bluuebunny/crossref_metadata_2025 huggingface dataset:
SHORTEST PATHS MULTIPLICITY IN GENERALIZED DE BRUIJN AND KAUTZ NETWORKS
Authors: DANIEL FREDERIC , AUTHIÉ GERARD
Published: November 2004

Generalized de Bruijn and Kautz networks are important since they allow networks of any size with vertices of fixed degree. Communication issues are related to easy construction/enumeration of shortest paths between vertex-couples. An easy method based on residue calculation is introduced to find multiple shortest paths if they exist, allowing better communication schemes. The main results concern the properties of multiple shortest paths (especially disjunction) and the number of vertex-couples separated by several shortest paths as a function of the graph size. Conditions to get or avoid networks with multiple shortest paths are proposed which can be useful for the design of communication schemes.
ON THE NUMBER OF ARC-DISJOINT HAMILTONIAN CIRCUITS IN THE DE BRUIJN GRAPH
Authors: ROWLEY ROBERT , BOSE BELLA
Published: November 2004

We give a constructive proof that there are d−1 arc-disjoint Hamiltonian circuits in the d-ary De Bruijn graph when d is a power of 2. We also demonstrate the existence of at least [Formula: see text] arc-disjoint Hamiltonian circuits in the general case, where [Formula: see text] is the prime factorization of d
FAULT TOLERANT ROUTING IN THE SUPERCUBE
Authors: AULETTA VINCENZO , RESCIGNO ADELE ANNA , SCARANO VITTORIO
Published: November 2004

In this paper we study the fault-tolerant properties of the Supercube, a new inter-connection network recently introduced by Sen [15]. The Supercube is a generalization of the Hypercube that can be realized for any number of nodes and not only for powers of 2. Moreover, it has the same diameter and connectivity of the Hypercube.

We shall prove that the diameter of the surviving route graph of the N-node Supercube SN, if less than [ log 2 N] nodes or edges fail, is at most 4 for any minimal routing, and exhibit a minimal routing for which the surviving route graph has diameter 2. Then, we will show that, when 2s+2s−1≤N<2s+1 the failures are [log2 N], the diameter of the surviving route graph is at most 5 for any minimal routing.

We will also prove that the fault diameter of SN is exactly [ log 2 N]+1 when N∉{2s+1−1, 2s+1−2, 2s+2s−1+1} and [ log 2 N]+2 otherwise.
GENUS TWO FREE ENERGY FOR HETEROTIC STRINGS
Authors: ORTÍN TOMÁS , OSORIO M. A. R.
Published: November 2004

We give an explicit expression for the genus two contribution to the thermal free energy for the heterotic string using Knizhnik's formula for the cosmological constant, and, by analyzing its divergencies we find the critical temperature, which is the same as in the one-loop case.
CANONICAL QUANTIZATION OF REGULARIZED STRING THEORY
Authors: FROLOV S. A. , SLAVNOV A. A.
Published: November 2004

Canonical quantization of a regularized string model taking into account changes in the type of constraints is performed. It is shown that a standard Hamiltonian analysis of this model leads to a renormalization of the critical dimension obtained in Refs. 4–9 by different methods.
SOME PHENOMENOLOGICAL ASPECTS OF THE SU(2)q × SU(2)l × U(1)Y MODEL: II
Authors: RIZZO THOMAS G.
Published: November 2004

We examine the implications of the recently proposed "ununified" SU (2)q × SU (2)l × U (1)Y model for the properties of the neutral gauge boson (Z1) observed in both e+e− and [Formula: see text] collisions. The mixing between the Z of the Standard Model (SM) and the Z′ which is present in the Ununified Model is found to be able to substantially alter radiatively corrected SM expectations for the properties of the Z1 for a wide range of model parameters, thus leading to reasonably strong constraints on the couplings and mass of the new gauge boson using current data from LEP. Bounds from HERA are also examined and are found to be less sensitive to the effects of radiative corrections.
DUAL VARIABLES FOR FERMIONS IN 2 + 1 DIMENSIONS
Authors: MARINO E. C. , STEPHANY RUIZ J. E.
Published: November 2004

Fermionic order and disorder variables are introduced and studied in (2 + 1)-dimensional field theories as a generalization of the corresponding operators in 1 + 1 dimensions.
A FORMULATION OF CHIRAL GAUGE THEORIES OFF AND ON THE LATTICE
Authors: KIEU T. D.
Published: November 2004

A formulation is proposed of Abelian chiral gauge theory which is invariant with respect to a gauge symmetry and admits both fermion and vector-boson mass terms, without invoking the Higgs mechanism. The issues of unitarity and renormalizability are discussed, and a lattice chiral regularization free from the problem of fermion-species doubling is constructed and compared with others.
THE SCHWINGER α-PARAMETRIC REPRESENTATION OF THE FINITE-TEMPERATURE FIELD THEORY: RENORMALIZATION II
Authors: BENHAMOU MABROUK , KASSOU-OU-ALI AHMED
Published: November 2004

We extend to finite-temperature field theories, involving charged scalar or nonvanishing spin particles, the α parametrization of field theories at zero temperature. This completes a previous work concerning the scalar theory. As there, a function θ, which contains all temperature dependence, appears in the α integrand. The function θ is an extension of the usual theta function. The implications of the α parametrization for the renormalization problem are discussed.
GENERAL COVARIANCE, TOPOLOGICAL QUANTUM FIELD THEORIES AND FRACTIONAL STATISTICS
Authors: GAMBOA J.
Published: November 2004

Topological quantum field theories and fractional statistics are both defined in multiply connected manifolds. We study the relationship between both theories in 2 + 1 dimensions and we show that, due to the multiply-connected character of the manifold, the propagator for any quantum (field) theory always contains a first order pole that can be identified with a physical excitation with fractional spin. The article starts by reviewing the definition of general covariance in the Hamiltonian formalism, the gauge-fixing problem and the quantization following the lines of Batalin, Fradkin and Vilkovisky. The BRST–BFV quantization is reviewed in order to understand the topological approach proposed here.
SOLUTIONS TO YANG–MILLS EQUATIONS: QUASI-INSTANTONS, QUASI-MONOPOLES AND QUASI-VORTICES
Authors: POPOV A. D.
Published: November 2004

Yang–Mills equations for semisimple gauge Lie groups G in d = 4 spaces with signatures (+ + + +) and (+ + − −) are considered. Generalizations of the one-monopole and one-instanton solutions to these equations for the group [Formula: see text] and for its real forms are obtained. For gauge fields of the vortex type, the Ansätze permitting the reduction of d = 4 self-duality equations to the d = 2 Liouville, sinh–Gordon and sine–Gordon, G/H sigma-model equations and to the equations of the relativistic string model are presented.
THE SPINNING MEMBRANE, SUPER-SU(∞)-GAUGE THEORIES AND MOYAL BRACKETS
Authors: CASTRO CARLOS
Published: November 2004

Several important topics concerning the membrane and its symmetries are discussed. The fact that a space–time-independent Lagrangian density for a gauge-field configuration of a (d – 1)-dimensional SU (∞) super Yang–Mills theory, reduced to one dimension (time), is equivalent to a Green–Schwarz formalism of the Euclidean Eguchi–Schild string action in d – 1 dimensions, naturally raises the question whether one can construct a Neveu–Ramond–Schwarz analog. The answer is in the negative; the world-sheet supersymmetric extension of the Eguchi–Schild action for the string cannot be viewed as a classical-vacuum configuration of a super-SU (∞)- gauge theory. For the second topic we construct a "supersymmetry" charge operator, Qf, which plays the role of a residual fermionic symmetry, for fixed time, of the light-cone spinning membrane. It is explicitly shown how the Yang–Mills type of actions and, in particular, the ones for vacuum-field configurations, associated with Q(∞) supergauge theories, are invariant under both Qf "supersymmetry" and the superalgebra of area-preserving superdiffeomorphisms of the light-cone spinning torus membrane, Q(∞). More general actions can be constructed which are invariant under deformations of this superalgebra. In this case the ordinary (graded) Poisson brackets are replaced by super Moyal brackets. Finally, we conjecture why these actions, in analogy with what happens with the light-cone supermembrane, should correspond to a superfiber bundle (over space–time) formulation of the supersymmetric-gauge quantum-mechanical models (SGQMM's) of Flume and Baake et al.; with the general supergroup of trigonometric structure constants of Fairlie, Fletcher and Zachos as the structure supergroup of the superfiber. To support our concluding conjecture, preliminary steps are outlined which are necessary in order to fix the light-cone gauge for the spinning-membrane action. We discuss why the Qf "supersymmetry" (the remnant world-volume light-cone local supersymmetry) and the Q(∞) supergauge transformations must arise as its residual symmetries.
GAUSSIAN ANALYSIS OF SYMMETRY BEHAVIOR
Authors: KIM S. K. , YANG J. , NAMGUNG W. , SOH K. S. , YEE J. H.
Published: November 2004

We use the functional variational method in the Schrödinger picture to examine the existence of two phases of the scalar ϕ4 theory in Minkowski and Einstein spaces. In the static Einstein space one of the phases shows the possibility of spontaneous symmetry breaking even when the renormalized mass is positive, while in the other phase symmetry breaking is prohibited owing to the infrared singularity caused by the finiteness of the spatial volume.
NON-RIEMANNIAN THEORIES OF GRAVITY AND LUNAR AND SATELLITE LASER RANGING
Authors: CIUFOLINI IGNAZIO , MATZNER RICHARD
Published: November 2004

Theories of gravity with a non-Riemannian manifold have been studied since the advent of Einstein's general relativity. In this paper, after an introduction on theories of gravity with a non-Riemannian spacetime and in particular on the nonsymmetric Moffat theory, we briefly describe the techniques of lunar and satellite laser ranging. Among the various applications of lunar and satellite laser ranging are several important measurements and tests of Einstein's general relativity as well as constraints on some alternative gravity theories. In particular, lunar and satellite laser ranging put strong validity limits on the 1983 nonsymmetric Moffat theory.
SU(3) PREDICTIONS FOR B MESON NONLEPTONIC WEAK DECAYS INTO (3/2)+-BARYON-(3/2)+-ANTIBARYON PAIRS
Authors: SHEIKHOLESLAMI S.M. , SIDANA GURPREET KAUR , KHANNA M.P.
Published: November 2004

Using SU(3) flavor symmetry of strong interactions, we have derived relations between the rates of B meson decays into (3/2)+ baryons and (3/2)+ antibaryons. The decays [Formula: see text] and [Formula: see text] have been observed. As more data become available, some of these relations may provide information on the importance of various competing effects involved in nonleptonic B meson decays.
STRUCTURE OF IRREDUCIBLE SU(2) PARAFERMION MODULES DERIVED VIA THE FEIGIN-FUCHS CONSTRUCTION
Authors: GRIFFIN PAUL A. , HERNÁNDEZ OSCAR F.
Published: November 2004

We show how the Feigin-Fuchs Coulomb-gas construction, with two free Gaussian bosons, can be used to derive the representation theory of the SU(2) parafermion models. We identify the generators of the chiral algebra within the bosonic Fock space and derive the chiral algebra of the finitely reducible models, which correspond to the SU(2) and SU(1, 1) parafermion algebras. We then focus on the SU(2) highest-weight modules in the remainder of the paper. Unitarity of the modules requires that the states of the parafermion theory be independent of the zero modes of two fermionic vertex operators of the bosonic theory. The expressions for the Virasoro highest weights of the models are doubly degenerate in the bosonic Fock space. We formulate the correlation functions of these operators in the parafermion Hilbert space, and in particular, the fusion rules for the Virasoro highest weights are derived in an elegant way. Finally, the irreducible parafermion characters are derived. We discuss the connection between our analysis and previous work on representation theory based on BRST cohomology.
THERMODYNAMICS OF A NEWTONIAN GRAVITATIONAL GAS IN TWO SPACE DIMENSIONS
Authors: MEISSNER KRZYSZTOF A. , SPALIŃSKI MICHAŁ
Published: November 2004

The partition function of a Newtonian gravitational gas in two space dimensions is related to the Euclidean quantum Liouville theory. A saddle point approximation is used to discuss a possible thermodynamic description of this system.
DOUBLE SCALING LIMIT IN O(N) VECTOR MODELS IN D DIMENSIONS
Authors: VECCHIA P. DI , KATO M. , OHTA N.
Published: November 2004

Using the standard 1/N expansion, we study O(N) vector models in D dimensions with an arbitrary potential. We limit ourselves to renormalizable theories. We show that there exists a value of the coupling constant corresponding to a critical point and that a double scaling limit can be performed as in D=0 and in the case of matrix models in D=0, 1. For D=1 the theory is renormalizable with an arbitrary potential and we find in general a hierarchy of critical theories labeled by an integer k. The universal partition function obtained in the double scaling limit is constructed. Finally, we show that the critical behaviour of those models is the same as a branched polymer model recently constructed by Ambjørn, Durhuus and Jónsson.
MULTIDIMENSIONAL EXACTLY SOLVABLE PROBLEMS IN QUANTUM MECHANICS AND PULLBACKS OF AFFINE COORDINATES ON THE GRASSMANNIAN
Authors: LOSEV A. , TURBINER A.
Published: November 2004

Multidimensional exactly solvable problems related to compact hidden-symmetry groups are discussed. Natural coordinates on homogeneous space are introduced. It is shown that a potential and scalar curvature of the problem considered have quite a simple form of quadratic polynomials in these coordinates. A mysterious relation between the potential and the curvature observed for SU(2) in Refs. 2 and 3 is obtained in a simple way.
COVARIANT sl2 DECOMPOSITION OF THE sln DRINFELD-SOKOLOV EQUATIONS AND THE Wn ALGEBRAS
Authors: BONORA L. , XIONG C.S.
Published: November 2004

In this paper we analyze sl2 content and covariance in sln W algebras. To achieve this we first work out the formulas for the sl2 case; then we examine different gauges in the sln case. Next we propose a decomposition of the covariant differential operator D(n+1), which appear in the Drinfeld-Sokolov equation in terms of conformal tensors and sl2-covariant differential operators. As an example we write down the complete classical W4 algebra and show that the above decomposition extends to all the Poisson brackets of this algebra.
NEW CRITICAL BEHAVIORS FOR ONE-HERMITIAN-MATRIX MODELS
Authors: PETROPOULOS P.M.S.
Published: November 2004

In the general framework of one-Hermitian-matrix models, we study critical behaviors such that δx~δRm/n~δSm; δx, δS and δR are, respectively, the bare cosmological constant and the orthogonal-polynomial coefficients around criticality. On the sphere, we prove the existence of consistent multicriticality conditions such that string equations exhibit the above behavior. We define a double scaling limit and write down exact equations for the specific heat for any (m, n) model. Their solutions are unambiguous and the only corrections come from genus-one topology. We compute exact correlation functions for well-defined scaling operators. These belong to two different sectors. One of them is such that any squared operator vanishes when inserted in any correlation function. We discuss briefly the flows between these multicritical points as well as the nature of the 2D field theories coupled to gravity which they can describe.
THE ROLE OF THE CONTACT ALGEBRA IN MULTIMATRIX MODELS
Authors: AOKI KENICHIRO , MONTANO DAVID , SONNENSCHEIN JACOB
Published: November 2004

In this paper we investigate the implications of the topological nature of the (1, q) matrix models. We show that the algebraic structure is enough to derive the correlation functions of pure gravity. A straightforward generalization for several primaries is presented. We further find that the recursion relations in the multimatrix models may be derived from the contact algebra alone. We show that the contact algebra, using the ghost number assignment derived from the KdV hierarchy, is consistent only for contacts with the puncture operator and its descendents. We discuss the role of the contact algebra and its consistency in general.
Z0 PARAMETERS AND Mtop FROM LEP 1990 DATA
Authors: BANERJEE S. , GANGULI S.N. , GURTU A.
Published: November 2004

The four detectors ALEPH, DELPHI, L3 and OPAL have collected ≈550,000 Z0 decays during the LEP run in 1990. We have made model-independent simultaneous fits to the LEP data to determine the Z0 parameters. The mass and widths of Z0 are Mz=91.177± 0.006±0.02 (LEP) GeV , Γz=2.481±0.010 GeV , Γ had =1.734±0.010 GeV and Γ lept =83.0 ± 0.4 MeV . The number of ν families is determined to be Nν=3.01±0.05. Simultaneous fits are performed within the Standard Model framework to the LEP data and constraining the value of sin 2 θw from the [Formula: see text] colliders we get the following values for top mass, electroweak mixing angle sin 2 θw and the radiative correction [Formula: see text], sin 2 θw=0.230±0.004 and ∆r=0.056±0.011.
LIMITS ON SELECTRON MASS FROM SN 1987A NEUTRINO DATA
Authors: BABU P. RAM , CHHABRA T.
Published: November 2004

A way to estimate photino contamination in neutrino flux from supernovas is suggested. By comparing the experimental and theoretically expected ratios of forward peaked events in the direction of the neutrino source and isotropic events, one can set a limit on selectron mass. As an example, the data from SN 1987A are used to set a limit on selectron mass. Assuming a hypothetical form of matter density variation of the supernova, the limits are obtained by varying the strength of Photino interactions.
MODULAR INVARIANTS OF KAČ-MOODY ALGEBRAS FROM SELF-DUAL LATTICES
Authors: ROBERTS PATRICK , TERAO HARUHIKO
Published: November 2004

A general method for the construction of modular invariant partition functions of Kač-Moody algebras using a covariant lattice approach is presented. The A-D-E series for [Formula: see text] conformal invariant theories and partition functions of [Formula: see text] are constructed explicitly to demonstrate the technique.
STATISTICS OF 2D SOLITONS
Authors: BREKKE LEE , IMBO TOM D.
Published: November 2004

We study the inequivalent quantizations of (1 + 1)-dimensional nonlinear sigma models with space manifold S1 and target manifold X. If X is multiply connected, these models possess topological solitons. After providing a definition of "spin" and "statistics" for these solitons and demonstrating a spin-statistics correlation, we give various exmples where the solitons can have exotic statistics. In some of these models, the solitons may obey a generalized version of fractional statistics called ambistatistics. The relevance of these 2D models to the statistics of vortices in (2 + 1)-dimensional spontaneously broken gauge theories is also discussed. We close with a discussion concerning the extension of our results to higher dimensions.
SIMULTANEOUS CREATION OF ELECTRON–POSITRON PAIRS AND PHOTONS IN ROBERTSON–WALKER UNIVERSES WITH STATICALLY BOUNDED EXPANSION
Authors: LOTZE K.-H.
Published: November 2004

We present, based upon quantum electrodynamics in Robertson–Walker flat universes, a thorough analysis of the creation of mutually interacting electron–positron pairs and photons from vacuum. Therefore we discuss at least qualitatively all processes contributing to the number densities of created particles up to the second order in the coupling constant.

For two particular expansion laws with Minkowskian in respectively in and out regions, we obtain exact solutions to the Dirac equation and investigate in detail the process of simultaneous creation of electron–positron pairs and photons and the related attenuation effect for fermionic particles. This is done for electrons and positrons which have nonrelativistic momenta at Compton time in rapidly expanding universes.

The results are compared with the zeroth-order creation of electron–positron pairs. Despite being smaller by a factor of roughly [Formula: see text], the interacting-particle creation is important mainly as a source of photons even in conformally flat universes.
EFFECTS OF ELECTRIC POLARIZABILITY OF NUCLEI IN LOW-ENERGY COLLISIONS AND ACTION RADIUS OF THE POLARIZATION POTENTIAL
Authors: PUPYSHEV V. V. , SOLOVTSOVA O. P.
Published: November 2004

Recent works devoted to investigating the role of electric polarizability of nuclei in elastic and nucleosynthesis reactions are critically and constructively reviewed, in order to formulate some problems of the low-energy potential scattering theory. Possible methods for solving these problems are outlined. One of the problems, a correct definition of the range of action of the polarization potential, is discussed in detail. An intuitively clear conception of this radius — the lower bound of the distance range, where the polarization potential may be replaced by identical zero — is used as a starting point. The fact that this bound should be defined in each concrete case is demonstrated by the results obtained by exploration of the pp reaction and the S-wave π±d-elastic collisions. Also discussed are numerical and analytical methods for finding the action radius depending on the studied function, the accuracy required for its evaluation, the scattering energy and the sign of the Coulomb potential.
GENERALIZED GAUGE TRANSFORMATIONS AND HIDDEN SYMMETRY IN THE STANDARD MODEL
Authors: COQUEREAUX R. , HÄUßLING R. , PAPADOPOULOS N. A. , SCHECK F.
Published: November 2004

A recently proposed, new construction of the Standard Model based on the graded Lie algebra SU (2|1) is analyzed in some depth. The essential ingredient is an algebraic superconnection which incorporates both the gauge fields and the Higgs fields and whose curvature automatically leads to a spontaneously broken realization of the theory. The mechanism of hiding the original algebraic structure is unorthodox and is due to the specific, "noncommutative" realization of SU (2|1). The model is characterized by a constant background supercurvature which is invariant under arbitrary, constant SU (2|1) gauge transformations. This background field whose effect is analogous to the action of a constant magnetic field on a spherical atom, is traced back to the differential in the space of (super)matrices by means of which the supercurvature is constructed. The same background field is responsible for the fact that the ground state has no more than the U (1) e.m. symmetry of electromagnetism, the SU (2)L × U (1) symmetry of the Standard Model being recovered only after "backshifting" the Higgs fields. Thus, the Higgs mechanism receives a new and geometrical interpretation.
A SIMULTANEOUS ANALYSIS FOR THE ΔI = 1/2 RULE, DIRECT CP VIOLATION, $K^0 -\bar K^0$ AND $B^0 -\bar B^0$ MIXINGS
Authors: WU Y. L.
Published: November 2004

To have a consistent picture, a simultaneous analysis for the K → ππ isospin amplitudes A0 and A2, the ΔI = 1/2 rule, CP-violating ε′/ε, and [Formula: see text] and [Formula: see text] mixings within the standard model is made by employing the recent reanalyzed values of the parameters and relating the penguin matrix elements involved in the K → ππ decays to the known matrix elements of the ΔI = 1/2 operator (Q2 − Q1) and ΔI = 3/2 operator (Q2 + 2Q1). The allowed values for all the relevant quantities are calculated in detail. A general bound for top quark mass mt, CP phase δ and ε′/ε is found: for δ in the second quadrant, 84 GeV ≤ mt ≤ 250 GeV , δ ≤ 173° and 1 × 10−4 < ε′/ε ≤ 1 × 10−2; for δ in the first quadrant, 126 GeV ≤ mt ≤ 664 GeV , δ ≥ 11º and 1 × 10−3 < ε′/ε ≤ 1 × 10−2 as mt ≤ 260 GeV . Taking the plausible central values of the parameters — |Vcb| = 0.041, |Vub|/|Vcb| = 0.12, BK = 0.75, [Formula: see text], xB = 0.70, ms = (100 ~ 125) MeV and Λ QCD = (200 ~ 300) MeV — as a "standard" set, we then obtain from the simultaneous analysis a consistent prediction: A0 = (3.24 ± 0.70) × 10−7, A2 = (0.145 ± 0.007) × 10−7, ω = A2/A0 = 0.046 ± 0.007 and mt ≃ 142 GeV , δ ≃ 152°, ε′/ε ≃ (2.5 ± 1.0) × 10−3. The possible implications for the experiments are also discussed.
A MATRIX MODEL FOR THE CLASSICAL NONLINEAR SCHRÖDINGER EQUATION
Authors: CHEKHOV L.
Published: November 2004

The effective scalar theory is constructed for the nonlinear Schrödinger (NS) matrix equation, which gives us the tool for investigating the two-point correlator and the partition function for some (classical) NS-like systems. The spatial dependence of the correlator coincides with the free correlator in all quantization schemes. For the classical NS system the effective two-matrix model is found (throughout this paper both the model with compactified space variables x ∈ S1 and the model corresponding to noncompactified x ∈ ℝ are implied).
INFINITE QUANTUM GROUP SYMMETRY OF FIELDS IN MASSIVE 2D QUANTUM FIELD THEORY
Authors: LECLAIR ANDRÉ , SMIRNOV F. A.
Published: November 2004

Starting from a given S-matrix of an integrable quantum field theory in 1 + 1 dimensions, and knowledge of its on-shell quantum group symmetries, we describe how to extend the symmetry to the space of fields. This is accomplished by introducing an adjoint action of the symmetry generators on fields, and specifying the form factors of descendents. The braiding relations of quantum field multiplets is shown to be given by the universal ℛ-matrix. We develop in some detail the case of infinite-dimensional Yangian symmetry. We show that the quantum double of the Yangian is a Hopf algebra deformation of a level zero Kac–Moody algebra that preserves its finite-dimensional Lie subalgebra. The fields form infinite-dimensional Verma module representations; in particular, the energy–momentum tensor and isotopic current are in the same multiplet.
MASS AND ENERGY-MOMENTUM TENSOR OF QUANTUM STRINGS IN GRAVITATIONAL SHOCK-WAVES
Authors: DE VEGA H. J. , SANCHEZ N.
Published: November 2004

We investigate at the quantum level the nonlinear transformation relating the string operators (zero modes and oscillators) and Fock space states before and after the collision with gravitational shock waves. This throws light on the rôle of the space–time geometry in this problem. We do all the treatment for a general shock wave space–time of any localized source. We compute the exact expectation values of the total number (N) and mass ( M 2) operators and show that they are finite, which generalize our previous results in the Aichelburg–Sexl geometry. We study the energy-momentum tensor of the string and compute the exact expectation values of all its components. We analyze vacuum polarization and quadratic fluctuations. All these physical magnitudes are finite. We express all of them in terms of exact integral representations in which the role of the real pole singularities characteristic of the tree level string spectrum (real mass resonances) are clearly exhibited. The presence of such poles is not at all related to the structure of the space–time geometry (which may or may not be singular).
SUPERCONFORMAL CONSTRUCTIONS ON TWO-DIMENSIONAL SIMPLICIAL COMPLEXES
Authors: HALPERN M. B. , OBERS N. A.
Published: November 2004

The superconformal master equation contains a large set of solvable fermionic constructions which live on an infinite class of 2-dimensional simplicial complexes. All the constructions have rational central charge, and irrational conformal weights are expected in the generic construction.
THE CHERN–SIMONS MODEL WITH BOUNDARY: A COHOMOLOGICAL APPROACH
Authors: BLASI A. , COLLINA R.
Published: November 2004

We consider a Chern–Simons model in the Landau gauge and introduce, following Symanzik ideas, a plane boundary which modifies the propagators. The BRS symmetry, restored at the classical level by a suitable choice of boundary counterterms becomes anomalous due to the lower dimensionality boundary breakings. The anomaly is recognized as the central charge of an algebra of conserved chiral currents defined on the boundary itself.
A FRESH LOOK AT ϕ − ω MIXING
Authors: ACHASOV N. N. , KOZHEVNIKOV A. A. , DUBROVIN M. S. , IVANCHENKO V. N. , PAKHTUSOVA E. V.
Published: November 2004

An unprejudiced analysis is made of the possibility of different theoretical descriptions of the decays ϕ → ρπ → π+π−π0 and ϕ → πγ, taking into account both the ϕ − ω mixing and the direct decays ϕ → ρπ and ϕ → πγ. For this purpose the data from the Neutral Detector on the reactions e+e− → π+π−π0, πγ, KLKS in the interval [Formula: see text] are used. Experimental data are shown not to permit one to answer the question: What is the origin of the decay ϕ → ρπ (πγ)? This decay can be almost completely caused either by the ϕ − ω mixing or by the direct decay ϕ → ρπ (ϕ → πγ). Intermediate cases are certainly possible. It is shown that to elucidate the situation at least an order of magnitude improvement of accuracy is required. Possibilities of studying this problem on the collider VEPP-2M and ϕ factories are discussed.
RANDOM SURFACES AND THE LIOUVILLE THEORY
Authors: KITAZAWA Y.
Published: November 2004

We review the physical properties of random surfaces from the view point of the continuum Liouville theory. We shall summarize physical motivations of this subject and the field-theoretic treatment of the random surfaces. In the case of subcritical strings propagating in less than two dimensions, a complete understanding has been obtained recently through matrix models. We discuss the Liouville theory understanding of these results by studying the correlation functions. We also discuss promising avenues of further investigations such as black holes in 2-dimensional gravity and 3- and 4-dimensional string theory which may be relevant to Ising 3 and QCD 4.
BOOTSTRAP TREES AND CONSISTENT S MATRICES
Authors: KOUBEK A. , MUSSARDO G. , TATEO R.
Published: November 2004

We analyze the tree structure arising from the recursive bootstrap equations, given the S matrix of the lightest particle. When S11 contains only one singularity, among all possible bootstrap systems, the only ones which give rise to a consistent set of S matrices coincide with those of sine–Gordon breathers at the reduction point ξ = 2π/(2n + 1). We also present our investigation of bootstrap systems defined by an S11 with a higher number of singularities. The only consistent examples we found belong to the set of minimal S matrices corresponding to Dynkin diagrams.
AN INVESTIGATION OF THE ${\mathscr R}^2$ GRAVITY, WITH RESPECT TO THE SYMMETRY OF A MASSLESS POINTLIKE PARTICLE
Authors: TOLKSDORF JÜRGEN
Published: November 2004

We show that the vacuum [Formula: see text] theory has no nontrivial solution admitting the same symmetry as the massless pointlike particle in flat space–time. This is interpreted as a special kind of "gravitational anomaly." The "conformal" part of the theory, however, is anomaly-free and admits an entire class of these vacuum solutions.

If we use an electromagnetic field as the source of these solutions it has to be unpolarized.
PREDICTIONS OF THE TOP-MODE STANDARD MODEL AT THE TWO-LOOP LEVEL
Authors: LAVOURA L.
Published: November 2004

I find increases in both masses of between 5 and 20 GeV, depending on the scale Λ at which the top-quark Yukawa coupling is assumed to diverge. These results are relevant to the predictions of the top-mode standard model.
DISCRETE "STRINGS" AND GAUGE MODEL OF THREE CONFINED RELATIVISTIC PARTICLES
Authors: FILIPPOV A. T. , GANGOPADHYAY D. , ISAEV A. P.
Published: November 2004

An approach to quantizing discrete gauge models resembling bosonic strings in the Hamiltonian formulation is described. The case of three particles endowed with chiral structure and incorporating the symmetry T1 ⊗ Sl (2, R)_ ⊗ Sl (2, R)_ is analyzed both in the path-integral and operator formulations. The propagator, spectrum, vacuum state and Regge trajectories are determined. The Regge trajectories are linearly rising and the spectrum is similar to one for discretized bosonic strings in space–time dimensions D ≥ 4. Possible applications to both nonperturbative string theory and bound states of relativistic quarks are outlined.
LIMITS ON THE MASS OF LIGHT (PSEUDO)SCALAR PARTICLES FROM BETHE-HEITLER e+e− and μ+μ− PAIR PRODUCTION IN A PROTON-IRON BEAM DUMP EXPERIMENT
Authors: BLÜMLEIN J. , BRUNNER J. , GRABOSCH H.J. , LANIUS P. , NOWAK S. , RETHFELDT C. , RYSECK H.E. , WALTER M. , KISS D. , JAKI Z. , BARABASH L.S. , BARANOV S.A. , BATUSOV Y.A. , BUNYATOV S.A. , DENISOV O.Y. , GORBUNOV N.V. , KAREV A.G. , KASARINOV M.Y. , KLIMOV O.L. , KUZNETSOV O.M. , LADYGIN E.A. , LYUKOV V.V. , MOJSENZ P.V. , OBUDOVSKI V.P. , PRAKHOV S.N. , SNYATKOV V.I. , ANYKEYEV V.B. , BAMBUROV N.S. , BORISOV A.A. , BOZHKO N.I. , BUGORSKY A.P. , CHERNISHENKO S.K. , CHUKIN G.L. , FAKHRUTDINOV R.M. , GALJAEV N.A. , GORYACHEV V.N. , KIRSANOV M.M. , KOZHIN A.S. , KRAVTSOV V.I. , KULIKOV A.V. , LIPAJEV V.V. , MUKHIN A.I. , MUKHIN S.A. , RYCHENKOV V.N. , SALOMATIN Y.I. , SAPUNOV Y.M. , SENKO V.A. , SHESTERMANOV K.E. , SPIRIDONOV A.A. , SYTIN A.N. , SYTNIK V.V. , TUMAKOV V.A. , VOVENKO A.S. , ZHIGUNOV V.P. , ZUDIN Y.A.
Published: November 2004

A search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton-iron beam dump experiment via the Bethe-Heitler process. No positive signal was observed. Limits are derived on the masses of these particles in the framework of the Standard Model and its minimal supersymmetric extension (MSSM) comparing the experimental results with expectations for Bethe-Heitler e+e− and μ+μ− pair production. The Higgs particle of the SU2L×U1 Standard Theory is excluded for masses in the range mH<0.9 MeV at 95% CL. Limits on light Higgs particles of the MSSM and Peccei-Quinn like axions are derived.
THE ASYMPTOTICS OF THE CORRELATION FUNCTIONS IN (1+1)d QUANTUM FIELD THEORY FROM FINITE SIZE EFFECTS IN CONFORMAL THEORIES
Authors: MIRONOV A. , ZABRODIN A.
Published: November 2004

Using the finite-size effects, the scaling dimensions and correlation functions of the main operators in continuous and lattice models of 1d spinless Bose-gas with pairwise interaction of rather general form are obtained. The long-wave properties of these systems can be described by the Gaussian model with central charge c=1. The disorder operators of the extended Gaussian model are found to correspond to some nonlocal operators in the XXZ Heisenberg antiferromagnet. This same approach is applicable to fermionic systems. Scaling dimensions of operators and correlation functions in the systems of interacting Fermi-particles are obtained. We present a universal treatment for 1d systems of different kinds which is independent of the exact integrability and which gives universal expressions for critical exponents through the thermodynamic characteristics of the system.
OBSERVATION OF CIRCULAR–METASTABLE DOUBLY EXCITED STATES OF BARIUM
Authors: CHEN L. , BOLZINGER T. , CHERET M. , ROUSSEL F. , SPIESS G. , GROSS M. , HARE J.
Published: November 2004

We report the observation of unusual doubly excited states of barium: Ba (5dj, 21c). One of the valence electrons of Ba is prepared in an oriented circular Rydberg state (n = 21, l = m = 20, denoted 21c) by the adiabatic crossed-fields method. The other electron is excited to a 6pj state which decays radiatively to a 5dj metastable level. The measured autoionization lifetime of Ba (5d5/2, 21c) is T ~ 1 μ s , whereas for Ba (5d3/2, 21c), τ is estimated to be longer than 400 μs. This very large difference of lifetimes between the fine-structure states of the inner electron has been analysed.
THE SURREY ATTENTIVE ROBOT VISION SYSTEM
Authors: PRETLOVE J.R.G. , PARKER G.A.
Published: November 2004

This paper presents the design and development of a real-time eye-in-hand stereo-vision system to aid robot guidance in a manufacturing environment. The stereo vision head comprises a novel camera arrangement with servo-vergence, focus, and aperture that continuously provides high-quality images to a dedicated image processing system and parallel processing array. The stereo head has four degrees of freedom but it relies on the robot end-effector for all remaining movement. This provides the robot with exploratory sensing abilities allowing it to undertake a wider variety of less constrained tasks. Unlike other stereo vision research heads, the overriding factor in the Surrey head has been a truly integrated engineering approach in an attempt to solve an extremely complex problem. The head is low cost, low weight, employs state-of-the-art motor technology, is highly controllable and occupies a small-sized envelope. Its intended applications include high-accuracy metrology, 3-D path following, object recognition and tracking, parts manipulation and component inspection for the manufacturing industry.
SIMULATION AND EXPECTATION IN SENSOR-BASED SYSTEMS
Authors: ROTH YUVAL , JAIN RAMESH
Published: November 2004

Simulations have traditionally been used as off-line tools for examining process models and experimenting with system models for which it would have been either impossible or too dangerous, expensive, or time-consuming, to perform with physical systems. We propose a novel way of regarding simulations as part of both the development and the working phases of systems. In our approach simulation is used within the processing and control loop of the system to provide sensor and state expectations. This minimizes the inverse sensory data analysis and model maintenance problems. We refer to this mode of operation as the verification mode, in contrast to the traditional discovery mode.

In order to provide simulations and planning that are intertwined with the control of a physical system, temporal issues have to be considered. By limiting the focus of the system to small portions of complex models which are temporarily relevant to the system’s operation, the system is able to maintain its models and respond faster. For this we employ the Context-based Caching (CbC) mechanism within our Mobile Platform Control and Simulation Program (MOSIM). CbC is a knowledge management technique which maintains large knowledge bases by making the necessary information available at the right time.
FORMAL TECHNIQUES IN THE DEVELOPMENT OF BLACKBOARD SYSTEMS
Authors: CRAIG IAIN D.
Published: November 2004

In a recent book, the author presented a mathematical specification of a blackboard system shell. The exercise suggested a method for developing blackboard systems with the aid of formal methods. This paper describes a formal method for the development of blackboard systems. The method is based, in part, on an informal one. Apart from the difference in emphasis (formal rather than informal), the new approach rests upon a formal definition of the architecture. The essential idea is that the mapping between the formal model of the problem domain (which is intended to be similar to the formal models proposed by, for example, Hayes) and the blackboard shell should be supported by formal proofs of correctness in a way identical to formal software engineering.

We present an informal method for constructing blackboard systems. The informal method forms the basis of the formal method whose initial stages are then described. We outline the formal treatment of control and suggest the use of temporal logic as a tool for reasoning about control. The paper ends with a review of the method.
A PROBABILISTIC STROKE-BASED VITERBI ALGORITHM FOR HANDWRITTEN CHINESE CHARACTERS RECOGNITION
Authors: HSIEH CHEN-CHUNG , LEE HSI-JIAN
Published: November 2004

This paper proposes a probabilistic approach to recognize handwritten Chinese characters. According to the stroke writing sequence, strokes and interleaved stroke relations are built manually as a 1-D string, called an on-line model, to describe a Chinese character. In an input character, strokes are first extracted by a tree searching method. The recognition problem is then formulated as an optimization matching problem in a multistage directed graph, where the number of stages is the length of the modelled stroke sequence. Nodes in a stage represent extracted strokes that have the same stroke type as defined in the on-line model and the link between two neighboring nodes corresponds to the relationship between the two extracted strokes. The probability that the extracted stroke belongs to the predefined stroke type is calculated from the stroke line segments, and the transition probability between two extracted strokes is the degree of satisfaction of the relationship defined in the on-line model. The Viterbi algorithm, which can handle stroke insertion, deletion, splitting, and merging, is applied to recover the sequence of strokes consisting of the unknown character. The similarity is defined to be the product of stroke probabilities and stroke transition probabilities in the stroke sequence. The unknown character is matched with all modelled characters and is recognized as the one with the highest similarity. Experiments with 540 characters uniformly selected from the database CCL/HCCR1 (250 variations/class) are conducted, and the recognition rate is about 92.8%, which proves the feasibility of the proposed recognition system.
M: AN APPROXIMATE REASONING SYSTEM
Authors: ZHAO QINPING , LI BO
Published: November 2004

A system of multivalued logical equations and its solution algorithm are put forward in this paper. Based on this work we generalize SLD-resolution into multivalued logic and establish the corresponding truth value calculus. As a result, M, an approximate reasoning system, is built. We present the language and inference rules of M. Furthermore, we analyse inconsistency of assignments to truth degrees and give the solving strategies of M.
METHODS FOR COMBINATION OF EVIDENCE IN FUNCTION-BASED 3-D OBJECT RECOGNITION
Authors: STARK LOUISE , HALL LAWRENCE O. , BOWYER KEVIN W.
Published: November 2004

Representation schemes traditionally used in model-based vision are contrasted with the “function-based” representation scheme. A system which utilizes function-based representation has been implemented and tested, using the object category “chair” for case study. Function-based description is used to recognize classes and identify subclasses of known categories of objects, even if the specific object has never been encountered previously. Interpretation of the functionality of an object is accomplished through qualitative reasoning about its 3-D shape. During the recognition process, evidence is gathered as to how well the functional requirements are satisfied by the input shape. An investigation of different types of operators used in the combination of the functional evidence has been made. Three pairs of conjunctive and disjunctive operators have been used in the recognition process of more than 100 object shapes. The results are compared and differences are discussed.
EXPERIMENTAL COMPARISON OF THE EFFECT OF ORDER IN RECURRENT NEURAL NETWORKS
Authors: MILLER CLIFFORD B. , GILES C. LEE
Published: November 2004

There has been much interest in increasing the computational power of neural networks. In addition there has been much interest in “designing” neural networks better suited to particular problems. Increasing the “order” of the connectivity of a neural network permits both. Though order has played a significant role in feedforward neural networks, its role in dynamically driven recurrent networks is still being understood. This work explores the effect of order in learning grammars. We present an experimental comparison of first order and second order recurrent neural networks, as applied to the task of grammatical inference. We show that for the small grammars studied these two neural net architectures have comparable learning and generalization power, and that both are reasonably capable of extracting the correct finite state automata for the language in question. However, for a larger randomly-generated ten-state grammar, second order networks significantly outperformed the first order networks, both in convergence time and generalization capability. We show that these networks learn faster the more neurons they have (our experiments used up to 10 hidden neurons), but that the solutions found by smaller networks are usually of better quality (in terms of generalization performance after training). Second order nets have the advantage that they converge more quickly to a solution and can find it more reliably than first order nets, but that the second order solutions tend to be of poorer quality than those of the first order if both architectures are trained to the same error tolerance. Despite this, second order nets can more successfully extract finite state machines using heuristic clustering techniques applied to the internal state representations. We speculate that this may be due to restrictions on the ability of first order architecture to fully make use of its internal state representation power and that this may have implications for the performance of the two architectures when scaled up to larger problems.
STRUCTURAL DESCRIPTION OF LINE IMAGES BY THE CROSS SECTION SEQUENCE GRAPH
Authors: SUZUKI TOSHIHIRO , MORI SHUNJI
Published: November 2004

In this paper, we propose the Cross Section Sequence Graph which describes line images in a simple and well structured form. It is composed of regular regions called cross section sequences and singular regions. A cross section sequence is a sequence of cross sections, each of which is constructed as a pair of boundary points almost perpendicular to the direction of the line. The sequence corresponds to a straight or curved line segment. The remaining regions are extracted as singular regions, each of which corresponds to an end point region, corner, branch, cross, and so on. The cross section sequence graph is useful for many kinds of feature extraction, especially for skeletonization since a singular region can be analyzed from adjacent regular regions. Experimental results show that the skeleton extracted from the cross section sequence graph is better than that of a pixel-wise skeletonization (thinning) in terms of both processing speed and the quality of the skeleton.
PARALLEL PATTERN COMPRESSION BY OCTAGONAL PROPAGATION
Authors: ARCELLI C. , BAJA G. SANNITI DI , KWOK P.C.K.
Published: November 2004

A 4-subiteration parallel thinning algorithm, based on 3×3 operations, is proposed. It is shown that by taking into account bidirectional compression in each subiteration, pixels belonging to a pair of successive contours, a 4-contour and an 8-contour, are removed from the pattern in every iteration. Therefore, contour pixel removal proceeds towards the inner part of the pattern according to the octagonal metric. This provides a resulting medial line which is centered in the pattern in a quasi-Euclidean sense and is less sensitive to pattern rotation. The performance of the algorithm is discussed and compared with that of some well-known parallel algorithms.
A PARALLEL THINNING ALGORITHM USING THE BOUNDING BOXES TECHNIQUES
Authors: UBEDA STÉPHANE
Published: November 2004

Thinning algorithms are widely used in pattern recognition. This processing stage is implemented on serial machines as well as on parallel machines. We can find two classes of thinning algorithms in the literature. The first class is composed of strongly sequential algorithms, based on contour tracing of the objects to be thinned. The second class is made of iterative processes in which fully parallel mask-based operators are used at each iteration.

The weakness of the contour tracing based methods is its strong dependence upon the original picture. Particularly, in the case of very complex pictures, this algorithm becomes inefficient.

The second thinning class of algorithms uses strongly regular operating processes. The general speed of those methods also depends upon the shapes to be thinned. The iteration number necessary to complete these iterative processes is proportional to the maximum thickness of the objects in the picture. The complexity of the contour of the objects does not influence the efficiency of the algorithm.

The goal of this paper is to keep the regularity of the second class of thinning processes, but to reduce the amount of standard parallel-operations. We use a partition of the original picture and we dynamically reduce the range of the full-parallel operator in its sub-picture.