bluuebunny/crossref_metadata_2025 huggingface dataset:
INTEGRABILITY AND SYMMETRIC SPACES I: THE GROUP MANIFOLD
Authors: FERREIRA L. A.
Published: November 2004

It is shown that any nonsingular Lagrangian describing the motion of a particle on a semisimple Lie group possesses a Fundamental Poisson bracket Relation (FPR) and consequently charges in involution. This property is independent of the dynamics of the model and can be derived in a quite simple and general way from the geometric and algebraic structures of the group manifold. The conditions a Hamiltonian has to satisfy in order those charges are to be conserved are discussed. These conditions lead to an algebra which plays an important role in the construction of conserved charges. In the second paper of the series, this work is extended to the coset spaces which are symmetric spaces.
PROPERTIES OF MESONS IN THE STATISTICAL MODEL
Authors: BANERJEE S. N. , DAS R. K. , SARKER A. K.
Published: November 2004

Within the framework of the statistical model, various properties of mesons are studied. The model which leads to an analytical expression for the number density of quark and antiquark, yields a mass formula of the S state levels of [Formula: see text], [Formula: see text], and [Formula: see text] families. The level spacing between the ground state and a radially excited state in ψ and ϒ families studied in this model reveals interesting relations between the sizes of the particles. With the wave function suggested from the model as an input, magnetic dipoles decays of π and K mesons have been investigated and reasonable agreement is obtained with the experimental findings (and theoretical estimates in some cases). Numerical estimates of the decay amplitudes of many a vector and pseudoscalar meson, are also found to be in accord with experimental and theoretical values.
PERTURBATIVE QED: THE SCHRÖDINGER PICTURE
Authors: HOYER PAUL
Published: November 2004

A derivation of ordinary QED perturbation theory is given in the Schrödinger picture. The path integral is restricted to fields in a finite time interval, ti ≤ t ≤ tf, with explicit boundary conditions given by vacuum state functionals at the initial and final times. The free photon vacuum functional is uniquely specified by the requirement of stationarity in time. For the free electron vacuum further conditions need to be imposed, e.g., the occupation of all negative energy states. The calculations are carried out using a discretized time interval of finite spacing dt, and exact results (to all orders in dt) are obtained for the free generating functionals in Coulomb gauge. Hence Feynman diagrams may be evaluated before the limits of continuous and infinite time are taken, with 1/dt and 1/(tf − ti) providing, respectively, an ultraviolet and an infrared cut-off on the energy integrals. The method may also be used for studying the time evolution of interacting states, in particular of bound states.
DYNAMICS OF COMPACTIFICATION IN EINSTEIN-YANG-MILLS THEORIES
Authors: KUBYSHIN Yu. A. , RUBAKOV V.A. , TKACHEV I.I.
Published: November 2004

We study the evolution of the universe in multi-dimensional theories with gauge fields at the stage when the process of compactification of extra dimensions takes place. It is shown that this process does not drive the four-dimensional inflationary expansion. The conditions for the existence of stable compactifying solutions are found. However, we find that in a wide interval of initial data, the evolution of the system does not lead to the formation of compact extra dimensions.
UNIVERSAL SUPERSYMMETRY BY ADDING 4+4 DIMENSIONS TO THE LIGHT CONE
Authors: SIEGEL W.
Published: November 2004

We extend the previous method for deriving manifestly Lorentz and gauge covariant free field theories from the light cone for arbitrary Poincare representations to arbitrary supersymmetry representations. In the former case the action was expressed in terms of a BRST algebra obtained by adding two commuting and two anticommuting dimensions; in the present case we add 4+4 to obtain the BRST and covariant supersymmetry generators, and we propose an action. When applied to strings this method introduces as coordinates the world-sheet metric, which may therefore be necessary for superstrings.
PHYSICS OF TOP AND CP VIOLATION IN B DECAYS IN THE LIGHT OF THE ARGUS MEASUREMENTS
Authors: BLINOV A.E. , KHOZE V.A. , URALTSEV N.G.
Published: November 2004

Implications of the significant [Formula: see text] mixing, observed by the ARGUS collaboration, on our present understanding of nature are discussed. Our emphasis is on the consequences of the standard model with a heavy top quark. We discuss also the future prospects of the observation of CP violation in B decays.
YANG-BAXTER ALGEBRAS, INTEGRABLE THEORIES AND QUANTUM GROUPS
Authors: De VEGA H.J.
Published: November 2004

The Yang-Baxter-Zamolodchikov-Faddeev (YBZF) algebras and their many applications are the subject of this reivew. I start by the solvable lattice statistical models constructed from YBZF algebras. All two-dimensional integrable vertex models follow in this way and are solvable via Bethe Ansatz (BA) and their generalizations. The six-vertex model solution and its q(2q−1) vertex generalization including its nested BA construction are exposed. YBZF algebras and their associated physical models are classified in terms of simple Lie algebras.

It is shown how these lattice models yield both solvable massive quantum field theories (QFT) and conformal models in appropriated scaling (continuous) limits within the lattice light-cone approach.

The method of finite-size calculations from the BA is described as well as its applications to derive the conformal properties of integrable lattice models. It is conjectured that all integrable QFT and conformal models follow in a scaling limit from these YBZF algebras.

A discussion on braid and quantum groups concludes this review.
CONSISTENT QUANTIZATION OF NONLINEAR SIGMA MODELS COUPLED TO WEYL FERMIONS
Authors: MORENO E. , VON REICHENBACH C. , SCHAPOSNIK F.A.
Published: November 2004

We discuss the quantization of 2-dimensional nonlinear sigma models defined in G/H spaces using the path-integral approach. We show that even when anomalies are present, a careful definition of the quantum effective action leads to a consistent quantum theory. The correct treatment of the H degrees of freedom uncovers the presence of a Wess-Zumino action and the anomaly is absorbed.
BOSON INTERFEROMETRY: A REVIEW OF HIGH ENERGY DATA AND ITS INTERPRETATION
Authors: LÖRSTAD BENGT
Published: November 2004

Experimental data on the correlation of identical bosons are reviewed and the interpretation discussed. A revived interest in the study of the Bose-Einstein effect has evolved after new significant data from collisions at high energy. There is evidence that it looks the same in general events of all kinds of reactions and that the main variable in describing the effect is the absolute value of the four-momentum transfer Q. There is a dependence on multiplicity density at high energy, and furthermore there is an indication of a special reaction mechanism for selected events of very high multiplicity density. New experiments planned are dedicated to studies of the different aspects of this interference effect.
AFFINE EXTENSION OF SUPERSYMMETRIC FIELD THEORY
Authors: CADAVID A.C. , FINKELSTEIN R.J.
Published: November 2004

It is shown that there is no obstacle to the affine extension of supersymmetric Yang-Mills theories. This result holds equally for loop and Kac-Moody algebras. It also holds for 4, 6, and 10 dimensions. By dimensional reduction of the 10-dimensional theory one obtains a supersymmetric action describing interacting Kac-Moody fields in four dimensions.
EQUIVALENCE OF STOCHASTIC AND HYDRODYNAMICAL QUANTIZATION
Authors: HAJRA K.
Published: November 2004

On the basis of earlier work on relativistic generalization of Nelson’s stochastic quantization procedure introducing an anisotropy in the internal space it is shown here that in the non-relativistic limit the equivalence of stochastic and hydrodynamical quantizations formulated respectively by Nelson and Takabayashi can be achieved. Some difficulties regarding interpretation in both the formalisms may possibly be removed from the geometry of internal space-time.
ULTRARELATIVISTIC NUCLEAR PHYSICS: FROM BECOMING TO BEING
Authors: GEIST W. M.
Published: November 2004

Basic theoretical ideas on a phase transition in heavy ion collisions to a thermalized plasma of free quarks and gluons are outlined. Major experiments are then described which made use of oxygen and sulphur beams with moderate (BNL) or high (CERN) momenta. Representative results pertaining to both average event features and quark-gluon plasma properties are discussed in some detail. This review addresses also interested non-specialists.
HEAVY LEPTON SIGNALS AT THE SSC
Authors: HINCHLIFFE IAN
Published: November 2004

Some signals for heavy leptons at the SSC are discussed. For the first time, a signal that can be extracted from the background was demonstrated. The signal involves isolated leptons and jets and does not require measurement of missing transverse momenta. The prospects for detection of a heavy lepton at hadron colliders are limited by the available luminosity rather than by the background.
ON ANYON SUPERCONDUCTIVITY
Authors: CHEN YI-HONG , WILCZEK FRANK , WITTEN EDWARD , HALPERIN BERTRAND I.
Published: November 2004

We investigate the statistical mechanics of a gas of fractional statistics particles in 2 + 1 dimensions. In the case of statistics very close to Fermi statistics (statistical parameter θ = π(1 − 1/n), for large n), the effect of the statistics is a weak attraction. Building upon earlier RPA calculation of Fetter, Hanna, and Laughlin for the case n = 2, we argue that for large n perturbation theory is reliable and exhibits superfluidity (or superconductivity after coupling to electromagnetism). We attempt to describe the order parameter of this superconducting phase in terms of "spontaneous breaking of commutativity of translations" as opposed to the usual pairing order parameters. The vortices of the superconducting anyon gas are charged, and superconducting order parameters of the usual type vanish. We investigate the characteristic P and T violating phenomenology.
CONSTRAINED HAMILTONIAN STRUCTURE OF THE CHIRALLY GAUGED WESS-ZUMINO-WITTEN MODEL
Authors: PERCACCI R. , RAJARAMAN R.
Published: November 2004

We construct the canonical formulation of the left-gauged non-Abelian Wess-Zumino-Witten (WZW) model in four dimensions using Dirac's method of constraints. This study is motivated by our interest in establishing the canonical consistency of anomalous non-Abelian gauge theories of chiral fermions, which are believed to be approximated by the corresponding WZW action in the low energy limit. We introduce in the action a free parameter α, reflecting some of the regularization ambiguities of the anomaly. We find that for α > 1, the WZW model is classically consistent and has a unique positive Hamiltonian, suggesting that the corresponding anomalous fermionic theory will also be consistent and unitary. The case α = 1 is also studied and is shown to have some remarkable properties. Finally, some implications of our results for the Faddeev-Shatashvili model are pointed out.
GEOMETRIC METHODS AND THE GAUGE STRUCTURE OF BERRY'S PHASE
Authors: BEDNARZ BERNARD F.
Published: November 2004

The use of geometric methods to obtain the connection associated with Berry's phase is discussed. Failures and successes in past attempts at using only geometry are presented. It is argued that this approach is most useful for Hamiltonians rotated on the parameter space.
ON THE RENORMALIZATION GROUP APPROACH TO STRING EQUATIONS OF MOTION
Authors: TSEYTLIN A. A.
Published: November 2004

We discuss the program of deriving the string field theory equations of motion for all (massless and massive) string modes as the renormalization group fixed point equations for the most general sigma model containing all possible ("nonrenormalizable") interactions. We review the approach based on the Wilson RG equation and point out the problem of cutoff dependence of the interaction term in the corresponding "quadratic" beta function. The relation between the sigma model path integral and the string scattering amplitudes is clarified. We suggest a new approach to the derivation of the generalized sigma model beta functions in which the central role is played by the condition of completeness of the set of interaction terms ("vertex opeators") present in the sigma model action. The use of the completeness relation makes it possible to obtain closed expressions for the sigma model partition function and the beta functions. The resulting beta functions contain all higher powers of the couplings (fields).
INFINITE-DIMENSIONAL ℤN-INDEXED LIE ALGEBRAS AND THEIR SUPERSYMMETRIC GENERALIZATIONS
Authors: RAMOS EDUARDO , SHROCK ROBERT E.
Published: November 2004

We exhibit a new infinite-dimensional Lie algebra involving operators Ln with indices n ∈ ℤN and depending on a vector of structure constants, v. Two different types of central extensions are also presented. By constructing an explicit representation, we show that this algebra has a natural mathematical basis in terms of the algebra of infinitesimal diffeomorphisms of (S1)N. For N ≥ 2, the space of states is shown to have properties very different from those of the N = 1 (Virasoro) case. Supersymmetric generalizations are also given.
SUPERCONFORMAL SYMMETRY AND GEOMETRY OF RICCI-FLAT KÄHLER MANIFOLDS
Authors: OOGURI HIROSI
Published: November 2004

A supersymmetric nonlinear σ-model provides us a tool for studying the dynamics of superstrings on a compactified space. If the compactified space is a Ricci-flat Kähler manifold, the nonlinear σ-model has extended superconformal symmetry and the partition function of the model is expressed in terms of characters of the superconformal algebra. The partition function must be modular invariant and this condition gives strong constraints on the spectrum of the model. These constraints are intimately related to geometry of the compactified space. Their implications to particle spectra of the compactified heterotic string theory are also discussed.
FOCK EXPANSION FOR QED BOUND STATES
Authors: HOYER PAUL
Published: November 2004

Using the path integral formulation of QED in the Schrödinger picture, we explicitly show the completeness of photon and electron states at equal (discrete) time. We then formulate an approximation of the bound state wave function, based on its maximal Fock state content, by restricting the intermediate states at all times in the bound state propagator. The approximation becomes (formally) exact as the restriction on the intermediate states is lifted. Hence the Fock expansion provides an alternative to bound state calculations based on the Bethe-Salpeter equation.

As an example, we study the bound states formed by a fermion f is an external potential, and by a fermion-antifermion pair [Formula: see text]. At the valence level of the Fock expansion, where the wave function is at all times restricted to f (or [Formula: see text]), we show that only instantaneous Coulomb exchange occurs between the fermions. The resulting bound state equation is similar to the Salpeter equation, but has only positive energy projectors.
STUDY OF CLUSTERS AND HEAVY CLUSTERS IN α-EMULSION INTERACTIONS AT 12A GEV/C
Authors: SHUKLA V. S. , BHALLA K. B. , GILL A. , KUMAR V. , LOKANATHAN S. , GUPTA V. K. , MANGOTRA L. K. , RAO N. K. , AGGARWAL M. M. , ARORA RENU , BHATIA V. S. , KAUR M. , MITTRA I. S.
Published: November 2004

The rapidity gap distributions observed in α-emulsion interactions at 12A GeV/c are analyzed to investigate the variation of cluster size with respect to the size of target nuclei and multiplicity of shower particles (ns) produced. It is observed that the cluster size increases with the increase in size of the target and with the increase in ns. We also observe rather weak indication of the production of heavy clusters using the method of Adamovich et al.
NONARCHIMEDEAN CONFORMAL FIELD THEORIES
Authors: MELZER EZER
Published: November 2004

We present a general formalism for conformal field theories defined on a non-Archimedean field. Such theories are defined by complex-valued correlation functions of fields of a [Formula: see text]-adic variable. Conformal invariance is imposed by requiring the correlation functions to be unchanged under fractional linear transformations, the latter forming the full analogue of the conformal group in two-dimensional, euclidean space-time. All fields in the theory can be taken to be "primary", under the "non-Archimedean conformal group". The conformal symmetry fixes completely the form of all correlation functions, once we are given the weight-spectrum of the theory and the OPE coefficients (which must be the structure constants of certain commutative, associative algebras). We explicitly construct non-Archimedean CFT's having the same weight spectrum as that of Archimedean models of central charge c < 1. The OPE coefficients of these "local" Archimedean and non-Archimedean models are related by adelic formulae.
SHEAF COHOMOLOGY AND FUNCTIONAL INTEGRATION
Authors: NASH CHARLES
Published: November 2004

Various analytic and topological properties of the spaces of functions arising in the functional integral are derived. It is shown that these spaces can possess attractive properties such as continuity, smoothness, and complex analyticity. We provide illustrations of the results with examples taken from several quantum field theories in varying dimensions.
MESONS AND DIQUARKS IN CHIRAL QCD: GENERATION OF CONSTITUENT QUARK MASSES
Authors: PRASCHIFKA J. , CAHILL R. T. , ROBERTS C. D.
Published: November 2004

A new technique for analyzing mesons and diquarks as [Formula: see text] and qq states bound by gluon exchange reveals how quarks acquire constituent masses. Our method, which involves the approximate reformulation of the Bethe-Salpeter equations for chiral QCD in terms of mass functionals, is covariant, has dynamically hidden chiral symmetry and is free of all divergences. From a numerical analysis of these mass functionals, we conclude that the quarks have a preferred or 'constituent' mass, as signalled by a dramatic peaking in the meson and diquark form factors. We obtain values for the bound state and constituent quark masses and also for the ρ → ππ decay width and the ω – ρ mass splitting.
GRAVITATIONAL BAG EFFECTS ON KALUZA KLEIN AND STRING EXCITATIONS
Authors: GUENDELMAN E. I.
Published: November 2004

Gravitational Bags are spherically symmetric solutions of higher-dimensional Kaluza Klein (K – K) theories, where the compact dimensions become very large near the center of the geometry, although they are small elsewhere. The K – K excitations therefore become very light when located near the center of this geometry and this appears to affect drastically the naive tower of the masses spectrum of K – K theories. In the context of string theories, string excitations can be enclosed by Gravitational Bags, making them not only lighter, but also localized, as observed by somebody, that does not probe the central regions. Strings, however, can still have divergent sizes, as quantum mechanics seems to demand, since the extra dimensions blow up at the center of the geometry. From a projected 4-D point of view, very massive string bits may lie inside their Schwarzschild radii, as pointed out by Casher, Gravitational Bags however are horizon free objects, so no conflict with macroscopic causality arises if the string excitations are enclosed by Gravitational Bags.
FEYNMAN GRAPH RULES FOR IINN-INTERACTION AND MATRIX ELEMENTS FOR A SIMPLIFIED pπ0 → pπ0 MODEL IN 5-DIMENSIONAL CONFORMAL QFT
Authors: LUNA-ACOSTA G. A.
Published: November 2004

Recently we reported a successful fitting of the kinematic predictions of the Mass Theory of 5-dimensional Conformal Relativity to the Hadron Spectra. We use results obtained there to study the dynamical properties of the trilinear boson-matter interaction Lagrangian implied by isospin SU(2) gauge invariance. The isovector massive gauge boson allows for two interpretations: a J = 1 field and the 5-D derivative of a J = 0 field. We construct the Feynman Graphs for the ΠNN-interaction and show that (1) any given graph is actually an infinite sum of similar graphs, one for each member of the Conformal Family Field of the virtual Hadron and (2) that the individual coupling of each of these members depends on its mass, giving rise to an effectively energy-dependent coupling. Based on these features, we speculate on the interesting possibility that Perturbation Theory may be usable for hadron processes and calculate the matrix elements for a simplified model of pπ0 → pπ0 to second order. Useful comparisons are made with the analogous treatment in ordinary QFT.
AFFINE EXTENSION OF SUPERGRAVITY
Authors: CADAVID A. C. , FINKELSTEIN R. J.
Published: November 2004

The affine extension of supergravity is investigated. We discuss only the loop algebra since the affine extension of the super-Poincaré algebra appears inconsistent. The construction of the affine supergravity theory has been carried out by the group manifold method and leads to an action describing infinite towers of gravitons and gravitinos that interact subject to the symmetries of the loop algebra. The equations of motion satisfy the usual consistency check.
VARIATIONAL APPROACH TO POLARON PROBLEM
Authors: BOGOLUBOV N.N. , KIREEV A.N. , KURBATOV A.M.
Published: November 2004

Variational Ansatz to describe the ground state of Fröhlich’s Polaron at all interaction strength is proposed. The best upper bounds to the polaron ground state energy are obtained in the limiting cases of weak and strong interactions. For intermediate couplings two simple models are investigated. The ground state energy does not exceed their minimal solution.
NUMERICAL STUDY OF THE Q-COLOR PROBLEM ON A LATTICE
Authors: CHEN XIYAO , PAN C.Y.
Published: November 2004

By using the finite size extrapolation method and combined with a Monte Carlo simulation we have calculated the zero temperature entropy of the q-state Potts Antiferromagnet in two and three dimensions which is identical to the q-color problem in two and three dimensions. The model is laid on a hypercubic lattice. When q=3 (in two dimensions) the result is in good agreement with Lieb’s exact answer. When q>3 (in two and three dimensions) the results are in strong support of Mattis’ recent conjecture for the q-color problem. This method can also treat the d>3 cases without serious difficulties.
NEUTRON DIFFRACTION STUDY ON Y-Ba-Cu-O
Authors: Zhang Baisheng , Ye Chuntang , Yang Zhen , Jin Lan , Gan Shu , Li Songlin , Hu Huachen , Zheng Xiangmiao , Chen Fengxiang , Zhang Wanjing , Li Chuanyi , Wu Ke , Chen Kaixuan
Published: November 2004

The structure of high Tc(88.7K) superconductor YBa2Cu3O7−δ has been studied at room temperature as well as at a temperature slightly below transition temperature by neutron powder diffraction technique. The room temperature data has been analysed using powder profile refinement based on the space group Pmmm. The structure parameters from the profile refinement are: lattice constants a=3.8033A, b=3.8737A , c=11.6275A with Y at 1h(0.5 0.5 0.5), Ba at 2t(0.5 0.5 0.1882), Cu-1 at 1a(0 0 0), Cu-2 at 2q(0 0 0.3565), O-1 at 2q(0 0 0.1600), O-2 at 2s(0.5 0 0.3767), O-3 at 2r(0 0.5 0.3795), O-4 at 1e(0 0.5 0) and O-5 at 1b(0.5 0 0). All sites except 2s, 1b, 1e are fully occupied; the refined populations for 2s, 1b, 1e are 1.74, 0.42, and 0.69 respectively, with Rp=8.40 , RI=5.21 . Thus, we get an oxygen deficiency δ=0.14 . It seems that no evidence for structural phase transition accompanying the superconducting transition was observed.
A STUDY OF YBa2Cu3O9−δ TYPE SUPERCONDUCTING SINGLE CRYSTALS
Authors: Lu H.X. , Wu J. , Zhang X.Y. , Gao X.K. , Li X.J. , Hu M.S. , Zhou H.N. , Mao X.Y. , Wang T.X. , Xin H.Q. , Shi Y.B.
Published: November 2004

Single crystals of Y-Ba-Cu-O type superconductors having the typical dimension 0.5 to 1 mm in the plane of the plate have been prepared. The analysis of compositions show that they correspond to YBa2Cu3O9−δ . Laue photographs, which prove the samples to be single crystals, show some diffraction spots instead of rings. The measurement of susceptibility and other measurements have been performed.
A STUDY ON INTERNAL FRICTION AND YOUNG’S MODULUS OF A HIGH Tc SUPERCONDUCTOR YBa2Cu3O7−x
Authors: Du Jia-ju , Yin Hua-qing , Mao Ou , Wang Xian , Jiang Jian-yi , Yao Wei-guo , Sun Jian-shan , Liu Lin
Published: November 2004

Young’s modulus (E) and internal friction (Q−1) measurements were performed. A Q−1 peak and a sign of anomaly of E were observed near the superconducting transition temperature. There are also two peaks and anomalies of E above Tc. The relation between these charactristic features with superconducting transition is discussed.
MAGNETIZATION OF HIGH Tc SUPERCONDUCTING Ba-Y-Cu-O
Authors: GUO Shuquan , YANG Qiansheng , LIU Guirong , CUI Changgeng , LI Shanlin , HUANG Yuzhen , CHEN Genhua , BI Jianqing , CHEN Liquan , ZHAO Zhongxian
Published: November 2004

Magnetizition of high Tc Ba-Y-Cu-O are measured at temperature of 1.5K-200K and magnetic feild up to 7T. The magnetization curves exhibit hysteresis. However the superconducting current density is very low. Magnetization slopes of different temperature at Meissner state are the same. It means that the superconducting phase is “bulk”.
OBSERVATION OF STRONG ELECTRON CORRELATIONS IN YBa2Cu3O7−δ BY hν DEPENDENT PHOTOELECTRON SPECTROSCOPY
Authors: PETROFF Y. , THIRY P. , ROSSI G. , REVCOLEVSCHI A. , JEGOUDEZ J.
Published: November 2004

After a review of the understanding of resonant photoemission phenomena we present photoemission spectra from single phase YBa2Cu3O7−δ which have been measured in the photon energy range 17–130 eV, at T=80 K, T=300 K and intermediate temperatures using synchrotron radiation. Intense satellites associated with the Cu 3d and O 2p bands are observed to undergo resonances at the Cu 3p and O 2s core level excitation thresholds respectively indicating the presence of holes in the Cu and O hybrid bands on both Cu and O sites. The strong correlation effects for the valence electrons suggest that one electron calculations may not be appropriate for a detailed description of the electronic properties of this material.
EXPERIMENTAL EVIDENCE OF ITINERANT Cu 3d9 - OXYGEN HOLE MANY BODY CONFIGURATION IN THE HIGH-TC SUPERCONDUCTOR YBa2Cu3O~7
Authors: Bianconi A. , Clozza A. , Castellano A. Congiu , Longa S. Della , Santis M. De , Cicco A. Di , Garg K. , Delogu P. , Gargano A. , Giorgi R. , Lagarde P. , Flank A.M. , Marcelli A.
Published: November 2004

Cu L3 x-ray absorption near edge structure (XANES) and Cu L 3 x-ray photoelectron spectroscopy (XPS) of YBa2Cu3O6.5+x are compared. The breakdown of one-electron picture of its electronic structure is reported. The data are interpreted by mixing of Cu 3d9 and of [Formula: see text] (where [Formula: see text] is a hole in the oxygen derived band, ligand hole) many body configuration in the initial state. The localization of Cu 3d9 configuration is indicated by the bare Coulomb interaction Udd~6 eV . The conductivity is assigned to the itinerant [Formula: see text] configuration. The experimental evidence that the additional oxygen x, giving higher Tc , increases the weight of the [Formula: see text] configuration is reported. The presence of holes on the oxygen atoms is confirmed by the Ols XPS spectra. The Cu3+(Cu 3d8) configuration is not observed in L3 XANES in agreement with valence band XPS giving the energy of the 3d8 excited state at about 12 eV above the ground state. An energy scheme of the many body configurations in YBa2Cu3O~7 is obtained.

These experiments give experimental evidence that the high Tc superconductivity is due to pairing of holes in the oxygen valence band interacting with localized electrons at the Cu sites.
DENSITY DEPENDENCE OF THE MAGNETIC AND TRANSPORT PROPERTIES OF YBa2Cu3O7 COMPOUNDS
Authors: Babić E. , Marohnić Ž. , Drobac D. , Prester M. , Brničević N.
Published: November 2004

The dependence of the normal state resistivity, resistive and magnetic superconducting transitions (Tc , Δ Tc ) and of the upper critical field slope (dHC2/dT|T=Tc) on density has been investigated for several YBa2Cu3O7 samples. Resistivity decreases rapidly with increasing density whereas Tc and resistive Δ Tc are insensitive to apparent density. However Δ T'c obtained from a.c. susceptibility decreases rapidly with increasing density. dHC2/dT|T=TC depends sensitively on the actual preparation condition. The lower critical field slope for the most dense sample is also deduced.
ANHARMONIC MODEL FOR HIGH-Tc SUPERCONDUCTORS
Authors: Plakida N.M. , Aksenov V.L. , Drechsler S.L.
Published: November 2004

A considerable enhencement of the superconducting transition temperature Tc in perovskite-type oxides is explained in the framework of the anharmonic model for superconductors with structurally unstable lattices. It is shown that interaction of electrons with highly anharmonic oxigen-ion vibrations of a rotational type results in a sufficiently large couplings constant λ. The obtained estimation for Tc is in agreement with experimental data for La(Y)BaCuO systems.
The Crystal Structure and Ordering of Nb5+ Doped High Tc Superconductors Ba3−yYyCu3−xNbxO9−z
Authors: Xiaowen Zhang , Heping Zhou , Jinfu Zhou , Zhengxiang Qiu , Xiaoming Wei , Liyin Cai , Binglin Gu
Published: November 2004

The crystal structure and ordering of Nb 5+ doped high Tc compounds has been identified by XRD and TEM. As examples, we have studied Ba2Y1Cu2.6Nb0.4O9−z and Ba2Y1Cu2.5Nb0.5O9−z , which consist of -two main phases, respectively. A face-centered cubic superlattice perovskite structure with a=8.4513 (Å) is common phase to both samples. In this phase, Y, Nb, and Cu are on B-sites with ordered Y and Nb in <111> direction. However, the second phase is different in these two samples. One contains a well-known ordered Ba-Y-Ba structure on A-sites as an orthorhombic perovskite superstructure, but another sample contains disordered Ba and Y on A-sites as a tetragonal perovskite structure with a=b=3.8667 (Å) and c=3.9429 (Å). Both samples are high Tc superconductors with Tc=90K .
SPIN-POLARIZED ELECTRONIC STRUCTURE OF INTERSTITIAL 3d TRANSITION ATOM IMPURITIES IN SILICON
Authors: KATAYAMA-YOSHIDA H.
Published: November 2004

We review our recent results of the first principles calculation of the electronic structure of interstitial 3d transition atom impurities in silicon using the impurity Green’s function method and full-potential linearized augmented plane wave (FLAPW) method. We give a unified physical picture to the hyperfine and superhyperfine interaction data, g-values, spin-multiplets, donor and acceptor ionization transition energies, and spin-lattice relaxation time, comparing with the available experimental data.
COHERENT-ANOMALY METHOD FOR QUANTUM SPIN SYSTEMS
Authors: ITO NOBUYASU , SUZUKI MASUO
Published: November 2004

The coherent-anomaly method (CAM) is applied to the Heisenberg model to test the applicability of the CAM for quantum spin systems. The Weiss, Bethe and constant coupling approximations are tried for the Heisenberg model on the simple cubic lattice and estimate the critical exponents of the susceptibility and spontaneous magnetization using the CAM. The results show that the CAM is also powerful for quantum spin systems. The detailed results of the Bethe approximation of the spin-1/2 isotropic Heisenberg model are presented.
RENORMALIZATION GROUP ANALYSIS OF THE ISING MODEL ON TWO-DIMENSIONAL QUASI-LATTICES
Authors: AOYAMA HIDEAKI , ODAGAKI TAKASHI
Published: November 2004

We present a renormalization group analysis of the two-dimensional Ising model on both the Kite-Dart and Rhombi Penrose lattices in which spins are located at the vertices of the lattice. We demonstrate the existence of the phase transition and obtain the critical temperature and the thermal critical index. The thermal critical index is found to be close to unity.
ATOMIC STRUCTURE OF THE ICOSAHEDRAL PHASE
Authors: Romeu D.
Published: November 2004

A growth mechanism derived from physical principles produces for the first time a physical quasicrystal modelling the Icosahedral phase. The model provides the location of impurity (small) atoms, explains x-ray and electron diffraction data, reproduces dark and bright field images and gives sensible values for the solute concentration, mean coordination number and packing density.
FROM QUASICRYSTALS TO CRYSTALS: AN ILLUSTRATIVE EXAMPLE
Authors: KRAMER P. , THOMAS U.
Published: November 2004

Non-periodic quasicrystal models with an atomic density stable on several cells result from the dualization method. For a two-cell quasicrystal model on the line, the restriction to a rational slope is explored. The quasicrystal becomes a periodic crystal as expected. In the two-cell model, the periodic crystal cell displays a finer subdivision into a sequence of cells from the quasicrystal model. This property is apparent in the Fourier transform of the atomic density.
HIGH TEMPERATURE SUPERCONDUCTIVITY IN Y-Ba-Cu-Nb-O SYSTEM
Authors: SURESHA N. G. , HIGO S. , HAKURAKU Y. , OTAWA T. , HONJO Y. , OGUSHI T.
Published: November 2004

Results of the resistivity and magnetic susceptibility measurements for an oxide superconductor with nominal compositions of Y 1 Ba 2( Cu 1−x Nb x)3 O 6+δ and Y 0.4 Ba 0.6 ( Cu 1−x Nb x) O 2+δ where x = 0.1, 0.15, 0.2, are reported. Superconducting transition temperatures, T c onset (T co ) and T c final (T cf ) are above 90 K and 80 K respectively. We have observed a gradual change in the X-ray powder diffraction patterns of the samples with the change in x.
MEAN FIELD THEORY OF RVB
Authors: FUKUYAMA Hidetoshi
Published: November 2004

Implication of mean field approximation to RVB are explored and the temperature dependences of various physical quantities are evaluated. The results are discussed in the light of recent experiments.
LOCALIZED VERSUS ITINERANT PICTURE OF HIGH-Tc SUPERCONDUCTING OXIDES
Authors: Oleś Andrzej M. , Zaanen Jan
Published: November 2004

The physical consequences of the model Hamiltonian which describes the [Formula: see text] and O(2px(y)) orbitals of CuO2 planes in high-Tc superconducting oxides are discussed in the localized and itinerant regime. We show by a direct calculation that the hole correlations at Cu sites are strong and that the antiferromagnetic state of La2CuO4 and YBa2Cu3O6 can be well described in terms of the itinerant model.
POSSIBLE MECHANISM OF PAIRING IN HIGH Tc SUPERCONDUCTORS: A MULTI-COMPONENT PLASMA MODEL
Authors: Mahanty J. , Das M. P.
Published: November 2004

Screening of a pair of point charges in a medium of electrons and ions is studied using the hydrodynamical model, treating the system as a multi-component plasma. When some of the ion plasma branches possess negative dispersion, the interaction potential of the pair can become attractive and large in certain regions of momentum space under certain conditions. By using this potential in the BCS gap equation, high transition temperatures have been obtained. Applicability of this model to oxide superconductors is discussed.
NUMERICAL ANALYSIS OF COUPLED SPIN-FERMION MODEL — PAIRING MECHANISM THROUGH EXTENDED KONDO SINGLET
Authors: IMADA Masatoshi , HATSUGAI Yasuhiro , NAGAOSA Naoto
Published: November 2004

A coupled spin-fermion model is investigated by the exact diagonalization of finite lattices to discuss magnetic mechanism of superconductivity. An extended cloud of singlet liquid (extended Kondo singlet) is found around the fermion in a strong coupling region characterized by strong Kondo coupling and large transfer. The existence of the bound state of two fermions is found. The relevance of its Cooper pairing to high-Tc superconductivity is discussed. The relation to the weak coupling region and also to the small transfer region in this model is discussed.
Superconductivity and Impurities in Layered Systems
Authors: GULACSI Zsolt , GULACSI Miklos
Published: November 2004

Different superconducting phases are described in layered systems, by taking into account in- and inter-layer couplings. The effect of in-layer magnetic and nonmagnetic impurities on these phases are discussed. The possible interferences with high Tc materials is also analysed.
JOSEPHSON JUNCTIONS IN SINGLE-CRYSTAL YBa2Cu3O7
Authors: Lebed A. G.
Published: November 2004

It's shown, that I − V characteristics of the epitaxial films[1] and unusual magnetic properties of the single crystals[2] may be attributed to the forming on the defects of the plural Josephson junctions. We have given the estimations of the dielectric gap, of the transparence of the corresponding energy barriers and the characteristic distance between them. It's studied the surface superconductivity in the magnetic field. We have marked, that non-trivial boundary condition for High-Tc superconductors[3] lead to the positive curvature on dependence Hc 3 (T) .
Distorted flux lines behavior in type II superconducting spherical shell: Application to high temperature superconductor
Authors: Saif A. G.
Published: November 2004

A model of a type II superconducting grains (of a spherical shell shape) is suggested to verify the properties of distorted flux lines (FLs) in high temperature superconductors (HTS). The magnetic fields distributions and current density are formulated. It will be shown that the magnetic field inside a superconducting region is composed of the penetrating applied field, FLs fields, and a stray field. Outside the superconductor, there is only the applied field and the stray field . However, in the normal interior region (r < a), there is only the stray field. Moreover, the forces on the flux line (FL) segments are completely determined.
VARIABLE RANGE HOPPING IN OXYGEN DEFICIENT YBa2Cu3Ox
Authors: BHATIA S. N. , WALIA R.
Published: November 2004

Our measurement of the resistivity and thermoelectric power from 20–300 K in the oxygen deficient YBa 2 Cu 3 O x annealed at 700, 800 and 850°C show good agreement with Mott's variable range hopping model below ~ 100 K.
OFF-DIAGONAL LONG RANGE ORDER OF THE REDUCED DENSITY MATRICES FOR A ONE-DIMENSIONAL SOLVABLE MODEL OF FERMIONS
Authors: PU FU-CHO , ZHAO BAO-HENG
Published: November 2004

A one-dimensional solvable model of fermions is mapped to the XXX ferromagnetic chain. At T = 0, it is shown that there is off-diagonal long range order for the reduced density matrix ρ2 in the model. In momentum space the single particle state pairs are coherently occupied. The momenta of the particles in each pair are equal but with opposite directions.
CHARACTERISTICS OF CH4/CF4 PLASMA AND FORMATION OF DIAMOND-LIKE CARBON FILMS
Authors: YANAGIHARA KENJI
Published: November 2004

CH 4/ CF 4 mixture gas plasmas were studied by a heated double probe method (HDPM) and the relation among plasma states, chemical reaction in the plasma and the characteristics of deposited films was investigated. Electron temperature determined by HDPM had a sharp minimum at the flow rate ratio of CH 4/ CF 4 = 1.8. At high discharge current (200 mA), a hard carbon film with amorphous structure was formed on various kinds of substrates. From the plasma mass spectra, HF molecules were found to play an important role in the plasma reaction and a stoichiometric reaction model was proposed. The unusual variation of the electron temperature was discussed on the basis of the reaction model.
ON THE DYNAMICS OF LOW-TEMPERATURE MODELS FOR PHASE TRANSITIONS WITH CONSERVED ORDER PARAMETER
Authors: BAUSCH R. , KREE R. , LUSAKOWSKI A. , TURSKI L. A.
Published: November 2004

Starting from the time-dependent Ginzburg-Landau model, we derive dynamic versions of a non-linear σ-model and a drumhead model, both with conserved order parameter. In both cases there appears a non-ordering field that adiabatically follows the order parameter. In this way a constraint is imposed on the dynamics which guarantees consistency of conservation of the order parameter and the symmetries of the models.
EFFECTS OF LOCALISATION IN ATOMIC-DISORDERED HIGH-Tc SUPERCONDUCTORS
Authors: DAVYDOV S. A. , GOSHCHITSKII B. N. , KARKIN A. E. , MIRMELSHTEIN A. V. , SADOVSKII M. V. , VORONIN V. I. , KOZHEVNIKOV V. L. , CHESHNITSKII S. M. , ALEKSASHIN B. A. , MIKHALYOV K. N. , SERIKOV V. V. , VERKHOVSKII S. V. , ZHDANOV YU. I.
Published: November 2004

The influence of disordering on the properties of high-T c superconductors is investigated. The results show that pairing takes place in the systems of localised electrons even in slightly disordered samples. Superconductivity exists till the radius of localisation exceeds the typical size of the Cooper pairing in highly disordered system.
INVESTIGATION BY XPS OF THE ELECTRONIC STRUCTURES OF THE n = 1, 2, 3 AURIVILLIUS PHASES
Authors: BOCQUET A. E. , DOBSON J. F. , HEALY P. C. , MYHRA S. , THOMPSON J. G.
Published: November 2004

The Aurivillius phases of order n = 1, 2, 3 have been investigated by X-ray photoelectron spectroscopy. It is found from these measurements that there are no obvious electronic similarities between these phases and the structurally related HTSC layer compounds.
"NONCRYSTALLOGRAPHIC" SYMMETRY AND QUASICRYSTALS
Authors: KUO K. H.
Published: November 2004

After the sensational discovery of the icosahedral quasicrystals, two dimensional quasicrystals with 8,10 and 12 fold rotational symmetries have also been found in various rapidly solidified alloys and experimental evidence will be presented here. Since these rotational symmetries are not compatible with the Bravais space lattices, they were called "noncrystallographic" point group symmetry in the past. However, it is argued that the long-range periodic translation order is only one of the results of the propagation of short-range orientation order and that the Bravais space lattice might not be a prerequisite of a crystal. During rapid solidification short-range orientation order predominates and therefore quasicrystals might occur with rotational symmetries not hitherto encountered.
A GENERAL ALGORITHM FOR THE GENERATION OF QUASILATTICES BY MEANS OF THE CUT AND PROJECTION METHOD USING THE SIMPLEX METHOD OF LINEAR PROGRAMMING AND THE MOORE-PENROSE GENERALIZED INVERSE
Authors: ARAGÓN J. L. , VÁZQUEZ POLO G. , GÓMEZ A.
Published: November 2004

A computational algorithm for the generation of quasiperiodic tiles based on the cut and projection method is presented. The algorithm is capable of projecting any type of lattice embedded in any euclidean space onto any subspace making it possible to generate quasiperiodic tiles with any desired symmetry. The simplex method of linear programming and the Moore-Penrose generalized inverse are used to construct the cut (strip) in the higher dimensional space which is to be projected.
THE INFLUENCE OF SURFACE DEFECTS AND FOREIGN ATOMS ON THE ADSORPTION KINETICS
Authors: RENDULIC K.D. , WINKLER A.
Published: November 2004

We describe the influence of surface structure, surface steps, point defects and foreign atoms on the physics of adsorption and desorption. The investigations are performed on the model systems H 2- Ni and H 2- Pt as representatives of adsorption on transition metals and H 2- Cu as an example for adsorption on a noble metal. The energy variation of the sticking coefficient and the angular variation of the adsorption and desorption probability are used to characterize the different physical processes occurring during adsorption.
HAMILTONIAN FORMULATION FOR THE THEORY OF MULTIPHOTON PROCESSES IN ATOMS BASED ON THE FIRST PRINCIPLES
Authors: BAKASOV A.A.
Published: November 2004

A Hamiltonian is derived on the basis of the first principles of quantum electrodynamics. The Hamiltonian is seen to describe two- and multiphoton processes. A problem of consequent derivation and microscopic substantiation of models of multiphoton processes widely used in quantum optics is solved. The first correction to the Pauli equation is obtained. The constant of interaction of a two-level atom with two photons is given in an explicit form. A method of calculating interaction constants for multilevel atoms with multiphoton transitions is presented. Other results obtained on the basis of the developed approach are announced.
ANYONS, THE QUANTUM HALL EFFECT, AND TWO-DIMENSIONAL SUPERCONDUCTIVITY
Authors: Canright G.S. , Girvin S.M.
Published: November 2004

We have studied the ground-state (GS) properties of fractional-statistics particles (anyons) by exact numerical solution for small systems. We have seen in our results (depending on the choice of parameters for the Hamiltonian) the fractional-statistics analogs of a number of well-known ground states for conventional particles, including particularly the quantum Hall state (which we relate to the observed ‘hierarchy’ states), and a superconducting GS, the latter being formed (for half-statistics particles or semions) by pairing. We suggest possible experimental signatures for distinguishing semion from fermion superconductors. We also directly test the ‘mean-field theory’ of statistics against our exact results, and find it to treat GS properties well.
Superfluidity of the Lattice Anyon Gas
Authors: Fradkin Eduardo
Published: November 2004

I consider a gas of “free” anyons with statistical paremeter δ on a two dimensional lattice. Using a recently derived Jordan-Wigner transformation, I map this problem onto a gas of fermions on a lattice coupled to a Chern-Simons gauge theory with coupling [Formula: see text]. I show that if [Formula: see text] and the density [Formula: see text], with r and q integers, the system is a superfluid. If q is even and the system is half filled the state may be either a superfluid or a Quantum Hall System depending on the dynamics. Similar conclusions apply for other values of ρ and δ.

The dynamical stability of the Fetter-Hanna-Laughlin goldstone mode is insured by the topological invariance of the quantized Hall conductance of the fermion problem. This leads to the conclusion that anyon gases are generally superfluids or quantum Hall systems.
ATOMIC ORDER IN QUASICRYSTALS IS SUPPORTED BY SEVERAL UNIT CELLS
Authors: KRAMER PETER
Published: November 2004

A non-periodic quasilattice on the line E1 is constructed by intersection and dualization from a square lattice in E2. A periodic charge density in E2 is constructed. The corresponding non-periodic charge density on E1 has stable support on the two quasilattice cells. Its Fourier transform is expressed through the charge densities in these cells.
AN $A_{n - 1}^{\left( 1 \right)} $ FAMILY OF SOLVABLE LATTICE MODELS
Authors: JIMBO MICHIO , MIWA TETSUJI , OKADO MASATO
Published: November 2004

We present a family of exactly solvable two dimensional lattice models labeled by three positive integers n, l, N. The local states of the models take on values in the level l dominant integral weights of [Formula: see text]. Successive states interchange level N dominant integral weights.
POLYACETYLENE: HELICES, HEAVY SOLITONS AND HYPERCONDUCTIVITY
Authors: BOŽOVIĆ IVAN
Published: November 2004

A list of experimental observations (structural, spectroscopical, on transport, isomerization, chemical reactions, etc.) on pristine and doped polyacetylene, (CH)x, which are not compatible with the accepted planar structures and the current theoretical models of charge transport in (CH)x, is compiled. It is proposed that (CH)x is helical and that certain defects (short cis segments) in trans-(CH)x behave like heavy solitons. These assumptions are shown to resolve all the above paradoxes.
BRAVAIS CLASSIFICATION OF NON-PERIODIC QUASILATTICES ON THE LINE
Authors: KRAMER PETER
Published: November 2004

The five Bravais lattices Y in IE 2 are interpreted as Euclidean cell complexes in the language of algebraic topology. A metrical dual Y* is constructed for each lattice Y. The unit cell of Y is rearranged into a set of klötze, i.e. cells with boundaries parallel 01 perpendicular to a fixed line. The five Bravais lattices yield eight types of non-periodic quasi-crystal models on the line.