bluuebunny/crossref_metadata_2025 huggingface dataset:
RELATION BETWEEN THE ALGEBRA OF CURRENTS AND THEIR DEFINITION IN CHIRAL GAUGE THEORIES
Authors: FOSCO C. , TRINCHERO R. C.
Published: November 2004

We consider anomalous commutators between the charge density and any component of the gauge current in chiral gauge theories. This is done using the BJL definition of commutators, and without quantizing the gauge field. We study the relation between the vacuum expectation value (VEV) of these commutators for the case of consistent and covariant gauge currents. We obtain a simple relation valid for any dimension and gauge group. This relation shows that the difference between the VEV's of the commutators for the consistent and covariant gauge currents depends only on the difference between the VEV's of the corresponding currents.
POISSON–LIE GROUPS AND CLASSICAL W-ALGEBRAS
Authors: FATEEV V. A. , LUKYANOV S. L.
Published: November 2004

This is the first part of a paper studying the quantum group structure of two-dimensional conformal field theory with additional symmetries. We discuss the properties of the Poisson structures possessing classical W-invariance. The Darboux variables for these Poisson structures are constructed.
RELATIVISTIC PARTICLES WITH FRACTIONAL SPIN AND STATISTICS
Authors: FORTE STEFANO
Published: November 2004

We develop the relativistic quantum mechanics of particles with fractional spin and statistics in 2 + 1 dimensions in the path-integral approach. We endow the elementary excitations of the theory with fractional spin through the coupling of the particle number current with a topological term. We work out the dynamics of the spin degrees of freedom, and display the relation between the spin action and the knot invariants of the paths contributing to the path integral. We show that the explicit spin-changing interaction can be traded for multivaluedness of the wave function, and we relate this to the representation theory of the Lorentz and Poincaré groups in 2 + 1 dimensions. We discuss the multiparticle dynamics and derive the spin–statistics theorem.
$B^0 - \bar{B}^0$ MIXING IN A MINIMAL DYNAMICALLY BREAKING MODEL WITH TOP QUARK CONDENSATION
Authors: KIMURA KUMIKO , KOKUBO SACHIKO , NITTA ATSUKO , SUGAMOTO AKIO
Published: November 2004

The [Formula: see text] mixing is studied through numerical estimation of box diagrams in a minimal dynamically breaking model with [Formula: see text] condensation. The calculation is performed in the bubble approximation in which the phenomenological introduction of the Kobayashi-Maskawa matrix is to be consistent with the gauge ivnariance. The value obtained for the mixing parameter is at most by a considerable percentage smaller than the usual standard model calculation at one loop.
ON THE COHERENCE CONDITION FOR RESONANT SPIN-FLAVOR PRECESSION OF MAJORANA SOLAR NEUTRINOS
Authors: HORVAT RAUL
Published: November 2004

One of the most attractive solutions to the solar-neutrino problem (including an anticorrelation of the solar-neutrino flux with sunspot activity) incorporates a Majorana neutrino having a flavor-changing transition moment as large as (0.1–1)×10−10 Bohr magnetons. This solution is compatible with all known laboratory, astrophysical and cosmological bounds. Here we show the consistency of the solution with the coherence condition for effective-mass eigenstates inside the sun.
CHAOS IN THE HERMITIAN ONE-MATRIX MODEL
Authors: SÉNÉCHAL DAVID
Published: November 2004

The recursion coefficients Ri, which appear in the orthogonal polynomial method of solution for the Hermitian one-matrix model, are determined numerically for values of N up to a thousand. For some cases a chaotic behavior appears in some range, preventing a smooth flow from odd to even multicrititical models. This behavior is studied both for single-well and multiwell potentials. For multiwell potentials, the coefficients Ri generically tend toward more than one function in the N→∞ limit, and this structure is analyzed for small i using the Gaussian approximation.
VIRASORO CONSTRAINTS ON THE MATRIX-MODEL PARTITION FUNCTION AND STRING FIELD THEORY
Authors: SEN ASHOKE
Published: November 2004

The one-matrix model at the kth multicritical point is known to describe the (2, 2k–1) minimal model coupled to gravity, and the partition function of this model is known to obey a set of Virasoro constraints generated by a set of differential operators Ln. Working at the tree level of string theory, and using the Feigin-Fuchs description of the (2, 2k–1) minimal model, we show that the Virasoro constraints generated by Li (0≤i≤k−2) can be identified with a set of gauge symmetries of the corresponding string field theory.
ANOMALIES AND EFFECTIVE ACTIONS IN TWO-DIMENSIONAL SUPERSPACE
Authors: DELDUC FRANÇOIS , GIERES FRANÇOIS
Published: November 2004

We derive a chirally split expression for the superdiffeomorphism anomaly in the two-dimensional superplane. The effective action from which this anomaly was obtained is related to the WZ-action associated with the superdiffeomorphism group. Furthermore, we show that the anomalous Ward identities generated by supercoordinate transformations encompass the wellknown OPE’s for the stress-energy supertensor. In conclusion, the extension to generic super Riemann surfaces is discussed.
INCLUSIVE PARTICLE SPECTRA FROM QCD CASCADES
Authors: DOKSHITZER YU. L. , KHOZE V.A. , TROYAN S.I.
Published: November 2004

New results in applications of the analytical perturbative approach to the description of particle distributions in QCD jets are presented. We study inclusive energy spectra of partons from QCD cascades truncated at different values of the cutoff parameter Q0, which can be used to model the energy distributions of massive hadrons in the framework of the local parton-hadron duality hypothesis. Results of straightforward numerical calculations of parton distributions which solve the MLLA evolution equations are compared to approximate formulas representing the spectra in terms of a few analytically calculated shape parameters.
THREE-D SINGLETONS AND 2-D C.F.T.
Authors: AR-RASHID A.M. HARUN , FRONSDAL C. , FLATO M.
Published: November 2004

Two-dimensional Wess-Zumino-Novikov-Witten theory is extended to three dimensions, where it becomes a scalar gauge theory of the singleton type. The three-dimensional formulation involves a scalar field valued in a compact group G, a Nakanishi-Lautrup field valued in Lie (G) and Faddeev-Popov ghosts. The physical sector, characterized by the vanishing of the Nakanishi-Lautrup field, coincides with the WZNW theory of the group G. Three-dimensional space-time structure involves a generalized metric, but only its boundary values are of consequence. An alternative formulation in terms of left and right movers (in three dimensions!) is also possible.
BERNSTEIN-GEL’FAND-GEL’FAND RESOLUTION OF W3 ALGEBRA IN THE LATTICE APPROACH
Authors: BOUGOURZI H.A. , KIKUCHI Y.
Published: November 2004

We describe the embedding structure of the Verma modules of the W3 algebra using the free field representation (FFR) in the lattice approach. This structure is expressed by a set of intertwining diagrams. In particular, we show how these diagrams can be used to achieve the Bernstein-Gel’fand-Gel’fand (BGG) resolution of the irreducible highest weight representation (IHWR) in terms of the Verma modules. As an application of prime importance, we show how the character of the W3 IHWR can be readily derived using the Rocha-Caridi procedure.
NEW EXCEPTIONAL $(A_1^{(1)})^{\oplus r} $ INVARIANTS AND THE ASSOCIATED GEPNER MODELS
Authors: FUCHS JÜRGEN , KLEMM ALBRECHT , SCHMIDT MICHAEL G. , VERSTEGEN DIRK
Published: November 2004

New modular invariant partition functions for tensor products of [Formula: see text] affine Lie algebras are presented. These exceptional modular invariants can be understood in terms of automorphisms of the fusion rules of the affine algebra or of its extensions. There are three isolated cases, as well as an infinite series of new invariants. As an application, the new modular invariants are employed to produce new Gepner type compactifications of the heterotic string.
PHYSICAL STATES AND SCALING PROPERTIES OF W GRAVITIES AND W STRINGS
Authors: DAS SUMIT R. , DHAR AVINASH , RAMA S. KALYANA
Published: November 2004

We discuss some physical aspects of W gravities and W strings. We identify global characteristics in W gravities (in addition to the usual Euler characteristic) and show how the dependence of the partition function on the various chemical potentials involves these quantities. We find the operators which create physical states in W3 and W4 gravities and discuss their relationship with screening operators. W strings are discussed in the framework of a natural way of coupling “matter” to W gravity, and the issues of extra dimensions and critical dimensions are clarified. We find a remarkable relationship between pure W gravities and ordinary gravity coupled to c<1 unitary minimal models.
THE AFFINE N = 4 YANG–MILLS THEORY
Authors: CADAVID A. C. , FINKELSTEIN R. J.
Published: November 2004

An affine field theory may be constructed by gauging an affine algebra. The momentum integrals of the affine N = 4 Yang–Mills theory are ultraviolet finite but diverge because the sum over states is infinite. If the affine symmetry is broken by postulating a nonvanishing vacuum expectation value for that component of the scalar field lying in the L0 direction, then the theory acquires a linear mass spectrum. This broken theory is ultraviolet finite too, but the mass spectrum is unbounded. If it is also postulated that the mass spectrum has an upper bound (say, the Planck mass), then the resulting theory appears to be altogether finite. The influence of the exotic states has been estimated and, according to the proposed scenario, is negligible below energies at which gravitational interactions become important. The final effective theory has the symmetry of a compact Lie algebra augmented by the operator L0.
STUDY OF HIGH ENERGY DENSITIES OVER EXTENDED NUCLEAR VOLUMES VIA NUCLEUS–NUCLEUS COLLISIONS AT THE CERN SPS
Authors: LAMARCHE FRANÇOIS , LEROY CLAUDE
Published: November 2004

Nucleus–nucleus collisions at very high energy are believed to create the conditions for the existence of a new state of matter, the so-called quark–gluon plasma. This possibility depends on the magnitude of the energy density really achieved during the collisions. Estimates of the energy density are model dependent and have been attempted according to various approaches: fire-ball model and Bjorken model. The understanding of the transverse energy flow measurements and of the stopping power helps to define a proper way to estimate the energy density beyond naive approaches. A space- and time-averaged energy density is shown to be a more reliable probe for the QGP search than is a naive estimate of the maximum energy density. The computation is performed within the framework of hydrodynamics. The data considered in this paper were obtained by experiments performed to study nucleus–nucleus collisions at the CERN Super Proton Synchrotron (CERN-SPS). The incident nuclei were accelerated at energies of 60 and 200 GeV/nucleon.
COLOR-SEXTET QUARK PRODUCTIONS AT HADRON COLLIDERS
Authors: TANAKA HIDEKAZU , WATANABE ISAMU
Published: November 2004

Production cross-sections of color-sextet quarks at hadron colliders are estimated in various energies and the results are compared with cross-sections of the conventional top quark productions. Particular attentions are paid for a model recently proposed in Ref. 2 in order to explain the dynamical mechanism of the electroweak symmetry breaking. The model may be tested at SSC and LHC if the sextet quarks dominantly decay semileptonically through effective fourfermion interactions, or if the sextet quarks have long enough lifetime to reach the detectors.
DERIVATION OF THE KLEIN–GORDON EQUATION FROM A GENERALIZED MARKOV PRINCIPLE
Authors: RAMANATHAN R.
Published: November 2004

The Klein–Gordon equation is derived from a generalized Markov principle in a five-dimensional space in which the Minkowski space is embedded as a subspace. Compactification of the parametric fifth dimension results in a nonlinear equation whose linearized version is the Klein–Gordon equation.
THE PERILS OF A 17 KeV NEUTRINO
Authors: GELMINI G. , NUSSINOV S. , PECCEI R. D.
Published: November 2004

Recent measurements of low Q-value beta decay spectra have again suggested the existence of a 17 KeV neutrino. Here we examine a large body of constraints, arising from astrophysics, cosmology, nuclear physics and elementary particle physics, on this particle. By comparing the derived bounds on its lifetime, decay modes and possible electromagnetic properties with a variety of model speculations on its nature, we conclude that such a particle is unlikely. Conversely, if such a neutrino were shown conclusively to exist, it would have profound implications for the nature of the symmetry breaking in the weak leptonic sector. It would most probably imply the existence of physical Goldstone bosons.
QUANTUM OSCILLATORS: APPLICATIONS IN STATISTICAL MECHANICS
Authors: NEŠKOVIĆ P. V. , UROŠEVIĆ B. V.
Published: November 2004

We consider a canonical ensemble of q oscillators. Using classical realization for q oscillator algebra,17 we calculate, for a small real q, the partition function and thermodynamic potentials F, E and S. We show that F reaches the minimum and E and S the maximum (as functions of the deformation parameter q) when q = 1 (for the classical oscillator). We argue about possible far-reaching consequences of this fact. As an application we obtain a first quantum correction to Planck's black body radiation law. We introduce the slightly deformed oscillator (SDO) model, which provides us with a significant amount of information about the system. When q = 1, our results are shown to coincide with classical results.
BOSONIC REALIZATION OF SU(3) PARAFERMION IRREDUCIBLE REPRESENTATION
Authors: WANG PEI , HU ZHAN-NING
Published: November 2004

A symmetrized bosonization for the SU(3) parafermion is given and extended to the case where parafermionic currents are defined on the root lattice. A vertex operator for the irreducible representation of parafermions and all of the screening operators are also found. In addition, the BRST cohomology and the character for SU(3) parafermions are discussed.
ON THE TWO-POINT APPROXIMATION TO THE EFFECTIVE CHIRAL ACTION FOR LARGE SOLITONS
Authors: ZUK J. A. , ADJALI I.
Published: November 2004

The two-point approximation to the effective chiral action with finite cut-off — as used to provide a low-energy soliton description of the nucleon — is studied in the limit of large soliton sizes, R. For some soliton profiles, the expectation that, in the large-R limit, the Casimir energy approaches a term linear in R with leading correction of order R−1 is not fulfilled. We classify these profiles and show that the two-point approximation can be used to elucidate the true behaviour in such cases. For the linear profile, the asymptotic curve is found to run parallel to the linear kinetic energy, but displaced by an analytically computable negative constant.
INFLATIONARY COSMOLOGY AND LARGE SCALE STRUCTURE OF THE UNIVERSE
Authors: PANCHAPAKESAN N. , SETHI SHIV K.
Published: November 2004

Scale-invariant (flat) fluctuation spectra are the most generic outcomes of inflation. However, current observations of large scale structure require more fluctuation power on large scales than flat spectra give. One such observation concerns the existence of large cosmological bubbles on the scales ~ (20–50) Mpc in the galaxy distribution. We attempt an explanation of these structures based on an inflationary model containing two scalar fields. One of these fields undergoes a first order phase transition, owing to the evolution of the other. We study the distribution of bubbles formed during the phase trnasition and show that for a wide range of choice of the free parameters in our model, a few bubbles can survive and grow to become the bubble structures observed at present.
LOW-ENERGY PREDICTIONS OF SUSY GUT’S: THE MINIMAL MODEL VERSUS THE FINITE MODEL
Authors: KAZAKOV D.I. , KONDRASHUK I.N.
Published: November 2004

We consider the low-energy predictions for sin2θW and τproton of SUSY GUT’s along the lines of Ref. 1. Special attention is paid to the dependence on the mass spectrum of superpartners and possible heavy inhabitants of the Great desert. The minimal and finite SUSY SU(5) models with light and heavy t squark and additional higgsino are considered. It is shown that modern precise LEP data are naturally reproduced within the finite SUSY SU(5) GUT with both light and heavy t squark and light higgsino with a reasonable SU(5) splitting.
THERMAL PROPERTIES OF PARASUPERSYMMETRIC OSCILLATOR
Authors: ITO IKUO , KON TADASHI
Published: November 2004

Parasupersymmetric oscillator model of one bosonic and one order p parafermionic degrees of freedom at finite temperature is investigated in the framework of Thermo Field Dynamics (TFD). The temperature dependent vacuum |O(β)> is constructed and the generator of thermal unitary transformation |O(β)>=e−iG(β)|O> is obtained. We also comment on a signal of the parasuper-symmetry breaking at finite temperature.
ACTION PRINCIPLE, VIRASORO STRUCTURE AND ANALYTICITY IN NONPERTURBATIVE TWO-DIMENSIONAL GRAVITY
Authors: YONEYA TAMIAKI
Published: November 2004

The consequences of symmetry properties of a previously proposed action principle which describes the theory space of two-dimensional gravity are investigated. The string equation corresponding to the double scaling limit of the one-matrix model with general polynomial potential is expressed as a bilinear equation for the τ function of the KP hierarchy. The Virasoro condition for the τ function is then shown to be a Ward-like identity derived from the string equation corresponding to a conformal symmetry of the action principle. The possibility of a Ginzburg-Landau type integral representation of the τ function as a version of noncritical closed string field theory in less-than-one-dimensional space-time is discussed. Finally, the role of analyticity with respect to the eigenvalue of the puncture operator in interpreting the action principle is emphasized.
WIGNER THEORY OF THE NAMBU STRING: (II) THE CLOSED STRING
Authors: COLOMO F. , LUSANNA L.
Published: November 2004

A set of relative variables for the closed string with P2>0 is found, which has Wigner covariance properties. They allow one to obtain global Lorentz-invariant abelianizations of the constraints, like for the open string, and then global Lorentz-invariant canonically conjugated gauge variables are found. But now there are two extra zero modes in the constraints and in the gauge variables, related to the gauge arbitrariness of the origin σ0 of the circle σ∈(−n, π) embedded in Minkowski space, σ↦xμ(σ). By means of the multitemporal approach a noncanonical redundant set of Dirac observables for the left and right modes is defined; they transform as spin-1 Wigner vectors and satisfy constraints of the same kind as in σ models. The quantization is not made, because a canonical basis of observables is still lacking, but the program to be followed to find them is just the same as the one delineated for the case of the open string.
THE CURRENT STATUS OF HIGH ENERGY ELASTIC SCATTERING
Authors: BLOCK MARTIN M. , KANG KYUNGSIK , WHITE ALAN R.
Published: November 2004

The recent total cross section, σtot, and ρ-value results from the Fermilab Tevatron Collider experiments,1,2 presented at the 4th “Blois” Workshop on Elastic and Diffractive Scattering, held at Elba in May 1991, provide a natural springboard from which to launch a focused review of the field.
CONFORMAL EDGE CURRENTS IN CHERN-SIMONS THEORIES
Authors: BALACHANDRAN A.P. , BIMONTE G. , GUPTA K.S. , STERN A.
Published: November 2004

We develop elementary canonical methods for the quantization of Abelian and non-Abelian Chern-Simons actions, using well-known ideas in gauge theories and quantum gravity. Our approach does not involve choice of gauge or clever manipulations of functional integrals. When the spatial slice is a disc, it yields Witten’s edge states carrying a representation of the Kac-Moody algebra. The canonical expressions for the generators of diffeomorphisms on the boundary of the disc are also found, and it is established that they are the Chern-Simons version of the Sugawara construction. This paper is a prelude to our future publications on edge states, sources, vertex operators, and their spin and statistics in 3D and 4D topological field theories.
THE STRING DIFFERENCE EQUATION OF THE D=1 MATRIX MODEL AND W1+∞ SYMMETRY OF THE KP HIERARCHY
Authors: AWADA M.A. , SIN S.J.
Published: November 2004

We give a connection between the D=1 matrix model and the generalized KP hierarchy. First, we find a difference equation satisfied by F, the Legendre transformation of the free energy of the D=1 matrix model on a circle of radius R. Then we show that it is a special case of the difference equation of the generalized KP hierarchy with its zero mode identified with the scaling variable of the D=1 string theory. We propose that the massive D=1 matrix model is described by the generalized KP hierarchy, which implies the manifest integrability of D=1 string theory. We also show that the (generalized) KP hierarchy has an underlying W1+∞ symmetry. By reduction, we prove that the generalized KdV hierarchy has a subalgebra of the above symmetry which again forms a W1+∞. We argue that there are no W constraints in D=1 string theory, which is in contrast to D<1 theories, where there are W1+∞ constraints.
DECAYS OF φ-MESON SUPPRESSED BY OZI AND G-PARITY ROLE OF MIXING AND OF DIRECT TRANSITIONS
Authors: ACHASOV N.N. , KOZHEVNIKOV A.A.
Published: November 2004

It is shown that the study of rare decays of φ-meson suppressed by both the OZI rule and G parity, on π+π−, ωπ0, ηπ+π− provide the possibility to elucidate the situation with the φ−ω and φ−ρ mixing. The role of mixing and the direct transitions is discussed in detail. The perspectives of studying the above decays on e+e− colliders with high luminosity in the vicinity of the φ-resonance (φ-factories) are considered.
PHASE HOLONOMY OF THE VACUUM IN THREE-DIMENSIONAL GAUGE THEORIES
Authors: LINK ROBERT
Published: November 2004

The phase two-form of Berry in the neighborhood of a degeneracy of the Fock vacuum of a semisimple, nonabelian, second-quantized, relativistic fermion-background gauge field Hamiltonian is shown to be that of the Dirac magnetic monopole—thus extending a result of Berry to field theory. The Dirac Hamiltonian for an SU(2) fermion on the two-sphere is solved in a particular two-parameter family of background instanton gauge potentials as an explicit illustrative example.
SYMMETRIC SPACE TWO-MATRIX MODELS
Authors: ANDERSON ARLEN
Published: November 2004

The radial form of the partition function of a two-matrix model is formally given in terms of a spherical function for matrices representing any Euclidean symmetric space. An explicit expression is obtained by constructing the spherical function by the method of intertwining. The reduction of two-matrix models based on Lie algebras is an elementary application. A model based on the rank one symmetric space isomorphic to RN is less trivial and is treated in detail. This model may be interpreted as an Ising model on a random branched polymer. It has the unusual feature that the maximum order of criticality is different in the planar and double-scaling limits.
EQUIVALENCE BETWEEN THE FOCK-SCHWINGER GAUGE AND THE FEYNMAN GAUGE
Authors: DELBOURGO R. , TRIYANTA
Published: November 2004

The principal attraction of the Fock-Schwinger (FS) gauge is that the gauge potentials are completely determined in terms of the electromagnetic fields by an inversion formula once the condition x·A=0 is fixed. We have reformulated the FS gauge propagator, first derived by Kummer and Weiser, in a more useful and manageable form and applied it to perturbation calculations in spinor and scalar QED and QCD. In that way we have been able to verify the on-mass-shell equivalence of these calculations to the covariant Feynman gauge.
POISSON BRACKET ALGEBRA FOR CHIRAL GROUP ELEMENTS IN THE WZNW MODEL
Authors: BIMONTE G. , SALOMONSON P. , SIMONI A. , STERN A.
Published: November 2004

We examine the Wess-Zumino-Novikov-Witten (WZNW) model on a circle and compute the Poisson bracket algebra for left- and right-moving chiral group elements. Our computations apply for arbitrary groups and arbitrary boundary conditions, the latter being characterized by the monodromy matrix. Unlike in previous treatments, the Poisson brackets do not require specifying a particular parametrization of the group valued fields in terms of angles spanning the group. We do however find it necessary to make a gauge choice, as the chiral group elements are not gauge invariant observables. (On the other hand, the quadratic form of the Poisson brackets may be defined independently of a gauge fixing.) Gauge invariant observables can be formed from the monodromy matrix and these observbles are seen to commute in the quantum theory.
UNITARY REPRESENTATIONS OF W INFINITY ALGEBRAS
Authors: ODAKE SATORU
Published: November 2004

We study the irreducible unitary highest weight representations, which are obtained from free field realizations, of W infinity algebras [Formula: see text] with central charges (2, 1, 3, 2M, N, 2M+N). The characters of these representations are computed.

We construct a new extended superalgebra [Formula: see text], whose bosonic sector is [Formula: see text]. Its representations obtained from a free field realization with central charge 2M+N, are classified into two classes: continuous series and discrete series. For the former there exists a supersymmetry, but for the latter a supersymmetry exists only for M=N.
GENERAL STUDY OF QUARK MASS MATRICES WITH FULL OFF-DIAGONAL MIXING
Authors: SHROCK ROBERT E.
Published: November 2004

We study an ansatz for the quark mass matrix in which all of the nondiagonal entries are nonzero, but which still allows the quark mixing angles to be calculated in terms of ratios of quark masses and certain phases. Analytic calculations of the orthogonal rotation matrices in the up and down quark sectors and the resultant observed quark mixing matrix are presented. Comparison with experimental data is given.
c=5/2 FREE FERMION MODEL OF WB2 ALGEBRA
Authors: AHN CHANGHYUN
Published: November 2004

We investigate the explicit construction of the WB2 algebra, which is closed and associative for all values of the central charge c, using the Jacobi identity and show the agreement with the results studied previously. Then we illustrate a realization of c=5/2 free fermion model, which is m→∞ limit of unitary minimal series, c(WB2)=5/2[1−12/(m+3)(m+4)] based on the cosets [Formula: see text] at level (1, m). We confirm by explicit computations that the bosonic currents in the WB2 algebra are indeed given by the Casimir operators of [Formula: see text].
EPSTEIN-FUNCTION ANALYSIS OF THE CASIMIR EFFECT AT FINITE TEMPERATURE FOR MASSIVE FIELDS
Authors: ELIZALDE E. , ROMEO A.
Published: November 2004

The Casimir free energy for a massive bosonic field subject to Dirichlet boundary conditions on hypercuboids of arbitrary dimensions is evaluated in the form of power and exponential expansions for the high- and low-temperature limits, respectively, with the aid of both homogeneous and inhomogeneous multidimensional Epstein zeta functions.
SPONTANEOUS SYMMETRY BREAKING IN N=2 SUPERGRAVITY WITH MATTER
Authors: ZINOVIEV YU. M.
Published: November 2004

New versions of the N=2 supergravity hidden sector have been constructed allowing for spontaneous symmetry breaking without a cosmological term and with two arbitrary scales—the partial super-Higgs effect in particular. On this basis, spontaneous symmetry breaking has been investigated in the models of N=2 supergravity with an arbitrary number of vector- and hypermultiplets. As has been shown, the possibility at achieving breaking without a cosmological term is connected with the presence of nilpotent combinations of compact and noncompact generators in an isometry group of a σ model.
REVIEW OF TAU LEPTON STUDIES AT LEP
Authors: RILES KEITH
Published: November 2004

In little more than two years of operation the four LEP experiments have produced a wealth of results on τ lepton production and decay at the Z0 resonance. Cross section and forward-backward charge asymmetry measurements agree well with Standard Model expectations and, along with similar measurements from hadronic and other leptonic Z0 decays, permit extraction of electroweak parameters such as sin2 θW and constrain the value of the top quark mass in the Standard Model. New measurements of the τ lifetime and of the branching ratios for inclusive and many exclusive decays equal or better the precision of previous measurements. Measurements from LEP also confirm nonzero values for the average τ polarization and for the forward/backward τ polarization asymmetry, providing independent determinations of electroweak parameters. In addition, searches have been carried out for new phenomena in tau production and decay, such as lepton flavor violation and CP violation, but so far no evidence for such effects has emerged.
THE EFFECTIVE LAGRANGIAN OF THREE DIMENSIONAL QUANTUM CHROMODYNAMICS
Authors: FERRETTI G. , RAJEEV S.G. , YANG Z.
Published: November 2004

We consider the low energy limit of three dimensional quantum chromodynamics (QCD) with an even number of flavors. We show that parity is not spontaneously broken, but the global (flavor) symmetry is spontaneously broken. The low energy effective Lagrangian is a nonlinear sigma model on the Grassmannian. Some Chern-Simons terms are necessary in the Lagrangian to realize the discrete symmetries correctly. We consider also another parametrization of the low energy sector which leads to a three dimensional analogue of the Wess-Zumino-Witten-Novikov model. Since three dimensional QCD is believed to be a model for quantum antiferromagnetism, our effective Lagrangian can describe their long wavelength excitations (spin waves).
CLEBSCH-GORDAN AND RACAH-WIGNER COEFFICIENTS FOR Uq(SU(1,1))
Authors: LISKOVA N. A. , KIRILLOV A. N.
Published: November 2004

The Clebsch-Gordan and Racah-Wigner coefficients for the positive (or negative) discrete series of irreducible representations for the noncompact form Uq(SU(1,1)) of the algebra Uq(sl(2)) are computed.
THE EDWARDS MODEL: THE GLASS TRANSITION
Authors: EDWARDS S.F.
Published: November 2004

The structure of the transport coefficients in the approach to the glass transition is characterized by an essential singularity in their behaviour as functions of the temperature, variously known as the Vogel-Fulcher or Dolittle or Williams-Landel-Ferry laws. This behaviour can be derived directly in certain simple models notably a glass of liquid crystal polymers where mean field theory may be applied. In this paper a new class of closed expressions for transport coefficients are derived and it is shown that they can be used to derive the Vogel-Fulcher law.
PARALLEL RECOGNITION OF HIGH DIMENSIONAL IMAGES
Authors: NIVAT M. , SAOUDI A.
Published: November 2004

We investigate the complexity of the recognition of images generated by a class of context-free image grammars. We show that the sequential time complexity of the recognition of an n × n image as generated by a context-free grammar is O(nM(n)), where M(n) is the time to multiply two boolean n × n matrices. The space complexity of this recognition is O(n3). Using a parallel random access machine (i.e. PRAM), the recognition can be done in O( log 2(n)) time with n7 processors or in O(n log 2(n)) time with n6 processors. We also introduce high dimensional context-free grammars and prove that their recognition problem is polylogarithmic.
DESIGN AND PERFORMANCE OF TRISH, A BINOCULAR ROBOT HEAD WITH TORSIONAL EYE MOVEMENTS
Authors: MILIOS EVANGELOS , JENKIN MICHAEL , TSOTSOS JOHN
Published: November 2004

We present the design of a controllable stereo vision head. TRISH (The Toronto IRIS Stereo Head) is a binocular camera mount, consisting of two fixed focal length color cameras with automatic gain control forming a verging stereo pair. TRISH is capable of version (rotation of the eyes about the vertical axis so as to maintain a constant disparity), vergence (rotation of each eye about the vertical axis so as to change the disparity), pan (rotation of the entire head about the vertical axis), and tilt (rotation of each eye about the horizontal axis). One novel characteristic of the design is that each camera can rotate about its own optical axis (torsion). Torsional movement makes it possible to minimize the vertical component of the two-dimensional search which is associated with stereo processing in verging stereo systems.
A LOW-COST ROBOT CAMERA HEAD
Authors: CHRISTENSEN HENRIK I.
Published: November 2004

Active vision involving the exploitation of controllable cameras and camera heads is an area which has received increased attention over the last few years. At LIA/AUC a binocular robot camera head has been constructed for use in geometric modelling and interpretation. In this manuscript the basic design of the head is outlined and a first prototype is described in some detail. Detailed specifications for the components used are provided together with a section on lessons learned from construction and initial use of this prototype.
A METHOD FOR PARALLEL SEARCH UNDER HIGHER-ORDER CONSTRAINTS
Authors: KOUTSOUGERAS CRIS , ISRAEL PEGGY
Published: November 2004

There is a relation between the old hill-climbing method and the optimization which is performed by neural nets. This view gives rise to a parallel search method which is presented in this paper. The search mechanism is guided by the optimization of a function which is inspired by the electrostatic field. It is also shown here that this mechanism can naturally accommodate higher-order constraints which the result of the search must satisfy. It is also shown how such constraints can be systematically accommodated by simply expanding the function whose optimization guides the search. This mechanism simulates a dynamic transformation of a cue in which constraints and observational background knowledge compete to influence the transformation.
ARTIFICIAL NEURAL NETWORK BASED CLASSIFICATION OF MAMMOGRAPHIC MICROCALCIFICATIONS USING IMAGE STRUCTURE FEATURES
Authors: CHITRE YATEEN , DHAWAN ATAM P. , MOSKOWITZ MYRON
Published: November 2004

Mammography associated with clinical breast examination and breast self-examination is the only effective and viable method for mass breast screening. Most of the minimal breast cancers are detected by the presence of microcalcifications. It is however difficult to distinguish between benign and malignant microcalcifications associated with breast cancer. Most of the techniques used in the computerized analysis of mammographic microcalcifications segment the digitized grey-level image into regions representing microcalcifications. Since mammographic images usually suffer from poorly defined microcalcification features, the extraction of microcalcification features based on segmentation process is not reliable and accurate. We present a second-order grey-level histogram based feature extraction approach which does not require the segmentation of microcalcifications into binary regions to extract features to be used in classification. The image structure features, computed from the second-order grey-level histogram statistics, are used for classification of microcalcifications. Several image structure features were computed for 100 cases of “difficult to diagnose” microcalcification cases with known biopsy results. These features were analyzed in a correlation study which provided a set of five best image structure features. A feedforward backpropagation neural network was used to classify mammographic microcalcifications using the image structure features. Four networks were trained for different combinations of training and test cases, and number of nodes in hidden layers. False Positive (FP) and True Positive (TP) rates for microcalcification classification were computed to compare the performance of the trained networks. The results of the neural network based classification were compared with those obtained using multivariate Baye’s classifiers, and the k-nearest neighbor classifier. The neural network yielded good results for classification of “difficult-to-diagnose” micro-calcifications into benign and malignant categories using the selected image structure features.
AUTOMATED DETECTION OF MAMMOGRAPHIC ASYMMETRY USING ANATOMICAL FEATURES
Authors: MILLER PETER , ASTLEY SUE
Published: November 2004

Breast asymmetry is an important radiological sign of cancer. This paper describes the first approach aiming to detect all types of asymmetry; previous asymmetry-based research has been focussed on the detection of mass lesions. The conventional approach is to search for brightness or texture differences between corresponding locations on left and right breast images. Due to the difficulty in accurately identifying corresponding locations, asymmetry cues generated in this way are insufficiently specific to be used as prompts for small and subtle abnormalities in a computer-aided diagnosis system. We have undertaken studies to discover more about the visual cues utilized by radiologists. As a result, we propose a new automatic method for detecting asymmetry based on the comparison of corresponding anatomical structures, identified by an automatic segmentation of breast tissue types. We describe methods for comparing the shape and brightness distribution of these regions, and we present promising results obtained by combining evidence for asymmetry.
BIFURCATION ANALYSIS OF CHUA'S CIRCUIT WITH APPLICATIONS FOR LOW-LEVEL VISUAL SENSING
Authors: ALTMAN EDWARD J.
Published: November 2004

Low level vision for feature detection, motion analysis, or image segmentation is typically performed in parallel and is computationally intensive. The dynamic nature of scenes and the requirements for real time processing place further demands upon visual sensing. Dynamical systems which mimic the complexity of natural scenes provide an alternative to traditional computer vision approaches. However the design of such systems and the synthesis of complex, nonlinear dynamical systems by the interactions of simpler, low order systems remains a critical problem.

One approach to this problem is to use the relative simplicity of Chua's circuit to provide a convenient model for the dynamics and bifurcation phenomena in more complex systems. In this paper the normal form is derived for Chua's circuit in which the piecewise-linear function is replaced by a cubic nonlinearity. A partial bifurcation analysis of the normal form equations is then used to show how Chua's system can be made to track the motion of low level image features through parameter variations in the bifurcation function.
CONTROLLING CHAOS IN CHUA'S CIRCUIT
Authors: JOHNSON G. A. , TIGNER T. E. , HUNT E. R.
Published: November 2004

The occasional proportional feedback (OPF) control technique has been successful in stabilizing periodic orbits in both periodically driven and autonomous systems undergoing chaotic behavior. By applying this technique to the well-known Chua's circuit, we are able to control a variety of periodic orbits including single-correction, low-period orbits and multiple-correction, high-period orbits. Also, by employing two control circuits, we are able to stabilize orbits that visit both regions of Chua's circuit's double-scroll attractor, applying corrections in each of these regions during a single orbit.
LYAPUNOV EXPONENTS FROM CHUA'S CIRCUIT
Authors: PARLITZ U.
Published: November 2004

The estimation of Lyapunov exponents from experimental data is demonstrated by means of a chaotic time series from Chua's circuit. The changes in the Lyapunov spectrum upon time reversal, the local thickness of the attractor, and the approximation errors of the locally linear fits are used as diagnostic tools to identify spurious Lyapunov exponents and to monitor the reliability of the results.
PIECEWISE-LINEAR ANALYSIS FOR CHUA'S CIRCUIT FAMILY, INCLUDING THE COMPUTATION OF LYAPUNOV EXPONENTS
Authors: BIEY MARIO , CHIALINA SILVANO , HASLER MARTIN , PREMOLI AMEDEO
Published: November 2004

A special purpose program has been developed to compute the time-domain solutions and the Lyapunov exponents for Chua's circuit family. Advantage has been taken of the piecewise-linear nature of the circuits and the small number of linear regions in order to obtain fast and accurate computations. Examples are given to illustrate the capabilities of the program, in particular, to illustrate the calculation of the Lyapunov exponents.
MODELLING AND SIMULATION OF CHUA'S CIRCUIT
Authors: LINDBERG ERIK
Published: November 2004

Experiments with modelling and simulation of Chua's circuit are presented in order to transfer a simple explanation of its behaviour from the wonderful fairy-tale world of mathematicians to the marvellous physical world of electronic engineers. It is demonstrated that the behaviour of the circuit is based on the interaction (superposition) of two different kinds of energy balance: (1) Chaotic behaviour based on the interaction of two unstable DC-states and (2) stable limit cycle behaviour based on the balance between the energy lost in the regions with mainly positive losses and the energy gained in the regions with mainly negative losses. Convergence problems observed in connection with simulation of the ideal piecewise-linear model are solved by means of a smooth continuous model of the nonlinear element based on the ideal operational amplifier model instead of a polynomial approximation. The preliminary results are presented. The NAP2 program made by the late Thomas Rübner-Petersen has been used for the simulations.
DRY TURBULENCE FROM A TIME-DELAYED CHUA'S CIRCUIT
Authors: SHARKOVSKY A. N. , MAISTRENKO YU. , DEREGEL PH. , CHUA L. O.
Published: November 2004

In this paper, we consider an infinite-dimensional extension of Chua's circuit (Fig. 1) obtained by replacing the left portion of the circuit composed of the capacitance C2 and the inductance L by a lossless transmission line as shown in Fig. 2. As we shall see, if the remaining capacitance C1 is equal to zero, the dynamics of this so-called time-delayed Chua's circuit can be reduced to that of a scalar nonlinear difference equation. After deriving the corresponding 1-D map, it will be possible to determine without any approximation the analytical equation of the stability boundaries of cycles of every period n. Since the stability region is nonempty for each n, this proves rigorously that the time-delayed Chua's circuit exhibits the "period-adding" phenomenon where every two consecutive cycles are separated by a chaotic region.
AREA OPTIMIZATION OF SPIRAL FLOORPLANS
Authors: CHEN CHENG-HSI , TOLLIS IOANNIS G.
Published: November 2004

Floorplan design is the first stage of VLSI layout design and perhaps the most important one. We consider the problem of determining a set of implementations that minimize the total area of spiral floorplans. The best known technique needs O (n3 log n) time, O (n3) space and generates O (n3) possible implementations of the floor rectangle. In this paper, we present an improved algorithm for solving the area optimization problem of spiral floorplans. Our algorithm computes the optimal implementations of the basic rectangles in O (n2 log n) time and O (n2) space, where each of the five basic rectangles has n implementations. The improvements on both time and space are crucial when multi-level spiral floorplans are considered.
COMPUTATION OF RELATIVE ROTATIONS IN SPIRAL HORSESHOES
Authors: McROBIE F.A.
Published: November 2004

An algorithm is presented for computing the relative rotations of orbits in a suspension of Smale horseshoes consisting of n stripes in spiral configuration. Bifurcational precedence relations in the creation of such horseshoes may thus be more readily determined. An application to a driven oscillator is discussed.
SENSITIVITY TO INITIAL CONDITIONS IN SPATIALLY DISTRIBUTED SYSTEMS
Authors: NICOLIS C. , NICOLIS G. , WANG Q.
Published: November 2004

Sensitivity to initial conditions in systems of large spatial extension giving rise to spatiotemporal chaos is studied analytically on a simple model and is found to obey a subexponential law. Numerical simulations suggest that this behavior is likely to be typical of spatiotemporal chaos in large classes of spatially extended systems.
ON FEEDBACK CONTROL OF CHAOTIC NONLINEAR DYNAMIC SYSTEMS
Authors: CHEN GUANRONG , DONG XIAONING
Published: November 2004

In this paper, some interesting analysis and simulations on the control of chaotic dynamic systems using conventional feedback control strategies are presented. The typical discrete-time chaotic Lozi system is investigated in some detail. The trajectories of the chaotic Lozi system are controlled to its equilibrium points using conventional feedback controls. Analysis on the design of the feedback controllers and its computer simulations are included.
ON A CLASS OF FRACTAL MATRICES (I) EXCESS-MATRICES AND THEIR SELF-SIMILAR PROPERTIES
Authors: BARBÉ ANDRÉ M.
Published: November 2004

An infinite class of integer valued matrices of unbounded size and of arbitrary dimensions is presented here as a generalization of the so-called excess-matrix associated with a particular cellular automaton. These matrices are constructed through a recursive arithmetical procedure, and show an intricate fractal-like distribution of integers. The elements in these matrices have a number theoretical interpretation which is directly related to a proper number-base representation of the coordinates of the element. These excess-matrices exhibit numerical and symbolical self-similarities under agglomerating and decimating coarse-graining operations, and under so-called disguising transformations.
A CLASSICAL APPROACH TO CONTROLLING THE LORENZ EQUATIONS
Authors: HARTLEY TOM T. , MOSSAYEBI FARAMARZ
Published: November 2004

This paper presents a classical approach to controlling the Lorenz equations, a well known chaotic system. It is shown that proportional-plus-integral control using an easily measurable state variable gives both good stability and tracking properties well into the normally chaotic region. Here the input signal to the Lorenz equations is the applied heat via the Rayleigh number. This paper demonstrates that widely used classical control approaches can stabilize a chaotic system and have it track input signals in its usually chaotic regime.
BASIN EROSION IN THE TWIN-WELL DUFFING OSCILLATOR: TWO DISTINCT BIFURCATION SCENARIOS
Authors: LANSBURY A. N. , THOMPSON J. M. T. , STEWART H. B.
Published: November 2004

A study is made of the control-phase portraits encountered in the twin-well Duffing oscillator, concentrating on the loss of stability of attractors confined to a single well of the potential. This loss of stability may be understood by examining the bifurcations which precede a single-well attractor touching its basin boundary. Two distinct bifurcation scenarios are described in which the basin boundary develops a fractal structure. This fractal structure accompanies the development of a homoclinic tangency between the inset and outset of the saddle whose inset determines the separatrix action. In the first scenario described, this fractal structure, or chaotic saddle, grows due to a sequence of fractal–fractal basin implosions which are caused by the completion of Smale cycles or heteroclinic chains; the subharmonics involved occur in decreasing order, after the main homoclinic tangency. The second scenario focuses on the bifurcational events which necessarily prepare the creation of a chaotic saddle; the subharmonics involved appear in increasing order, before the main homoclinic event. Both basin erosion scenarios are consistent with a geometric model of the twin-well Duffing oscillator based on a three layer template; in the first scenario, the full three-layer template participates; while in the second scenario, only two layers, a standard horseshoe, play a role.