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Articles 1 - 30 of 43
Full-Text Articles in Physical Sciences and Mathematics
Hyperfine Splitting Of Low-Lying Heavy Baryons, Joseph Schechter, Masayasu Harada, Asif Qamar, Francesco Sannino, Herbert Weigel
Hyperfine Splitting Of Low-Lying Heavy Baryons, Joseph Schechter, Masayasu Harada, Asif Qamar, Francesco Sannino, Herbert Weigel
Physics - All Scholarship
We calculate the next-to-leading order contribution to the masses of the heavy baryons in the bound state approach for baryons containing a heavy quark. These 1/N_C corrections arise when states of good spin and isospin are generated from the background soliton of the light meson fields. Our study is motivated by the previously established result that light vector meson fields are required for this soliton in order to reasonably describe the spectrum of both the light and the heavy baryons. We note that the inclusion of light vector mesons significantly improves the agreement of the predicted hyperfine splitting with experiment. …
Phase Structure Of Dynamical Triangulation Models In Three Dimensions, Simon Catterall, Ray L. Renken, John B. Kogut
Phase Structure Of Dynamical Triangulation Models In Three Dimensions, Simon Catterall, Ray L. Renken, John B. Kogut
Physics - All Scholarship
The dynamical triangulation model of three-dimensional quantum gravity is shown to have a line of transitions in an expanded phase diagram which includes a coupling mu to the order of the vertices. Monte Carlo renormalization group and finite size scaling techniques are used to locate and characterize this line. Our results indicate that for mu < mu1 ~ -1.0 the model is always in a crumpled phase independent of the value of the curvature coupling. For mu < 0 the results are in agreement with an approximate mean field treatment. We find evidence that this line corresponds to first order transitions extending to positive mu. However, the behavior appears to change for mu > mu2 ~ 2-4. The simplest scenario that is consistent with the data is the existence of a critical end point.
Remark On The Potential Function Of The Linear Sigma Model, Joseph Schechter, David Delphenich
Remark On The Potential Function Of The Linear Sigma Model, Joseph Schechter, David Delphenich
Physics - All Scholarship
It is shown that the potential functions for the ordinary linear sigma model can be divided into two topographically different types depending on whether the quantity R\equiv (m_\sigma /m_\pi)^2 is greater than or less than nine. Since the Wigner-Weyl mode (R=1) and the Nambu-Goldstone mode (R=\infty belong to different regions, we speculate that this classification may provide a generalization to the broken symmetry situation, which could be convenient for roughly characterizing different possible applications of the model. It is noted that a more complicated potential does not so much change this picture as add different new regions.
Effects Of Self-Avoidance On The Tubular Phase Of Anisotropic Membranes, Mark Bowick, Emmanuel Guitter
Effects Of Self-Avoidance On The Tubular Phase Of Anisotropic Membranes, Mark Bowick, Emmanuel Guitter
Physics - All Scholarship
We study the tubular phase of self-avoiding anisotropic membranes. We discuss the renormalizability of the model Hamiltonian describing this phase and derive from a renormalization group equation some general scaling relations for the exponents of the model. We show how particular choices of renormalization factors reproduce the Gaussian result, the Flory theory and the Gaussian Variational treatment of the problem. We then study the perturbative renormalization to one loop in the self-avoiding parameter using dimensional regularization and an epsilon-expansion about the upper critical dimension, and determine the critical exponents to first order in epsilon.
Singular Structure In 4d Simplicial Gravity, Simon Catterall, R. Renken, John B. Kogut
Singular Structure In 4d Simplicial Gravity, Simon Catterall, R. Renken, John B. Kogut
Physics - All Scholarship
We show that the phase transition previously observed in dynamical triangulation models of quantum gravity can be understood as being due to the creation of a singular link. The transition between singular and non-singular geometries as the gravitational coupling is varied appears to be first order.
Statistical Topography Of Glassy Interfaces, Alan Middleton, Chen Zeng, Jane Kondev, David Mcnamara
Statistical Topography Of Glassy Interfaces, Alan Middleton, Chen Zeng, Jane Kondev, David Mcnamara
Physics - All Scholarship
Statistical topography of two-dimensional interfaces in the presence of quenched disorder is studied utilizing combinatorial optimization algorithms. Finite-size scaling is used to measure geometrical exponents associated with contour loops and fully packed loops. We find that contour-loop exponents depend on the type of disorder (periodic ``vs'' non-periodic) and they satisfy scaling relations characteristic of self-affine rough surfaces. Fully packed loops on the other hand are unaffected by disorder with geometrical exponents that take on their pure values.
Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino
Toy Model For Breaking Super Gauge Theories At The Effective Lagrangian Level, Joseph Schechter, Francesco Sannino
Physics - All Scholarship
We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale m. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An amusing feature of the model is the emergence of the ordinary QCD degrees of freedom which were hidden in the auxiliary fields of the supersymmetric effective Lagrangian.
Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson
Numerical Observation Of A Tubular Phase In Anisotropic Membranes, Mark Bowick, Marco Falcioni, Gudmar Thorleifsson
Physics - All Scholarship
We provide the first numerical evidence for the existence of a tubular phase, predicted by Radzihovsky and Toner (RT), for anisotropic tethered membranes without self-avoidance. Incorporating anisotropy into the bending rigidity of a simple model of a tethered membrane with free boundary conditions, we show that the model indeed has two phase transitions corresponding to the flat-to-tubular and tubular-to-crumpled transitions. For the tubular phase we measure the Flory exponent \nu_F and the roughness exponent \zet. We find \nu_F=0.305(14) and \zeta=0.895(60), which are in reasonable agreement with the theoretical predictions of RT --- \nu_F=1/4 and \zeta=1.
Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen
Efficiency Of Molecular Hydrogen Formation On Silicates, Gianfranco Vidali, Valerio Pirronello, Ofer Biham, Chi Liu, Lyiong Shen
Physics - All Scholarship
We report on laboratory measurements of molecular hydrogen formation and recombination on an olivine slab as a function of surface temperature under conditions relevant to those encountered in the interstellar medium. On the basis of our experimental evidence, we recognize that there are two main regimes of H coverage that are of astrophysical importance; for each of them we provide an expression giving the production rate of molecular hydrogen in interstellar clouds.
Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich
Multiflavor Massive Schwinger Model With Non-Abelian Bosonization, Joseph Schechter, David Delphenich
Physics - All Scholarship
We revisit the treatment of the multiflavor massive Schwinger model by non-Abelian Bosonization. We compare three different approximations to the low-lying spectrum: i) reading it off from the bosonized Lagrangian (neglecting interactions), ii) semi-classical quantization of the static soliton, iii) approximate semi-classical quantization of the ``breather'' solitons. A number of new points are made in this process. We also suggest a different ``effective low-energy Lagrangian'' for the theory which permits easy calculation of the low-energy scattering amplitudes. It correlates an exact mass formula of the system with the requirement of the Mermin-Wagner theorem.
Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel
Generalization Of The Bound State Model, Joseph Schechter, Masayasu Harada, Francesco Sannino, Herbert Weigel
Physics - All Scholarship
In the bound state approach the heavy baryons are constructed by binding, with any orbital angular momentum, the heavy meson multiplet to the nucleon considered as a soliton in an effective meson theory. We point out that this picture misses an entire family of states, labeled by a different angular momentum quantum number, which are expected to exist according to the geometry of the three-body constituent quark model (for N_C=3). To solve this problem we propose that the bound state model be generalized to include orbitally excited heavy mesons bound to the nucleon. In this approach the missing angular momentum …
Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson
Minimal Dynamical Triangulations Of Random Surfaces, Simon Catterall, Mark Bowick, Gudmar Thorleifsson
Physics - All Scholarship
No abstract provided.
Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson
Minimal Dynamical Triangulations Of Random Surfaces, Mark Bowick, Simon Catterall, Gudmar Thorleifsson
Physics - All Scholarship
We introduce and investigate numerically a minimal class of dynamical triangulations of two-dimensional gravity on the sphere in which only vertices of order five, six or seven are permitted. We show firstly that this restriction of the local coordination number, or equivalently intrinsic scalar curvature, leaves intact the fractal structure characteristic of generic dynamically triangulated random surfaces. Furthermore the Ising model coupled to minimal two-dimensional gravity still possesses a continuous phase transition. The critical exponents of this transition correspond to the usual KPZ exponents associated with coupling a central charge c=1/2 model to two-dimensional gravity.
The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson
The Poisson Ratio Of Crystalline Surfaces, Marco Falcioni, Mark Bowick, Emmanuel Guitter, Gudmar Thorleifsson
Physics - All Scholarship
A remarkable theoretical prediction for a crystalline (polymerized) surface is that its Poisson ratio (\sigma) is negative. Using a large scale Monte Carlo simulation of a simple model of such surfaces we show that this is indeed true. The precise numerical value we find is (\sigma \simeq -0.32) on a (128^2) lattice at bending rigidity (kappa = 1.1). This is in excellent agreement with the prediction (\sigma = -1/3) following from the self-consistent screening approximation of Le Doussal and Radzihovsky.
Quantitation Of Ethidium-Stained Closed Circular Dna In Agarose Gels, Michael F. Shubsda, Jerry Goodisman, James C. Dabrowiak
Quantitation Of Ethidium-Stained Closed Circular Dna In Agarose Gels, Michael F. Shubsda, Jerry Goodisman, James C. Dabrowiak
Chemistry - All Scholarship
The fluorescence of ethidium bromide (EB) bound to equimolar amounts of supercoiled form I and unstrained linear form III pBR322, SV40 and PM2 DNA in agarose gels has been measured by scanning a photographic negative of the gel with a microdensitometer. For SV40 and PM2 DNA, commonly used staining conditions cause both forms, i.e. linear and supercoiled, to fluoresce to the same extent. This obviates the need to use a correction factor for the fluorescence of form I DNA when measuring the amount of this form relative to the amounts of unstrained forms in agarose gels. In the case of …
A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh
A One-Pass Algorithm For Accurately Estimating Quantiles For Disk-Resident Data, Khaled Alsabti, Sanjay Ranka, Vineet Singh
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
The '-quantile of an ordered sequence of data values is the element with rank ' \Theta n, where n is the total number of values. Accurate estimates of quantiles are required for the solution of many practical applications. In this paper, we present a new algorithm for estimating the quantile values for disk-resident data. Our algorithm has the following characteristics: (1) It requires only one pass over the data; (2) It is deterministic; (3) It produces good lower and upper bounds of the true values of the quantiles; (4) It requires no a priori knowledge of the distribution of the …
A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor
A Load Balancing Technique For Multiphase Computations, Jerrell Watts, Marc Rieffel, Stephen Taylor
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
Parallel computations comprised of multiple, tightly interwoven phases of computation may require a different approach to dynamic load balancing than single-phase computations. This paper presents a load sharing method based on the view of load as a vector, rather than as a scalar. This approach allows multiphase computations to achieve higher efficiency on large-scale multicomputers than possible with traditional techniques. Results are presented for two large-scale particle simulations running on 128 nodes of an Intel Paragon and on 256 processors of a Cray T3D, respectively.
Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer
Semantics Vs. Syntax Vs. Computations: Machine Models For Type-2 Polynomial-Time Bounded Functionals, James S. Royer
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
This paper investigates analogs of the Kreisel-Lacombe-Shoenfield Theorem in the context of the type-2 basic feasible functionals. We develop a direct, polynomial-time analog of effective operation in which the time bounding on computations is modeled after Kapron and Cook's scheme for their basic polynomial-time functionals. We show that if P = NP, these polynomial-time effective operations are strictly more powerful on R (the class of recursive functions) than the basic feasible functions. We also consider a weaker notion of polynomial-time effective operation where the machines computing these functionals have access to the computations of their procedural parameter, but not to …
Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar
Concurrent Simulation Of Plasma Reactors, Marc Rieffel, Stephen Taylor, Jerrell Watts, Sadasivan Shankar
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
This paper summarizes the computational techniques behind a novel concurrent simulation method used for studying the neutral flow inside plasma reactors. The technique is intended to cope with low pressure flow (less than 1.5 Torr) in realistic three-dimensional geometries. It is based on the Direct Simulation Monte Carlo method to accurately model rarefied gas flow. The concurrent formulation operates on a broad variety of shared-memory multiprocessors, multicomputers, and networked workstations.
Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka
Practical Algorithms For Selection On Coarse-Grained Parallel Computers, Ibraheem Al-Furaih, Srinivas Aluru, Sanjay Goil, Sanjay Ranka
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
In this paper, we consider the problem of selection on coarse-grained distributed memory parallel computers. We discuss several deterministic and randomized algorithms for parallel selection. We also consider several algorithms for load balancing needed to keep a balanced distribution of data across processors during the execution of the selection algorithms. We have carried out detailed implementations of all the algorithms discussed on the CM-5 and report on the experimental results. We demonstrate that the randomized algorithms are superior to their deterministic counterparts.
Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka
Integer Sorting Algorithms For Coarse-Grained Parallel Machines, Khaled Alsabti, Sanjay Ranka
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
Integer sorting is a subclass of the sorting problem where the elements have integer values and the largest element is polynomially bounded in the number of elements to be sorted. It is useful for applications in which the size of the maximum value of element to be sorted is bounded. In this paper, we present a new distributed radix-sort algorithm for integer sorting. The structure of our algorithm is similar to radix sort except that it typically requires less number of communication phases. We present experimental results for our algorithm on two distributed memory multiprocessors, the Intel Paragon and the …
Hpjava: Data Parallel Extensions To Java, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xinying Li
Hpjava: Data Parallel Extensions To Java, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xinying Li
Northeast Parallel Architecture Center
We outline an extension of Java for programming with distributed arrays. The basic programming style is Single Program Multiple Data (SPMD), but parallel arrays are provided as new language primitives. Further extensions include three distributed control constructs, the most important being a data-parallel loop construct. Communications involving distributed arrays are handled through a standard library of collective operations. Because the underlying programming model is SPMD programming, direct calls to MPI or other communication packages are also allowed in an HPJava program.
A Comparison Of Annealing Techniques For Academic Course Scheduling, M.A. Saleh Elmohamed, Geoffrey C. Fox, Paul Coddington
A Comparison Of Annealing Techniques For Academic Course Scheduling, M.A. Saleh Elmohamed, Geoffrey C. Fox, Paul Coddington
Northeast Parallel Architecture Center
In this study we have tackled the NP-hard problem of academic class scheduling (or timetabling) at the university level. We have investigated a variety of approaches based on simulated annealing, including mean-field annealing, simulated annealing with three different cooling schedules, and the use of a rule-based preprocessor to provide a good initial solution for annealing. The best results were obtained using simulated annealing with adaptive cooling and reheating as a function of cost, and a rule-based preprocessor. This approach enabled us to obtain valid schedules for the timetabling problem for a large university, using a complex cost function that includes …
Random Number Generators For Parallel Computers, Paul D. Coddington
Random Number Generators For Parallel Computers, Paul D. Coddington
Northeast Parallel Architecture Center
Random number generators are used in many applications, from slot machines to simulations of nuclear reactors. For many computational science applications, such as Monte Carlo simulation, it is crucial that the generators have good randomness properties. This is particularly true for large-scale simulations done on high-performance parallel computers. Good random number generators are hard to find, and many widely-used techniques have been shown to be inadequate. Finding high-quality, efficient algorithms for random number generation on parallel computers is even more difficult. Here we present a review of the most commonly-used random number generators for parallel computers, and evaluate each generator …
Webflow - A Visual Programming Paradigm For Web/Java Based Coarse Grain Distributed Computing, Dimple Bhatia, Vanco Burzevski, Maja Camuseva, Geoffrey C. Fox
Webflow - A Visual Programming Paradigm For Web/Java Based Coarse Grain Distributed Computing, Dimple Bhatia, Vanco Burzevski, Maja Camuseva, Geoffrey C. Fox
Northeast Parallel Architecture Center
We present here the recent work at NPAC aimed at developing WebFlow---a general purpose Web based visual interactive programming environment for coarse grain distributed computing. We follow the 3-tier architecture with the central control and integration WebVM layer in tier-2, interacting with the visual graph editor applets in tier-1 (front-end) and the legacy systems in tier-3. WebVM is given by a mesh of Java Web servers such as Jeeves from JavaSoft or Jigsaw from MIT/W3C. All system control structures are implemented as URL-addressable servlets which enable Web browser-based authoring, monitoring, publication, documentation and software distribution tools for distributed computing. We …
Java For Parallel Computing And As A General Language For Scientific And Engineering Simulation And Modeling, Geoffrey C. Fox, Wojtek Furmanski
Java For Parallel Computing And As A General Language For Scientific And Engineering Simulation And Modeling, Geoffrey C. Fox, Wojtek Furmanski
Northeast Parallel Architecture Center
We discuss the role of Java and Web technologies for general simulation. We classify the classes of concurrency typical in problems and analyze separately the role of Java in user interfaces, coarse grain software integration, and detailed computational kernels. We conclude that Java could become a major language for computational science, as it potentially offers good performance, excellent user interfaces, and the advantages of object-oriented structure.
Experiments With "Hp Java", Bryan Carpenter, Yuh-Jye Chang, Geoffrey C. Fox, Donald Leskiw
Experiments With "Hp Java", Bryan Carpenter, Yuh-Jye Chang, Geoffrey C. Fox, Donald Leskiw
Northeast Parallel Architecture Center
We consider the possible role of Java as a language for High Performance Computing. After discussing reasons why Java may be a natural candidate for a portable parallel programming language, we describe several case studies. These cover Java socket programming, message-passing through a Java interface to MPI, and class libraries for data-parallel programming in Java.
Pcrc-Based Hpf Compilation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xiaoming Li
Pcrc-Based Hpf Compilation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xiaoming Li
Northeast Parallel Architecture Center
This paper describes an ongoing effort supported by ARPA PCRC (Parallel Compiler Runtime Consortium) project. In particular, we discuss the design and implementation of an HPF compilation system based on PCRC runtime. The approaches to issues such as directive analysis and communication detection are discussed in detail. The discussion includes fragments of code generated by the compiler.
A Prototype Fortran-To-Java Converter, Geoffrey C. Fox, Xiaoming Li, Zheng Qiang, Wu Zhigang
A Prototype Fortran-To-Java Converter, Geoffrey C. Fox, Xiaoming Li, Zheng Qiang, Wu Zhigang
Northeast Parallel Architecture Center
This is a report on a prototype of a FORTRAN 77 to Java converter, f2j. Translation issues are identified, approaches are presented, a URL is provided for interested readers to download the package, and some unsolved problems are brought up. F2j allows value added to some of the investment onFORTRAN code, in particular, those well established FORTRAN libraries for scientific and engineering computation.