bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Tensile Residual Stress Mitigation in Alloy 22 Welds Due to Laser Peening
Authors: DeWald Adrian T. , Rankin Jon E. , Hill Michael R. , Lee Matthew J. , Chen Hao-Lin
Published: November 2004

This paper examines the effects of laser peening on Alloy 22 (UNS N06022), which is the proposed material for use as the outer layer on the spent-fuel nuclear waste canisters to be stored at Yucca Mountain. Stress corrosion cracking (SCC) is a primary concern in the design of these canisters because tensile residual stresses will be left behind by the closure weld. Alloy 22 is a nickel-based material that is particularly resistant to corrosion; however, there is a chance that stress corrosion cracking could develop given the right environmental conditions. Laser peening is an emerging surface treatment technology that has been identified as an effective tool for mitigating tensile redisual stresses in the storage canisters. The results of laser-peening experiments on Alloy 22 base material and a sample 33 mm thick double-V groove butt-weld made with gas tungsten arc welding (GTAW) are presented. Residual stress profiles were measured in Alloy 22 base material using the slitting method (also known as the crack-compliance method), and a full 2D map of longitudinal residual stress was measured in the sample welds using the contour method. Laser peening was found to produce compressive residual stress to a depth of 3.8 mm in 20 mm thick base material coupons. The depth of compressive residual stress was found to have a significant dependence on the number of peening layers and a slight dependence on the level of irradiance. Additionally, laser peening produced compressive residual stresses to a depth of 4.3 mm in the 33 mm thick weld at the center of the weld bead where high levels of tensile stress were initially present.
Effect of Geometry and Materials on Residual Stress Measurement in Thin Films by Using the Focused Ion Beam
Authors: Kang Ki-Ju , Darzens Severine , Choi Gee-Seob
Published: November 2004

Recently, a new method for residual stress measurement in thin films by using the focused ion beam (FIB) has been proposed by the authors. It is based on the combined capability of the FIB imaging system and of high-resolution strain mapping software (VIC-2D). A simple equation based on two-dimensional elasticity is used to evaluate the residual stress from the displacements due to introducing a slot. The slot length is assumed to be much larger than the slot width or depth. And the effect of the slot width was neglected. However, it is often hard, depending on film materials, to introduce a narrow and deep slot by FIB. In this work some practical issues regarding the slot geometry are addressed. Through two- and three-dimensional finite element analyses, it is explored how the slot length, width and measurement location affect the displacements which are the basic data for residual stress evaluation. As a result, the validity and limit of the equations based on two-dimensional elasticity are evaluated. Also, the effect of material dissimilarity between film and substrate is explored. Finally, examples for a diamond-like carbon film on glass substrate and an aluminum oxide film thermally grown upon an alloy are presented.
Modeling Cyclic Deformation of HSLA Steels Using Crystal Plasticity
Authors: Xie C. L. , Ghosh S. , Groeber M.
Published: November 2004

High strength low alloy (HSLA) steels, used in a wide variety of applications as structural components are subjected to cyclic loading during their service lives. Understanding the cyclic deformation behavior of HSLA steels is of importance, since it affects the fatigue life of components. This paper combines experiments with finite element based simulations to develop a crystal plasticity model for prediction of the cyclic deformation behavior of HSLA-50 steels. The experiments involve orientation imaging microscopy (OIM) for microstructural characterization and mechanical testing under uniaxial and stress–strain controlled cyclic loading. The computational models incorporate crystallographic orientation distributions from the OIM data. The crystal plasticity model for bcc materials uses a thermally activated energy theory for plastic flow, self and latent hardening, kinematic hardening, as well as yield point phenomena. Material parameters are calibrated from experiments using a genetic algorithm based minimization process. The computational model is validated with experiments on stress and strain controlled cyclic loading. The effect of grain orientation distributions and overall loading conditions on the evolution of microstructural stresses and strains are investigated.
A Slip-Based Model for Strength Evolution During Cyclic Loading
Authors: Turkmen H. S. , Miller M. P. , Dawson P. R. , Moosbrugger J. C.
Published: November 2004

Motivated by the strong dependence of strain-hardening processes on slip system activity, a slip system hardening formulation that explicitly employs accumulated slip system shear strains and net crystal shearing rates is introduced within a polycrystal plasticity modeling formulation for predicting material response during cyclic deformation. The model, which is a slight modification of the Voce hardening model commonly employed for large strain forming simulations, was employed to model the behavior of 304L stainless steel subjected to uniaxial and multiaxial nonproportional multiple-step experiments and multiaxial multiple-phase angle experiments. The model successfully captured the pseudosaturation response that is common during the multiple-step tests and captured many of the loop-shape and stress-level features of the multiple-phase angle experiments.
Measurement and Microstructural Evaluation of Creep-Induced Changes in Magnetic Properties of a 410 Stainless Steel
Authors: Polar A. , Indacochea J. E. , Wang M. L. , Singh V. , Lloyd G.
Published: November 2004

There is a compelling desire by power generating plants to continue running existing stations and components for several more years, despite many of them have surpassed their design service life. The idea is to avoid premature retirement, on the basis of the so-called design life, because actual useful life could often be well in excess of the design life. This can most readily be achieved by utilizing nondestructive monitoring methods to monitor the degradation of the microstructure, either when a station is down for maintenance or preferably when it is under operation. This study evaluates the use of quasi static hysteresis measurements as a possible procedure to evaluate creep in a 410 martensitic stainless steel, a material utilized in power plant components. The creep rupture tests were conducted at stresses of 100 and 200 MPa, temperatures of 500°C and 620°C, and the times varied between 48 and 120 hours. Following the creep tests all specimens were evaluated magnetically and then metallurgically by optical and scanning electron microscopy, x-ray diffraction (XRD) and by energy dispersive spectroscopy (EDS). The microstructural changes were compared with the magnetization changes. It was determined that the changes in the hysteresis curves were clearly detectable and correlated with the creep-induced damage.
Cage Instabilities in Cylindrical Roller Bearings
Authors: Ghaisas Niranjan , Wassgren Carl R. , Sadeghi Farshid
Published: November 2004

A six-degree-of-freedom model was developed and used to simulate the motion of all elements in a cylindrical roller bearing. Cage instability has been studied as a function of the roller-race and roller-cage pocket clearances for light-load and high-speed conditions. The effects of variation in inner race speed, misalignment, cage asymmetry, and varying size of one of the rollers have been investigated. In addition, three different roller profiles have been used to study their impact on cage dynamics. The results indicate that the cage exhibits stable motion for small values of roller-race and roller-cage pocket clearances. A rise in instability leads to discrete cage-race collisions with high force magnitudes. Race misalignment leads to a rise in instability for small roller-cage pocket clearances since skew control is provided by the sides of the cage pocket. One roller of larger size than the others causes inner race whirl and leads to stable cage motion for small roller-race clearances without any variation in roller-cage pocket clearance. Cage asymmetry and different roller profiles have a negligible impact on cage motion.
Wear-Rate Uncertainty Analysis
Authors: Schmitz Tony L. , Action Jason E. , Burris David L. , Ziegert John C. , Sawyer W. Gregory
Published: November 2004

Wear due to relative motion between component surfaces is one of the primary modes of failure for many engineered systems. Unfortunately, it is difficult to accurately predict component life due to wear as reported wear rates generally exhibit large scatter. This paper analyzes a reciprocating tribometer in an attempt to understand the instrument-related sources of the scatter in measured wear rates. To accomplish this, an uncertainty analysis is completed for wear-rate testing of a commercially available virgin polytetrafluoroethylene pin on 347 stainless steel counterface. It is found that, for the conditions selected in this study, the variance in the experimental data can be traced primarily to the experimental apparatus and procedure. Namely, the principal uncertainty sources were found to be associated with the sample mass measurement and volume determination.
A comparison of vowel normalization procedures for language variation research
Authors: Adank Patti , Smits Roel , van Hout Roeland
Published: November 2004

An evaluation of vowel normalization procedures for the purpose of studying language variation is presented. The procedures were compared on how effectively they (a) preserve phonemic information, (b) preserve information about the talker’s regional background (or sociolinguistic information), and (c) minimize anatomical/physiological variation in acoustic representations of vowels. Recordings were made for 80 female talkers and 80 male talkers of Dutch. These talkers were stratified according to their gender and regional background. The normalization procedures were applied to measurements of the fundamental frequency and the first three formant frequencies for a large set of vowel tokens. The normalization procedures were evaluated through statistical pattern analysis. The results show that normalization procedures that use information across multiple vowels (“vowel-extrinsic” information) to normalize a single vowel token performed better than those that include only information contained in the vowel token itself (“vowel-intrinsic” information). Furthermore, the results show that normalization procedures that operate on individual formants performed better than those that use information across multiple formants (e.g., “formant-extrinsic” F2-F1).
On the design of long T-shaped acoustic resonators
Authors: Li Deyu , Vipperman Jeffrey S.
Published: November 2004

In this work we present a more general mathematical model for the calculation of resonance frequencies for long, T-shaped acoustic resonators. The method is based upon wave propagation and, unlike previous theories, no constraints on the geometry of the resonator are imposed. In addition, a new end-correction model based upon Rayleigh’s end corrections is proposed and evaluated. The theory is used to develop a plane-wave multimodal-based design theory, which permits higher-order 1-dimensional modes of the T-shaped acoustic absorber to be used for absorbing high-frequency noise within enclosures. A series of experiments are conducted on round and square cross section resonators to validate the theory, evaluate the end correction models, and demonstrate design examples.
Modeling of nonlinear shear waves in soft solids
Authors: Zabolotskaya Evgenia A. , Hamilton Mark F. , Ilinskii Yurii A. , Meegan G. Douglas
Published: November 2004

An evolution equation for nonlinear shear waves in soft isotropic solids is derived using an expansion of the strain energy density that permits separation of compressibility and shear deformation. The advantage of this approach is that the coefficient of nonlinearity for shear waves depends on only three elastic constants, one each at second, third, and fourth order, and these coefficients have comparable numerical values. In contrast, previous formulations yield coefficients of nonlinearity that depend on elastic constants whose values may differ by many orders of magnitude because they account for effects of compressibility as well as shear. It is proposed that the present formulation is a more natural description of nonlinear shear waves in soft solids, and therefore it is especially applicable to biomaterials like soft tissues. Calculations are presented for harmonic generation and shock formation in both linearly and elliptically polarized shear waves.
Experimental study of the diffracted sound field around jagged edge noise barriers
Authors: Menounou Penelope , Ho You Jeong
Published: November 2004

Noise barriers are commonly used to protect communities from transportation noise. In the present study, three types of barriers, modeled as half planes, have been tested in the laboratory: a conventional rigid barrier with a straight top edge, a straight top edge barrier covered with sound absorbing material, and a rigid barrier with a jagged top edge. Measurements were taken not just behind the barriers, but around them on a plane perpendicular to their top edge. Measured signals were compared against theoretical predictions contributing to further validation of a theoretical model. The sound absorbing material was found to affect the diffracted field more in the front of the barrier than behind it. The diffracted field in front of a jagged edge barrier, similar to the field behind it, was found to depend on the geometry of the edge in the area where the shortest diffraction path intersects the edge profile. Last, the performance of the three barriers was compared with one another in all areas around the barrier. It was found that the jagged edge barrier provides shielding similar to the sound absorbing barrier but at a fraction of the cost.
A resonant, self-pumped, circulating thermoacoustic heat exchanger
Authors: Swift G. W. , Backhaus S.
Published: November 2004

An asymmetrical constriction in a pipe functions as an imperfect gas diode for acoustic oscillations in the pipe. One or more gas diodes in a loop of pipe create substantial mean flow, approximately proportional to the amplitude of the oscillations. Measurements of wave shape, time-averaged pressure distribution, mass flow, and acoustic power dissipation are presented for a two-diode loop. Analysis of the phenomena is complicated because both the mean flow and the acoustic flow are turbulent and each affects the other significantly. The quasi-steady approximation yields results in rough agreement with the measurements. Acoustically driven heat-transfer loops based on these phenomena may provide useful heat transfer external to thermoacoustic and Stirling engines and refrigerators.
The effect of recording and analysis bandwidth on acoustic identification of delphinid species
Authors: Oswald Julie N. , Rankin Shannon , Barlow Jay
Published: November 2004

Because many cetacean species produce characteristic calls that propagate well under water, acoustic techniques can be used to detect and identify them. The ability to identify cetaceans to species using acoustic methods varies and may be affected by recording and analysis bandwidth. To examine the effect of bandwidth on species identification, whistles were recorded from four delphinid species (Delphinus delphis, Stenella attenuata, S. coeruleoalba, and S. longirostris) in the eastern tropical Pacific ocean. Four spectrograms, each with a different upper frequency limit (20, 24, 30, and 40 kHz), were created for each whistle (n=484). Eight variables (beginning, ending, minimum, and maximum frequency; duration; number of inflection points; number of steps; and presence/absence of harmonics) were measured from the fundamental frequency of each whistle. The whistle repertoires of all four species contained fundamental frequencies extending above 20 kHz. Overall correct classification using discriminant function analysis ranged from 30% for the 20-kHz upper frequency limit data to 37% for the 40-kHz upper frequency limit data. For the four species included in this study, an upper bandwidth limit of at least 24 kHz is required for an accurate representation of fundamental whistle contours.
Acoustic-phonetic correlates of talker intelligibility for adults and children
Authors: Hazan Valerie , Markham Duncan
Published: November 2004

This study investigated acoustic-phonetic correlates of intelligibility for adult and child talkers, and whether the relative intelligibility of different talkers was dependent on listener characteristics. In experiment 1, word intelligibility was measured for 45 talkers (18 women, 15 men, 6 boys, 6 girls) from a homogeneous accent group. The material consisted of 124 words familiar to 7-year-olds that adequately covered all frequent consonant confusions; stimuli were presented to 135 adult and child listeners in low-level background noise. Seven-to-eight-year-old listeners made significantly more errors than 12-year-olds or adults, but the relative intelligibility of individual talkers was highly consistent across groups. In experiment 2, listener ratings on a number of voice dimensions were obtained for the adults talkers identified in experiment 1 as having the highest and lowest intelligibility. Intelligibility was significantly correlated with subjective dimensions reflecting articulation, voice dynamics, and general quality. Finally, in experiment 3, measures of fundamental frequency, long-term average spectrum, word duration, consonant–vowel intensity ratio, and vowel space size were obtained for all talkers. Overall, word intelligibility was significantly correlated with the total energy in the 1- to 3-kHz region and word duration; these measures predicted 61% of the variability in intelligibility. The fact that the relative intelligibility of individual talkers was remarkably consistent across listener age groups suggests that the acoustic-phonetic characteristics of a talker’s utterance are the primary factor in determining talker intelligibility. Although some acoustic-phonetic correlates of intelligibility were identified, variability in the profiles of the “best” talkers suggests that high intelligibility can be achieved through a combination of different acoustic-phonetic characteristics.
The comb waveform as an efficient method for wideband transducer measurements
Authors: Boober Walter H. , Lau Gorham G. , Benjamin Kim C. , Walsh Kenneth M.
Published: November 2004

An efficient acoustic calibration technique based on a uniformly weighted comb waveform is presented. The method takes advantage of the linear, time invariant nature of the measurement configuration and the comb’s wide bandwidth to capture all spectral components of interest for a device under test in a single ping. Measured results comparing single ping comb measurements with conventionally obtained tonal measurements are presented. The examples given illustrate the accuracy and utility of this technique for the calibration of broadband systems.
LOCALIZATION IN TWO-DIMENSIONAL SU(2) LATTICE GAUGE THEORY AND A NEW MULTIGRID METHOD
Authors: BÄKER M.
Published: November 2004

We show numerically that the lowest eigenmodes of the two-dimensional Laplace operator with SU(2) gauge couplings and periodic boundary conditions are strongly localized. A connection is drawn to the Anderson localization problem. A new multigrid algorithm, capable of dealing with these modes, shows no critical slowing down for this problem independent of the disorder.
N-BODY CLASSICAL SYSTEMS AND NEURAL NETWORKS ON A 3D SIMD MASSIVE PARALLEL PROCESSOR: APE100/QUADRICS
Authors: PAOLUCCI P.S.
Published: November 2004

A number of physical systems (e.g., N body Newtonian, Coulombian or Lennard-Jones systems) can be described by N2 interaction terms. Completely connected neural networks are characterised by the same kind of connections: Each neuron sends signals to all the other neurons via synapses. The APE100/Quadricsmassive parallel architecture, with processing power in excess of 100 Gigaflops and a central memory of 8 Gigabytes seems to have processing power and memory adequate to simulate systems formed by more than 1 billion synapses or interaction terms. On the other hand the processing nodes of APE100/Quadrics are organised in a tridimensional cubic lattice; each processing node has a direct communication path only toward the first neighboring nodes. Here we describe a convenient way to map systems with global connectivity onto the first-neighbors connectivity of the APE100/Quadrics architecture. Some numeric criteria, which are useful for matching SIMD tridimensional architectures with globally connected simulations, are introduced.
LATTICE BOLTZMANN APPROACH TO VISCOUS FLOWS BETWEEN PARALLEL PLATES
Authors: SZILÁGYI BÉLA , SUSAN-RESIGA ROMEO , SOFONEA VICTOR
Published: November 2004

Four different kinds of laminar flows between two parallel plates are investigated using the Lattice Boltzmann Method (LBM). The LBM accuracy is estimated in two cases using numerical fits of the parabolic velocity profiles and the kinetic energy decay curves, respectively. The error relative to the analytical kinematic viscosity values was found to be less than one percent in both cases. The LBM results for the unsteady development of the flow when one plate is brought suddenly at a constant velocity, are found in excellent agreement with the analytical solution. Because the classical Schlichting’s approximate solution for the entrance-region flow is not valid for small Reynolds numbers, a Finite Element Method solution was used in order to check the accuracy of the LBM results in this case.
AUXILIARY FIELDS AND THE SIGN PROBLEM
Authors: SAMSON J.H.
Published: November 2004

The auxiliary-field quantum Monte Carlo method is reviewed. The Hubbard-Stratonovich transformation converts an interacting Hamiltonian into a non-interacting Hamiltonian in a time-dependent stochastic field, allowing calculation of the resulting functional integral by Monte Carlo methods. The method is presented in a sufficiently general form to be applicable to any Hamiltonian with one- and two-body terms, with special reference to the Heisenberg model and one- and many-band Hubbard models. Many physical correlation functions can be related to correlation functions of the auxiliary field; general results are given here. Issues relating to the choice of auxiliary fields are addressed; operator product identities change the relative dimensionalities of the attractive and repulsive parts of the interaction. Frequently the integrand is not positive-definite, rendering numerical evaluation unstable. If the auxiliary field violates time-reversal invariance, the integrand is complex and this sign problem becomes a phase problem. The origin of this sign or phase is examined from a number of geometrical and other viewpoints and illustrated by simple examples: the phase problem by the spin (1/2) Heisenberg model, and the sign problem by the attractive SU(N) Hubbard model on a triangular molecule with negative hopping integrals. In the latter case, widely studied in the Jahn-Teller literature, the sign is due neither to fermions nor spin, but to frustration. This system is used to illustrate a number of suggested interpretations of the sign problem.
INTEGRATION OF SYMBOLIC COMPUTING IN ACCELERATOR CONTROL
Authors: ARRUAT M. , AUTIN B. , HEMELSOET G.H. , MARTINI M. , WILDNER E.
Published: November 2004

Modern symbolic computing programs address not only the manipulation of mathematical functions, but also process control. Symbolic computing can thus be a powerful tool for developing algorithmic engines that can be fully integrated in the controls environment and facilitates modular design of control systems. This technique has been applied to a special class of accelerator problems, namely the beam steering in transfer lines and accelerator rings in the CERN PS Complex. An optimizer for beam trajectories has first been developed off line then linked on line to process interface routines for prototyping. A beam optics program with a full graphics environment and symbolic functions was used to generate necessary information for the optimizer. An application program has then been written to integrate the system into the controls environment.
THE DEVELOPMENT OF AN OBJECT-ORIENTED SYSTEM WHICH INTEGRATES SIMULATION AND RECONSTRUCTION WITHIN A COMMON FRAMEWORK
Authors: FUCHS PAUL
Published: November 2004

A common problem for small experiments is that the design of the data acquisition, the simulation of the experiment and the reconstruction and analysis of real data is broken up into several disjoint development phases. Software development is necessary in all phases, yet continuity and an overall design strategy is lacking. This leads to duplication of software components and interface problems from one phase to the next and prohibits the generation of code which is reusable over the lifetime of many experiments. We address this problem within an object-oriented paradigm.
RENORMALIZATION GROUP SYMMETRY AND SOPHUS LIE GROUP ANALYSIS
Authors: SHIRKOV DMITRIJ V.
Published: November 2004

We start with a short discussion of the content of a term Renormalisation Group in modern use. By treating the underlying solution property as a reparametrisation symmetry, we relate it with the self-similarity symmetry well-known in mathematical physics and explain the notion of Functional Self-similarity. Then we formulate a program of constructing a regular approach for discovering RG-type symmetries in different problems of mathematical physics. This approach based upon S. Lie group analysis allows one to analyse a wide class of boundary problems for different type of equations. Several examples are mentioned.
Knots and Numbers in ϕ4 Theory to 7 Loops and Beyond
Authors: BROADHURST D.J. , KREIMER D.
Published: November 2004

We evaluate all the primitive divergences contributing to the 7-loop β-function of ɸ4 theory, i.e. all 59 diagrams that are free of subdivergences and hence give scheme-independent contributions. Guided by the association of diagrams with knots, we obtain analytical results for 56 diagrams. The remaining three diagrams, associated with the knots 10124, 10139, and 10152, are evaluated numerically, to 10 sf. Only one satellite knot with 11 crossings is encountered and the transcendental number associated with it is found. Thus we achieve an analytical result for the 6-loop contributions, and a numerical result at 7 loops that is accurate to one part in 1011. The series of ‘zig-zag’ counterterms, [Formula: see text], previously known for n=3, 4, 5, 6 loops, is evaluated to 10 loops, corresponding to 17 crossings, revealing that the n-loop zig-zag term is [Formula: see text], where [Formula: see text] are the Catalan numbers, familiar in knot theory. The investigations reported here entailed intensive use of REDUCE, to generate O(104) lines of code for multiple precision FORTRAN computations, enabled by Bailey’s MPFUN routines, running for O(103) CPUhours on DecAlpha machines.
NUMERICAL APPROACH TO TWO-LOOP THREE POINT FUNCTIONS WITH MASSES
Authors: FUJIMOTO Junpei , SHIMIZU Yoshimitsu , KATO Kiyoshi , KANEKO Toshiaki
Published: November 2004

Extending the method successful for one-loop integrals, the computation of two-loop diagrams with general internal masses is discussed. For the two-loop vertex of nonplanar type, as an example, we show a calculation related to [Formula: see text] vertex.
Towards a Complete Feynman Diagrams Automatic Computation System
Authors: PERRET-GALLIX D.
Published: November 2004

Complete Feynman diagram automatic computation systems are now coming of age after many years of development. They are made available to the high energy physics community through user-friendly interfaces. Theorists and experimentalists can benefit from these powerful packages for speeding up time consuming calculations and for preparing event generators. The general architecture of these packages is presented and the current development of the one-loop diagrams extension is discussed. A rapid description of the prominent packages and tools is then proposed. Finally, the necessity for defining a standardization scheme is heavily stressed for the benefit of developers and users.
A PROGRAMMABLE ACTIVE MEMORY IMPLEMENTATION OF A NEURAL NETWORK FOR SECOND LEVEL TRIGGERING IN ATLAS
Authors: LUNDHEIM LARS , LEGRAND IOSIF , MOLL LAURENT
Published: November 2004

In the second level triggering for ATLAS “Regions of Interest” (RoIs) are defined in (etha, phi) corresponding to possibly interesting particles. For each RoI physically meaningful parameters are extracted for each subdetector. Based on these parameters a classification of the particle type is made. A feed-forward neural net with 12 input variables, a 6-node intermediate layer, and 4 output nodes has earlier been suggested for this task.

The reported work consists of an implementation of this neural net using a DECPeRLe-1, a Programmable Active Memory (PAM). This is a reconfigurable processor based on Field Programmable Gate Arrays (FPGAs), which has also been used for real-time implementation of feature extraction algorithms for second level triggering.

The implementation is pipelined, runs with a clock of 25 MHz, and uses 0.64 microseconds for one particle classification. Integer arithmetic is used, and the performance is comparable to a floating point version.
APPLICATION OF A HIGH SPEED ANALOG NEURAL NETWORK CHIP IN THE FIRST LEVEL RZ-TRIGGER OF THE H1-EXPERIMENT AT HERA
Authors: TRAN T. TONG , SCHIEK S. , SCHMIDT G. , BEHREND H.J. , FRANKE G. , KANDER M. , KAMMEYER K.D.
Published: November 2004

We present the application of a high speed analog neural network chip of the MESA Research Institute in the first level RZ-Trigger of the H1-Experiment at HERA. Using this neural network chip with a settling time of about 50 ns we can reach a first level trigger decision within the HERA bunch-chrossing time of 96 ns.
TAGGING THE S QUARK IN THE HADRONIC DECAYS OF THE Z
Authors: ANGELIS ALESSANDRO DE , COSMO GABRIELE , COSSUTTI FABIO
Published: November 2004

The selection of samples of events enriched in hadronic decays of the Z into [Formula: see text] pairs is made difficult by the poor knowledge of jet fragmentation. A Feed-Forward Neural Network can help in maximizing the performance of the classification. This will offer the possibility to test the universality of the Standard Model of the electroweak interaction, and to perform measurements in the sector of nonperturbative QCD.
PSEUDOSPHERICAL SURFACES, SOLITON EQUATIONS AND COMPUTER ALGEBRA
Authors: STEEB W.-H.
Published: November 2004

Soliton equations can be derived from pseudospherical surfaces. Using computer algebra we show how the sine-Gordon equation can be derived. Extensions to other soliton equations are straightforward.
MONTE CARLO SIMULATION OF AGEING: BEYOND BIT-STRING MODELS
Authors: BERNARDES AMERICO T. , STAUFFER DIETRICH
Published: November 2004

Penna's bit-string model of biological ageing due to the accumulation of deleterious mutations is generalized to allow for more than one disease per year. The results remain qualitatively unchanged except for a more complicated non-monotonic approach to equilibrium. We also look at "mutational meltdown", the extinction of the whole population if all mutations are deleterious and heritable, and why the Penna model can escape this extinction. No dependence on population size is found for mutational meltdown, with up to 108 individuals.
NONCOMMUTATIVE U(1) SUPER-YANG–MILLS THEORY: PERTURBATIVE SELF-ENERGY CORRECTIONS
Authors: BICHL A. A. , ERTL M. , GERHOLD A. , GRIMSTRUP J. M. , POPP L. , PUTZ V. , SCHWEDA M. , GROSSE H. , WULKENHAAR R.
Published: November 2004

The quantization of the noncommutative [Formula: see text], U(1) super-Yang–Mills action is performed in the superfield formalism. We calculate the one-loop corrections to the self-energy of the vector superfield. Although the power-counting theorem predicts quadratic ultraviolet and infrared divergences, there are actually only logarithmic UV and IR divergences, which is a crucial feature of noncommutative supersymmetric field theories.
COHOMOLOGICAL BRST ASPECTS OF THE MASSLESS TENSOR FIELD WITH THE MIXED SYMMETRY (k,k)
Authors: CIOBÎRCĂ COSTIN-CĂTĂLIN , CIOROIANU EUGEN-MIHĂIŢĂ , SALIU SOLANGE-ODILE
Published: November 2004

The main BRST cohomological properties of a free, massless tensor field that transforms in an irreducible representation of GL(D,ℝ), corresponding to a rectangular, two-column Young diagram with k>2 rows are studied in detail. In particular, it is shown that any nontrivial co-cycle from the local BRST cohomology group H(s|d) can be taken to stop either at antighost number (k+1) or k, its last component belonging to the cohomology of the exterior longitudinal derivative H(γ) and containing nontrivial elements from the (invariant) characteristic cohomology H inv (δ|d).
EXACT SOLUTIONS IN OPEN BOSONIC STRING FIELD THEORY AND MARGINAL DEFORMATION IN CFT
Authors: KLUSOŇ J.
Published: November 2004

In this paper we continue our study of the exact solution in open bosonic string field theory. We present new solution in the string field theory defined on the background corresponding to the boundary conformal field theory describing D25-brane. Then we will study the fluctuation modes around this solution and we determine their basic properties from the linearized equation of motion of the string field theory defined above the classical solution.
MATRIX MODELS OF NONCOMMUTATIVE 3D LATTICE GAUGE THEORIES
Authors: BAZZOCCHI F. , CIRAFICI M. , MACCAFERRI C. , PROFUMO S.
Published: November 2004

We investigate through the Morita equivalence the problem of mapping, odd dimensional noncommutative lattice gauge theories onto suitable matrix models. We specialize our analysis to three-dimensional noncommutative QED (NCQED) and scalar QED (NCsQED), for which we explicitly build the corresponding matrix model.
ALGEBRAIC CONNECTIONS ON PARALLEL UNIVERSES
Authors: COQUEREAUX R. , HÄUβLING R. , SCHECK F.
Published: November 2004

For any manifold M we introduce a ℤ-graded differential algebra Ξ, which, in particular, is a bimodule over the associative algebra C(M⋃M). We then introduce the corresponding covariant differentials and show how this construction can be interpreted in terms of Yang-Mills and Higgs fields. This is a particular example of noncommutative geometry. It differs from the prescription of Connes in the following way: the definition of Ξ does not rely on a given Dirac-Yukawa operator acting on a space of spinors.
ONE-LOOP FINITE TEMPERATURE EFFECTIVE ACTION FOR COMPOSITE FIELDS IN CURVED SPACE
Authors: BALAKRISHNAN J.
Published: November 2004

We obtain high temperature results for the one-loop effective action for composite fields in interaction with an Abelian gauge field and minimally coupled to gravity in a curved background space-time, using the Vilkovisky-DeWitt approach, by making a local expansion in the Riemann tensor and its derivatives. We also give results for the fields minimally coupled to gravity in an arbitrary curved background space-time at zero temperature, and for the case where the fields are nonminimally coupled to gravity in Euclidean de Sitter space. The results obtained are gauge-invariant and gauge-condition-independent on-shell as well as off-shell.
A FREE FIELD REPRESENTATION OF THE SCREENING CURRENTS OF $U_q (\widehat{{\rm sl}(3)})$
Authors: BOUGOURZI A. H. , WESTON ROBERT A.
Published: November 2004

We construct five independent screening currents associated with the [Formula: see text] quantum current algebra. The screening currents are expressed as exponentials of the eight basic deformed bosonic fields that are required in the quantum analog of the Wakimoto realization of the current algebra. Four of the screening currents are "simple," in that each one is given as a single exponential field. The fifth is expressed as an infinite sum of exponential fields. For reasons which we will discuss, we expect that the structure of the screening currents for a general quantum affine algebra will be similar to the [Formula: see text] case.
CHARGED VORTEX DYNAMICS IN GINZBURG–LANDAU THEORY OF THE FRACTIONAL QUANTUM HALL EFFECT
Authors: ALLEN THEODORE J. , BORDNER ANDREW J.
Published: November 2004

We write a Ginzburg–Landau Hamiltonian for a charged order parameter interacting with a background electromagnetic field in 2 + 1 dimensions, which we propose as an effective theory for the fractional quantum Hall effect. We further propose to identify vortex excitations of the theory with Laughlin's fractionally charged quasiparticles. Using the method of Lund we derive a collective coordinate action for vortex defects in the order parameter and demonstrate that the vortices are charged. We examine the classical dynamics of the vortices and then quantize their motion, demonstrating that their peculiar classical motion is a result of the fact that the quantum motion takes place in the lowest Landau level. The classical and quantum motion in two-dimensional regions with boundaries is also investigated. The quantum theory is not invariant under magnetic translations. Magnetic translations add total time derivative terms to the collective action, but no extra constants of the motion result.
ON THE ANYON TWO-POINT CORRELATION FUNCTION IN THE ABELIAN HIGGS MODEL WITH CHERN–SIMONS TERM
Authors: MÜLLER V. F.
Published: November 2004

In the noncompact Abelian Higgs model with Chern–Simons term, formulated on a (2 + 1)-dimensional space–(Euclidean)time lattice, a Euclidean functional integral representation of a gauge-invariant four-point correlation function with insertions is given. From this representation the two-point correlation function of the nonlocal anyon fields has to be generated by shifting two matter fields, which act as countercharges, to infinity after the infinite volume limit has been performed. By devising an expansion in a Coulomb-like phase of the model, these limiting procedures are analyzed. The removal of the countercharges only leads to a finite limit after an appropriate renormalization which is worked out in some detail.
BOUNDARY BOUND STATES IN AFFINE TODA FIELD THEORY
Authors: FRING ANDREAS , KÖBERLE ROLAND
Published: November 2004

We demonstrate that the generalization of the Coleman–Thun mechanism may be applied to the situation where one considers scattering processes in 1 + 1 dimensions in the presence of reflecting boundaries. For affine Toda field theories we find that the binding energies of the bound states are always half the sum over a set of masses having the same color with respect to the bicoloration of the Dynkin diagram. For the case of E6 affine Toda field theory we compute explicitly the spectrum of all higher boundary bound states. The complete set of states constitutes a closed bootstrap.
THEORY OF LOOPS AND STRINGS WITH MATTER IN THE ADJOINT REPRESENTATION
Authors: MAHARANA JNANADEVA , SINGH LAMBODAR P.
Published: November 2004

We have presented canonical and path integral formulations of a theory of loops and closed strings with the matter field quanta transforming in the adjoint representation of the SU (N) gauge group. The physical processes arising out of the interactions of loops and closed strings are discussed.
MULTIPLICITY CHARACTERISTICS OF PARTICLES PRODUCED IN 12C-EMULSION COLLISIONS AT 4.5 A GeV/c
Authors: AHMAD M. S. , KHAN M. Q. R. , SIDDIQUE K. A. , HASAN R.
Published: November 2004

Experimental data on multiplicities and correlations of charged particles of different types produced in collisions of 4.5 A GeV/c carbon-12 with emulsion are reported and discussed. The data are compared with the results of other experiments on nucleus–nucleus and hadron–nucleus collisions. It is found that the particle production mechanism in nucleus–nucleus collisions is almost the same as in hadron–nucleus collisions. It is also observed that the shower particles' multiplicity distributions obey a KNO type scaling law, which supports the aforementioned result.
PATH SPACE DECOMPOSITIONS FOR THE VIRASORO ALGEBRA AND ITS VERMA MODULES
Authors: KAUFMANN RALPH M.
Published: November 2004

Starting from a detailed analysis of the structure of path spaces of the [Formula: see text] fusion graphs and the corresponding irreducible Virasoro algebra quotients V(c, h) for the (2, q odd) models, we introduce the notion of an admissible path space representation. The path spaces [Formula: see text] over the [Formula: see text] graphs are isomorphic to the path spaces over Coxeter A graphs that appear in FB models. We give explicit construction algorithms for admissible representations. From the finite-dimensional results of these algorithms we derive a decomposition of V(c, h) into its positive and negative definite subspaces w.r.t. the Shapovalov form and the corresponding signature characters. Finally, we treat the Virasoro operation on the lattice induced by admissible representations, adopting a particle point of view. We use this analysis to decompose the Virasoro algebra generators themselves. This decomposition also takes into account the nonunitarity of the (2, q) models.
DIRAC SEA EFFECTS IN A LINEAR σ MODEL WITH VECTOR AND AXIAL VECTOR FIELDS
Authors: DE SOUSA C. A.
Published: November 2004

We propose a new approach to collective phenomena in a linear σ model which includes classical vector–isovector and pseudovector–isovector fields. The main purpose is to describe meson modes composed of two ingredients: phenomenological structureless fields and [Formula: see text] excitations of the vacuum. This procedure, performed in the context of many-body techniques, provides a natural renormalization process through the [Formula: see text] excitations.
DISCUSSION OF AN ALTERNATIVE APPROACH TO DESCRIPTION OF TIME EVOLUTION IN THE NEUTRAL KAONS SYSTEM
Authors: URBANOWSKI K.
Published: November 2004

Long time properties of the effective Hamiltonian H||(t) governing the time evolution in a given subspace of the total state space of the system considered are discussed. The effects of the early time behavior of the eigenstates |lt=0> and |st=0> for H||(t) in the case of the subspace of neutral kaons (or other similar particles) are discussed, and suppositions as to how they should manifest themselves in experiments are made. The hypothesis that |lt=0> and |st=0> could be eigenstates for CP transformation is formulated and a method for its verification is proposed. Comparison is made of parameters characterizing the properties of the neutral kaons system obtained by the LOY method and by the method based on the use of the Hamiltonian H||(t).
FLAT CONNECTIONS FOR CHARACTERS IN IRRATIONAL CONFORMAL FIELD THEORY
Authors: HALPERN M. B. , SOCHEN N.
Published: November 2004

Following the paradigm on the sphere, we begin the study of irrational conformal field theory (ICFT) on the torus. In particular, we find that the affine-Virasoro characters of ICFT satisfy heatlike differential equations with flat connections. As a first example, we solve the system for the general g/h coset construction, obtaining an integral representation for the general coset characters. In a second application, we solve for the high-level characters of the general ICFT on simple g, noting a simplification for the subspace of theories which possess a nontrivial symmetry group. Finally, we give a geometric formulation of the system in which the flat connections are generalized Laplacians on the centrally extended loop group.
COMBINATORIAL INVARIANTS FROM FOUR-DIMENSIONAL LATTICE MODELS
Authors: BIRMINGHAM DANNY , RAKOWSKI MARK
Published: November 2004

We study the subdivision properties of certain lattice gauge theories based on the discrete Abelian group Zp, in four dimensions. The Boltzmann weights are shown to be invariant under all type (k, l) subdivision moves, at certain discrete values of the coupling parameter. The partition function then provides a combinatorial invariant of closed fourmanifolds; however, we further prove that the invariant is unity for all manifolds in this class. Attention is then focused on a bounding three-manifold, and we show that type 2 and type 3 Alexander subdivision of a bounding simplex is equivalent to the insertion of an operator which is equal to a delta function on trivial bounding holonomies. The original four-dimensional model then gives rise to a topological model on its boundary.
ON NON-SUPERSYMMETRIC FINITE QUANTUM FIELD THEORIES
Authors: GRANDITS PETER
Published: November 2004

In a previous paper, requiring finiteness of Yukawa couplings in one-loop approximation, a no-go theorem for the finiteness of non-supersymmetric gauge theories with gauge group SU (n) was proven. Interestingly enough the gauge group SU(5), prominent in GUT models, was not covered by this proof. However, with somewhat more effort the no-go theorem can be extended to this case.

Considering an even larger class of particle contents, we show that the number of possibly finite theories is greatly reduced. It should be stressed that our results are based upon two-loop finiteness of the gauge coupling, although in order to find really finite theories the finiteness conditions on the quartic scalar couplings have to be considered too.
A GEOMETRIC MODEL OF THE ARBITRARY SPIN MASSIVE PARTICLE
Authors: KUZENKO S.M. , LYAKHOVICH S.L. , SEGAL A.YU.
Published: November 2004

A new model of the relativistic massive particle with arbitrary spin [the (m, s) particle] is suggested. The configuration space of the model is the product of Minkowski space and a two-dimensional sphere: ℳ6=ℝ3, 1×S2. The system describes Zitterbevegung at the classical level. Together with explicitly realized Poincare symmetry, the action functional turns out to be invariant under two types of gauge transformations having their origin in the presence of two Abelian first class constraints in the Hamilton formalism. These constraints correspond to strong conservation for the phase space counterparts of the Casimir operators of the Poincaré group. Canonical quantization of the model leads to equations on the wave functions which prove to be equivalent to the relativistic wave equations for the massive spin s field.
SOME QUANTUM ASPECTS OF COMPLEX VECTOR FIELDS WITH CHERN-SIMONS TERM
Authors: DEL CIMA O.M. , DE CARVALHO F.A.B. RABELO
Published: November 2004

Complex vector fields with Maxwell, Chern-Simons and Proca terms are minimally coupled to an Abelian gauge field. The consistency of the spectrum is analyzed and one-loop quantum corrections to the self-energy are explicitly computed and discussed. The incorporation of two-loop contributions and the behavior of tree level scattering amplitudes in the limit of high center-of-mass energies are commented on.
THE SU(2) NONLINEAR σ MODEL IN 2+1 DIMENSIONS: PERTURBATION THEORY IN A POLYNOMIAL FORMULATION
Authors: FOSCO C.D. , MATSUYAMA T.
Published: November 2004

We construct a perturbation theory for the SU(2) nonlinear σ model in 2+1 dimensions using a polynomial, first-order formulation, where the variables are a non-Abelian vector field Lμ [the left SU(2) current], and a non-Abelian pseudovector field θμ, which imposes the condition Fμv(L)=0. The coordinates on the group do not appear in the Feynman rules, but their scattering amplitudes are easily related to those of the currents. We show that all the infinities affecting physical amplitudes at one-loop order can be cured by normal-ordering, presenting the calculation of the full propagator as an example of an application.
TACHYONS AND HIGHER ORDER WAVE EQUATIONS
Authors: BARCI D.G. , BOLLINI C.G. , ROCCA M.C.
Published: November 2004

We consider a fourth order wave equation having normal as well as tachyonic solutions. The propagators are, respectively, the Feynman causal function and the Wheeler-Green function (half advanced and half retarded). The latter is consistent with the elimination of tachyons from free asymptotic states.

We verify the absence of absorptive parts from convolutions involving the tachyon propagator.