bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamic‐based in vivo transfection of retinoic X receptor‐α gene can enhance vitamin A‐induced attenuation of liver fibrosis in mice
Authors: Chen Chen , Zhang Jinsheng , Li Jinjun , Huang Jin , Yang Chen , Huang Guangcun , Shi Jianying
Published: November 2004

Abstract: Background/Aim: In hepatic stellate cells isolated from rat fibrotic livers, the amount of retinoid X receptor‐alpha (RXR‐α) mRNA is greatly reduced. However, the effectiveness of retinoids in the treatment of liver fibrosis is controversial. We hypothesized that increasing the expression levels of RXR‐α in livers will improve the response of liver fibrosis to retinoids treatment.

Methods: pTracer‐CMV2 vector harboring both green fluorescent protein and RXR‐α genes was given to mice with carbon tetrachloride (CCl4)‐induced liver fibrosis, by hydrodynamic‐based in vivo transfection. Vitamin A was simultaneously administered to the mice. Sirius red staining and measurement of hydroxyproline content were performed to evaluate liver fibrosis. The incorporation of 5‐bromo‐2‐deoxyribouridine (BrdU) was carried out to determine liver cell proliferation.

Results: Successful transfection and expression of exogenous RXR‐α gene in the liver was determined by observance of green fluorescence under a confocal microscope, and detection of RXR‐α protein by immunohistochemistry. Hepatic fibrosis, evaluated by both Sirius red staining with image analysis and quantity of hydroxyproline in livers of RXR‐α‐transfected group, tapered off remarkably. The hydroxyproline content and Sirius red‐positive staining area on liver sections from RXR‐α‐transfected mice decreased by 34.3% and 54.63%, respectively, compared with the control group receiving empty vector. The labeling index of BrdU in non‐parenchymal cells was much lower in livers from the RXR‐α‐transfected group than that of empty vector‐transfected group.

Conclusions: Hydrodynamic‐based in vivo transfection of the RXR‐α gene can enhance the vitamin A‐induced attenuation of liver fibrosis in mice. One of the possible mechanisms of action for this gene treatment is inhibition of non‐parenchymal cell proliferation mainly composed of hepatic stellate cells in fibrotic livers.
Epithelial-to-Mesenchymal Transition Generates Proliferative Human Islet Precursor Cells
Authors: Gershengorn Marvin C. , Hardikar Anandwardhan A. , Wei Chiju , Geras-Raaka Elizabeth , Marcus-Samuels Bernice , Raaka Bruce M.
Published: November 2004

Insulin-expressing beta cells, found in pancreatic islets, are capable of generating more beta cells even in the adult. We show that fibroblast-like cells derived from adult human islets donated postmortem proliferate readily in vitro. These mesenchymal-type cells, which exhibit no hormone expression, can then be induced to differentiate into hormone-expressing islet-like cell aggregates, which reestablishes the epithelial character typical of islet cells. Immunohistochemistry, in situ hybridization, and messenger RNA measurements in single cells and cell populations establish the transition of epithelial cells within islets to mesenchymal cells in culture and then to insulin-expressing epithelial cells.
Nucleosome Arrays Reveal the Two-Start Organization of the Chromatin Fiber
Authors: Dorigo Benedetta , Schalch Thomas , Kulangara Alexandra , Duda Sylwia , Schroeder Rasmus R. , Richmond Timothy J.
Published: November 2004

Chromatin folding determines the accessibility of DNA constituting eukaryotic genomes and consequently is profoundly important in the mechanisms of nuclear processes such as gene regulation. Nucleosome arrays compact to form a 30-nanometer chromatin fiber of hitherto disputed structure. Two competing classes of models have been proposed in which nucleosomes are either arranged linearly in a one-start higher order helix or zigzag back and forth in a two-start helix. We analyzed compacted nucleosome arrays stabilized by introduction of disulfide cross-links and show that the chromatin fiber comprises two stacks of nucleosomes in accord with the two-start model.
Electron Coherence in a Melting Lead Monolayer
Authors: Baumberger F. , Auwärter W. , Greber T. , Osterwalder J.
Published: November 2004

We used angle-resolved photoemission spectroscopy to measure the electronic dispersion and single-particle spectral function in a liquid metal. A lead monolayer supported on a copper (111) surface was investigated as the temperature was raised through the melting transition of the film. Electron spectra and momentum distribution maps of the liquid film revealed three key features of the electronic structure of liquids: the persistence of a Fermi surface, the filling of band gaps, and the localization of the wave functions upon melting. Distinct coherence lengths for different sheets of the Fermi surface were found, indicating a strong dependence of the localization lengths on the character of the constituent atomic wave functions.
Common and Distinct Elements in Cellular Signaling via EGF and FGF Receptors
Authors: Schlessinger Joseph
Published: November 2004

Signaling pathways that are activated by epidermal growth factor (EGF) or fibroblast growth factor (FGF) receptors have been identified and compared (detailed Connections Maps are available at
Science
's Signal Transduction Knowledge Environment). Both receptors stimulate a similar complement of intracellular signaling pathways. However, whereas activated EGF receptors (EGFRs) function as the main platform for recruitment of signaling proteins, signaling through the FGF receptors (FGFRs) is mediated primarily by assembly of a multidocking protein complex. Moreover, FGFR signaling is subject to additional intracellular and extracellular control mechanisms that do not affect EGFR signaling. The differential circuitry of the intracellular networks that are activated by EGFR and FGFR may affect signal specificity and physiological responses.
BIOMEDICAL APPLICATIONS OF PIXE AT FUDAN UNIVERSITY
Authors: ZENG XIANZHOU , YAO HUIYING , SUN YONGNIAN , WU XIANKANG , YANG FUJIA
Published: November 2004

The aspects of the PIXE technique in the Van de Graaff Laboratory of Fudan University are reported. The analytical precision is within 5% when handling with care and within 10% in routine analysis. Some recent applications of PIXE are presented, including the pathogeny analysis of Kashin-Beck’s disease and cancer, hair analysis of pregnant women and an unknown primate, and PIXE analysis in DNA study.
PIXE ANALYSIS OF CELLULAR ELEMENT CONTENTS FOR INVESTIGATION OF HEAT INACTIVATION OF MAMMALIAN CELLS
Authors: MATSUMOTO SHINJI , TSUCHIYA KANAME , CHIBA REN
Published: November 2004

PIXE analysis was successfully applied to the measurement of cellular elements of mammalian cells in relation to the study of hyperthermia. V79 cells were heated at 44.0°C for 30 min or 1 h and the following element releases or uptakes were determined with PIXE measurement of samples obtained after appropriate periods of incubation at 37°C. Linear relationships were confirmed between the produced X-ray yields of P, S, Cl, K and Ca and the cell numbers. The cellular contents P, S, and K decreased promptly after the heat treatment and recovered gradually in the following incubation. Changes in the contents of Cl and Ca did not show abrupt decreases. Curiously, the content of Ca increased after the treatment at 44.0°C for 30 min. The results suggest that various structural modifications were induced in the membrane by the heat treatment.
HIGH-RESOLUTION PIXE USING BRAGG’S SPECTROMETER
Authors: TERASAWA M.
Published: November 2004

K, L, and M X-rays in the wavelengths between 6Å and 130Å generated by the bombardment of 200 keV protons and other heavy ions were measured by means of a wavelength dispersive Bragg’s spectrometer. The X-ray peak intensity was fairly high in general, while the background was very low. The technique was favorably applied to a practical analysis of several light elements (Be, B, C, N, O, and F). Use of moderate-energy heavy ions considering the wavelength selectivity in X-ray generation was effective for the element analysis. The high-resolution spectrometry in the analytical application of ion-induced X-ray generation was found to be useful for the study of fine electronic structure, e.g. satellite and hypersatellite X-ray study, and of the chemical state of materials.
THE SCANNING SIMULATION METHOD FOR MACROMOLECULES
Authors: MEIROVITCH HAGAI
Published: November 2004

We discuss the statistical properties of the scanning simulation method for macromolecules and its variant, the double scanning method. We summarize results (in particular critical exponents and transition temperatures) obtained for a wide range of models, branched polymers, polymers adsorbed on a surface and polymers at their collapse transition (the Flory θ-point). We describe application of the methods for studying the stability of polypeptides and discuss plans for future work.
“SUPERRADIANCE” EFFECT IN A GRAVITATIONAL ANTENNA
Authors: PREPARATA GIULIANO
Published: November 2004

I show that the cross-section for absorption of a gravitational wave in a massive resonating antenna is greatly enhanced (about six orders of magnitude) upon its classical estimate if the atoms of the antenna perform coherent oscillations, as predicted by the new approach to “superradiance” in condensed matter.
RELATIVISTIC ROTATING DISK: THE GENERAL SOLUTION
Authors: TURAKULOV Z. Y.
Published: November 2004

A general model of the piecewise-smooth spacetime whose smooth regions are the Kerr space pieces is constructed. The model includes three arbitrary constants and one arbitrary function depending on the coordinates. The Einstein tensor does not vanish only on the common boundary of the smooth regions and contains the δ-function as a factor, so that this boundary is interpreted as an infinitesimally thin rotating disk. The shape of the Einstein tensor indicates the absence of the pressure and motion of the source matter in the direction normal to the disk.
THE BOSONIC STRING REPRESENTED AS Φ3 GRAPHS: NEW MONTE-CARLO SIMULATIONS
Authors: AMBJØRN J. , BOULATOV D. , KAZAKOV V. A.
Published: November 2004

We discuss a new method for measuring the critical exponent γ for the partition function of the bosonic string. The statistics seems very good and the fit to γconsistent with the assumed asymptotic form for the partition function for dimensions d=1–6. The results are in agreement with analytical results when the target space dimension is d=0, but disagree when d=1. We conjecture that this is due to the appearance of logarithmic corrections to the asymptotic form of the partition function. These corrections might persist for d>1 and might render the determination of γquite difficult.
HIGHER INTEGRALS OF MOTION IN A PERTURBED k = 1 SU(2) WESS-ZUMINO-WITTEN THEORY
Authors: KOBAYASHI KEN-ICHIRO , UEMATSU TSUNEO
Published: November 2004

We investigate higher integrals of motion in the k = 1 SU(2) Wess-Zumino-Witten (WZW) model perturbed by a certain relevant operator. While the perturbed system is a special case of a Sine-Gordon theory, it is shown to the lowest order in perturbation theory that there exist extra conserved currents due to the SU(2) symmetry in the original WZW model.
NEW CRITICAL BEHAVIOR IN d = 0 LARGE-N MATRIX MODELS
Authors: DAS SUMIT R. , DHAR AVINASH , SENGUPTA ANIRVAN M. , WADIA SPENTA R.
Published: November 2004

The non-perturbative formulation of 2-dimensional quantum gravity in terms of the large-N limit of matrix models is studied to include the effects of higher order curvature terms. This leads to matrix models whose potential contains a symmetry breaking term of the form Tr ϕAϕA, where A is a given fixed matrix. This is studied in d = 0 dimensions and effectively induces additional terms of the form ( Tr ϕk)2 in the one matrix potential. An exact solution to leading order of the potential V(ϕ) = 1/2 Tr ϕ2 + g/N Tr ϕ4 + g′/N2 ( Tr ϕ2)2 is presented leading to 3 phases: γ = −1/2 (smooth surfaces), γ = 1/2 (branched polymer) and γ = 1/3 (intermediate phase). Including a Tr ϕ6 term in the potential gives rise to an additional phase with γ = 1/4. It is conjectured that for the general polynomial potential there are phases with γ = 1/n, n = 2, 3, …. The γ > 0 phases may correspond to c > 1 matter coupled to 2-dimensional gravity.
A CALCULATION OF THE COSMOLOGICAL CONSTANT IN A TOY MODEL
Authors: GASS RICHARD
Published: November 2004

I calculate the expectation value of the cosmological constant in a model with a scalar field interacting with wormholes. The results show that there exist models for which <Λ>α≠0 even though P(α) is sharply peaked about α=0.
NEW TESTS OF THE GRAVITATIONAL REDSHIFT EFFECT
Authors: KRISHER TIMOTHY P.
Published: November 2004

Tests of the gravitational redshift effect provide a way to check the validity of the Einstein Equivalence Principle (EEP) and, more specifically, of general relativity. If the EEP is valid, then the redshift should be the same for different clocks. Also, according to general relativity, the redshift should depend upon only the total mass of a gravitating body without reference to its detailed composition. These predictions have been tested mainly in the gravitational field of the Earth. It is now possible to measure, with space probes, the redshift effect to good accuracy in the vicinity of other bodies in the solar system, in particular at the massive outer planets. The present and future status of these experiments is discussed.
GAUGED SIGMA MODELS FROM 2 + 1 DIMENSIONS AND THE ISSUE OF UNITARITY
Authors: ABOUELSAOOD A. , POPE C. N. , SEZGIN E. , SHEN X.
Published: November 2004

As a Lagrangian realization of the Goddard-Kent-Olive G/H coset construction, Castellani, D'Auria and Levi recently proposed a gauged Wess-Zumino-Witten model in which the topological term is a difference of Chern-Simons forms. We show that their Lagrangian is actually an ungauged Wess-Zumino-Witten model plus a gauge field coupled linearly to an H-current, thus describing non-abelian chiral bosons with a linear constraint. We carry out the Dirac quantization procedure and show that the Hamiltonian is of the current-current form with indefinite signature, thus signaling instability. We also clarify the relationship of this model with that of Moore and Seiberg, which does provide an anomaly-free formulation of the GKO coset construction.
TOPOLOGICAL PREGEOMETRY
Authors: FLOREANINI R. , PERCACCI R.
Published: November 2004

We show that Einstein's gravity can be induced from a topological sigma model.
REMARKS AND RIGOROUS BOUNDS RELATING TO THE DECAY Z → πγ AND ITS RELATIONSHIP TO THE ANOMALY
Authors: WEST GEOFFREY B.
Published: November 2004

It is rigorously shown that the amplitude for the decay Z → πγ must fall at least as fast as [Formula: see text]. Consequently its branching ratio must be smaller than 10−4; with slightly less conservative assumptions, this limit reduces to 5 × 10−6. The anomaly, the triangle graph and the Ward identities are shown to be consistent with both these bounds and the rate for π0 → 2γ.
BROKEN SYMMETRY IN WORMHOLES
Authors: GONZÁLEZ-DÍAZ P. F.
Published: November 2004

In order to have a positive, finite value of the effective gravitational constant for the Tolman-Hawking wormhole, it is necessary to break the reflection symmetry a → − a, τ → − τ in the classical and quantum-dynamical equations for these wormholes. The quantum-mechanical consequence from that symmetry breaking is that the wormhole spectrum is no longer given in terms of harmonic oscillator wavefunctions, but it generalizes to a spectrum of quantum states given by parabolic cylinder functions.
CANONICAL FORMULATION OF 2D INDUCED GRAVITY
Authors: EGORIAN ED. SH. , MANVELIAN R. P.
Published: November 2004

The origin of SL (2, ℝ) symmetry in the 2D induced gravity from the viewpoint of the theory of systems with constraints is investigated in this paper.
STUDY OF INTERMITTENCY IN HADRONIC Z0 DECAYS
Authors: DE ANGELIS ALESSANDRO
Published: November 2004

The study of the factorial moments of the rapidity distribution and of the (y, ϕ) distribution for hadrons produced in the decay of the Z0, by means of the DELPHI detector at LEP, has shown no deviations from the predictions of Parton-Shower models. Intermittent behavior observed in the latter case has been found to be compatible with jet cascading mechanism.
PHOTON AS GOLDSTONE BOSON IN (2 + 1)-DIMENSIONAL HIGGS MODEL
Authors: KOVNER A. , ROSENSTEIN B. , ELIEZER D.
Published: November 2004

We examine the relationship between the masslessness of a photon and symmetry realizations in (2 + 1)-dimensional scalar QED. We find that this masslessness is a direct consequence of spontaneous breaking of a global symmetry, whose generator is the magnetic flux. The pertinent order parameter for the Higgs-Coulomb phase transition is identified with the VEV of the magnetic vortex creation operator V(x). We calculate, using weak coupling perturbation theory, the VEV and the correlator of V(x) in both phases. This turns out to be equivalent to evaluating the Euclidean QED partition function in the presence of the external current which produces a magnetic monopole (with the contribution of the Dirac string subtracted). In the Coulomb phase  is finite, while in the Higgs phase it vanishes.
THE β-FUNCTION IN TOPOLOGICAL SIGMA MODELS
Authors: BIRMINGHAM DANNY , RAKOWSKI MARK
Published: November 2004

The one-loop β-function is computed for topological sigma models. By gauge fixing the topological shift symmetry in the delta-function gauge, we find that the theory is finite with vanishing β-function. A similar result is shown to hold for supersymmetric quantum mechanics.
QUANTIZATION AND COCYCLES ON THE SUPERTORUS AND LARGE-N LIMITS FOR THE CLASSICAL LIE SUPERALGEBRAS
Authors: FRADKIN E.S. , LINETSKY V. Ya.
Published: November 2004

The Poisson superbracket Lie superalgebra on the supertorus T2d|N is considered and its quantization is carried out. It is shown that there exists a non-trivial supercentral extension by means of 2d arbitrary c-numbers (when N is even), or 2d Grassmann numbers (when N is odd). It is shown that the infinite-dimensional superalgebras on the supertorus T2d|N can be considered as certain generalizations and large-M limits of the classical superalgebras A(M| M) and Q(M) (when N is even and odd respectively).
TOPOLOGICAL LANDAU-GINZBURG MODELS
Authors: VAFA CUMRUN
Published: November 2004

We derive a general expression for correlation functions of topological Landau-Ginzburg models on an arbitrary genus Riemann surface. The expressions we find for the correlation functions suggest that for ĉ>1 the perturbation of the theory by chiral primary fields of dimensions bigger than one is rather singular, though perturbation by relevant chiral primary fields seems sensible regardless of the value of ĉ.
ON SOME MATHEMATICAL PROBLEMS OF 2D-GRAVITY AND Wh- GRAVITY
Authors: SCHWARZ ALBERT
Published: November 2004

The points of infinite-dimensional Grassmannian corresponding to the τ-functions connected with 2D-gravity and Wh-gravity are studied.
SELF-TUNING FIELDS AND RESONANT CORRELATIONS IN 2d-GRAVITY
Authors: POLYAKOV A.M.
Published: November 2004

We show that minimal models coupled to quantum gravity have special type of resonant correlations defined by the free field representations and are explicitly computable. The key phenomena in these models are shown to be discontinuity of the number of degrees of freedom at exceptional values of momenta and incomplete decoupling of the spurious states.
EQUIVALENCE OF LIOUVILLE THEORY AND 2-D QUANTUM GRAVITY
Authors: D’HOKER ERIC
Published: November 2004

The equivalence of 2-dimensional quantum gravity and Liouville theory quantized with the standard translation invariant measure, is shown to hold to all orders in perturbation theory. Also, an explicit equation for the Liouville effective action as a function of the effective potential is derived from Weyl Ward identities. We speculate on some of the non-perturbative aspects of the theory.
ON THE LAGRANGIAN OF A RELATIVISTIC SPINNING PARTICLE IN QUANTUM ELECTRODYNAMICS
Authors: SHVARTSMAN SH. M.
Published: November 2004

It is shown that the relativistic spinning particle action that takes into account all radiative corrections can be constructed in reparametrization invariant and local supersymmetric form.
PLANE WAVE GRAVITONS, CURVATURE SINGULARITIES AND STRING PHYSICS
Authors: BROOKS ROGER
Published: November 2004

Bounded (compactifying) potentials arising from a conspiracy between plane wave graviton and dilaton condensates are discussed. So are string propagation and supersymmetry in space-times with curvature singularities.
NO SIEGEL ANOMALY FOR D=4 HETEROTIC σ-MODELS ON GROUP MANIFOLDS
Authors: KUZENKO S.M. , SOLOVIEV O.A.
Published: November 2004

We prove that the conditions for cancellation of the anomaly in Siegel symmetry for the D=4 heterotic σ-models on group manifold and the (1, 0) non-Abelian lefton-righton Thirring models are the same as in the free string case.
THREE-DIMENSIONAL SIMPLICIAL QUANTUM GRAVITY AND GENERALIZED MATRIX MODELS
Authors: AMBJØRN JAN , DURHUUS BERGFINNUR , JÓNSSON THÓRDUR
Published: November 2004

We consider a discrete model of Euclidean quantum gravity in three dimensions based on a summation over random simplicial manifolds. We derive some elementary properties of the model and discuss possible “matrix” models for 3-D gravity.
DRESSED QUARKS AND PROTON’S SPIN
Authors: YANG XIN-HUA , WONG CHUN WA , CHU KEH-CHENG
Published: November 2004

The effect on the proton spin of mixing gluon and sea quark configurations is studied in a perturbative treatment based on the MIT bag model. As little as 29% of the proton spin is found to remain as the intrinsic spin of quarks when they are “dressed” by gluons.
SCHWARZSCHILD SOLUTION IN ASHTEKAR FORMALISM
Authors: FUKUYAMA TAKESHI , KAMIMURA KIYOSHI
Published: November 2004

Spherically symmetric solution of Einstein gravity is studied in the framework of Ashtekar formalism. Schwarzschild solution takes a similar form to the 't Hooft–Polyakov monopole solution. In the former, the gauge field behaves as r−2 at large distance in contrast to r−1 in the latter.
THE RESUMMATION OF TOP QUARK EFFECTS IN THE STANDARD MODEL AND THE 1/Nc EXPANSION
Authors: PERIS S.
Published: November 2004

It is discussed in the Standard Model how a 1/N c expansion, where N c is the number of colors, may be a useful tool for resumming perturbative effects due to a heavy top quark. In particular, some recently proposed formulae for the two-loop resummation of the MW − MZ interdependence in terms of mt are re-obtained and, within the approximation of keeping only the leading term in 1/N c , it is shown how they are, as a matter of fact, valid to all orders in the top mass.
A FRACTIONAL KdV HIERARCHY
Authors: BAKAS IOANNIS , DEPIREUX DIDIER A.
Published: November 2004

We construct a new system of integrable nonlinear differential equations associated with. the operator algebra [Formula: see text] of Polyakov. Its members are fractional generalizations of KdV type flows corresponding to an alternative set of constraints on the 2-dim. SL(3) gauge connections. We obtain the first non-trivial examples by dimensional reductiion from self-dual Yang–Mills and then generate recursively the entire hierarchy and its conserved quantities using a bi-Hamiltonian structure. Certain relations with the Boussinesq equation are also discussed together with possible generalizations of the formalism to SL (N) gauge groups and [Formula: see text] operator algebras with arbitrary N and l.
OCTONIONIC MULTI S8 CHIRAL AND GRAVITATIONAL INSTANTONS
Authors: REŞIT DÜNDARER A.
Published: November 2004

An 8-dimensional generalization of the sigma model is given and it is shown that these fields have topological charge n and satisfy a self-duality equation for the octonionic mappings xn: S8 → S8. Furthermore the Euler–Poincaré index I E and the Pontryagin index I P are generalized to eight dimensions and it is shown that I E = n, I P = 0 for the above mappings.
A TOPOLOGICAL QUANTUM THEORY INTERPRETATION OF INTEGRABLE MODELS
Authors: DAYI ÖMER F.
Published: November 2004

An integrable model can be interpreted as a constrained Hamiltonian system by treating constants of motion of the former as constraints of the latter. The new constrained Hamiltonian system, when we deal with a finite initial phase space, after quantization does not have local excitations if operator ordering does not cause anomalies. So that it is a topological quantum theory. As an example, operator quantization of the Toda lattice where the ordering is important, is studied.
VORTICES IN THE ABELIAN CHERN–SIMONS–HIGGS MODEL AND DUALITY IN ANYON SUPERCONDUCTIVITY
Authors: YANG Z.
Published: November 2004

Vortices in the Abelian Chern–Simons–Higgs model (CSH) are anyons, in agreement with expectations on general ground. If the CSH is considered as a low energy effective theory of charged anyons, the vortices then have the same electric charge and dual spin and statistics as the original anyons.
GAUGE SYMMETRY IN SPINOR SPACE
Authors: KAO W. F.
Published: November 2004

It is possible to generalize the global similarity transformation in spinor space to a U4 gauge transformation. This gauge transformation is commute with Lorentz transformation if Lorentz transformation is defined in a gauge-covariant way which will be described in this letter. Moreover, this theory is invariant under the conventional U (1) gauge symmetry. Possible implications are also discussed.
BOUNDS ON MIXING ANGLES OF FERMIONS WITH THEIR EXOTIC PARTNERS USING LEP 1990 DATA
Authors: BHATTACHARYYA G. , DATTA A. , GANGULI S. N. , RAYCHAUDHURI A.
Published: November 2004

We have studied the bounds on mixing angles of fermions with their exotic partners which may stem from different possibilities of new physics. The tree level effects of mixing have been taken care of by a modification of the effective vector and axial-vector couplings of Z to the fermions. The radiative corrections arising from new physics of exotic fermions are assumed to be negligible; as a result the ρ parameter and the effective sin 2 θw are calculated within the framework of the Standard Model. Mixing angles have been treated as free parameters during simultaneous fits to the combined data of cross-sections and lepton asymmetries from the four LEP experiments which have collected over 550,000 Z0 decays in 1990. Fitted values of mixing angles and the upper bounds at 90% C. L. are discussed.
IRF MODELS ASSOCIATED WITH REPRESENTATIONS OF THE LIE SUPERALGEBRAS gl(m|n) AND sl(m|n)
Authors: DEGUCHI TETSUO , FUJII AKIRA
Published: November 2004

We present two families of exactly solvable interaction round a face (IRF) models associated with representation of the Lie superalgebras gl (m|n) and sl (m|n). These IRF models are the generalizations of integrable spin chains with bosons and fermions. We also presents fusion models associated with higher representation of gl (m|n) and sl (m|n). We introduce restricted IRF models both for gl (m|n) and sl (m|n).
DISCRETE AND CONTINUUM APPROACHES TO THREE-DIMENSIONAL QUANTUM GRAVITY
Authors: OOGURI HIROSI , SASAKURA NAOKI
Published: November 2004

It is shown that, in the three-dimensional lattice gravity defined by Ponzano and Regge, the space of physical states is isomorphic to the space of gauge-invariant functions on the moduli space of flat SU(2) connections over a two-dimensional surface, which gives physical states in the ISO(3) Chern–Simons gauge theory. To prove this, we employ the q-analogue of this model defined by Turaev and Viro as a regularization to sum over states. A recent work by Turaev suggests that the q-analogue model itself may be related to an Euclidean gravity with a cosmological constant proportional to 1/k2, where q=e2πi/(k+2).
W± PROPAGATOR ON THE RESONANCE REGION
Authors: LÓPEZ CASTRO G. , LUCIO J. L. M. , PESTIEAU J.
Published: November 2004

We determine the analytical expression of the lowest order W-boson propagator on the resonance region, which satisfies the requirement of electromagnetic gauge invariance.
SUPERSYMMETRY IN QUANTUM MECHANICS
Authors: LAHIRI ANURADHA , ROY PRODYOT KUMAR , BAGCHI BIJAN
Published: November 2004

A pedagogical review on supersymmetry in quantum mechanis is presented which provides a comprehensive coverage of the subject. First, the key ingredients on the quantization of the systems with anticommuting variables are discussed. The supersymmetric Hamiltotian in quantum mechanics is then constructed by emphasizing the role of partner potentials and the superpotentials. We also make explicit the mathematical formulation of the Hamiltonian by considering in detail the N=1 and N=2 supersymmetric (quantum) mechanics. Supersymmetry is then discussed in the context of one-dimensional problems and the importance of the factorization method is highlighted. We treat in detail the technique of constructing a hierarchy of Hamiltonians employing the so-called ‘shape-invariance’ of potentials. To make transparent the relationship between supersymmetry and solvable potentials, we also solve several examples. We then go over to the formulation of supersymmetry in radial problems, paying a special attention to the Coulomb and isotropic oscillator potentials. We show that the ladder operator technique may be suitably modified in higher dimensions for generating isospectral Hamiltonians. Next, the criteria for the breaking of supersymmetry is considered and their range of applicability is examined by suitably modifying the definition of Witten’s index. Finally, we perform some numerical calculations for a class of potentials to show how a modified WKB approximation works in supersymmetric cases.
HEAT-KERNEL APPROACH TO THE ZETA-FUNCTION REGULARIZATION OF THE CASIMIR ENERGY FOR DOMAINS WITH CURVED BOUNDARIES
Authors: ELIZALDE E. , ROMEO A.
Published: November 2004

We combine a zeta-function definition and heat-kernel series to derive Casimir energy expansions parametrizing the UV divergences in the presence of arbitrarily shaped smooth boundaries. Their terms, in the form of a geometrical object times a divergence, allow for drawing conclusions on the scale dependence and on the finiteness of the vacuum energy when limiting surfaces have been introduced. Different behaviors are found depending, among other factors, on the even or odd character of the space dimension. A number of controversial points are cleared up and some misstatements in the literature are properly rigorized.
A HIGHER-ORDER ANALYSIS OF THE EFFECTS OF BREAKING SUPERSYMMETRY FOR NON-LINEAR σ-MODELS
Authors: HELAYËL-NETO J.A. , WILLIAM SMITH A.
Published: November 2004

Arbitrary (1, 1) and (1.0) two-dimensional nonlinear σ-models, modified by the addition of coupling terms which explicitly break supersymmetry, are studied. The geometrical meaning of these additional terms is discussed. Supergraph methods, suitably extended to include the case of broken supersymmetry, are set and employed in explicit higher-loop computations to keep track of the effect that the explicit breaking of supersymmetry has on the ultraviolet behavior of the originally supersymmetric models.
A GEOMETRIC FIELD THEORY OF CLOSED STRINGS: D=4, N=1 LOOP SUPERGRAVITY
Authors: Castellani Leonardo
Published: November 2004

We present a classical field theory of interacting loops, whose low energy limit is D=4, N=1 supergravity. In Fourier modes, the theory is obtained by gauging the infinite dimensional algebra KM (SuperPoincaré) ⊕ Virasoro, where KM indicates the Kac-Moody extension. Taylor expanding the superloop vielbein in the “internal” coordinates yields towers of D=4 fields with arbitrarily high spins. The superloop diffeomorphisms relate all the higher spin fields. The field equations are obtained by requiring the closure of the generalized supersymmetries. Two different mechanisms give rise to masses for the higher modes: (i) a Kaluza-Klein type mass generation from “internal” loop coordinates, (ii) a non-vanishing background value for the zero mode of the Virasoro gauge field.
A PARAMETER-FREE CALCULATION OF PROTON-NUCLEUS MULTIPLICITIES IN A RAPIDITY WINDOW
Authors: LAM C. S. , KIANG D. , OCHIAI T.
Published: November 2004

Average multiplicities and multiplicity distributions in fixed rapidity windows are calculated for proton-nucleus collisions. A geometrical wounded nucleon model is used for the calculation, whose only input comes from the data of proton-proton collisions. Agreements with the proton-nucleus data are good in the forward hemisphere and for the small rapidity intervals in the backward hemisphere, but not so good for large rapidities in the backward hemisphere.
ABOUT THE LATEST RESULTS ON THE VECTOR MESON PAIR PRODUCTION IN γγ-COLLISIONS
Authors: ACHASOV N.N. , KARNAKOV V.A. , SHESTAKOV G.N.
Published: November 2004

The resonance type enhancements discovered recently near the γγ→VV′ reaction thresholds are discussed in detail. It is shown that the signal in the reaction γγ→ρω can be caused by the [Formula: see text] state production. The data on the reaction γγ→K*+K*− are explained by the charged K* Regge exchange. The partial-wave compositions are presented for the OPE and OKE mechanisms in the reactions γγ→ωω and [Formula: see text]. The reaction γγ→φρ is discussed. It is pointed out too that the enhancements in γγ→ρω, [Formula: see text], γγ→ωω in the region 1.8–2 GeV can be caused by the production of the radial excitations of the tensor mesons. The possible further strategy of the search for the [Formula: see text] states in γγ collisions and in the other reactions is discussed.
INDUCED WZW-TYPE TERM IN DUAL FIELD THEORY
Authors: NIELSEN N.K.
Published: November 2004

One-loop quantum equivalence is investigated by proper time regularization for a nonlinear σ-model in two dimensions on a group manifold and its dual theory constructed by Fradkin and Tseytlin. The one-loop effective actions are found to deviate by a finite local counterterm with a structure similar to that of a Wess-Zumino-Witten term.
A COMMENT ON TOPOLOGICAL FIELD THEORY QUANTIZATION AND STOCHASTIC PROCESSES
Authors: CUGLIANDOLO L.F. , LOZANO G. , MONTANI H. , SCHAPOSNIK F.A.
Published: November 2004

We discuss the relation between different quantization approaches to topological field theories by deriving a connection between Bogomol’nyi and Langevin equations for stochastic processes which evolve towards an equilibrium state governed by the topological charge.
EXTENDED CONFORMAL ALGEBRA WITH N=2 SUPERSYMMETRY
Authors: INAMI T. , MATSUO Y. , YAMANAKA I.
Published: November 2004

We construct an N=2 supersymmetric extension of Zamolodchikov’s W algebra. The generators of this extended conformal algebra consist of the stress-tensor superfield and a pair of chiral currents [Formula: see text] of integer or half-integer spin Δ and opposite U(I) charges ±τ. The algorithm for deriving the operator product algebra [Formula: see text] is given for general Δ and the algebra is worked out explicitly for Δ=3/2. The N=2 super-W algebra has an interesting feature not shared by other conformal algebras, i.e. it has two types of algebra—short and long algebras.
POISSON STRUCTURE AND INTEGRABILITY OF THE NEUMANN-MOSER-UHLENBECK MODEL
Authors: AVAN J. , TALON M.
Published: November 2004

Neumann’s model, describing the motion of a particle on an N-sphere under harmonic forces, is studied from the point of view of classical and quantum integrability. Classical integrability is derived from a generalized structure, “R-S couple” or “D-matrix” for the Poisson brackets of the Lax operator. The already-known set of conserved quantities for this model turns out to follow straightforwardly from this structure. It gives rise to a set of commuting operators at the quantum level, and the algebra of Lax operators directly follows from the classical one.
ON THE STRANGE PARTICLE PRODUCTION IN THE NUCLEAR PIONIZATION MODEL
Authors: AMEEV S. SH. , TULEGENOV M. SH. , SHMONIN V.L.
Published: November 2004

The processes of K+- and K−-meson production in reactions Ne+NaF , Ne+Pb and Si+Si at E kin =2.1 GeV/N are considered within the framework of the nuclear pionization model. Model calculations are in agreement with experimental data. It is shown that K+-mesons having small absorption cross-section are produced at the relatively early stage of the cluster expansion whereas K−-mesons having large absorption cross-section are produced simultaneously with pions at the relatively late stage of the process.
CONFORMAL FIELD THEORY ON SURFACES WITH BOUNDARIES AND NONDIAGONAL MODULAR INVARIANTS
Authors: BERN Z. , DUNBAR D. C.
Published: November 2004

We show that the operator content of a conformal field theory defined on surfaces with boundaries and crosscaps is more restricted when the periodic sector is described by nondiagonal modular invariants than in the case of diagonal modular invariants. By tensoring, the restrictions can be alleviated, leading to a rich structure. Such constructions are useful, for example, in lower-dimensional open superstring models.
FUNCTIONAL RELATIONS FOR TRANSFER MATRICES OF THE CHIRAL POTTS MODEL
Authors: Baxter R.J. , Bazhanov V.V. , Perk J.H.H.
Published: November 2004

It has recently been shown that the solvable N-state chiral Potts model is related to a vertex model with N-state spins on vertical edges, two-state spins on horizontal edges. Here we generalize this to a “j-state by N-state” model and establish three sets of functional relations between the various transfer matrices. The significance of the “super-integrable” case of the chiral Potts model is discussed, and results reported for its finite-size corrections at criticality.
CONFORMAL PROPERTIES OF CRITICAL ISING MODEL CORNER TRANSFER MATRICES
Authors: DAVIES Brian , PEARCE Paul A.
Published: November 2004

The scaling spectra of finite-size Ising model corner transfer matrices (CTMs) are studied at criticality, using the fermion algebra. The low-lying eigenvalues collapse like 1/ log N for large N as predicted by conformal invariance. The shift in the largest eigenvalue is evaluated analytically using a generalized Euler-Maclaurin summation formula giving πc/6 log N with central charge c=1/2. The spectrum generating functions, for both fixed and free boundary conditions, are expressed simply in terms of the c=1/2 Virasoro characters χ∆(q) with modular parameter q= exp (−π/ log N) and conformal dimensions ∆=0, 1/2, 1/16.
FIRST ORDER PHASE TRANSITIONS IN A SOLID WITH FINITE SIZE
Authors: CABRERA G.G.
Published: November 2004

First order phase transitions are rounded in solids of finite size. It is shown here that the above rounding is monitored by the correlation length ξL of the finite system, or equivalently by the so-called mass gap for the quantum Hamiltonian version of the model. Scaling with size is studied as a function of variable boundary conditions for the cylinder geometry (infinite strips with finite width), and a striking crossover is found in the mass gap behavior when the coupling g along the boundary becomes anti-periodic. For g>0, the rounding is exponential with size and an accurate determination of the spontaneous magnetization (order parameter) of the infinite system is obtained from numerical extrapolations.
ENTROPIC REPULSION BETWEEN FLUCTUATING SURFACES
Authors: JANKE W.
Published: November 2004

The statistical mechanics of fluctuating surfaces plays an important role in a variety of physical systems, ranging from biological membranes to world sheets of strings in theories of fundamental interactions. In many applications it is a good approximation to assume that the surfaces possess no tension. Their statistical properties are then governed by curvature energies only, which allow for gigantic out-of-plane undulations. These fluctuations are the “entropic” origin of long-range repulsive forces in layered surface systems. Theoretical estimates of these forces for simple model surfaces are surveyed and compared with recent Monte Carlo simulations.
MULTI-DIMENSIONAL FRÖHLICH BIPOLARON AND DIMENSIONAL SCALING
Authors: SIL SHREEKANTHA , CHATTERJEE ASHOK
Published: November 2004

The formation and stability of the Fröhlich bipolaron in a multi-dimensional polar crystal is investigated within the framework of strong coupling Landau-Pekar theory. The ground state energy, the effective mass and the size of the bipolaron are calculated. It is shown that Fröhlich bipolarons can exist in both two and three dimensions, the bipolaronic binding being stronger in lower dimensions. The dimensional scaling relations satisfied by the ground state energy and the effective mass of the bipolaron are also obtained.
A THEORETICAL STUDY OF LATTICE INSTABILITIES IN LaCuO
Authors: FLACH S. , PLAKIDA N. M. , AKSENOV V. L.
Published: November 2004

Starting from experimental findings of structural phase transitions in LaCuO a microscopical model is introduced to describe the softening of the tilting mode associated with CuO 6-octahedra rotations. The interaction of the soft mode with the acoustic phonons is taken into account. Using the standard method of double-time retarded Green functions the equations of motion are solved within a pseudoharmonic approximation. With the help of experimental data we calculate the potential parameters of oxygen by moving in the tilting mode, the sound velocity step at the transition point I4/ mmm → Cmca and the value of the soft-mode splitting in the orthorhombic phase. The corresponding free energy of our model is investigated in order to describe the transition Cmca → P4 2/ ncm . The Sr,Ca,Ba-doping and the exchange of Cu by Co, Ni are discussed within the presented model approach.
CRITICAL BEHAVIOR OF THE DRIVEN DIFFUSIVE LATTICE GAS
Authors: Schmittmann B.
Published: November 2004

This paper reviews simulational and theoretical investigations of critical behavior in a stochastic, interacting lattice gas under the influence of a uniform external driving field. By studying this model system one wishes to gain a deeper understanding of steady states far from thermal equilibrium, and their dynamic universality classes. The major result in the case of attractive particle-particle interactions is the emergence of a novel non-equilibrium fixed point, different from the Wilson-Fisher fixed point of the equilibrium system. The fluctuations of internal energy, the structure factor and the two-point correlations all display surprising features associated with the non-equilibrium nature of the system. For repulsive interactions and small driving forces, one finds a continuous, Ising-like transition which turns first order for larger fields until it is completely destroyed.
EFFECTIVE-MASS APPROXIMATION IN GRADED CRYSTALS
Authors: FU Y. , CHAO K. A.
Published: November 2004

The effective mass approximation (EMA), when applied to graded crystals, needs a modified form [Formula: see text] for the kinetic energy operator, where 2α + β = −1 and m(z) is the position-dependent effective mass. We have analyzed the energy dispersion of the EMA Hamiltonian, and performed a one-dimensional and a three-dimensional exact calculation to determine the proper value of β. Our conclusion is that when β = −1 the EMA provides better agreement with the exact solutions.
AMORPHIZATION OF HYDRIDED Fe2Er-SINGLE-CRYSTALS TRIGGERED BY A LATTICE INSTABILITY
Authors: FECHT H.J. , FU Z.
Published: November 2004

Specific heat measurements at constant concentration of hydrided, initially single-crystalline Fe2Er powder samples exhibit a lambda-type anomaly during the transition from the crystalline to the amorphous state. The logarithmic temperature-dependence of the specific heat results from local fluctuations in the crystalline phase, rather than thermally activated lattice defects. This is suggestive of an instability underlying the “melting” transition to a glass that has been predicted if vitrification occurs in the vicinity of the extrapolated triple point between crystal, liquid and glass.
PHOTOEMISSION CALCULATION WITH A SIMPLE MODEL FOR THE PHOTON FIELD: APPLICATION TO ALUMINIUM
Authors: DAS P. , THAPA R.K. , KAR N.
Published: November 2004

Photoemission cross-sections are calculated, using a simple “local” dielectric function for computing the photon field in the surface region and free electron wavefunctions. Comparisons are made with the experimental data for the frequency-dependent normal photoemission from the Fermi level of aluminium, and the importance of the variation of the photon field in the surface region is pointed out.
INTRINSIC MAGNETIZATION RELAXATION PROPERTIES OF Y1:2:3
Authors: XUE Y.Y. , HUANG Z.J. , GAO L. , HOR P.H. , MENG R.L. , TAO Y.K. , CHU C.W.
Published: November 2004

The intrinsic magnetization relaxation rate R(T)≡dM(t, T)/d ln t and the pinning potential U0(T) have been determined for single crystalline and melt-textured YBa2Cu3O7 (Y1:2:3) high temperature superconductors of different sizes in their critical state. In contrast to previous reports, R(T) is a monotonically decreasing function and U0(T), deduced from R(T), a monotonically increasing function of temperature. The unusual temperature dependence of U0 is qualitatively explained in terms of a collective flux pinning. The U0-distribution model previously proposed for HTS’s is not consistent with certain experimental observations.
SPIN-SINGLET LAUGHLIN-HALPERIN TYPE WAVEFUNCTIONS FOR THE QUANTUM HALL STATES
Authors: XIE X.C. , ZHANG F.C.
Published: November 2004

We construct a class of spin-singlet wavefunctions for the filling factors ν=2/(2m±1), where m is an odd integer, and ν=1/2 quantum Hall states, based on Halperin’s generalization of the Laughlin wavefunction to systems without full spin polarization. The properties of the ν=2/(2m±1) states are consistent with the results obtained from the numerical calculations of small systems.
METASTABLE STATES AND IRREGULAR BEHAVIOUR IN A JOSEPHSON JUNCTION WITH NONLINEAR RESISTANCE
Authors: AMBIKA G. , JOSEPH K. BABU , NANDAKUMARAN V.M.
Published: November 2004

We consider a resistively shunted Josephson junction with a resistance that depends inversely on voltage. It is shown that such a junction in the underdamped case can give rise to extremely long-lived metastable states even in the absence of external noise. We investigate numerically this metastable state and its transition to a chaotic state. The junction voltages corresponding to these states are studied.
ON SINGULAR ANYON WAVEFUNCTIONS
Authors: GRUNDBERG J. , HANSSON T.H. , KARLHEDE A. , LEINAAS J.M.
Published: November 2004

We show that quantum mechanics allows anyon wavefunctions that are singular as the particles approach each other. An extra real parameter, which determines the nature of this singular behaviour, is necessary to have a well defined quantum mechanical problem. In realistic models, anyons are expected to have an internal structure, corresponding to a smearing of the statistical flux. We study such models and find that, in generic cases, only regular wavefunctions are allowed.
LONGITUDINAL CORRELATION LENGTH IN DIRECTED PERCOLATION AND RELATED MODELS: A POSSIBLE NEW SCALING MECHANISM
Authors: HENKEL MALTE , PRIVMAN VLADIMIR
Published: November 2004

The finite-size scaling of the correlation length for directed and undirected systems is reviewed with emphasis on the asymptotic eigenvalue degeneracy associated with long-range order or long-range connectivity. The standard scaling mechanism for matching asymptotic behaviors on approach to criticality applies for Ising and other models. However, numerical evidence suggests that for directed percolation in 2D a modified formulation is appropriate, incorporating irrelevant-variable corrections in a new pattern of asymptotic scaling.
LOCALIZED LOW-FREQUENCY VIBRATIONAL MODES IN A SIMPLE MODEL GLASS
Authors: SCHOBER H.R. , LAIRD BRIAN B.
Published: November 2004

By molecular dynamics we produce a glass of soft spheres quenched to zero temperature. Normal mode analysis of the vibrational spectrum shows the existence of (quasi)localized modes at low frequencies. The structure of the glass around the centers of these modes deviates significantly from the average. The effective masses of these soft modes range upward from about 10 atomic masses.