAUCK J. , MIKA K.
Published: November 2004

The Ruddlesden-Popper phases can be described as a stacking of v or v′ CaTiO 3 and w or w′ MO structural units with bcc M lattice and O at octahedral interstices. 50% of all octahedral interstices in the bcc M lattice are occupied in CaTiO 3, 33% in MO. The Aurivillius phases can be derived as complementary structures with an occupation of the 67% vacant sites of MO leading to MO 2 units similar to the CaF 2 structure. 14 different structures are obtained as combinations of up to 8 v and w units. The structures can also be described by the sequence of coordination numbers of metal atoms with respect to oxygen. The superconducting phases known so far are with different donor elements: e + for Ruddlesden-Popper phases and e – for Aurivillius phases.
INTERTWINERS AND A-D-E LATTICE MODELS
Authors: PEARCE PAUL A. , ZHOU YU-KUI
Published: November 2004

Intertwiners between A-D-E lattice models are presented and the general theory developed. The intertwiners are discussed at three levels: at the level of the adjacency matrices, at the level of the cell calculus intertwining the face algebras and at the level of the row transfer matrices. A convenient graphical representation of the intertwining cells is introduced. The utility of the intertwining relations in studying the spectra of the A-D-E models is emphasized. In particular, it is shown that the existence of an intertwiner implies that many eigenvalues of the A-D-E row transfer matrices are exactly in common for a finite system and, consequently, that the corresponding central charges and scaling dimensions can be identified.
THE YANG-BAXTER EQUATION IN KNOT THEORY
Authors: WU F.Y.
Published: November 2004

The role played by the Yang-Baxter equation in generating knot invariants using the method of statistical mechanics is reexamined and elucidated. The formulation of knot invariants is made precise with the introduction of piecewise-linear lattices and enhanced vertex and interaction-round-a-face (IRF) models with strictly local weights. It is shown that the Yang-Baxter equation and the need of using its solution in the infinite rapidity limit arise naturally in the realization of invariances under Reidemeister moves III. It is also shown that it is essential for the vertex models be charge-conserving, and that the construction of knot invariants from IRF models follows directly from the vertex model formulation.
CORRELATION BETWEEN ATOMIC-SCALE STRUCTURES AND MACROSCOPIC ELECTRICAL PROPERTIES OF METAL-COVERED Si(111) SURFACES
Authors: HASEGAWA SHUJI , INO SHOZO
Published: November 2004

In this review, we discuss the relation between the atomic-scale structures (atomic arrangements and electronic states) and the macroscopic electrical properties (surface conductance and Schottky barriers) of metal(Ag, Au, or In)-covered Si (111) surfaces. These surfaces have been one of the most intensively investigated systems with the use of a variety of modern surface science techniques, and diversified information at atomic scales has been obtained. The data of reflection high-energy electron diffraction, scanning tunneling microscopy/spectroscopy, photoemission spectroscopies, and others are utilized here for characterizing the structures. Surface conductance and Schottky barriers, on the other hand, have also been the major areas in semiconductor physics for, especially device-oriented, research, but these have rarely been studied in combination with atomic-scale structures. These electrical properties have recently been found to be crucially dependent on the local atomic structures of well-defined surfaces/interfaces. The atomic arrangements and the resulting surface/interface electronic states govern the Fermi-level pinning and band bending which determine the electrical properties of semiconductor surfaces/interfaces.
ON THE ELECTRONIC STRUCTURE OF C60
Authors: SAMUEL STUART
Published: November 2004

We determine the electronic energy levels of C60 using a combination of theoretical and experimental results. The hopping Hamiltonian for the truncated icosahedron is solved analytically for the unequal coupling case using group lattice methods. Then, an analysis of previously preformed experiments on electronic structure is undertaken. When these approaches are combined, a fairly clear picture of the location of the electronic levels emerges.
A DILUTE NEUTRAL-CLUSTER APPROXIMATION FOR THE QUANTUM WASHBOARD POTENTIAL
Authors: CHEN YONG-CONG
Published: November 2004

We study the mobility of a quantum particle in a biased cosine potential V(x)= V0 cos (k0x)–Fx and subject to an Ohmic-like dissipation. It is found that for [Formula: see text], there exists a set of discrete points αp=2p/(2p–1) at which the series for the mobility in powers of V0 may be partially summed via a dilute neutral-cluster approximation (in the sense that the coefficients are viewed as 1-d Coulomb chains). Detailed analyses are carried out for p=1 and 2, with p=1 recovering the so-called dilute-dipole approximation in a general way. In addition, the zero-temperature coefficients of [Formula: see text] and [Formula: see text] for the linear mobility are proved to be rigorously zero for α<1.
STRUCTURAL AND ELECTRONIC ORIGIN OF THE HIDDEN NESTING AND CHARGE DENSITY WAVES IN TRANSITION METAL OXIDES AND BRONZES
Authors: CANADELL ENRIC , WHANGBO MYUNG-HWAN
Published: November 2004

By employing the concept of hidden nesting, we examined why charge density wave (CDW) instabilities occur in the two-dimensional (2D) metals, purple bronzes AMo 6 O 17 (A=K, Na, Tl), Magnéli phases Mo 4 O 11 and monophosphate tungsten bronzes (MPTB’s). These oxide metals consist of metal-oxygen (M-O) layers made up of MO 6 (M=Mo, W) octahedra, and the t 2g-block bands of these M-O layers are partially filled. The M-O layers are divided into three sets of parallel chains containing t 2g-orbitals, and the t 2g-orbitals of each MO 6 octahedron act as δ-orbitals toward the M-O axes perpendicular to the chains. Consequently, the t 2g-block bands of AMo 6 O 17, Mo 4 O 11 and MPTB’s can be described in terms of three hidden one-dimensional (1D) bands, which explains why these 2D metals possess three hidden 1D Fermi surfaces and give rise to the associated CDW instabilities. The hidden nesting concept is applicable to the diphosphate tungsten bronzes, which are apparently 2D metallic because their W-O layers have 1D bands dispersive in two orthogonal directions. In general, the electronic instabilities of any systems with several partially filled bands are expected to arise from hidden nesting.
CHARGE DENSITY WAVE PROPERTIES OF MOLYBDENUM BRONZES
Authors: DUMAS JEAN , SCHLENKER CLAIRE
Published: November 2004

The physical properties of the low dimensional molybdenum bronzes showing charge density wave (CDW) instabilities are reviewed. The mechanisms of the Peierls transition, CDW and spin density wave (SDW) instabilities are first introduced. The properties of the quasi-one-dimensional (1D) blue bronze, A 0.30 MoO 3, including non linear transport due to the depinning of the incommensurate CDW, are described. The transport properties and the effect of pressure on the superconducting properties of the quasi-1D Li purple bronze Li 0.9 Mo 6 O 17 are reported. Finally, one presents the properties of the commensurate CDW state of the quasi-2D purple bronze KMo 6 O 17, especially under high magnetic field and hydrostatic pressure.
MIXING AND PHASE SEPARATION IN LIQUID CRYSTAL/MATRIX SYSTEMS
Authors: SMITH GEORGE W.
Published: November 2004

We review mixing and phase separation (demixing) in mixtures of low molecular weight liquid crystals (LCs) and organic matrices, with emphasis on aspects relevant to the formation of polymer-dispersed liquid crystal films. These films, which contain a myriad of micron-sized LC droplets, are of interest because of their electro-optic properties. Film formation is simple: A liquid crystal and a liquid polymer precursor are initially mixed to form a single phase. Subsequently the polymer is hardened, and LC microdroplets phase-separate from the matrix. Although matrix hardening can be achieved in several ways, this review focuses on curing, during which cross-linking reactions lead to an increased matrix molecular weight. Topics discussed include: phase behavior of the binary system before, during, and after cure and LC/matrix solubilities. The Flory-Huggins model for phase separation (as modified by several workers) has provided a theoretical basis for the studies. Principal experimental tools have been calorimetry and light scattering.

Uncured LC/matrix binaries possess phase diagrams with an upper critical solution temperature. Such systems, when heated through the mixing temperature, exhibit a decrease in specific heat, the (negative) excess specific heat of mixing, ∆ C mix . A plot of ∆ C mix vs. LC concentration exhibits a minimum, from which we can estimate LC and uncured-matrix solubilities. Matrix cure plays a major role in the phase separation process: In partially-cured samples, ∆ C mix transitions persist until cure is nearly complete, at which time a fraction of the LC is permanently phase-separated, with the rest remaining dissolved in the matrix.

The kinetics of phase separation can be determined by calorimetry or light scattering. Cure rates have been shown to control LC microdroplet size, with fast cures leading to small droplets. Calorimetry of the fully cured system also allows us to determine the solubility of liquid crystal in the polymer matrix, as well as the fraction of phase-separated LC. An approximation based on the lever rule and the Flory-Huggins spinodal curve provides an upper bound for the solubilities and also describes their temperature dependence.
THE GROUND STATE STRUCTURE AND MODULAR TRANSFORMATIONS OF FRACTIONAL QUANTUM HALL STATES ON A TORUS
Authors: KESKI-VAKKURI ESKO , WEN XIAO-GANG
Published: November 2004

The structure of ground states of generic FQH states on a torus is studied by using both effective theory and electron wavefunction. The relation between the effective theory and the wavefunction becomes transparent when one considers the ground state structure. We find that the non-abelian Berry’s phases of the abelian Hall states generated by twisting the mass matrix are identical to the modular transformation matrix for the characters of Gaussian conformal field theory. We also show that the Haldane-Rezayi spin singlet state has a ten fold ground state degeneracy on a torus which indicates such a state is a non-abelian Hall state.
LANDAU DESCRIPTION OF THE SUPERCONDUCTING PHASE TRANSITION
Authors: KIOMETZIS MICHAEL , SCHAKEL ADRIAAN M.J.
Published: November 2004

Focusing on an order parameter that signals the breakdown of a global symmetry, we employ a dual formulation of the Ginzburg-Landau model to obtain a Landau description of the phase transition of three-dimensional type-II superconductors at zero magnetic field. In the superconducting phase the dual theory is a complex |ψ|4 theory interacting via a shielded Coulomb potential mediated by a massive vector mode which may be pictured as representing the magnetic field. In the normal, high-temperature phase the vector mode decouples and the theory reduces to a pure |ψ|4 theory with a broken global U(1) symmetry. The resulting massless Goldstone mode represents the photon. The phase transition between the two phases is continuous with critical exponents given by those of a superfluid with reversed temperature axis.
DIFFRACTION AND SQUEEZED LIGHT
Authors: TUCCI ROBERT R.
Published: November 2004

We discuss the effect of diffraction on squeezed light propagation. All electric fields concerned are approximated to be monochromatic and paraxial. We consider: (1)(propagation without gain) a squeezed signal propagating in free space, and (2)(propagation with gain) a squeezed signal propagating in a non-linear crystal which amplifies the signal by a process of frequency halving (degenerate parametric amplification). The pump beam required for this process is assumed to have a Gaussian amplitude profile. For propagation without gain, our expression for the final signal is exact, but for propagation with gain, it is given as a perturbative expansion. The lowest order term in the expansion neglects diffraction of the signal and assumes flat pump wavefronts. Higher order terms include these factors and thus improve the accuracy with which the signal’s transverse behavior is described. We present graphs showing the dependence of squeezing on pump and signal beam parameters. We also find and discuss approximate formulas that characterize these graphs in various regimes.
SOME STUDIES ON ARITHMETICAL CHAOS IN CLASSICAL AND QUANTUM MECHANICS
Authors: BOLTE JENS
Published: November 2004

Several aspects of classical and quantum mechanics applied to a class of strongly chaotic systems are studied. The latter consists of single particles moving without external forces on surfaces of constant negative Gaussian curvature whose corresponding fundamental groups are supplied with an arithmetic structure.

It is shown that the arithmetical features of the considered systems lead to exceptional properties of the corresponding spectra of lengths of closed geodesics (periodic orbits). The most significant one is an exponential growth of degeneracies in these geodesic length spectra. Furthermore, the arithmetical systems are distinguished by a structure that appears as a generalization of geometric symmetries. These pseudosymmetries occur in the quantization of the classical arithmetic systems as Hecke operators, which form an infinite algebra of self-adjoint operators commuting with the Hamiltonian.

The statistical properties of quantum energies in the arithmetical systems have previously been identified as exceptional. They do not fit into the general scheme of random matrix theory. It is shown with the help of a simplified model for the spectral form factor how the spectral statistics in arithmetical quantum chaos can be understood by the properties of the corresponding classical geodesic length spectra. A decisive role is played by the exponentially increasing multiplicities of lengths. The model developed for the level spacings distribution and for the number variance is compared to the corresponding quantities obtained from quantum energies for a specific arithmetical system.

Finally, the convergence properties of a representation for the Selberg zeta function as a Dirichlet series are studied. It turns out that the exceptional classical and quantum mechanical properties shared by the arithmetical systems prohibit a convergence of this important function in the physically interesting domain.
PRESSURE-INDUCED STRUCTURAL EFFECTS IN SEMICONDUCTORS
Authors: CRAIN J.
Published: November 2004

Recent advances in the understanding of pressure-induced structural and electronic effects in semiconductors have been made possible through developments in both experimental and computational physics. It is shown that the A N B 8−N compounds which include the tetrahedrally coordinated III–V semiconductors exhibit a far richer degree of pressure-induced structural polymorphism than was originally believed. In addition, entirely new factors such as defects, short-range order and irreversibility have been identified as playing potentially important roles in the high pressure behavior of semiconductors. The experimental results are reviewed and discussed in the context of models which are amenable to investigation by modern theoretical and computational methods.
VARIATIONAL APPROACH TO THE PHASE DIAGRAM OF RIGID MEMBRANES
Authors: BETTOLO MARCONI U. MARINI , MARITAN A.
Published: November 2004

D-dimensional elastic networks randomly embedded in a d>D dimensional euclidean space, are studied employing Hartree (Gaussian) approximation. In presence of an energy depending on the mean curvature this approach leads to the prediction of a phase transition between a flat and a crumpled regime as the bending rigidity decreases in agreement with previous approximate calculations.
STABILITY OF ALL-COUPLING LARGE OPTICAL SINGLET BIPOLARONS
Authors: CHATTERJEE ASHOK , SIL SHREEKANTHA
Published: November 2004

A variational calculation is performed to obtain the stability criteria, effective mass and the size of a large optical singlet bipolaron for the entire range of the coupling parameters in both two and three dimensions. It is shown that the bipolaron binding is stronger in thin films than in bulk crystals. It is suggested that Cu 2 O and TiCl in the form of thin films might exhibit bipolaronic effects.
SEMICONDUCTOR EXCITON OPTICAL BISTABILITY AS INFLUENCED BY FREE CARRIERS
Authors: AN NGUYEN BA , DAN NGUYEN TRUNG , NGUYEN HOANG XUAN
Published: November 2004

Exciton density in an optically excited semiconductor is calculated as a function of pumping light intensity. In a certain domain in the detuning-intensity plane there may appear bistability of exciton density which is shown considerably influenced by the presence of free carriers. The carrier-induced effect manifests itself in the modification of phase diagrams leading to changes of the hysteresis loop size in both intensity-controlled and frequency-controlled bistabilities.
GENERALIZED HANNAY ANGLE FOR THE MOST GENERAL TIME-DEPENDENT HARMONIC OSCILLATOR
Authors: KOBE DONALD H. , ZHU JIONGMING
Published: November 2004

The most general time-dependent Hamiltonian for a harmonic oscillator is both linear and quadratic in the coordinate and the canonical momentum. It describes in general a harmonic oscillator with mass, spring “constant,” and friction (or antifriction) “constant,” all of which are time dependent, that is acted on by a time-dependent force. A generalized Hannay angle, which is gauge invariant, is defined by making a distinction between the Hamiltonian and the energy. The generalized Hannay angle is the classical counterpart of the generalized Berry phase in quantum theory. When friction is present the generalized Hannay angle is nonzero. If the Hamiltonian is (incorrectly) chosen to be the energy, the generalized Hannay angle is different. Nevertheless, in the adiabatic case the same total angle is obtained.
LIGHT PROPAGATION THROUGH UNPERFORATED METALLIC STRUCTURE: PLASMON RESONANCE INDUCED TRANSPARENCY
Authors: LUO XIANGANG , WANG HAO , SHI JIEPING , YAO HANMIN
Published: November 2004

The transmission properties of rectangular one-dimensional unperforated metallic periodic structures for frequencies close to the surface plasmon band are investigated experimentally and theoretically. The results reveal that it is possible to obtain unexpectedly large transmissions through thick unperforated metallic structures. The mechanisms of enhanced transmissions are attributed to resonant excitations of three kinds of plasmon radiations: coupled surface plasmon polaritons, horizontal localized groove plasmon mode, and vertical localized groove plasmons mode. Once the surface plasmon polaritons and the vertical groove plasmon modes are excited simultaneously, the transmission approaches to maximum at the coincident condition.
COUPLING AND FEEDBACK EFFECTS IN EXCITABLE SYSTEMS: ANTICIPATED SYNCHRONIZATION
Authors: CISZAK MARZENA , TORAL RAÚL , MIRASSO CLAUDIO
Published: November 2004

This paper reviews our recent work on the synchronization of excitable systems in a master–slave configuration and when the slave system includes a delayed self-coupling term. Particularly, we address the existence of the so-called anticipated synchronization, i.e. a dynamical regime in which the slave system is able to reproduce in advance the evolution of the master. This is most remarkable since the anticipated synchronization appears even when the excitable spikes are induced by random terms, such as white noise. After providing a short review of the general theory of synchronization as well as the main features of excitable systems, we present numerical and experimental results in coupled excitable systems of the FitzHugh–Nagumo type driven by different types of noise. The experiments have been done in electronic implementations of the model equations. We present the conditions (values of the coupling intensity and delay time) for which the anticipated synchronization regime is a stable one and show that it is possible to increase the anticipation time by using a cascade of several coupled systems. We use a particular limit of the FitzHugh–Nagumo system, as well as a simple excitable model, to give evidence that the physical reason for the existence of anticipated synchronization is the lowering of the excitability threshold of the slave due to the coupling. Finally, we propose a hypothesis for a possible explanation of the zero-lag synchronization observed in some real neuron systems.
MESOSCOPIC FLUCTUATIONS IN HIGH MAGNETIC FIELDS — ARE THEY STILL UNIVERSAL?
Authors: GEIM A. K. , MAIN P. C. , EAVES L.
Published: November 2004

Universal conductance fluctuations (UCF) arise in mesoscopic systems as a direct consequence of the quantum interference of electron waves. The universal feature of the fluctuations is that, at finite temperature, their behaviour can be expressed in terms of one parameter, the phase breaking length of electrons Lϕ. Though the mesoscopic fluctuations have also been observed in high magnetic fields, ω c τ > 1, where ω c is the cyclotron frequency and τ the electron scattering time, it was widely believed that the magnetic field had to suppress the fluctuations. However, experiments on an orthodox mesoscopic system have found out no signs of the suppression. The fluctuation amplitude remains unchanged in high magnetic fields while the period of fluctuations changes dramatically. This indicates the breakdown of universal scaling at high magnetic fields.
TRACE MAPS FOR QUARTERNARY QUASIPERIODIC LATTICES
Authors: IGUCHI KAZUMOTO
Published: November 2004

We derive trace maps for the quarternary quasiperiodic lattices in one dimension, which are constructed by four letters, a, b, c, and d. We prove that the dimension of the trace map is ten.
CLASSICAL XY SYSTEMS UNDER TIME DEPENDENT MAGNETIC FIELDS
Authors: GOLDSTEIN ROBERT S.
Published: November 2004

The phase diagram of the hard-spin XY model with infinite-range coupling under time dependent magnetic fields is investigated. Phases are distinguished by measuring time-average magnetization (TAM). For the case of an oscillating (AC) magnetic field, three phases with non-zero TAM are found in addition to a zero TAM phase. All phases are found to be synchronous with the driving frequency. The non-zero TAM-zero TAM transition line diverges to infinite magnetic field amplitude for low temperatures. An unusual type of hysteresis due to the infinite range coupling appears. Some strategic points in the phase diagram are analytically explained. Also, we interpolate between the AC and rotating magnetic field cases (investigated previously by Kuramoto's group) by studying an 'elliptical' magnetic field case.
IRREVERSIBILITY BEHAVIOR OF Bi4Sr3Ca3Cu4O16 ROLLER-SPLAT COOLING SUPERCONDUCTORS
Authors: SOSNOWSKI J. , CLAD R. , EL FARSI R. , KUENTZLER R.
Published: November 2004

The irreversibility behavior of high-T c superconductors of composition Bi 4 Sr 3 Ca 3- Cu 4 O 16 prepared by the roller-splat cooling method has been investigated. Magnetic measurements were performed in a strong magnetic field or liquid helium temperature. Magnetization hysteresis curves and minor hysteresis loops were obtained and, flux creep and flux trapping measurements carried out for polycrystalline bulk and powdered samples. The results of measurements were discussed and the flux creep parameters and the first penetration field value estimated.
ATTRACTIVE CORRELATED ELECTRON-PAIR GROUND STATE OF RESONANT BOSONS
Authors: CHAKRAVERTY B. K.
Published: November 2004

We consider a strictly one-band Hamiltonian of electrons with attractive interaction between them. We show that in the interesting intermediate density regime, where V ≤ ε F , the system admits a mixed state of free fermions and dynamic correlated pairs or resonant bosons. The inevitable coupling between the two sub-system produces a superconducting ground state. This should be called Schafroth Condensation.
A REVIEW ON HYDROGEN ADSORPTION ON Si(100)
Authors: LU Z. H. , GRIFFITHS K. , NORTON P. R.
Published: November 2004

The paper reviews recent advances in the understanding of hydrogen adsorption on the Si (100)−(2 × 1) surface. Absolute measurement of deuterium coverage over a wide range of exposure allow us to identify different reaction process. Channeling analysis sees changes of surface structure down several layers below the surface on various hydride terminated Si(100) surfaces.
TRANSPORT PROPERTIES OF LixCu(1 − x)O
Authors: FEDUZI R. , LANZA F. , DALLACASA V.
Published: November 2004

The resistivity of Li doped CuO polycrystalline samples is discussed following the variable-range hopping mechanism (VRH) form, exp ((T0/T)1/4), between 80 and 300 K. The T0 have been measured to be in the range of 107 − 108 K . In the CuO undoped system, the VRH mechanism does not fit appreciably the resistivity data in the range of temperature considered. However, when Li is introduced, this behaviour is followed, leading us to suggest that the Li doped CuO could be view as a disordered system. At higher temperatures, the thermal activation mechanism takes place.
HIGH RESISTIVITY IN THE QUASICRYSTALS
Authors: KOHMOTO MAHITO , HIRAMOTO HISASHI
Published: November 2004

We argue that the electronic states in the quasicrystals have a tendency to be localized where the density of states is small (pseudogap). This combined with the Hume-Rothery type argument for the stabilization of the quasicrystals which assumes the existence of a pseudogap at the Fermi energy offers a possible explanation of the high resistivities found in the experiments. A one-dimensional example is discussed which shows the localization behavior mentioned above.
COLLECTIVE EFFECTS IN RANDOM SEQUENTIAL ADSORPTION OF DIFFUSING HARD SQUARES
Authors: WANG JIAN-SHENG , NIELABA PETER , PRIVMAN VLADIMIR
Published: November 2004

We study by Monte Carlo computer simulations random sequential adsorption (RSA) with diffusional relaxation, of lattice hard squares in two dimensions. While for RSA without diffusion the coverage approaches its maximum jamming value (large-time fractional coverage) exponentially, added diffusion allows the deposition process to proceed to the full coverage. The approach to the full coverage is consistent with the ~ t−1/2 power law reminiscent of the equilibrium cluster coarsening in models with nonconserved order-parameter dynamics.
THE PHYSICAL PROPERTIES OF RuS2 − xSex SINGLE CRYSTALS
Authors: LIN SHOEI-SHENG , HUANG JENG-KUANG , HUANG YING-SHENG
Published: November 2004

In this review, the preparation and characterization of the pyrite-type compound RuS 2 and RuSe 2, as well as the mixed anion compositions RuS 2 − x Se x, are systematically reported. Unusual temperature dependence in electrical transport properties characterize these compounds. Electrolyte electroreflectance measurements were used to get a better understanding of their band structure. Long-wavelength optical phonons have been studied by Raman scattering measurements at room temperature. The nature of defect in these compounds were studied by electron paramagnetic resonance (EPR) investigation. A chalcogen point defect model was established to account for the spin S = 1/2 paramagnetic species detected by EPR.
POPULATION DYNAMICS FOR SPIN-POLARON-PAIRS IN HIGH-Tc SUPERCONDUCTORS
Authors: MOTA RONALDO
Published: November 2004

A study of the population dynamics for spin-polaron-pairs in high-T c superconductors is presented. A particular population dynamical model and its appropriateness is discussed. Numerical results are obtained for the x-dependence of the critical temperature using the logistic growth model and a good concordance with experimental data has been obtained for T c as a function of x for La 2 − x Sr x CuO 4. A discussion of various aspects and implications of the model is given.
THEORETICAL STUDIES OF TRANSIENT RAMAN SCATTERING OF NON-EQUILIBRIUM CARRIERS IN SEMICONDUCTORS — EFFECTS OF CARRIER COLLISIONS
Authors: CHIA C. , SANKEY OTTO F. , TSEN K. T.
Published: November 2004

We present a comprehensive theory for time-resolved Raman scattering from non-equilibrium electrons in direct bandgap semiconductors. Specifically, we include (1) the effects of probing with ultrashort laser pulse: (2) the effects of finite carrier collision time; (3) the effects of band structure; and (4) the effects of damping in the optical transition, in the calculations of Raman scattering cross section. Both elastic and inelastic scattering processes are taken into account in formulating the effects of carrier collision time. The effects of damping in the optical transitions have to be considered for the experimental condition of probing with above-bandgap laser excitations even if under some circumstances they do not drastically change the lineshape of the single-particle-scattering spectrum due to spin-density fluctuations.
STUDY OF Ba CORE LEVEL BINDING ENERGIES IN A YBa2Cu3O~7 THIN FILM
Authors: SRIVASTAVA P. , SAINI N. L. , SEKHAR B. R. , SHARMA S. K. , CHAUHAN H. S. , GARG K. B. , MERCEY B. , LECOEUR PH. , MURRAY H.
Published: November 2004

A thin film of superconducting YBa 2 Cu 3 O ~7 (YBCO) system (Tc ~ 89 K ) has been studied by x-ray photoelectron spectroscopy (XPS) to investigate the core level electronic structure. The Ba 3d and 4d core level XPS spectra show three binding energy components with the high binding energy component originating from the non-superconducting surface of the system. The role of oxygen ordering/disordering has been discussed to explain the origin of the other two bulk-dependent components. An attempt has been made to resolve some of the discrepancies in the Ba core level spectra reported earlier.