bluuebunny/crossref_metadata_2025 huggingface dataset:
THE PROCESSES e+e−→W±H∓AND e+e−→H+H−IN SUPERSTRING INSPIRED EXTRA U(1) MODEL
Authors: BHATIA USHA , SHARMA N.K.
Published: November 2004

We investigate the processes e+e−→W±H∓ and e+e−→H+H− in a superstring inspired model having an additional ZE. The cross section at Z2 resonance for e+e−→W±H∓ are considerably large, giving about a thousand events per day at LEP II energy for the planned luminosity. The invariant mass spectrum for l±vl obtained from W± decay is shown to be distinct and could be decisive in the detection of the process. The cross section for the process e+e−→H+H− is relatively small and may provide around five events per day for the envisaged luminosity. The dominant background problem caused by e+e−→W+W− in both processes may be reduced by applying appropriate cuts on the polar angle of the thrust axis.
SIMULATIONS OF DYNAMIC PION PRODUCTION IN 60 AND 200 A GEV COLLISIONS OF 16O+197AU
Authors: WILSON J.R. , MCABEE T.L. , ALONSO C.T.
Published: November 2004

We have investigated collisions of 16O with 197Au at bombarding energies of 60 and 200 GeV/N in the laboratory frame. Our hydrodynamics-based 3-D model, with a modified gamma-law equation of state, includes detailed dynamic pion production and propagation. A comparison of hydrodynamic simulations with and without the inclusion of pions shows that including the pion channel yields results which more closely reproduce the experimental data. We show direct comparisons of several predicted observables with experimental measurements made over various pseudorapidity ranges. In general, we find that while our overall energy agreement with calorimetry experiments is good, and our predicted spatial distributions are in fair agreement with experimental data, our model produces pions which are too energetic and too few in balancing proportions. Our results indicate that most of the emitted (measured) pions emerge from the cooler surface, and not from the hot, dense interior of the hadronic composite.
NONSTANDARD PRODUCTION OF THE STANDARD HIGGS
Authors: LAMPE B. , VLACHOS N.
Published: November 2004

New interactions beyond the Fermi scale can be studied systematically in an effective Lagrangian approach. We have examined the contribution of all SU3×SU2×U1 invariant-effective operators of dimension six containing the Higgs field, to the Higgs production rates in e+e−, ep and [Formula: see text] collisions and in toponium decay. Restrictions from low energy phenomenology on the strength of these operators are also discussed.
CALCULATION OF SCALAR FORM FACTORS OF NONTOPOLOGICAL SOLITONS
Authors: CELENZA L.S. , PANTZIRIS A. , SHAKIN C.M.
Published: November 2004

We study a “toy” model which describes the bound state of two scalar particles. We parameterize the “soft” part of the wave function of the bound state using results obtained in the study of a nontopological soliton model. (This part of the wave function has predominantly lowmomentum components.) We improve this wave function by considering a single “hard” scattering, which we treat in perturbation theory. Thus, we have a model in which the wave function has both “soft” and “hard” parts, in the language used when performing perturbative QCD studies. (The relation of these results to those obtained for electromagnetic form factors in perturbative QCD studies requires further analysis.) We find that the form factor calculated using the “soft” part of the wave function behaves as F(Q2)=F(0)/(1+λ2Q2), where Q2=−q2>0. The individual hard scattering terms yield form factors which have the same form, except for a change of the scale factor, λ. We discuss the approach to the asymptotic form, F(Q2)~Q−2, for the various amplitudes which are summed to obtain the complete form factor. We also discuss the modification of the form factor under a change in mass scale. This modification is relatively simple to study since, in our model, there is only a single dimensionful parameter, κ, which sets the scale for all other dimensional parameters.
CLASSIFICATION OF SYMMETRY BREAKING PATTERNS IN HETEROTIC STRINGS ON Z3 ORBIFOLD
Authors: FUJITSU AKIRA , KITAZOE TETSURO , TABUSE MASAYOSHI , NISHIMURA HARUHIKO
Published: November 2004

Symmetry breaking patterns of E8×E′8 on Z3 orbifold are completely analyzed for physically acceptable models by using a kind of Weyl transformation and modular invariance. It is shown that SU(3)×SU(2)×U(1)n cannot be obtained by using any kind of a shift vector and Wilson lines and that the minimal group including SU(3)×SU(2)×U(1) is SU(3)2×U(1)n which is realized by a shift vector and Wilson lines. All models accessible to realistic low energy theories are listed out and an example is described to get SU(3)×SU(2)×UY(1) by using Higgs mechanism with anomalous U(1) channel. The example is able to give massless quark, lepton and Higgs to suppress proton decay by Planck mass scale and to make left-handed neutrino massless.
ON THE DAMPING OF THE ANGULAR MOMENTUM OF A SPHERICAL HARMONIC OSCILLATOR AS A MODEL FOR HEAVY ION COLLISIONS
Authors: ISAR A. , SANDULESCU A. , SCHEID W.
Published: November 2004

In the frame of the Lindblad theory of open quantum systems, the spherical harmonic oscillator with opening operators linear in the coordinates and the momenta of the considered system is analyzed. Explicit expressions for the damping of the energy, angular momentum and its projection, including the coupling of the harmonic oscillator due to the environment, are obtained.
FUSION AND BRAIDING IN W-ALGEBRA EXTENDED CONFORMAL THEORIES (II): GENERALIZATION TO CHIRAL SCREENED VERTEX OPERATORS LABELLED BY ARBITRARY YOUNG TABLEAUX
Authors: BILAL ADEL
Published: November 2004

In a previous work, we defined the chiral screened vertex operators of W-algebra extended conformal theories by fusion of elementary ones. After reviewing how to obtain the braid group representation matrices, realizing the exchange algebra for those chiral vertex operators corresponding to the symmetric tensor representations of An, we generalize our results to chiral screened vertex operators associated with arbitrary An representations. The fused braiding matrices for antisymmetric tensor screened vertex operators are computed explicitly and shown to have a very simple form. Closure of the exchange algebra in the general case is proved using the relation with the Boltzmann weights of the An face models. Since, in the unitary case, the W-algebras are realized as cosets ĝk⊕ĝ1/ĝk+1, the present results can also be reinterpreted in terms of fusion of braiding matrices of the ĝ WZW models. As an example, the simplest W-algebra extended theory, the 3-state Potts model, is discussed in some detail.
THE SPACE OF STRING CONFIGURATIONS IN STRING FIELD THEORY
Authors: BORDES JOSÈ , LIZZI FEDELE
Published: November 2004

In this paper we consider the set of maps from the interval [0, π] which constitute the argument of the functionals of a String Field Theory. We show that in order to correctly reproduce results of the dual model one has to include all square integrable functions in the functional integral, or Ω0 in terms of Sobolev spaces.
GAUGE FIXING FOR LINEARIZED GRAVITY AND ANTISYMMETRIC TENSOR FIELDS
Authors: GANGOPADHYAY DEBASHIS
Published: November 2004

Using the functional stochastic scheme, the gauge fixing term for linearized gravity is shown to be related to longitudinal modes within the framework of the usual set of momentum projection operators. A similar analysis is done for non-Abelian antisymmetric tensor field by replacing derivatives with covariant derivatives in all relevant equations and by constructing suitable operators for projecting out transverse and longitudinal modes.
SOME LANDAU-GINZBURG MODELS FROM CONFORMAL FIELD THEORY
Authors: LI KEKE
Published: November 2004

A method of constructing critical (fixed point) Landau-Ginzburg action from operator algebra is applied to several classes of conformal field theories, including lines of c = 1 models and the coset models based on SU(2) current algebra. For the c = 1 models, the Landau-Ginzberg potential is argued to be physically consistent, and it resembles a modality-one singularity with modal deformation representing exactly the marginal deformation. The potentials for the coset models manifestly possess correct discrete symmetries.
STUDY OF POWER-LAW CORRECTIONS TO SCALING IN A RELATIVISTIC QUARK MODEL
Authors: CELENZA L. S. , PANTZIRIS A. , SHAKIN C. M. , WANG HUI-WEN
Published: November 2004

We study the approach to scaling in a relativistic quark model which we have used previously to fit the experimental data for the structure function [Formula: see text] (for all x) and for [Formula: see text] (for x > 0.4). We present values for these structure functions calculated in our model and also present an analytic form which provides a good fit to the numerical results. Our model supports one form of the power-law corrections suggested in the literature. [We reproduce the sign and magnitude of the parameter which appears in a phenomenological form used in a recent analysis made by the BEBC Collaboration. Our results are also consistent with a recent BCDMS Collaboration analysis which finds no need for "higher-twist" terms for Q2 > 20 (Gev) 2.] We also discuss certain complications which may arise when one attempts to study "higher-twist" behavior at both small and large x with a single sign for the phenomenological power-law correction term. (In particular, we predict a change in sign of the power-law correction to scaling between x = 0.65 and x = 0.7.) In addition, we calculate R(x, Q2) and find a good fit to the experimental data using the same parameters which were used in our fits to [Formula: see text] and [Formula: see text].
HOW TO REGULARIZE SYSTEMS WITH CONSTRAINTS: SOME SIMPLE EXAMPLES
Authors: EYAL OFER
Published: November 2004

We will solve some constrained systems by regularizing them, compare them with the known results, and apply this regularization method to the superparticle system.
SUPERSYMMETRIC EXTENSION OF LOCAL LORENTZ SYMMETRY IN THE VIERBEIN FORMALISM OF EINSTEIN GRAVITY
Authors: ABE MITSUO
Published: November 2004

The supersymmetric extension of local Lorentz symmetry in the vierbein formalism is presented in detail. In contrast to supergravity, this new supersymmetry is purely internal, that is, totally irrelevant to general coordinate transformations. Because of its non-Poincaré nature, the degrees of freedom of bosons and fermions need not be equal and it is unnecessary to introduce gravitino. Instead, it is important to introduce a new type of nonlinear realization, called “ξ-field realization”. The Einstein Lagrangian density is trivially superinvariant and the Dirac theory can be supersymmetrized. A globally superinvariant gauge-fixing plus FP-ghost Lagrangian density is constructed in the BRS-invariant way. In the simplest case, canonical quantization is explicitly carried out and unitarity is proved. It is shown that the manifestly covariant canonical formalism of quantum gravity is extended to the supersymmetric form without spoiling its beauty in contrast to supergravity. This supersymmetric theory provides a natural link between quantum gravity and gauge theory; its implies that the chiral gauge group should be SO (N).
B′ MIXING AND THE PSEUDOSCALAR DECAY CONSTANT
Authors: HOU WEI-SHU
Published: November 2004

The possibilities of B′ meson mixing is discussed. It is found that if fB′ is not much smaller than fπ, B's (or B'd) mixing is possible if |Vt′s Vt′b′/Vcb′| is large, but only for not too heavy b′ masses, e.g. below LEP I energies. The B'b meson will have large mixing for a broad range of parameters; however, it is hard to produce. The vector mesons (B′*) may exhibit mixing phenomena as well. A discussion of our present understanding of meson decay constants of a heavy-light system [Formula: see text] is given. Further efforts on this problem is needed, which will have an impact on our understanding of B mixing as well.
CLASSICAL SOLUTIONS OF THE MANY-TIME FUNCTIONAL EQUATIONS OF MOTION OF THE NAMBU STRING
Authors: COLOMO F. , LONGHI G. , LUSANNA L.
Published: November 2004

In this paper the many-time approach for the open Nambu string is developed. This enables discussion of the model in a general gauge. The corresponding functional equations of motion are solved; the restriction to the orthonormal gauge gives the standard results. These solutions are a preliminary and necessary step in the search for a complete set of observables, which will be the argument of a subsequent paper.
THE PHASE-SPACE VIEW OF INFLATION I: THE NON-MINIMALLY COUPLED SCALAR FIELD
Authors: AMENDOLA LUCA , LITTERIO MARCO , OCCHIONERO FRANCO
Published: November 2004

The Phase Space portrait of a cosmological model with a scalar field coupled to curvature is discussed in detail, analytically and numerically, for any value of the coupling constant ξ and any power law (ϕ2n) potential. The results, particularly intuitive from the graphical point of view, generalize previous studies on the phase space with minimal coupling (ξ = 0) and quadratic or quartic potentials to the entire parameter space (ξ, n). We find global inflationary attractors, often in analytical form, with or without the correct Friedmannian limit. If the coupling constant is negative, escaping regions may occur, while, if it is positive, a forbidden region cuts out a large part of the phase space. Semiclassical instability of vacuum states and singularity-free trajectories are also discussed.
A MODIFIED CHERN-SIMONS TERM: CHIRAL SPIN SYSTEMS AND ANYON SUPERCONDUCTIVITY
Authors: BALACHANDRAN A.P. , LANDI G. , RAI B.
Published: November 2004

In this paper, starting from a system of noninteracting spins in a plane and introducing an appropriate density function for spins, we arrive at a metric independent continuum chiral model. The Lagrangian of this model is a variant of the CP 1 Chern-Simons term and is characterized by an interesting variety of gauge and symmetry groups and topological features. Certain significant aspects of this model or variants thereof are also shared by the mean field approach to the anyon gas, the CP 1 model with the Chern-Simons term and the RVB description of the strongly coupled Hubbard model. The class of models studied here may therefore be useful in the investigation of the latter systems.
EFFECTIVE ACTION FOR INDUCED GRAVITY ON A 2-DIMENSIONAL MANIFOLD
Authors: YOSHIDA K.
Published: November 2004

The generating functional of the correlation functions of the stress energy-tensor in conformal field theory is explicitly constructed first on the Euclidean plane and then on an arbitrary Riemann surface. For the first case, one finds “anti-holomorphic” SL(2C) symmetry as the counterpart of the SL(2C) current algebra of Polyakov’s quantized gravity in 2 dimensions.

For a general real 2-dimensional manifold, one expects a fundamental change due to the breaking of SL(2C) symmetry and to loss of locality.
MODULAR INVARIANCE AND FUSION RULE ALGEBRAS: CLASSIFICATION OF THE THREE-OPERATOR CASE
Authors: CASELLE M. , PONZANO G.
Published: November 2004

We show how to handle together constraints coming from associativity, modular invariance and analyticity in RCFT's. In particular, looking at the theories with three operators we classify fusion rule algebras, central charges and conformal weights fulfilling such constraints. We also show that all allowed theories with three operators are algebraic.
PRECISIQN DETERMINATIONS OF ELECTROWEAK PARAMETERS FROM ep—COLLISIONS AT HERA—ENERGIES
Authors: WEBER A.
Published: November 2004

We have studied HERA's capability of precisely measuring various parameters of the electroweak standard model. The analysis was performed in kinematical regions, x≥0.01 and x≥0.1, where systematic errors are expected to be under control. The statistical precision reachable for standard model parameters, extracted from R≡σ NC /σCC and NC asymmetries A for polarized e± beams, was estimated for both regions. Heavy flavor contributions, which amount up to 15% to the cross sections, were included via the boson-gluon fusion process. Furthermore the influence of various uncertainties (parton distributions, quark masses, σL/σT fixing input parameters) was estimated. For x≥0.01 the uncertainties due to parton densities are sizeable, the total rates (cross sections), however, increase strongly in contrast to the region x≥0.1.
A TOPOLOGICAL APPROACH TO REPRESENTATIONS OF THE IWAHORI-HECKE ALGEBRA
Authors: LAWRENCE R. J.
Published: November 2004

In this paper a topological construction of representations of the [Formula: see text]-series of Hecke algebras, associated with 2-row Young diagrams, will be announced. This construction gives the representations in terms of the monodromy representation obtained from a vector bundle over the configuration space of η points in the complex plane. The fibres are homology spaces of configuration spaces of points in a punctured complex plane, with a suitable twisted local coefficient system, and there is thus a natural flat connection on the vector bundle. It is also shown that there is a close correspondence between this construction and the work of Tsuchiya and Kanie, in which the monodromy of n-point functions for a conformal field theory on P1 is used to produce a braid group representation which factors through the Hecke algebra.
SOME PROPERTIES OF FERROELECTRICS SUBJECTED TO A STEADY STATE TEMPERATURE GRADIENT
Authors: SAJOSCH H. J.
Published: November 2004

A new approach to phase transitions in ferroelectrics in nonequilibrium state is given. It has been shown that if a temperature gradient is imposed on a ferroelectric crystal, then the features of the phase transformation become more complex. Using a simple thermodynamic approach we explain the experimentally observed temperature shift of the spontaneous polarization and pyroelectric coefficient, and the substructure of the dielectric response. All these results are compared with other investigation results, a short review of which is given too.
A SIMPLE WAY TO UNDERSTAND THE ELECTRONIC STRUCTURES OF THE Tl–Ba–Ca–Cu–O HIGH Tc SUPERCONDUCTORS
Authors: WONG YAT-TING , CHAN A. W. EDITH , HOFFMANN ROALD
Published: November 2004

The extended Hückel tight-binding method is used to analyze the electronic structures of two families of superconductors, TlBa 2 Ca n−1 Cu n O 2n+3 and Tl 2 Ba 2 Ca n−1 Cu n O 2n+4. Three members from each family are examined. All of them appear to be conductors with σ antibonding half-filled bands crossing the Fermi levels. The band structures suggest that the oxidation states of Cu and Tl are around +2 and +3, respectively. The calcium and barium atoms, apart from acting as electron donors, have little effect on the dispersion of the bands near the Fermi level. However, the calcium atoms do produce a small splitting of the half-filled bands. One of the proposed superconducting mechanisms, involving oxidation of Cu 2+ by Tl 3+ is discussed. So is the role of vacancies. If there is an oxygen vacancy in TlBa 2 Ca 3 Cu 4 O 11, it should prefer the equatorial or basal position in the Cu-O layer. The oxygen-oxygen repulsions may play a crucial role in determining the unit cell parameters.
QUANTUM SPIN CHAINS: CONFORMAL INVARIANCE AND INTEGRABILITY
Authors: BARBER Michael N. , BATCHELOR Murray T.
Published: November 2004

Recent exact results concerning the behaviour of antiferromagnetic spin chains are reviewed with emphasis on conformal invariance and integrability.
MACROSCOPIC SUPERPOSITION IN SUPERCONDUCTING CIRCUITS
Authors: SPILLER T.P. , CLARK T.D. , PRANCE R.J. , PRANCE H. , POULTON D.A.
Published: November 2004

We discuss the quantum mechanical superposition of macroscopically different states in the light of experiments performed on superconducting circuits, and conclude that compelling evidence for this effect exists.
LOCAL ELECTRONIC STRUCTURE OF Tl2Ca2Ba2Cu3O10 AND COMPARISON WITH LA-OXIDES AND Y-OXIDES
Authors: WANG HUAI-YU , LIU FU-SUI , WANG EN-GE , WANG CHONG-YU
Published: November 2004

Local electronic densities of states of Tl 2 Ca 2 Ba 2 Cu 3 O 10 (2223) are calculated by tight-binding approximation. The nearest and the next-nearest neighbor transitions are considered, and the results are compared with each other. After the latter is considered, the densities of states are smoothened and the semiconductor-like characteristic of the Tl-O layers disappears. Through comparison of 2223 with the other two high Tc ceramics La 2−x Sr x CuO 4 and YBa 2 Cu 3 O 7−x, it is believed that they have the same leading superconductive mechanism besides inter-plane interactions.
MODIFIED ANYON (MANYON) THEORY OF HETEROGENEOUS ELECTRONIC PHASES
Authors: MARKIEWICZ R.S.
Published: November 2004

There is a purely electronic analog to spinodal decomposition in alloys. A number of examples of such phase separation are presented, including one of potential interest to high-Tc superconductivity. It is speculated that, under some circumstances, the heterogeneous state may be described by a modification of the anyon theory.
EFFECT OF SILVER DOPING ON INFRARED REFLECTANCE AND Tc OF SUPERCONDUCTING GdBa2Cu(1−x)3Ag3xO7
Authors: MEMON A. , KHAN M.N. , AL-DALLAL S. , TANNER D.B. , PORTER C.D.
Published: November 2004

Infrared reflectance of GdBa 2 Cu (1−x)3 Ag 3xO7 ceramic superconductor with the composition of x=0.025 and 0.05 have been performed in the frequency range of 100–5000 cm−1. All the infrared active phonon modes allowed by the selection rules were observed in the reflection spectra of these compounds. The optical conductivity as calculated from K-K analysis further confirms the existence of these optical phonons. Besides the increase of the reflectivity in the silver doped samples, an extra phonon mode is observed, which is normally not seen at room temperature reflectance of GdBa 2 Cu 3 O 7 compounds. The four probe resistivity measurement show zero resistance at 88 K for x=0, and 78 K for x=0.025 in GdBa 2 Cu (1−x)3 Ag 3x O 7 compound.
SPHERICAL MODEL ON THE BETHE LATTICE VIA THE STATISTICS OF WALKS
Authors: CASSI DAVIDE , PIMPINELLI ALBERTO
Published: November 2004

We give in explicit form a very general relation between the solution of the spherical model on a graph and the statistics of walks on the same graph. Such formulation sheds light on the role of topology in the statistical behaviour of model systems, since a graph is meant as a geometrical entity with no regard to any embedding space. This includes, of course, euclidean and fractal lattices as in particular cases. In this work we also show how this relation can be exploited to actually compute the thermodynamics of the model on a class of infinite graphs by giving the exact solution on Bethe lattices, where no euclidean metrics can be defined.
THE PROPERTIES OF RBa2(Cu1−xAgx)3O7 SUPERCONDUCTORS
Authors: KHAN M. N. , AL-DALLAL S. , MEMON A.
Published: November 2004

We present superconducting properties and structural analysis of R Ba 2( Cu 1−x Ag x)3 O 7 (with R = Y , Eu and Gd) ceramic compounds. Transition temperatures improve with a small amount of Ag. Results of powder X-ray diffraction (indicate no detectable substitution of Ag into the R Ba 2( Cu 0.999 Ag 0.001)3 O 7 oxide system. We also found that no superconductivity was observed above 10 K for R Ba 2( Cu 0.4 Ag 0.6)3 O 7 compounds. The superconductivity is discussed in relation to the results of X-ray diffraction study.
SCALING BEHAVIOR OF PROBLEM SOLVING SYSTEMS
Authors: CLEARWATER SCOTT H.
Published: November 2004

Problem solving is a ubiquitous phenomenon currently being studied in a number of fields. Still at issue is the problem of scaling up to large problems. Distributed systems with a focus on the architecture and communications of the processors are one possible solution. The model presented here differs by focussing on the distribution of search modifying heuristics available to processors that can be used to speed problem solving. This paper characterizes the shape of speed-up with respect to the heuristics and shows some of the implications for problem solving. Theoretical justifications are given and tested using a rule learning program.
THE DISAPPEARANCE OF TWO-DIMENSIONAL LONG RANGE ORDER IN THE HEISENBERG MODEL WITH COMPETING INTERACTIONS
Authors: BARABANOV A. F. , MAKSIMOV L. A. , STARYKH O. A.
Published: November 2004

In the frustrated Heisenberg model with first (J1) and second (J2) nearest neighbours interactions on a square lattice the transition from the long range order state (LROS) to spin liquid state (SLS) is found at α = J1/J2 ≅ 0.25. SLS is characterized by the gap in spin excitation spectrum at T = 0 and, hence, by exponential decay of spin correlation function at large distance. As a result, correlation length is temperature independent in SLS in accordance with neutron experiments on doped La 2 CuO 4.
EXCITON CONFINEMENT IN SEMICONDUCTOR MULTIPLE QUANTUM WELLS
Authors: FU Y. , CHAO K. A.
Published: November 2004

Exciton binding energy in semiconductor multiple quantum well (MQW) systems is analyzed with both the variational method and the perturbation theory. The intrinsic deficiency of the use of the two-dimensional exciton envelop wave function is clearly demonstrated. Using a GaAs/Al x Ga 1−xAs MQW as an example to calculate the exciton binding energy with a variational three-dimensional trial envelop function, we found that in many realistic samples the spatial extension of an exciton covers a region of several lattice constant dA + dB, where dA is the barrier width and dB is the well width.
OPTICAL REFLECTIVITY STUDY ON THE SINGLE CRYSTALLINE (La1−xSrx)2CuO4
Authors: TAJIMA S. , UCHIDA S. , ISHII H. , TAKAGI H. , TANAKA S. , KAWABE U. , HASEGAWA H. , AITA T. , ISHIBA T.
Published: November 2004

The optical reflectivity spectra were measured for single crystalline La2CuO4 and La1.8Sr0.2CuO4 over a wide energy range from 12meV to 3eV. Comparing the phonon spectrum of single crystal with that of polycrystal, the observed four phonon modes can be classified into the two—the vibrations parallel and perpendicular to the c-axis. The infrared spectrum of La1.8Sr0.2CuO4 shows the normal Drude-type behavior without any extra excitation.
INVESTIGATION OF PHOTOLITHOGRAPHY FOR FABRICATING OF YBCO SUPERCONDUCTING THIN FILMS DEVICES WITH CHEMICAL ETCHING
Authors: SHAO K. , CAO C.H. , ZHU H. , SHEN H.Y. , LI J.T. , WANG S.G. , CUI G.J. , DAI Y.D. , ZHANG Y. , ZENG X.H. , JIANG H.M. , YANG T.Y. , LI J.Z. , WU X.W. , BAO Z.L. , WANG S.Z. , LI C.Y.
Published: November 2004

We have investigated the photolithography on the superconducting YBCO thin films with chemical etching. It was found that the films can be etched by HCl—H3PO4 mixing acid and the side-etching can be suppressed down to one micrometer. The influence on the critical temperature can be minimized to two degrees under well-controlled conditions.
A NEW SUPERCONDUCTING PHASE IN Bi-Sr-Ca-Cd-Cu-O SYSTEM
Authors: CHEN X.H. , CHEN Z.Y. , QIAN Y.T. , CHEN J. , XU M.K. , HE Z.H. , XIA J.S. , FAN M.H. , ZHANG Q.R.
Published: November 2004

A new superconducting phase Bi 4 Sr 3 Ca 2.3 Cd 0.7 Cu 6 O y with zero-resistance T c =75 K has been found. It is possessed of orthorhombic cell with the cell parameters a=5.357 Å, b=5.450 Å, and c=24.339 Å. The zero-resistance T c decreases monotonically with increasing x for 0.7<x≤3.0, while the materials remains in the same phase, and the sample transforms into semiconductor when x=3.0 for the Bi 4 Sr 3 Ca 3-x Cd x Cu 6 O y system.
UPPER BOUND ON THE TWO-POINT CORRELATION FUNCTION OF A SYSTEM OF COUPLED ANHARMONIC OSCILLATORS
Authors: BOGOLUBOV, Jr. N.N. , SANKOVICH D.P.
Published: November 2004

A quantum system of coupled anharmonic oscillators on v-dimensional hypercubic lattice is considered. The upper bound on the pair correlator is obtained. For the representation of creation-annihilation operators this system corresponds to a lattice boson gas model with δ-type repulsion. We prove the existence of Bose condensation at sufficiently low temperatures, and hence of a phase transition in three or more dimensions. An estimate of the critical temperature is obtained.
QUANTUM BEATS OF EXCITONS IN QUANTUM WELLS
Authors: LEO KARL , SHAH JAGDEEP , GÖBEL ERNST O. , DAMEN THEODORE C. , SCHMITT-RINK STEFAN , SCHÄFER WILFRIED , MÜLLER JOACHIM F. , KÖHLER KLAUS
Published: November 2004

We briefly review our recent observations of quantum beats of excitons in quantum wells. The quantum beats are observed as an oscillatory structure in the polarization decay of energetically closely spaced excitons which are coherently excited by ultrashort laser pulses.
MECHANISMS OF FERMI-LEVEL PINNING IN METAL-SEMICONDUCTOR STRUCTURES
Authors: MASRI PIERRE
Published: November 2004

We present the state of art of different models relevant to Fermi level pinning in metal-semiconductor heterostructures.
SCHOTTKY BARRIER HEIGHT AND ATOMIC STRUCTURE OF EPITAXIAL Pb/Si(111) INTERFACES
Authors: HESLINGA D.R. , KLAPWIJK T.M. , WEITERING H.H. , HIBMA T.
Published: November 2004

We review experiments on epitaxial Pb/Si (111) interfaces. Emphasis is laid on the interplay between structural and electrical properties, in particular the relation of the Schottky barrier height (SBH) with the structure of the first monoatomic Pb adlayer. Two structures can be formed, which differ only in the arrangement of the first layer of Pb and Si atoms at the interface. One, a Si (111)(7×7)- Pb structure, has a SBH of 0.70 eV. The other, a Si (111)(√3×√3) R 30°- Pb structure has a SBH of 0.93 eV. Angle resolved photoemission results favor an interpretation in terms of Fermi level pinning by a discrete locali::ed interface state.
THEORIES OF CLUSTER-IMPACT FUSION WITH ATOMIC AND MOLECULAR CLUSTER BEAMS
Authors: KIM Y.E. , RABINOWITZ M. , CHULICK G.S. , RICE R.A.
Published: November 2004

Apparently disparate experimental results have been obtained for deuterium-deuterium (D-D) fusion products from the impact of atomic and molecular cluster beams on deuterated targets. Unexpectedly high fusion rates observed with beams of D 2 O clusters in the energy range 10–1000 eV per deuteron have been a formidable challenge to theoretical physics with previous attempts to explain these surprisingly high yields being unsuccessful. A further challenge exists because the resultant models also do not explain why fusion is not observed in similar experiments with beams of D clusters. We present a theory in which heavy atomic partners in the molecule play a vital role in producing the observed rates, and which can also explain the apparently conflicting experimental results.
SUBSTITUTION EFFECT OF Ni AND Zn FOR Cu IN Bi(Pb)-Sr-Ca-Cu-O System
Authors: WANG N.L. , SHA J. , TAN M.C. , WANG J.S. , ZHANG Q.R.
Published: November 2004

The substitution effects of Ni and Zn for Cu in Bi(Pb)-Sr-Ca-Cu-O system have been studied. The transition temperature Tc decreases at nearly the same rate with the Ni and Zn contents in 2212 phase. The impurities also depress the transition temperature in 2223 phase. It is suggested that the depression of Tc is not caused by reduction of hole concentration, change of unpaired d electron numbers, oxygen vacancies, or, related to it, the formal average valence state of Cu , but is rather due to the partial elimination of the singlet bound state formed from the combination Cu 3d x2 - y2 - O 2 p σ We also discussed the structure disorder which may bring about impurity scattering and localization effects.
ORBITAL PARAMAGNETISM IN TWO-DIMENSIONAL LATTICES
Authors: KUSMARTSEV F.V.
Published: November 2004

We calculate the ground state energy and the magnetization of spinless fermions on a two-dimensional lattice in an external magnetic field. We prove that the absolute minimum of the energy corresponds to a flux value equal to the filling, i.e. the “commensurate flux phase” state is preferable. The magnetization of these fermions has a paramagnetic character of special orbital type.
BROKEN SYMMETRY AND DOMAIN STRUCTURE
Authors: NEWMAN C.M. , STEIN D.L.
Published: November 2004

In Ising-like systems, there is a temperature T*, strictly between zero and the usual critical temperature, above which any region of arbitrary size is completely contained within a domain which prefers energetically to be flipped.
1/f NOISE FROM DIFFUSION IN LATTICE GASSES
Authors: JENSEN HENRIK JELDTOFT
Published: November 2004

Numerical studies of a lattice gas consisting of repulsive particles found 1/fβ power spectra for the total number of particles on the lattice. The value of β depends on the definition of the dynamics of the models. Models with deterministic dynamics have β=1, whereas for stochastic dynamic β=1.5. The scaling relation a+β=3 where α is the lifetime exponent is found to be fulfilled approximately. A discussion of the numerical observations in terms of driven diffusion equations is given.
PARAMAGNETIC ANOMALY AROUND 240 K IN BiSrCaCu2Oy HIGH-Tc SUPERCONDUCTOR
Authors: YUAN SONGLIU , ZHOU XIANYI , JIN SIZHAO , WANG YUGUI , WANG SHUNXI , CHEN ZHAOJIA
Published: November 2004

Electron paramagnetic behaviors of BiSrCaCu 2 O y high-T c superconductor are studied at different temperatures by observation of electron paramagnetic resonance (EPR). No EPR was detected below superconducting transition temperature T c besides a signal near zero field. However, two types of EPR signals exist in this sample above T c . One of them (at the higher field) is almost independent of temperature and its behavior is similar to that of the free electron. Another one (at the lower field) may be related to copper and oxygen ions and its average Lande factor ḡ-value, EPR linewidth and integrated intensity seem to change anomalously at around 240 K. We propose that the anomaly observed may be due to that the sample undergoes a displacive phase transition at around 240 K.
THE EFFECT OF GAMMA IRRADIATION ON THE DISLOCATION RELAXATION PEAK OF COPPER
Authors: ZEIN M. , ALNASER W.E.
Published: November 2004

The effect of gamma irradiation on the dislocation relaxation maximum, i.e. the Bordoni peak, of two high purity copper single crystals of orientation <110> has been studied at a frequency of 10 MHz. It was found that as the irradiation dose increases the Bordoni peak height [Formula: see text] and its temperature Tm decreases in both specimens. A specimen of width to length ratio 1:10, i.e. easy glide, seems to be more sensitive to gamma irradiation than one of aspect ratio 1.3:1. The peak height and its temperature in the former specimen was found to be always higher than in the latter when both were irradiated with a similar dosage. The relation between [Formula: see text] and the gamma irradiation dose is of the form [Formula: see text] where y equals 1.4 or 1.5 depending on the mechanical treatment. Moreover, the study suggests that Q−1 is proportional to the dislocation loop length L in the form [Formula: see text] where n has values of 1.4 and 1.5 which agrees with the pair-kink generation model first proposed by Seeger.
FRACTIONAL STATISTICS ON COMPACT SURFACES
Authors: EINARSSON TORBJORN
Published: November 2004

General kinematical restrictions on quantum-theories of N identical anyons have been established by using braid groups. For an orientable compact surface (without boundary) of genus g, the statistical parameter θ is a rational multiple of π, θ=πp/v (p and v mutually prime integers), and the number of components of the wavefunction is (a multiple of) vg. The particle-number is N=rv+1−g (r integer) for spinless (S=0) and N=rv for spinning (S=θ/2π) anyons. The restrictions for spinning anyons are consistent with results for fractional quantum Hall systems, nonlinear O(3) field theory, and Chern-Simons theory. The multi-component structure, which appears for g≥1, reflects an internal collective degree of freedom. A comparison with the multi-component wavefunctions needed to describe systems with fractionally charged quasi-particles yields consistency relations between charge and statistics. Non-orientable surfaces do not allow fractional statistics.
NEW NONLINEAR OPTICAL MATERIAL ZnS.BaSO4
Authors: ZHA XINWEI , YU QENLI , LI JIANQI
Published: November 2004

A new nonlinear optical material, ZnS.BaSO 4, is first reported. It generates second-harmonic radiation with a power efficiency about one thousand times that of KDP. The structure properties of this material has been studied by electron diffraction.
OBSERVATION OF FRACTIONAL SPIN DEGREES OF FREEDOM IN AN S=1 LINEAR CHAIN HEISENBERG ANTIFERROMAGNET
Authors: HAGIWARA M. , KATSUMATA K.
Published: November 2004

We have studied the typical spin one linear chain Heisenberg antiferromagnet, Ni ( C 2 H 8 N 2)2 NO 2( ClO 4) containing a small amount of Cu2+ by electron spin resonance (ESR) technique. The ESR results are successfully explained by the model that the valence bonds in the valence bond solid state are broken at the Cu 2+ sites resulting in fractional spin degrees of freedom at the Ni 2+ sites neighboring the Cu 2+.
RANDOM WALK IN AMORPHOUS MATERIALS
Authors: LIMOGE Y. , BOCQUET J. L.
Published: November 2004

Among the properties of non-crystalline materials one of the least understood is the mass transport. Depending on the measurement which is done the transport appears either as gaussian or dispersive. We show in this paper that the key point for the understanding of diffusion properties lies in a proper introduction of both aspects of disorder, site and saddle, in random models.
LATTICE GAS SIMULATION OF OXYGEN ORDERING IN YBa2Cu3O6+x SHOWING DYNAMICAL SCALING
Authors: POULSEN H. F. , ANDERSEN N. H. , ANDERSEN J. V. , BOHR H. , MOURITSEN O. G.
Published: November 2004

A 2-dimensional anisotropic lattice model for the oxygen ordering in the high Tc superconductor of the YBa 2 Cu 3 O 7+x type is shown to exhibit an ordering dynamics that obey algebraic growth laws which depend on whether it is an Ortho-I or Ortho-II phase. It is possible to relate this dynamical scaling behavior to a similar scaling in the experimentally observed temporal variation of the superconductivity transition temperature and hence suggesting a specific coupling between the coherence of oxygen order in the basal Cu-O planes and the superconducting state. Furthermore it is possible to explain the variation in the transition temperature with the oxygen density x by a phase mixing model of Ortho-II/Ortho-I domains and an assumption about the charge transfer between the basal and superconducting plane.
ON THE ANTIFERROMAGNETISM IN (2 + 1)-DIMENSIONAL SUPERFLUID 3He-A
Authors: SCHAKEL ADRIAAN M. J.
Published: November 2004

By functionally integrating over the fermionic degrees of freedom an effective action is obtained that describes the antiferromagnetic properties of superfluid 3 He-A in 2 + 1 dimensions at zero temperature. It is shown that this one-loop-induced action is the O(3) nonlinear σ-model augmented by a topological term, the so-called Hopf or Chern-Simons term.
DUAL PROPERTIES OF LATTICE SYSTEMS WITH BROKEN Z2 SYMMETRY
Authors: SAMAJ L.
Published: November 2004

The dual properties of Ising and gauge systems in arbitrary dimensions which global or local Z2 symmetry is broken by an applied field are studied. The concept of the ghost spin enables one to construct a duality transformation which maps an arbitrary (originally Z2 symmetric) model in a nonzero field onto the corresponding theory whose Z2 symmetry is also broken by an applied field. The analysis of the structure of the duality transformation shows that the presence of a field effectively increases the lattice dimension by one.
ELECTRIC CURRENT EFFECT ON YBa2Cu3O6.5+δ CERAMICS PROPERTIES AND COMPOSITION
Authors: NEFEDOV V. I. , SOKOLOV A. N. , BELSKY N. K. , OCHERTYANOVA L. I. , FILATOV A. V. , VOLKOV YE. A. , RAMENDIK G. I. , KOZAKOV A. T. , DEMYANCHENKO A. V.
Published: November 2004

The changes of the YBa 2 Cu 3 O 6.5+δ properties and composition caused by dc and ac treatments at 77 K have been studied. Considerable changes of the cations and oxygen concentrations due to dc effect have been observed for the first time. Elements have been found to migrate both along the sample length according to the electrode polarity and between the sample bulk and the surface. Small impurities such as S, Si, K and Cl have been observed to migrate along the sample length as well. The composition variations are accompanied by changes of magnetic properties and intragrain critical current density. Some aspects of HTSC degradation under these conditions are discussed.
NUMERICAL STUDY OF AXIAL CURRENT DENSITY ON CATHODE END SURFACE OF MPD THRUSTER
Authors: SHESHADRI T. S.
Published: November 2004

The axial current density distribution on the cathode end surface of MPD thrusters is investigated numerically. Plasma temperature and propellant choice are found to be the most important factors determining the magnitude of the axial current density. The axial current density does not have the characteristics of the radial current density found in earlier studies. It is also found that plasma velocity and thruster geometry have only weak effects on the axial current density.
SMALL HYSTERESIS LOOPS INVESTIGATIONS ON HIGH Tc OXIDE SUPERCONDUCTORS
Authors: SOSNOWSKI J. , RAABE J. , BOBRYK E. , GILEWSKI A. , WARCHULSKA J.
Published: November 2004

Results of investigations on small hysteresis loops of yttrium-based high temperature ceramical compounds are presented. A proposed theoretical model describing the magnetic induction profile in a sample has been used for numerical approximation of the experimental data. The results of this fitting procedure then allow one to obtain detailed information on the pinning force's magnetic field dependence as well as the critical current of ceramical compounds.
PREPARATION OF BUFFER LAYERS ON SAPPHIRE FOR HIGH Tc SUPERCONDUCTING THIN FILMS
Authors: WU X. D. , MUENCHAUSEN R. E.
Published: November 2004

Sapphire is a preferred substrate for high frequency applications where small dielectric constants and low loss tangents are required. It is also much cheaper than other oxide subsrates such as SrTiO 3, LaAlO 3, NdGaO 3, MgO, and yttria-stabilized zirconia (YSZ) for high T c superconducting thin films. Unfortunately, sapphire is not chemically compatible with the high T c superconductors at the processing temperature required to obtained good superconducting properties. As a result, an appropriate buffer layer on sapphire is required.
MAGNETIC FLUCTUATIONS AND NORMAL STATE PROPERTIES OF THE t − J MODEL AT FINITE DOPINGS
Authors: LI Y. M. , SHENG D. N. , SU Z. B. , YU L.
Published: November 2004

A loop expansion beyond the mean field approximation is developed to study the effects of magnetic fluctuations on normal state properties of the t – J model at finite dopings, using the Schwinger boson approach. The calculated conductivity consists of a Drude peak and a broad band, while the electron density of states is linear in |ω| at the scale of J, in consistency with experiments on oxide superconductors. The antiferromagnetic nature of fluctuations is found to be essential for these properties.
TRANSIENT AND STEADY STATE PROPERTIES OF THE INVERSE FARADAY EFFECT — SIMULATION AND THEORY
Authors: EVANS M.W.
Published: November 2004

A computer simulation of the inverse Faraday effect in a chiral and achiral ensemble has shown the presence of dynamic magnetisation and second order orientational rise/fall transients due to the conjugate product of a circularly polarised visible frequency laser pulse. Neither effect is known analytically, and the simulated transients are potentially directly comparable with experimental data using modified Kerr effect apparatus.
FINITE SIZE CORRECTIONS FOR MULTIPARTICLE SPIN-½ NONLINEAR SCHRÖDINGER MODEL
Authors: LIU YI-MIN , PU FU-CHO , SU HANG
Published: November 2004

Applied Euler-Maclaurin formula, we compute the finite size correction to the energy of the ground state for the Spin-½ Nonlinear Schrödinger model. We get conformal anomaly for this model at the critical point (T=0).
VARIATION OF Tc IN SINGLE PHASE Bi2Sr2Ca1Cu2O8−x SYSTEM
Authors: KHAN M. NASIR , KHWAJA F.A. , FARID RAANA
Published: November 2004

The variation of Tc in a single-phase high temperature superconductor Bi 2 Sr 2 Ca 1 Cu 2 O 8−x is studied using techniques like X-ray diffraction, magnetic and electric measurements. The samples of Bi-Sr-Ca-Cu-O (with nominal composition 2212) are synthesized by solid state reaction using appropriate amounts of Bi 2 O 3, SrCO 3, CaCO 3 and CuO powders. The Tc is found to vary from 92 K to 115 K in the quenched samples. These changes in the value of Tc have been related to the changes in the inter-layer spacing. It is concluded that an increase in the electron density due to shortening of the inter-layer increases the attractive interaction between pairs and is thus responsible for the high Tc in these superconductors.
ANOMALOUS INCREASE OF THE TRANSPORT AND INDUCTIVE CRITICAL CURRENT DENSITY DUE TO LOW DC-FIELD COOLING IN SINTERED RBa2Cu3O7−x HIGH Tc SUPERCONDUCTORS
Authors: PUIG T. , PONT M. , MUÑOZ J.S.
Published: November 2004

The transport critical current density of bulk sintered samples of RBa2Cu3O7−x with R=Y, Gd, Ho, and Er has been determined at 77 K from I–V curves at different applied dc-magnetic fields (0≤H≤20 Oe), also the ac-susceptibility as a function of ac-field amplitude has been measured with a superimposed dc-magnetic field from 0 to 30 Oe at 77 K.

The transport and magnetic (inductive) critical current densities, are clearly larger in field cooled samples than in zero field cooled samples. Likewise, the degree of shielding as determined from the ac-susceptibility measurements is larger for field cooled samples than for zero field cooled. This anomalous behaviour can be explained in terms of the magnetic flux pinning present in the grains when the sample is field cooled, which leads to a decrease in the magnetic induction of the intergrain region and therefore to a higher intergranular critical current density compared to a zero field cooled sample.
ESR OBSERVATION OF Cu2+INYBa2Cu3−xSnxO7−δ(x=0.05~1.5)
Authors: HOU B.H. , WANG Y.X. , LIANG R.Y. , JIN S.Z.
Published: November 2004

The ESR spectra of YBa2Cu3−xSnxO7−δ(x=0.05~1.5) at various temperatures between 100 K and 300 K are reported. An anomalous change of Cu2+ ESR spectra has been observed. The influence of tin component on superconductivity is not serious when the tin content x is smaller than 1.1. The stronger the Cu2+ ESR signal the lesser is the copper content in the sample.
RELAXATION TIME SCALES OF CRITICAL STOCHASTIC MODELS
Authors: PRIVMAN V. , LUBACHEVSKY B.D.
Published: November 2004

We review recent results on the discrete density and time behavior of single-variable stochastic models. New applications of scaling ideas and numerical simulations in studies of time scales of the discrete evolution near critical fixed points are emphasized.
DEGENERATE CRYSTALLINE PHASE IN A TWO-DIMENSIONAL SYSTEM OF HARD DIMERS
Authors: WOJCIECHOWSKI K.W.
Published: November 2004

Monte Carlo simulations showing thermodynamic stability of a non-periodic solid phase in a system of two-dimensional hard, homonuclear dimers are reviewed briefly. The thermodynamic stability of this phase, called degenerate (or disordered) crystal, follows from a huge degeneracy of the close packed structure of the dimers. The degenerate crystalline phase and its various analogues constitute intermediate steps on a path joining periodically ordered crystalline states with completely disordered states of matter.
ELECTRICAL RESISTIVITY AND DYNAMIC TEMPERATURE X-RAY DIFFRACTION OF Co-B LIQUID QUENCHED AMORPHOUS ALLOYS
Authors: NAQVI S.M.M.R. , SHAMS NAJMA , RIZVI S. DABIR. H. , ABBAS TAHIR , RAZA S.M. , ZIA-UL-HAQUE S.M.
Published: November 2004

The crystallization behaviour of Liquid Quenched Amorphous alloys of Co-B has been investigated by Dynamic Temperature X-Ray Diffraction (DTXD) at a heating rate of 50 K per hour. The result of DTXD were consolidated by measuring electrical resistivity. The products of devitrification indicates that crystallization of the amorphous mass occurs in stages and the sequence of phases appearing during heating follows the same order as has been depicted in Co-B phase diagram obtained during solidification from liquid state.