bluuebunny/crossref_metadata_2025 huggingface dataset:
NONPERTURBATIVE APPROACHES TO DETERMINING THE BEHAVIOR OF THE GLUON PROPAGATOR AND QUARK PROPAGATOR IN QUANTUM CHROMODYNAMICS BY SCHWINGER-DYSON EQUATIONS
Authors: HÄDICKE A.
Published: November 2004

The attempts to describe the behavior of the gluon propagator and quark propagator by using truncated Schwinger-Dyson equations and Slavnov-Taylor identities are reviewed. Special attention is paid to the problem of infrared behavior of Green’s functions. The most important attempts to calculate the gluon propagator using the axial as well as the covariant gauge are critically discussed. Furthermore, an approach concerning the gluon propagator is presented, with the background-field method as its basis. All the calculations confirm more or less the existence of an infrared singularity in the gluon propagator of the form q−4 in momentum space.

The calculations to determine the behavior of the dynamical mass function of quarks, where the results concerning the gluon propagator are taken into account, show that chiral symmetry is dynamically broken. Furthermore, it turns out that there is no polelike singularity in the quark propagator. These results agree with the expectations from the confinement philosophy.
THE INTERACTION OF CHERN-SIMONS VORTICES
Authors: JACOBS LAURENCE , KHARE AVINASH , KUMAR C. NAGARAJA , PAUL SAMIR K.
Published: November 2004

We study the interaction between two vortices in the Abelian Higgs model with an added term of the Chern-Simons form. We argue that our results may be relevant to the physics of high temperature superconductors, and suggest possible experimental tests of this theory.
AN R2 MODEL OF STRONG GRAVITY
Authors: EL-TAHIR ALI
Published: November 2004

A metric based on the simplest nonlinear Lagrangian, which is identified with the square of the scalar curvature R, is considered. The region where the metric is dominated by this Lagrangian is assumed to be confined to the vicinity of the gravitational source where gravity is strongest. Expressions for R and the metric are obtained as functions of the radial distance, exhibiting nonsingular solutions.
TETRAHEDRA AND POLYNOMIAL EQUATIONS IN TOPOLOGICAL FIELD THEORY
Authors: CHAIR NOUREDDINE , ZHU CHUAN-JIE
Published: November 2004

Some tetrahedra in SUk(2) Chern-Simons-Witten theory are computed. The results can be used to compute an arbitrary tetrahedron inductively by fusing with the fundamental representation. The results obtained are in agreement with those of quantum groups. By associating a (finite) topological field theory (FTFT) to every rational conformal field theory (RCFT), we show that the pentagon and hexagon equations in RCFT follow directly from some skein relations in FTFT. By generalizing the operation of surgery on links in FTFT, we also derive an explicit expression for the modular transformation matrix S(k) of the one-point conformal blocks on a torus in RCFT and the equations satisfied by S(k), in agreement with those required in RCFT. The implication of our results on the general program of classifying RCFT is also discussed.
ANISOTROPIC SCALING IN RELATIVISTIC FIELD THEORY
Authors: ROBERTSON DAVID G.
Published: November 2004

We study the behavior of relativistic quantum field theories under anisotropic scale transformations, of the general form pμ→σμvpv, where σμv are a set of constant scale parameters. We derive, for an arbitrary theory, the linear response to such a transformation, and show how this may be used to determine the renormalization group flow of the anisotropic effective theory. Some applications of the formalism are suggested, including a possible strategy for motivating phenomenological string models of hadrons, starting from microscopic QCD.
STUDY OF NONPERIPHERAL La139 COLLISIONS WITH EMULSION NUCLEI AT 1.2 A GeV
Authors: GILL A. , BHALLA K.B. , KUMAR V. , LOKANATHAN S. , PALSANIA H.S. , SHUKLA V.S. , BADYAL S.K. , BHASIN A. , GUPTA V.K. , KACHROO S. , KITROO S. , MANGOTRA L.K. , RAO N.K.
Published: November 2004

We have used two methods to categorize central events based on target fragmentation (heavy particle multiplicity, nh≥28) and total charged particle multiplicity (nch>70). Multiplicity and angular distributions of black, gray, shower, alpha and fragments have been studied for central collisions of the La139 projectile with emulsion nuclei, and compared with lighter projectiles. We observed that the results obtained for central reactions using these two criteria (nh≥28 or nch>70) were similar. The study of the angular distribution of target fragments indicates that more than one source may be responsible for their production.
HIGHLY UNSTABLE FUNDAMENTAL STRINGS IN INFLATIONARY COSMOLOGIES
Authors: GASPERINI M. , SÁNCHEZ N. , VENEZIANO G.
Published: November 2004

We characterize a regime of extreme (Jeans-like) instability, for strings evolving in cosmological backgrounds, in which the string’s proper size grows asymptotically like the scale factor of the expanding universe. We develop a new approximation scheme, based on the asymptotic proportionality of world-sheet and conformal times, for the systematic, quantitative description of such a nonlinear regime. We find that only inflationary geometries (accelerated expansion) are compatible with this instability, and we derive an equation of state for a perfect fluid of unstable strings. The effective pressure is negative, but not large enough to sustain by itself a phase of accelerated expansion.
$q\bar q$ PAIRS IN THE GENERALIZED VECTOR MESON DOMINANCE MODEL FOR THE NUCLEAR SHADOWING EFFECT IN DEEP INELASTIC SCATTERING
Authors: NAKANO K.
Published: November 2004

The [Formula: see text] pair component of the virtual photon in deep inelastic scattering is considered in the context of the generalized vector meson dominance model in order to explain the shadowing effect within the conventional nuclear model. The [Formula: see text]-nucleon interaction is estimated by the additive quark model. The nuclear effect is taken into account by the detailed evaluation of the microscopic passage of both hardonic and electromagnetic components of the virtual photon through the nuclear medium. Good predictions of the structure function ratio are obtained from the shadowing region to the usual EMC effect in terms of the conventional nuclear model, but the finer target dependence in the shadowing region is not obtained.
THE LATTICE ABELIAN CHERN-SIMONS GAUGE THEORY
Authors: KAVALOV AL. R. , MKRTCHYAN R.L.
Published: November 2004

Some properties of the previously proposed lattice version of the Abelian Chern-Simons gauge theory are studied. The lattice analog of BF systems is constructed, and the properties of both theories are found to be in close correspondence with those of the continuous theory. The correspondence with two-dimensional lattice statistical systems is established and the lattice origin of the framing of Wilson loops is shown.
UNITARY THEORY OF TWO-DIMENSIONAL QUANTUM GRAVITY AND ITS EXACT COVARIANT OPERATOR SOLUTION
Authors: ABE MITSUO , NAKANISHI NOBORU
Published: November 2004

The manifestly covariant canonical operator formalism of two-dimensional quantum gravity is formulated on the basis of Sato’s gauge-fixing of the Weyl invariance. The unitarity problem, due to ghost-counting mismatch, is resolved by making the gravitational FP ghosts also play the role of the Weyl FP ghosts. All two-dimensional (anti)commutators between fundamental fields are explicitly obtained.
ON TYPE II SUPERSTRINGS: THE σ MODEL AND COMPACTIFICATION TO D=4
Authors: CASTELLANI LEONARDO , D’ AURIA RICCARDO , FRANCO DAVIDE
Published: November 2004

We present a geometric construction of the σ model describing type II superstrings propagating on an arbitrary Mtarget. Specializing the covering space of the internal target manifold to be the nine-dimensional group manifold SU(2)3, we discuss the massless vertices both in the (4+9)-dimensional a model and in the D=4 superconformal theory, and show how they are related via dimensional reduction.
TOWARDS A CONSISTENT FOUR-DIMENSIONAL SUPERSTRING (I)
Authors: DURACHTA J.W.
Published: November 2004

A Kaluza-Klein “compactification” Ansatz is applied to the D=10, N=1, heterotic, Green-Schwarz superstring to produce a D=4, N=4 theory. It is demonstrated that κ symmetry is preserved under the procedure, a necessary condition for the 4D theory to retain the consistency of the 10D one. This is the first time that the Kaluza-Klein scheme has been reported to have been applied to superspace.
SCREENING CURRENTS IN FREE-FIELD REPRESENTATIONS OF KAC-MOODY ALGEBRAS
Authors: BOUGOURZI A.H. , HO-KIM Q. , KIKUCHI Y. , LAM C.S.
Published: November 2004

A general procedure is presented whereby screening currents of the vertex type can be constructed from any Kac-Moody algebra in free-field representation. This method is applied to sl(n) and sp(4), where explicit free-field representations for the Kac-Moody algebra are available. In this way we obtain for the first time the correct form of the screening currents expressed by infinite series. It is also noted that both the Kac-Moody and the screening currents can be formulated on a lattice, a formalism which can simplify calculations and reveal the intricate structures of these currents.
MODIFIED BAG MODEL AND t-FLAVORED HADRON SPECTROSCOPY
Authors: NAYAK SRIPATI KUMAR , SINGH LAMBODAR P.
Published: November 2004

Masses of t-flavored hadrons have been computed using a modified bag model well suited for considering heavy quarks inside the bag. Results have been obtained for mt=50 GeV and 150 GeV as representative masses of the light and heavy top scenarios.
DYNAMICAL STRING MODEL ON THE BASIS OF A SEMICLASSICAL UNIFIED STRING-FLUX TUBE MODEL
Authors: SAILER K. , SCHÖNFELD TH. , SCHRAM ZS. , SCHÄFER A. , GREINER W.
Published: November 2004

We present the dynamical string model of high-energy hadronic processes, developed by us recently. To describe the dynamical aspects of the decay of hadrons and those of the hadron-hadron interaction correctly, a semiclassical unified string-flux tube model of hadrons is used. Specific aspects of this model are discussed: (i) the transverse extension of gluon flux tubes, (ii) the decay of highly excited flux tubes, (iii) the gluon structure functions of hadronic flux tubes and their connection with the total cross section of the flux tube-flux tube interaction at high energies. The dynamical string model is applied to the numerical simulation of e+e− annihilation and pp collision at high energies.
A REMARKABLE REPRESENTATION OF THE SO(3, 2) KAC-MOODY ALGEBRA
Authors: DOBREV V.K. , SEZGIN E.
Published: November 2004

We construct a minimal representation of the SO(3, 2) Kac-Moody algebra which is based on the spin-zero singleton (the Rac) representation of SO(3, 2). The representation is minimal in the sense that the central charge k of the SO(3, 2) Kac-Moody algebra is chosen to take the special value of [Formula: see text], which allows imposition of the maximum number of reducibility conditions. For the Rac, this is the unique choice for the remarkable property of maximum reducibility which is consistent with unitarity. To ensure unitarity, we furthermore impose an invariance condition under the maximal compact subalgebra SO(3) × SO(2).
QUARK-MASS MATRICES IN THE TWO-GENERATION SU(2)L × SU(2)R × U(1)B−L × U(1)H GAUGE MODEL
Authors: BANDYOPADHYAY KRISHNANATH , BHOWMICK DEBASIS , KUNDU MURARI MOHAN , RAY ASIM K.
Published: November 2004

We have studied the quark-mass matrices, Cabibbo mixing and CP violation in the two-generation SU(2)L × SU(2)R × U(I)B−L × U(1)H model. It is shown that the model leads to phenomenologically consistent quark-mass matrices but cannot accommodate CP violation in spite of the right-handed and horizontal gauge interactions. The absence of Cabibbo mixing for leptons is explained, but for the quark sector it is shown to be ≃0.21.
COMPLEX FREE FERMION SUPERSTRINGS AS GROUPFOLD COMPACTIFICATIONS
Authors: CERESOLE ANNA T. , FRÉ PIETRO , GLIOZZI FERDINANDO , VINTI STEFANO
Published: November 2004

We consider the class of superstring vacua arising from the free fermion construction based on the SU (3) ⊗ SO (5) or SU (2) ⊗ SU (4) supercurrent. The internal free fermions have complex boundary conditions. We show that these vacua admit a geometric interpretation as compactifications on twisted WZW models.
BRST STOCHASTIC QUANTIZATION
Authors: HÜFFEL HELMUTH
Published: November 2004

After a brief review of the BRST formalism and of the Parisi-Wu stochastic-quantization method, the BRST-stochastic-quantization scheme is introduced. This scheme allows the second quantization of constrained Hamiltonian systems in a manifestly gauge-symmetry-preserving way. The examples of the relativistic particle, the spinning particle and the bosonic string are worked out in detail. The paper is closed with a discussion on the interacting field theory associated with the relativistic-point-particle system.
EQUIVALENCE OF THE STRING EQUATIONS OF MOTION AND THE σ-MODEL WEYL-INVARIANCE CONDITIONS AT ORDER α′2: DEPENDENCE ON THE DILATON FIELD
Authors: BENTO M.C. , BERTOLAMI O. , ROMÃO J.C.
Published: November 2004

We study the structure of effective actions of closed-string theory at order α′2, when the dilaton field is included. We show, in particular, that the way field-redefinition ambiguities are fixed at order a’ affects the order-α′2 results, and find that, as a consequence, different forms for the effective action existing in the literature are in fact equivalent. We discuss the implications of our results for the conjectured relationship between string equations of motion and σ-model β functions.
SUPERGRAVITY AND SUPERSTRINGS IN (2+1) DIMENSIONS
Authors: STERN A.
Published: November 2004

We study n=1 supergravity written on a two-dimensional disc (× time) in the absence of any sources. The dynamics of the boundary of the disc is equivalent to that of a superstring in (2+1)-dimensional Minkowski space. The relevant current algebra for the theory corresponds to the central extension of the super-Poincaré loop group. We find unitary representations of the current algebra by applying both a highest weight state construction and the method of induced representations.
A NOVEL APPROACH TO DOUBLE COMMUTATORS IN CHIRAL GAUGE THEORIES CONSISTENT WITH THE JACOBI IDENTITY
Authors: BANERJEE R. , ROTHE H.J.
Published: November 2004

We give a BJL-type prescription for calculating a double commutator which manifestly respects the Jacobi identity. This prescription is used to calculate the double commutators of currents and electric fields in chiral gauge theories, where they are known to violate the Jacobi identity in an iterative computation. We then derive a consistency equation relating the Schwinger terms of the double commutators of currents and the divergence anomaly. While this consistency equation is violated by the iterative scheme in four space-time dimensions, it is found to be satisfied using our prescription.
$B' - \bar B'$ MIXING IN THE SUPERSYMMETRIC FOUR-GENERATION STANDARD MODEL
Authors: AHN Y.J.
Published: November 2004

We calculate the box diagrams of the [Formula: see text] system which involve W boson, charged Higgs boson or gluino with nonvanishing external quark momenta in the minimal supersymmetric four-generation standard model. We find that the contribution of the gluino box diagram is negligible compared to those of other diagrams, and that the charged Higgs box diagram dominates over the W boson box by a factor of 2–5 for most of the parameter ranges. This means that [Formula: see text] mixing in this model will be much bigger than that of the minimal standard model. When the ratio v2/v1 of the vev’s of the two neutral Higgs fields is smaller than ~0.6 or bigger than ~30, the dominance of the charged Higgs box becomes more significant.
ALGEBRAIC THEORY OF SUPERSELECTION SECTORS AND THE MEASUREMENT PROBLEM IN QUANTUM MECHANICS
Authors: LANDSMAN N.P.
Published: November 2004

A synthesis is attempted between the algebraic theory of superselection sectors (not necessarily of infinite systems), which is based on the representation theory of C* algebras (which we review), and recent ideas on the measurement problem, classical behavior in open quantum systems, and the peculiar nature of subsystems in quantum mechanics. The key point is a proper use of the notion of a state, in combination with an appropriate choice of algebras of observables for which the superposition “principle” may be invalid. In this way, a major part of the measurement problem becomes equivalent to the study of superselection sectors in models for a measurement situation, and can in principle be resolved unambiguously. Special emphasis is placed on the transition from pure to mixed states, and the (non)uniqueness of the decomposition of the latter into pure states.
CHIRAL ALGEBRAS—TWO EXAMPLES
Authors: COHEN RON
Published: November 2004

We examine the chiral algebras of quotient superconformal theories by studying two examples: the SO(n) HSS models and the models based on the SU (n) group. We study the automorphism group which identifies fields in each model, and its fixed-point fields. We calculate the Poincare polynomial for the SU (n) example, see whether there are duality relations and find new Landau-Ginzburg scalar theories. For the second example we explain how to calculate the number of fields in the algebra and show a duality relation by giving the duality map explicitly.
CHARACTER IDENTITIES IMPLIED BY SUPER-W3 INVARIANCE AND GENERALIZED COULOMB GAS DESCRIPTIONS
Authors: CASELLE M.
Published: November 2004

We study the super-W3, c=10/7 model and show that super-W3 invariance implies stringent constraints on the characters of the model. Taking into account these field identifications we can construct a Coulomb gas description of the model within the approach of Ref. 1. We suggest that Ref. 1 could be a general framework for constructing Coulomb gas descriptions for isolated solutions of W algebras not related to classical Lie algebras.
NEW CLASS OF METRIC THEORIES OF GRAVITY NOT DESCRIBED BY THE PARAMETRIZED POST-NEWTONIAN (PPN) FORMALISM
Authors: CIUFOLINI IGNAZIO
Published: November 2004

After an introduction to theories of gravity alternative to general relativity, metric theories (Sec. 1) and the parametrized post-Newtonian (PPN) formalism (Sec. 2), we define a new class of metric theories of gravity (Sec. 3). It turns out that the post-Newtonian approximation of these new theories is not described by the PPN formalism (Sec. 4); in fact, in the limit of weak field and slow motions, the post-Newtonian expression of the metric tensor contains an, a priori, infinite set of new terms and correspondingly an, a priori, infinite set of new PPN parameters. As a consequence, the parametrized post-Newtonian formulas describing the classical relativistic tests should include these new parameters, and therefore the experimental values of the classical relativistic effects should not be used to put limits only on the standard ten PPN parameters. Finally, we note that a subset of this new class of theories has the same post-Newtonian limit and value of the PPN parameters as general relativity, and therefore is automatically in agreement with the classical general-relativistic tests (Sec. 4, theory III).
STUDY OF PHASE SEPARATION IN THE HUBBARD MODEL1
Authors: Moreo A.
Published: November 2004

We study the behavior of the mean number of particles  as a function of the chemical potential μ in the two dimensional Hubbard model with both attractive and repulsive interaction, using a quantum Monte Carlo method. Working at U/t=10, 4 and −4 on lattices with 4×4, 6×6 and 8×8 sites, we do not find evidence of phase separation.
Strong Correlation Transport and Coherence
Authors: Kotliar G.
Published: November 2004

We discuss the notion of fermi liquid coherence in the different regimes of the Anderson lattice. For finite doping heavy fermion (HF) behaviour results when the kondo exchange energy JK is smaller than the oxygen oxygen overlap tpp. High temperature superconductors (HTS) are in the opposite regime (JK≫tpp). Doping the charge transfer insulator state introduces Zhang Rice singlet like states in the gap. These states, at zero temperature, continuously evolve into Kondo resonances as tpp is increased. The mechanism for destruction of coherence, at finite temperatures, is qualitatively different in the HF and the HTS regime. We study the temperature dependence of the transport coefficients when the charge transfer gap is large, in the temperature regime T≫Tcoh. We discuss our results in connection with the anomalous properties of the copper oxides.
COMPOSITE CHERN-SIMONS GAUGE BOSON IN ANYON GAS
Authors: HIEU NGUYEN VAN , SON NGUYEN HUNG
Published: November 2004

It was shown that in a free anyon gas there exists a composite vector gauge field with the effective action containing a Chern-Simons term. The momentum dependence of the energy of the composite boson was found. The mixing between Chern-Simons boson and photon gives rise to the appearance of new quasiparticles -Chern-Simons polaritons. The dispersion equations of Chern-Simons polaritons were derived.
DIELECTRIC RELAXATION IN DIPOLAR LIQUIDS
Authors: BAGCHI B. , CHANDRA A.
Published: November 2004

A review of the recent theoretical developments in the dielectric relaxation of a dense dipolar liquid is presented. Dielectric relaxation in binary liquids and collective dipolar excitations are among the different topics that have been discussed here.
SYMBOLIC DYNAMICS FOR THE CIRCLE MAP
Authors: ZHENG WEI-MOU
Published: November 2004

The circle map is studied directly by means of symbolic sequences. By using the Farey representation of real numbers and the Farey transformations for symbols the oriented itineraries are analysed. The generalised Farey transformations for symbols are introduced for supercritical maps. Joints and the skeleton are described for the bifurcation structure.
ENTROPY OF A HARMONIC OSCILLATOR IN CONTACT WITH A SQUEEZED RESERVOIR
Authors: TUCCI ROBERT R.
Published: November 2004

We consider a harmonic oscillator (h.o.) in contact with a non-minimum uncertainty squeezed reservoir (but isolated from contact with other non-squeezed reservoirs). We calculate the h.o.’s density matrix and thermodynamic entropy. We interpret the derivatives of the entropy in terms of two temperatures, one for each quadrature of the reservoir. A change in the total (random) energy of the h.o. is shown to equal the sum of changes in the energies of each h.o. quadrature separately (a version of the First Law of thermodynamics). A change in the total entropy of the h.o. system is likewise shown to equal the sum of changes in the entropies of each h.o. quadrature separately (Second Law of thermodynamics). We also present equations that correspond to the so called “Fundamemental equation” and “Gibbs-Duhem equation” for the h.o system under consideration.
ORDER PARAMETERS OF FRUSTRATED SPIN SYSTEMS
Authors: ANGELUCCI ANTIMO
Published: November 2004

We present a study of the ground states and of the low energy fluctuations of the frustrated Heisenberg spin chain, both classical and quantum. Analyzing this simple model we draw some general conclusions about the antiferro-helix “transition” of general classical Heisenberg models. We derive the low energy action describing the fluctuations about the helical phases and we infer the possible existence of nontrivial topological terms in the quantum counterparts.
THERMAL DEPINNING AND “MELTING” OF THE FLUX-LINE LATTICE IN HIGH-Tc SUPERCONDUCTORS
Authors: BRANDT ERNST HELMUT
Published: November 2004

In high-Tc superconductors (HTSC) the thermal fluctuation of the vortex lattice (VL) may become large since the vortex lattice is soft due to the strong overlap of the vortex fields and since the temperature T can be high. It was thus argued that the three-dimensional (3D) vortex lattice is thermally entangled and may “melt”. This type of transition and the consequences of melting are not clear as yet since the always present pinning of the vortex cores by material inhomogeneities may cause similar disorder. In HTSC the pinning energy may become comparable with kBT because the coherence length ξ (vortex radius) is small and T may be high. Therefore, thermally activated depinning competes with possible effects of “flux melting”, and the “irreversibility line” in the B-T-plane (B=magnetic field) should better be called “depinning line”. Due to the diffusive character of flux motion the depinning line of a given experiment, a line of constant flux diffusivity D(T, B), depends on the frequency or sweep rate, on the size and shape of the superconductor, and on the field orientation; it is thus not a material property alone.

In this review it is argued that theories predicting “new phases of vortex matter” (flux solid, flux liquid, vortex plasma, vortex glass, and hexatic vortex glass) may be improved by replacing the 2D straight-vortex interaction by the correct 3D interaction between all vortex segments. This interaction (a) facilitates vortex crossing and reconnection, (b) reduces the elastic energy of short-wavelength tilt by a very large factor (non-local elasticity), and (c) yields the correct reduction of the tilt energy by the crystal anisotropy. The non-local elasticity of the VL is reviewed and a general solution of the anisotropic London theory for arbitrary vortex arrangements is given. A very useful phenomenological theory of layered superconductors is the Lawrence-Doniach model, which defines a 2D Ginzburg-Landau function in each layer. The point vortices in the layers interact with each other magnetically and, between neighboring layers, by Josephson coupling. At sufficiently large fields their thermal fluctuation is quasi-2D and, at an in general different field, their pinning becomes 2D.
JAYNES-CUMMINGS MODEL WITH DISPLACED NUMBER STATES
Authors: BUŽEK V. , JEX I. , BRISUDOVÁ M.
Published: November 2004

We investigate the dynamics of the Jaynes-Cummings model with the cavity field initially prepared in the displaced number state. The time evolution of the atomic population inversion, squeezing of the cavity field and the emission spectra from the two-level atom are studied.
THE PHASE DIAGRAM OF THE HUBBARD MODEL
Authors: LONG M. W.
Published: November 2004

A brief review of the types of ideas which have been used to investigate the phase diagram of the Hubbard model is presented. No clear solution emerges although the competitions at work are established. Hartree-Fock, Gutzwiller's projection, Nagaoka's theorem, Kanamori's paramagnetism, Lieb's exact results and charge-spin separation are the main concepts.
THE t-J AND FRUSTRATED HEISENBERG MODELS: A STATUS REPORT ON NUMERICAL STUDIES
Authors: DAGOTTO ELBIO
Published: November 2004

Recent numerical work on the t-J model and the frustrated spin-[Formula: see text] Heisenberg antiferromagnet is reviewed. Lanczos results are mainly discussed but other methods are also mentioned. Static and dynamical properties of one and more holes in the t-J model are presented. The current active search for nontrivial ground states of the frustrated Heisenberg model is summarized. It is concluded that numerical methods are providing useful information in the study of these models.
SO4 SYMMETRY IN A HUBBARD MODEL
Authors: YANG CHEN NING , ZHANG S. C.
Published: November 2004

For a simple Hubbard model, using a particle-particle pairing operator η and a particle-hole pairing operator ζ, it is shown that one can write down two commuting sets of angular momenta operators J and J′, both of which commute with the Hamiltonian. These considerations allow the introduction of quantum numbers j and j′, and lead to the fact that the system has SO 4 = ( SU 2 × SU 2)/ Z 2 symmetry. j is related to the existence of superconductivity for a state and j′ to its magnetic properties.
MOTT TRANSITION IN AN EXACTLY SOLVABLE K.S.S.H. MODEL
Authors: Montorsi Arianna , Rasetti Mario
Published: November 2004

The solution of the K.S.S.H.-like model shown to be exactly solvable in any number of dimensions, for a particular choice of the coupling constant describing the hopping process amplitude, both for finite size and in the thermodynamic limit, is discussed in detail. The analysis of the zero-temperature phase space in d = 2 shows that the model exhibits a transition in the number of doubly occupied sites order parameter, which at half-filling coincides with the Mott transition found for the Hubbard model in the Gutzwiller approximation.
COMPLEX DYNAMICS IN COUPLED NONLINEAR ELEMENT SYSTEMS
Authors: OTSUKA KENJU
Published: November 2004

This paper reviews complex dynamics which arise through the interaction of simple nonlinear elements without chaotic response, including self-induced switching among local attractors (chaotic itinerancy) and related phenomena. Several realistic physical systems consisting of coupled nonlinear elements are considered on the basis of computer experiments: coupled nonlinear oscillator (e.g., discrete complex time-dependent Ginzburg-Landau equation) systems, coupled laser arrays, and a coupled multistable optical chain model.
FRACTAL ANALYSIS OF ELECTROLYTICALLY-DEPOSITED PALLADIUM HYDRIDE DENDRITES
Authors: BURSILL L. A. , PENG JULIN , FAN XUDONG
Published: November 2004

The fractal scaling characteristics of the surface profile of electrolytically-deposited palladium hydride dendritic structures have been obtained using convention and high-resolution transmission electron microscopy. The results are in remarkable agreement with the modified diffusion-limited aggregation model due to Vicsek (Phys. Rev. Lett.54 (1985) 1828).
EVOLUTION OF THE DOMAIN STRUCTURE DURING THE NUCLEATION-AND-GROWTH PROCESS WITH NON-CONSERVED ORDER PARAMETER
Authors: SEKIMOTO KEN
Published: November 2004

We review the recent theoretical developments in the study of domain structure dynamics through nucleation-and-growth processes of first-order phase transitions with non-conserved order parameters. We introduce the spatial and space-time correlation functions of the domain structures based on the model proposed by Kolmogorov, Johnson, Mehl and Avrami. Our main purpose is to show why and how the rigorous correlation functions can be derived from their model.
PERIMETER AND AREA GENERATING FUNCTIONS OF THE STAIRCASE AND ROW-CONVEX POLYGONS ON THE RECTANGULAR LATTICE
Authors: LIN K. Y. , TZENG W. J.
Published: November 2004

The two-variable perimeter and area generating functions derived recently by Brak and Guttmann for the staircase and row-convex polygons on the square lattice are generalized to the rectangular lattice. We consider the three-variable generating function [Formula: see text] where cn,m,r is the number of appropriate polygons with 2n horizontal steps, 2m vertical steps and area r. Two generating functions G(x, y, z) for the staircase and row-convex polygons are derived. We also calculate the generating functions for the first and second area-weighted moments by the perturbation method of Lin.
THE ROOT LATTICE D4 AND PLANAR QUASILATTICES WITH OCTAGONAL AND DODECAGONAL SYMMETRY
Authors: BAAKE M. , JOSEPH D. , SCHLOTTMANN M.
Published: November 2004

Quasiperiodic patterns with eight- and twelvefold symmetry are presented which share the root lattice D4, i.e., the 4-D face-centered hypercubic lattice, for their minimal embedding in four-space. We derive the patterns by means of the dualization method and investigate key properties like vertex configurations, local deflation/inflation symmetries and kinematic diffraction. The generalized point symmetries (and thus the Laue group) of these patterns are the dihedral groups d8 and d12, respectively, which share a common subgroup, d4. We introduce a contiunous one-parameter rotation between the two phases which leaves this subgroup invariant. This should prove useful for modelling alloys like V 15 Ni 10 Si where quasicrystalline phases with eight- and twelvefold symmetry coexist.
THERMAL CONDUCTIVITY OF HIGH TEMPERATURE SUPERCONDUCTORS
Authors: NUÑEZ REGUEIRO MANUEL D. , CASTELLO DARÍO
Published: November 2004

We review and analyze the data on the thermal conductivity of both ceramic and single crystal samples of high temperature superconductors. A universal pattern can be extracted and interpreted in the following way: phonons are the main heat carriers in these materials, and in the high temperature range the thermal conductivity κ is almost constant due to phonon scattering against disorder; below the superconducting transition temperature κ increases as phonon scattering against carriers condensing into the superconducting state decreases and at still lower temperatures there is a region in which a T2 law is obeyed that most probably is due to resonant phonon scattering against low energy excitations, i.e. tunneling systems similar to those found in disordered materials. The origin of the relevant disorder is discussed.
MICROWAVE ATTENUATION IN ISOTOPICALLY DISORDERED ANHARMONIC CRYSTALS
Authors: PAINULI C. P. , BAHUGUNA B. P. , INDU B. D.
Published: November 2004

The impurity-anharmonicity interactions, along with anharmonicities, mass and force constant changes have been taken into account to investigate the expressions for microwave attenuation in anharmonic crystals. A remarkable change in the phonon frequency shifts and widths has been reported due to the defect anharmonicity interactions. The usual method of central and non-central force constant parameters has been ignored here and parameter free expressions have been reported.
SOLITON-LIKE PHONON LOCALIZED MODES IN DIATOMIC NONLINEAR LATTICE CHAIN
Authors: SHI ZHU-PEI , HUANG GUOXING , TAO RUIBAO
Published: November 2004

We have studied the localization of multivibrational states in diatomic nonlinear lattice chain. A simple model Hamiltonian presented here describes a system containing two kinds of phonons. The equations of motion for these boson operators are two partial differential equations with nonlinear coupling in long-wave approximation. With the help of the method of multiple scales, these equations are reduced to the nonlinear Schrödinger equation. It is shown that soliton-like phonon localized modes, multi-phonon localized modes can exist. The possibility of observing the gap solitons (phonon localized modes in the frequency gap) in diatomic nonlinear lattice chain is predicted.
CHARACTERIZING LOSS OF MEMORY IN CHAOTIC DYNAMICAL SYSTEMS
Authors: AMRITKAR R.E. , GADE P.M.
Published: November 2004

We discuss different methods of characterizing the loss of memory of initial conditions in chaotic dynamical systems.
EFFECT OF VACUUM FIELD RABI OSCILLATIONS ON THIRD ORDER NONLINEAR SUSCEPTIBILITY
Authors: MIR MUBEEN A. , NASREEN TAHIRA , RAZMI M.S.K.
Published: November 2004

Third order nonlinear susceptibility of two-level atoms dressed by the cavity vacuum is studied to see the effect of Rabi oscillations. It is found that while the interference effects remove the peaks of on-resonance third harmonic generation, peak splitting is seen for Raman scattering and two photon processes.
ANYON SUPERCONDUCTIVITY BEYOND THE RANDOM PHASE APPROXIMATION
Authors: KHVESHCHENKO D.V. , KOGAN IAN I.
Published: November 2004

We carry out a revision of the mechanism of anyon superconductivity found in the Random Phase Approximation. It is shown that the Debye screening of a statistical Coulomb-like interaction produced by contributions beyond the RPA destroys the abovementioned mechanism. The linear mode appeared in the particle-hole channel within the RPA is identified with a finite damping zero-sound. As an alternative mechanism an attraction of anyons which could lead to a formation of boson composites is observed. A finite temperature phase transition, hydrodynamics and electrodynamics of anyon system are described from this alternative point of view.
SIX-VERTEX MODELS AS FERMI GASES
Authors: ORLAND PETER
Published: November 2004

The two-dimensional six-vertex model with a particular choice of external field is known to be equivalent to a theory of free Fermions. Two conditions are made on the six-vertex weights. A simple physical interpretation of the ordered and disordered phases is found. The Fermi sea is filled and the free energy, correlation length, order parameter, correlation functions and phase diagram are determined.
ATTENUATION OF LASER-GENERATED ACOUSTIC SIGNALS IN LIQUIDS
Authors: TERZIĆ MIRA
Published: November 2004

The dependence of the optoacoustic wave amplitude in liquids on propagation distance was investigated for various values of the diffraction parameter. The results of the theoretical model are discussed and the computed results are compared to the experimental data obtained from optoacoustic waves generated in water and in n-heptane by means of a hybride CO 2 laser, for rigid and free boundary conditions of the liquid. The coefficients for amplitude attenuation based solely on diffraction, i.e. diffraction attenuation coefficient, are evaluated, as are the total attenuation coefficients. A simple method to correct experimental diffraction data obtained with non-ideal liquids is proposed.
TOWARD A RIGOROUS THEORY OF THE SCREENED ELECTRON-ELECTRON INTERACTIONS IN METALS
Authors: CHEN HUA , MATTIS DANIEL C.
Published: November 2004

A microscopic formula for the effective two-body interaction between electrons or holes in an ideal metal is derived within the linear response theory. Both the zero-range Hubbard interaction U0 and the long-range Coulomb interaction, denoted by ΔV(q), are included. The effective interaction, which is necessarily spin-dependent, is expressed in terms of the exact charge and spin density-density correlation functions and of their higher order mixtures. These correlation functions are analyzed diagrammatically. Attention is paid to clarifying the different roles played by U0 and ΔV(q). We also display the corresponding new formula for the free energy. Comparison is made with previous theories.
BETHE APPROXIMATION SCHEME FOR ITINERANT ELECTRON SYSTEMS
Authors: BECHI MARIA , LIVI ROBERTO , MONTORSI ARIANNA
Published: November 2004

After reviewing the fermi-linearization approach to interacting electron systems, we propose here a refinement of the method based on the extension to itinerant ferminon systems of the philosophy of the Bethe-Peierls treatment of classical systems. We focus our attention on a Hubbard-like model, deriving a general self-consistent scheme which we solve explicitly in the simplest case. We obtain a rich phase-space, exhibiting in particular two phase transitions depending on the band filling. Among the results, we discuss in detail the local magnetic moment, by comparing the outcome of our scheme to some known numerical results in one and two dimensions respectively.
MODEL OF INTERATOMIC INTERACTIONS AND VIBRATIONAL SPECTRUM OF Tl2CaBa2Cu2O8
Authors: BELOSLUDOV V.R. , LAVRENTIEV M. YU. , SYSKIN S.A.
Published: November 2004

A model of interatomic interactions of Tl2CaBa2Cu2O8 , which takes into account coulombic interaction and covalent bonds, is presented. Vibrational spectrum is calculated using that model, and a comparison with experiments on Raman scattering is given.
THE TWO-ATOM DICKE MODEL IN A SQUEEZED VACUUM: THE FLUORESCENT SPECTRUM INCLUDING DIPOLE-DIPOLE INTERACTION
Authors: PURI R.R. , JOSHI AMITABH , BULLOUGH R.K.
Published: November 2004

The spectrum of resonance fluorescence from a system of two identical coherently driven two-level atoms interacting with a broadband squeezed bath is studied by including the atomic dipole-dipole interaction. The spectral characteristics are studied by solving the master equation numerically and also by deriving the analytic expressions in the limit of strong driving field.
APPLICATIONS OF ULTRAFAST LASER SPECTROSCOPY TO THE STUDY OF SEMICONDUCTOR PHYSICS
Authors: OCKMAN NATHAN , WANG WUBAO , ALFANO R.R.
Published: November 2004

This article reviews the application of some of the principal methods of picosecond and femtosecond laser spectroscopy to the investigation of the dynamics of carriers, phonons and surface structure in semiconductors.

The measurement of the temporal evolution of photoinduced luminescence, absorption, reflection and scattering in semiconductors makes it possible to obtain the lifetimes of photogenerated electrons, holes, excitons and phonons in both the bulk and quantum wells and superlattice structures. The information produced by these studies is necessary for the basic understanding of the underlying physics of semiconductors. In addition, the parameters obtained from these studies are needed for evaluating ultrafast transport, switching, photoconductive response and imaging in semiconductor materials, which will determine their limitations for use in high-speed and high-frequency devices and computers.

For measuring time resolved luminescence, the principal techniques used, namely, the streak camera, the optical Kerr gate and the up-conversion gate are thoroughly discussed. Several pump and probe methods are described for the determination of time resolved absorption, reflection and Raman scattering. For absorption measurements where the probe wavelength differs from the pump, the former is generated in nonlinear media by means of stimulated Raman scattering and the supercontinuum for the UV and visible regions and by parametric and difference frequency generation for the near- and mid-IR. Nonlinear optics techniques considered are degenerate and nondegenerate four-wave mixing and transient grattings among which photon echoes yield the momentum relaxation of hot electrons. Coherent anti-Stokes Raman scattering (CARS) and phase conjugate Raman scattering (PC) are described to determine phonon dephasing times and the nonlinear susceptibility, χ3.
PRESSURE EFFECTS ON HIGH-Tc SUPERCONDUCTORS CURRENT TRANSFER
Authors: SVISTUNOV V.M. , D’YACHENKO A.I. , TARENKOV V. YU.
Published: November 2004

The efficiency of high pressure technique for the evidence of the Josephson nature of the intergranular contacts in metal ceramics has been demonstrated. With this technique it has been found that the abnormal hysteresis in fields of the order of tens kOe was not connected with the short-circuited contacts between the granules. The reason for the hysteresis lies in the ambiguity of the magnetization of the granules versus the change in the magnetic field direction. The critical current stability of the Josephson conteacts to high magnetic fields is due to both the inhomogeneity of the contacts and the existence of Abrikosov vortices within the superconducting electrode links.
TWO PHASES OF THE ANYON GAS AND BROKEN ${\mathcal T}$ SYMMETRY: SOME EXACT RESULTS
Authors: CANRIGHT G. S. , ROJO A. G.
Published: November 2004

We report the first exact finite-temperature studies of anyons. Our method is an extension to finite T of earlier numerical work with small numbers of anyons on a lattice. We study the spontaneous magnetization M0(T), since this signature has been identified as a key signature of broken [Formula: see text] symmetry for anyon models. Our results confirm the two-phase picture suggested by earlier work: we find a low-temperature regime where M0 is very small or zero, and a high-temperature regime where M0 is of [Formula: see text] per particle. In the high-temperature regime we can obtain an excellent estimate of M0(T) in the thermodynamic limit (which we will call [Formula: see text]), since our finite-size results extrapolate smoothly with little scatter. Our values for [Formula: see text] can then be compared with the results of μSR experiments on high-temperature superconductors, which set an upper experimental bound on the internal fields from such moments. We find that [Formula: see text] in a bulk material of many planes will almost certainly give a signal well above this threshold if (and only if) the planes are ordered ferromagnetically. In the antiferromagnetic case (which is strongly favored energetically) the signal from [Formula: see text] is probably undetectable. Finally, we estimate the transition temperature Tc from our finite-size studies, obtaining a value on the order of a few hundred Kelvins.
ANTIFERROMAGNETIC ORDERING OF SYMMETRY BREAKING IN MULTIPLE PLANES
Authors: ROJO A. G. , CANRIGHT G. S.
Published: November 2004

We present a multiplane model for the anyon problem. Anyons on different planes are coupled via a Coulomb–type interaction. We solve exactly finite clusters and show that the "antiferromagnetic" order of the chirality is favored for both attractive and repulsive interplane coupling. We also discuss a simple model that can be treated analytically and that has the same qualitative behavior as the exact results. Our results apply to the low density limit, in which finite currents exist in each plane. These currents also occur in the high temperature (nonsuperfluid) phase of the anyon system, and so our results should apply also to that regime.
INTERBAND ANYON PLASMON EXCITATIONS IN AN ALTERNATING-LAYERED INTERACTING ANYON GAS SYSTEM
Authors: Gumbs Godfrey , Huang Danhong
Published: November 2004

With the use of a self-consistent mean-field theory, where the anyon gauge field is approximated by its expectation value and the Coulomb interaction is calculated in the Hartree approximation, we have calculated the coupled acoustic anyon plasmon modes for an alternating-layered interacting anyon gas structure. In a single-layer system, we obtain a phonon mode for a noninteracting anyon gas. This is different from the result given by the random- phase approximation. When the Coulomb interaction is included, this phonon mode is suppressed. In a multi-layered system, we get an acoustic anyon plasmon mode with its sound velocity renormalized by the Coulomb interaction. The uniform liquid ground state is shown to be stable against solid crystallization.
Collective Mode of Semion Systems
Authors: Xie X. C. , He Song , Das Sarma S.
Published: November 2004

The ground and the excited states of a two-dimensional anyon system are studied via finite-size numerical calculations and single-mode approximation in a spherical geometry. It is shown that Laughlin's mean field theory gives an accurate description of the ground state properties. We find, consistent with earlier analytic theories, that the collective mode of the system exhibits a linear dispersion in the long wavelength limit, and predict a novel roton minimum at a finite value of the wavenumber q. We also discuss the consequences on the anyon spectrum of having a model repulsive interaction between the particles.
Relativistic Wave Equation for Anyons
Authors: Nair V. P.
Published: November 2004

I describe how, starting from fundamental symmetry principles, a relativistic theory of anyons can be formulated.
On the Constraint Equation for the Lowest Landau Level in Fractional Quantum Hall System
Authors: Sheng Dong-Ning , Su Zhao-Bin , Sakita B.
Published: November 2004

In the framework of collective field theory, We apply the Chern-Simon field theory treatment to the constraint equation for the lowest Landau level to investigate the generic properties for the quasi-particles of the FQH system. It shows a transparent connection to the Laughlin's wave functions. If we take an average over the wave functional for the constraint equation, the resulted equation can be interpreted as the vortex equation for the fractionally charged quasi-particles. Introducing a generalized ρ (density)-ϑ (phase) transformation, not only the fractional statistics and the hierarchy scheme can be drawn from the constraint equation, it also gives rise an interesting picture that vortices condense as a Halperin like wave fuction on a Laughlin like background condensate of ν=1/m.
ARE THERE THREE KINDS OF SUPERCONDUCTIVITY?
Authors: KIEHN R. M.
Published: November 2004

A Maxwell system of differential forms induces a coarse topology on a space time variety. This topology can be refined by certain extremal constraints of domain closure that lead to three topologically distinct, reactive impedances, Z1, Z2, Z3. These non-dissippative impedances are rational fraction ratios of topological invariants. The closure conditions induce physical constraints that permit Z1 to be identified with ordinary type I and II superconductive domains, and Z3 with the fractional quantum Hall effect. Only Z2 admits the time-reversal and parity symmetry breaking associated with Anyon theories.