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Articles 1 - 30 of 44
Full-Text Articles in Physical Sciences and Mathematics
Black Holes With Magnetic Charge And Quantized Mass, A. Yu. Ignatiev, G. C. Joshi, Kameshwar C. Wali
Black Holes With Magnetic Charge And Quantized Mass, A. Yu. Ignatiev, G. C. Joshi, Kameshwar C. Wali
Physics - All Scholarship
We examine the issue of magnetic charge quantization in the presence of black holes. It is pointed out that quantization of magnetic charge can lead to the mass quantization for magnetically charged black holes. We also discuss some implications for the experimental searches of magnetically charged black holes.
Monte Carlo Renormalization Of 2d Simplicial Quantum Gravity Coupled To Gaussian Matter, Simon Catterall, Eric B. Gregory, G. Thorleifsson
Monte Carlo Renormalization Of 2d Simplicial Quantum Gravity Coupled To Gaussian Matter, Simon Catterall, Eric B. Gregory, G. Thorleifsson
Physics - All Scholarship
We extend a recently proposed real-space renormalization group scheme for dynamical triangulations to situations where the lattice is coupled to continuous scalar fields. Using Monte Carlo simulations in combination with a linear, stochastic blocking scheme for the scalar fields we are able to determine the leading eigenvalues of the stability matrix with good accuracy both for c = 1 and c = 10 theories.
New Analytical Results On Anisotropic Membranes, Mark Bowick, Alex Travesset
New Analytical Results On Anisotropic Membranes, Mark Bowick, Alex Travesset
Physics - All Scholarship
We report on recent progress in understanding the tubular phase of self-avoiding anisotropic membranes. After an introduction to the problem, we sketch the renormalization group arguments and symmetry considerations that lead us to the most plausible fixed point structure of the model. We then employ an epsilon-expansion about the upper critical dimension to extrapolate to the physical interesting 3-dimensional case. The results are $\nu=0.62$ for the Flory exponent and $\zeta=0.80$ for the roughness exponent. Finally we comment on the importance that numerical tests may have to test these predictions.
Dynamics Of The Conformal Mode And Simplicial Gravity, Simon Catterall, Emil Mottola, T. Bhattacharya
Dynamics Of The Conformal Mode And Simplicial Gravity, Simon Catterall, Emil Mottola, T. Bhattacharya
Physics - All Scholarship
We review the derivation of the Liouville action in 2DQG via the trace anomaly and emphasize how a similar approach can be used to derive an effective action describing the long wavelength dynamics of the conformal factor in 4D. In 2D we describe how to make an explicit connection between dynamical triangulations and this continuum theory, and present results which confirm the equivalance of the two approaches. By reconstructing a lattice conformal mode from DT simulations it should be possible to test this equivalence in 4D also.
Anisotropic Membranes, Simon Catterall, Mark Bowick, Simeon Warner, Gudmar Thorleifsson, Marco Falcioni
Anisotropic Membranes, Simon Catterall, Mark Bowick, Simeon Warner, Gudmar Thorleifsson, Marco Falcioni
Physics - All Scholarship
We describe the statistical behavior of anisotropic crystalline membranes. In particular we give the phase diagram and critical exponents for phantom membranes and discuss the generalization to self-avoiding membranes.
Putative Light Scalar Nonet, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino
Putative Light Scalar Nonet, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino
Physics - All Scholarship
We investigate the "family" relationship of a possible scalar nonet composed of the a_0(980), the f_0(980) and the \sigma and \kappa type states found in recent treatments of \pi\pi and \pi K scattering. We work in the effective Lagrangian framework, starting from terms which yield "ideal mixing" according to Okubo's original formulation. It is noted that there is another solution corresponding to dual ideal mixing which agrees with Jaffe's picture of scalars as qq\bar q \bar q states rather than as q\bar q states. At the Lagrangian level there is no difference in the formulation of the two cases (other …
The Tubular Phase Of Self-Avoiding Anisotropic Crystalline Membranes, Mark Bowick, Alex Travesset
The Tubular Phase Of Self-Avoiding Anisotropic Crystalline Membranes, Mark Bowick, Alex Travesset
Physics - All Scholarship
We analyze the tubular phase of self-avoiding anisotropic crystalline membranes. A careful analysis using renormalization group arguments together with symmetry requirements motivates the simplest form of the large-distance free energy describing fluctuations of tubular configurations. The non-self-avoiding limit of the model is shown to be exactly solvable. For the full self-avoiding model we compute the critical exponents using an epsilon-expansion about the upper critical embedding dimension for general internal dimension D and embedding dimension d. We then exhibit various methods for reliably extrapolating to the physical point (D=2,d=3). Our most accurate estimates are nu=0.62 for the Flory exponent and zeta=0.80 …
Disorder-Induced Topological Defects In A D=2 Elastic Medium At Zero Temperature, Alan Middleton
Disorder-Induced Topological Defects In A D=2 Elastic Medium At Zero Temperature, Alan Middleton
Physics - All Scholarship
The density and correlations of topological defects are investigated numerically in a model of a d=2 elastic medium subject to a periodic quenched random potential. The computed density of defects decreases approximately exponentially with the defect core energy. Comparing the defect-free ground state with the ground state with defects, it is found that the difference is described by string-like excitations, bounded by defect pairs, which have a fractal dimension of 1.250(3). At zero temperature, the disorder-induced defects screen the interaction of introduced vortex pairs.
H2 Formation On Interstellar Grains In Different Physical Regimes, Gianfranco Vidali, Ofer Biham, Itay Furman, N. Katz, Valerio Pirronello
H2 Formation On Interstellar Grains In Different Physical Regimes, Gianfranco Vidali, Ofer Biham, Itay Furman, N. Katz, Valerio Pirronello
Physics - All Scholarship
An analysis of the kinetics of H2 formation on interstellar dust grains is presented using rate equations. It is shown that semi-empirical expressions that appeared in the literature represent two different physical regimes. In particular, it is shown that the expression given by Hollenbach, Werner and Salpeter [ApJ, 163, 165 (1971)] applies when high flux, or high mobility, of H atoms on the surface of a grain, makes it very unlikely that H atoms evaporate before they meet each other and recombine. The expression of Pirronello et al.\ [ApJ, 483, L131 (1997)] -- deduced on the basis of accurate measurements …
Pion-Pion Scattering In Two Dimensions, Joseph Schechter, D. Delphenich, S. Vaidya
Pion-Pion Scattering In Two Dimensions, Joseph Schechter, D. Delphenich, S. Vaidya
Physics - All Scholarship
Massive two-flavor QED_2 is known to have many similarities to the two-flavor QCD_4. Here we compare the \pi-\pi scattering amplitudes (actually an analog process in QED_2) of the two theories. The QED_2 amplitude is computed from the bosonized version of the model while the QCD_4 amplitude is computed from an effective low energy chiral Lagrangian. A number of interesting features are noted. For example, the contribution of the two-dimensional Wess-Zumino-Witten (WZW) term in QED_2 is structurally identical to the vector meson exchange contribution in QCD_4. Also it is shown that the QED_2 amplitude computed at tree level is a reasonable …
Evidence For A Scalar Kappa(900) Resonance In Pi-K Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino
Evidence For A Scalar Kappa(900) Resonance In Pi-K Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz, Francesco Sannino
Physics - All Scholarship
Motivated by the 1/N_c\ expansion, we study a simple model in which the pi-K scattering amplitude is the sum of a current-algebra contact term and resonance pole exchanges. This phenomenological model is crossing symmetric and, when a putative light strange scalar meson, kappa, is included, satisfies the unitarity bounds to well above 1 GeV. The model also features chiral dynamics, vector meson dominance and appropriate interference between the established scalar K*(1430) resonance and its predicted background. We briefly discuss the physical significance of the results and directions for further work.
Quadratic Electro-Optic Effects In Bacteriorhodopsin: Measurement Of Γ(-Ω;0,0,Ω) In Dried Gelatin Thin Films, Mikio Yamazaki, Jerry Goodisman, Robert R. Birge
Quadratic Electro-Optic Effects In Bacteriorhodopsin: Measurement Of Γ(-Ω;0,0,Ω) In Dried Gelatin Thin Films, Mikio Yamazaki, Jerry Goodisman, Robert R. Birge
Chemistry - All Scholarship
Quadratic electro-optic effects (dc or low frequency Kerr effect) of bacteriorhodopsin dispersed in dried gelatin thin films are examined in the near resonance region at three wavelengths: 633, 647, and 676 nm. The films show relatively large quadratic electro-optic effects compared to other molecular dispersed systems. The purple membrane is fixed within the polymerized gelatin matrix, and we show that the electronic contribution to γ dominates over possible orientational contributions. At 676 nm. the quadratic electro-optic coefficient s1133( - ω;0,0,ω) is 6.7 × 10-20 m2/V2 and the third order nonlinear susceptibility X1133(3) …
The Nature Of The Continuum Limit In The 2d Rp^2 Gauge Model, Simon Catterall, M. Hasenbusch, R. R. Horgan, R. Renken
The Nature Of The Continuum Limit In The 2d Rp^2 Gauge Model, Simon Catterall, M. Hasenbusch, R. R. Horgan, R. Renken
Physics - All Scholarship
The RP(2) gauge model is studied in 2D. We use Monte-Carlo renormalization techniques for blocking the mean spin-spin interaction, , and the mean gauge field plaquette. The presence of the O(3) renormalized trajectory is verified and is consistent with the known three-loop beta-function. The first-order `vorticity' transition observed by Solomon et al. is confirmed, and the location of the terminating critical point is established. New scaling flows in (,) are observed associated with a large exponent kappa in the range 4~5. The scaling flows give rise to a strong cross-over effect between regions of high and low vorticity …
Definitional Interpreters For Higher-Order Programming Languages, John C. Reynolds
Definitional Interpreters For Higher-Order Programming Languages, John C. Reynolds
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
Abstract. Higher-order programming languages (i.e., languages in which procedures or labels can occur as values) are usually defined by interpreters that are themselves written in a programming language based on the lambda calculus (i.e., an applicative language such as pure LISP). Examples include McCarthy’s definition of LISP, Landin’s SECD machine, the Vienna definition of PL/I, Reynolds ’ definitions of GEDANKEN, and recent unpublished work by L. Morris and C. Wadsworth. Such definitions can be classified according to whether the interpreter contains higher-order functions, and whether the order of application (i.e., call by value versus call by name) in the defined …
Dynamic Management Of Heterogeneous Resources, Jerrell Watts, Marc Rieffel, Stephen Taylor
Dynamic Management Of Heterogeneous Resources, Jerrell Watts, Marc Rieffel, Stephen Taylor
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
This paper presents techniques for dynamic load balancing in heterogeneous computing environments. That is, the techniques are designed for sets of machines with varying processing capabilities and memory capacities. These methods can also be applied to homogenous systems in which the effective compute speed or memory availability is reduced by the presence of other programs running outside the target computation. To handle heterogeneous systems, a precise distinction is made between an abstract quantity of work, which might be measured as the number of iterations of a loop or the count of some data structure, and the utilization of resources, measured …
Skew-Insensitive Parallel Algorithms For Relational Join, Khaled Alsabti, Sanjay Ranka
Skew-Insensitive Parallel Algorithms For Relational Join, Khaled Alsabti, Sanjay Ranka
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
Join is the most important and expensive operation in relational databases. The parallel join operation is very sensitive to the presence of the data skew. In this paper, we present two new parallel join algorithms for coarse grained machines which work optimally in presence of arbitrary amount of data skew. The first algorithm is sort-based and the second is hash-based. Both of these algorithms employ a preprocessing phase (prior to the redistribution phase) to equally partition the work among the processors. The proposed algorithms have been designed for memory resident-data. However, they can be extended to disk resident-data. These algorithms …
Visual Interactive Modeling In A Java-Based Hierarchical Modeling And Simulation System, Robert G. Sargent, Thorsten Daum
Visual Interactive Modeling In A Java-Based Hierarchical Modeling And Simulation System, Robert G. Sargent, Thorsten Daum
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
The desired set of properties of a modern simulation system is presented. The portion of the Hierarchical Modeling And Simulation System-Java (HiMASS-j) used for specifying Hierarchical Control Flow Graph (HCFG) Models is described. The specification of HCFG Models in HiMASS-j is by visual interactive modeling through the use of graphical user interfaces and dialog boxes. HCFG Models are specified using two complementary hierarchical specification structures: one to specify the components that comprise a model and how these components are interconnected, and the other to specify the behaviors of individual atomic components. A simulation of a traffic intersection using HiMASS-j is …
Towards A Java Environment For Spmd Programming, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xiaoming Li
Towards A Java Environment For Spmd Programming, Bryan Carpenter, Guansong Zhang, Geoffrey C. Fox, Xiaoming Li
Northeast Parallel Architecture Center
As a relatively straightforward object-oriented language, Java is a plausible basis for a scientific parallel programming language. We outline a conservative set of language extensions to support this kind of programming. The programming style advocated is Single Program Multiple Data (SPMD), with parallel arrays added as language primitives. Communications involving distributed arrays are handled through a standard library of collective operations. Because the underlying programming model is SPMD programming, direct calls to other communication packages are also possible from this language.
A High Level Spmd Programming Model: Hpspmd And Its Java Language Binding, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li
A High Level Spmd Programming Model: Hpspmd And Its Java Language Binding, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li
Northeast Parallel Architecture Center
This report introduces a new language, HPJava, for parallel programming on message passing systems. The language provides a high level SPMD programming model. Through examples and performance results, the features of the new programming style, and its implementation, are illustrated.
Language Bindings For A Data-Parallel Runtime, Bryan Carpenter, Geoffrey C. Fox, Donald Leskiw, Xinying Li, Yuhong Wen
Language Bindings For A Data-Parallel Runtime, Bryan Carpenter, Geoffrey C. Fox, Donald Leskiw, Xinying Li, Yuhong Wen
Northeast Parallel Architecture Center
The NPAC kernel runtime, developed in the PCRC (Parallel Compiler Runtime Consortium) project, is a runtime library with special support for the High Performance Fortran data model. It provides array descriptors for a generalized class of HPF-like distributed arrays, support for parallel access to their elements, and a rich library of collective communication and arithmetic operations for manipulating these arrays. The library has been successfully used as a component in experimental HPF translation systems. With prospects for early appearance of fully-featured, efficient HPF compilers looking questionable, we discuss a class of more easily implementable data-parallel language extensions that preserve many …
Jworb - Java Web Object Request Broker For Commodity Software Based Visual Data Ow Metacomputing Programming Environment, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Jworb - Java Web Object Request Broker For Commodity Software Based Visual Data Ow Metacomputing Programming Environment, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Northeast Parallel Architecture Center
Programming environments and tools that are simultaneously sustainable, highly functional, robust and easy to use have been hard to come by in the HPDC area. This is partially due to the difficulty in developing sophisticated customized systems for what is relatively small part of the worldwide computing enterprise. As the commodity software becomes naturally distributed with the onset of Web and Intranets, we observe now a new trend in HPDC community [1, 8, 12] to base high performance computing on the modern enterprise computing technologies. .. JWORB is a multi-protocol Java server under development at NPAC, currently capable of handling …
Considerations In Hpjava Language Design And Implementation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li, Yuhong Wen
Considerations In Hpjava Language Design And Implementation, Guansong Zhang, Bryan Carpenter, Geoffrey C. Fox, Xinying Li, Yuhong Wen
Northeast Parallel Architecture Center
This paper discusses some design and implementation issues in the HPJava language. The language is briefly reviewed, then the class library that forms the foundation of the translation scheme is described. Through example codes, we illustrate how HPJava source codes can be translated straightforwardly to ordinary SPMD Java programs calling this library. This is followed by a discussion of the rationale for introducing the language in the first place, and of how various language features have been designed to facilitate efficient implementation.
Java/Corba Based Real-Time Infrastructure To Integrate Event-Driven Simulations, Collaboration And Distributed Object/Componentware Computing, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Java/Corba Based Real-Time Infrastructure To Integrate Event-Driven Simulations, Collaboration And Distributed Object/Componentware Computing, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Northeast Parallel Architecture Center
We are discussing the four major standard candidates for distributed object/componentware computing: Java, CORBA, COM and WOM within our proposed coordination framework we call Pragmatic Object Web (POW). We describe our integration approach based on multi-protocol middleware server JWORB (Java Web Object Request Broker) that currently integrates HTTP and IIOP and which we now further develop to also support COM and WOM core functionalities. We are also experimenting with visual data ow authoring front-ends using NPAC WebFlow system on top of JWORB based software bus. Finally, we illustrate our technologies in one major application domain- DoD Modeling and Simulation- where …
Common Runtime Support For High Performance Languages, Geoffrey C. Fox
Common Runtime Support For High Performance Languages, Geoffrey C. Fox
Northeast Parallel Architecture Center
Widespread adoption of parallel computing depends on the availability of improved software environments. An essential component of these environments will be high-level languages. Several languages for exploiting data-parallelism (or task-parallelism) have been developed, or are under development. The stated goal of this project has been to provide a public domain infrastructure for runtime support of these high-level languages. The targeted languages include parallel versions of Fortran and C++, but our intention has been to provide uniform runtime support for many source languages.
Darp: Java-Based Data Analysis And Rapid Prototyping Environment For Distributed High Performance Computations, Erol Akarsu, Geoffrey C. Fox, Tomasz Haupt
Darp: Java-Based Data Analysis And Rapid Prototyping Environment For Distributed High Performance Computations, Erol Akarsu, Geoffrey C. Fox, Tomasz Haupt
Northeast Parallel Architecture Center
The integration of a compiled and interpreted HPF gives us an opportunity to design a powerful application development environment targeted for high performance parallel and distributed systems. This Web based system follows a three-tier model. The Java front-end holds proxy objects which can be manipulated with an interpreted Web client (a Java applet) interacting dynamically with compiled code through a tier-2 server. Although targeted for HPF back-end, the system’s architecture is independent of the back-end language, and can be extended to support other high performance languages.
Techniques For Empirical Testing Of Parallel Random Number Generators, Paul D. Coddington, Sung-Hoon Ko
Techniques For Empirical Testing Of Parallel Random Number Generators, Paul D. Coddington, Sung-Hoon Ko
Northeast Parallel Architecture Center
Parallel computers are now commonly used for computational science and engineering, and many applications in these areas use random number generators. For some applications, such as large-scale Monte Carlo simulations, it is crucial that the random number generator have good randomness properties. Many programs are available for testing the quality of sequential random number generators, but very little work has been done on testing parallel random number generators. We present some techniques for empirical testing of random number generators on parallel computers, using tests based on computational science applications as examples. In particular, we focus on tests based on parallel …
Object Web (Java/Corba) Based Rti To Support Metacomputing M&S, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Object Web (Java/Corba) Based Rti To Support Metacomputing M&S, Geoffrey C. Fox, Wojtek Furmanski, Hasan T. Ozdemir
Northeast Parallel Architecture Center
We present here our Pragmatic Object Web based approach to High Performance Modeling and Simulation and we describe the associated middleware software recently prototyped at NPAC: JWORB (Java Web Object Request Broker) which integrates HTTP and IIOP protocols, and Object Web RTI which implements DMSO RTI 1.3 on top of the JWORB based CORBA / Java software bus. We explain how JWORB and OW RTI are used to build WebHLA – an interactive FMS training environment and we outline our plan towards WebHLA based Virtual Prototyping Environments for Testing, Evaluation and Simulation Based Acquisition.
Arginine To Glutamine Substitutions In The Fourth Module Of Xenopus Interphotoreceptor Retinoid-Binding Protein, Mark S. Braiman, Claxton A. Baer, Ellen E. Van Niel, Jeffrey W. Cronk, Michael T. Kinter, Nicholas E. Sherman, Federico Gonzalez-Fernandez
Arginine To Glutamine Substitutions In The Fourth Module Of Xenopus Interphotoreceptor Retinoid-Binding Protein, Mark S. Braiman, Claxton A. Baer, Ellen E. Van Niel, Jeffrey W. Cronk, Michael T. Kinter, Nicholas E. Sherman, Federico Gonzalez-Fernandez
Chemistry - All Scholarship
Interphotoreceptor retinoid-binding protein (IRBP) is unusual for a lipid-binding protein in that its gene is expressed uniquely by cells of photoreceptor origin and consists of four homologous repeats, each coding for a module of~300 amino acid residues. All-trans retinol binding domains, which appear to be present in each module, are composed of conserved hydrophobic regions [Baer et al, Exp Eye Res 1998; 66:249-262]. Here we investigate the role of highly conserved arginines contained in these regions.
Verification And Validation Of Simulation Models, Robert G. Sargent
Verification And Validation Of Simulation Models, Robert G. Sargent
Electrical Engineering and Computer Science - All Scholarship
This paper discusses verification and validation of simulation models. The different approaches to deciding model validity are presented; how model verification and validation relate to the model development process are discussed; various validation techniques are defined; conceptual model validity, model verification, operational validity, and data validity are described; ways to document results are given; and a recommended procedure is presented.
A Global Communication Optimization Technique Based On Data-Flow Analysis And Linear Algebra, Mahmut Kandemir, P. Banerjee, Alok Choudhary, J. Ramanujam
A Global Communication Optimization Technique Based On Data-Flow Analysis And Linear Algebra, Mahmut Kandemir, P. Banerjee, Alok Choudhary, J. Ramanujam
Electrical Engineering and Computer Science - All Scholarship
Reducing communication overhead is extremely important in distributed-memory message-passing architectures. In this paper, we present a technique to improve communication that considers data access patterns of the entire program. Our approach is based on a combination of traditional data-flow analysis and a linear algebra framework, and works on structured programs with conditional statements and nested loops but without arbitrary goto statements. The distinctive features of the solution are the accuracy in keeping communication set information, support for general alignments and distributions including block-cyclic distributions and the ability to simulate some of the previous approaches with suitable modifications. We also show …