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Articles 1 - 30 of 40
Full-Text Articles in Physical Sciences and Mathematics
Viscoelastic Depinning Of Driven Systems: Mean-Field Plastic Scallops, M. Cristina Marchetti, Alan Middleton, Thomas Prellberg
Viscoelastic Depinning Of Driven Systems: Mean-Field Plastic Scallops, M. Cristina Marchetti, Alan Middleton, Thomas Prellberg
Physics - All Scholarship
We have investigated the mean field dynamics of an overdamped viscoelastic medium driven through quenched disorder. The model introduced incorporates coexistence of pinned and sliding degrees of freedom and can exhibit continuous elastic depinning or first order hysteretic depinning. Numerical simulations indicate mean field instabilities that correspond to macroscopic stick-slip events and lead to premature switching. The model is relevant for the dynamics of driven vortex arrays in superconductors and other extended disordered systems.
Interacting Topological Defects On Frozen Topographies, Mark Bowick, David R. Nelson, Alex Travesset
Interacting Topological Defects On Frozen Topographies, Mark Bowick, David R. Nelson, Alex Travesset
Physics - All Scholarship
We propose and analyze an effective free energy describing the physics of disclination defects in particle arrays constrained to move on an arbitrary two-dimensional surface. At finite temperature the physics of interacting disclinations is mapped to a Laplacian Sine-Gordon Hamiltonian suitable for numerical simulations. We then specialize to the case of a spherical crystal at zero temperature. The ground state is analyzed as a function of the ratio of the defect core energy to the Young's modulus. We argue that the core energy contribution becomes less and less important in the limit R >> a, where R is the radius of …
Light Scalar Mesons, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Light Scalar Mesons, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Physics - All Scholarship
We review how a certain effective chiral Lagrangian approach to pi pi scattering, pi K scattering and eta-prime decay to eta pi pi provides evidence for the existence of light scalars sigma(550) and kappa(900) as well as describing the f0(980) and the a0(980). An attempt to fit these into a nonet suggests that their structure is closer to a dual quark-dual antiquark than to a quark-antiquark. A possible mechanism to explain the next higher mass scalar nonet is also proposed.
Performance Of The Cleo Iii Lif-Tea Ring Imaging Cherenkov Detector In A High Energy Muon Beam, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar
Performance Of The Cleo Iii Lif-Tea Ring Imaging Cherenkov Detector In A High Energy Muon Beam, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar
Physics - All Scholarship
The CLEO III Ring Imaging Cherenkov detector uses LiF radiators to generate Cherenkov photons which are then detected by proportional wire chambers using a mixture of CH$_4$ and TEA gases. The first two photon detector modules which were constructed, were taken to Fermilab and tested in a beam dump that provided high momentum muons. We report on results using both plane and "sawtooth" shaped radiators. Specifically, we discuss the number of photoelectrons observed per ring and the angular resolution. The particle separation ability is shown to be sufficient for the physics of CLEO III.
Chiral Lagrangian Treatment Of Pi Eta Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Chiral Lagrangian Treatment Of Pi Eta Scattering, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Physics - All Scholarship
We study pi eta scattering in a model which starts from the tree diagrams of a non-linear chiral Lagrangian including appropriate resonances. Previously, models of this type were applied to pi pi and pi K scattering and were seen to require the existence of light scalar sigma(560) and kappa(900) mesons and to be consistent with the f0(980). The present calculation extends this to include the a0(980), thereby completing a possible nonet of light scalars, all ``seen'' in the same manner. We note that, at the initial level, the pi eta channel is considerably cleaner than the pi pi and pi …
Reconstructing The Conformal Mode In Simplicial Gravity, Simon Catterall, Emil Mottola
Reconstructing The Conformal Mode In Simplicial Gravity, Simon Catterall, Emil Mottola
Physics - All Scholarship
We verify that summing 2D DT geometries correctly reproduces the Polyakov action for the conformal mode, including all ghost contributions, at large volumes. The Gaussian action is reproduced even for central charges greater than one lending strong support to the hypothesis that the space of all possible dyamical triangulations approximates well the space of physically distinct metrics independent of the precise nature of the matter coupling.
The Skyrme Model For Baryons, Joseph Schechter, H. Weigel
The Skyrme Model For Baryons, Joseph Schechter, H. Weigel
Physics - All Scholarship
We review the Skyrme model approach which treats baryons as solitons of an effective meson theory. We start out with a historical introduction and a concise discussion of the original two flavor Skyrme model and its interpretation. Then we develop the theme, motivated by the large N_C approximation of QCD, that the {\it effective} Lagrangian of QCD is in fact one which contains just mesons of all spins. When this Lagrangian is (at least approximately) determined from the meson sector it should then yield a zero parameter description of the baryons. We next discuss the concept of chiral symmetry and …
Numerical Investigation Of The Thermodynamic Limit For Ground States In Models With Quenched Disorder, Alan Middleton
Numerical Investigation Of The Thermodynamic Limit For Ground States In Models With Quenched Disorder, Alan Middleton
Physics - All Scholarship
The effect of open boundary conditions for four models with quenched disorder are studied in finite samples by numerical ground state calculations. Extrapolation to the infinite volume limit indicates that the configurations in ``windows'' of fixed size converge to a unique configuration, up to global symmetries. The scaling of this convergence is consistent with calculations based on the fractal dimension of domain walls. These results provide strong evidence for the ``two-state'' picture of the low temperature behavior of these models. Convergence in three-dimensional systems can require relatively large windows.
Mechanism For A Next-To-Lowest Lying Scalar Meson Nonet, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Mechanism For A Next-To-Lowest Lying Scalar Meson Nonet, Joseph Schechter, Deirdre Black, Amir H. Fariborz
Physics - All Scholarship
Recent work suggests the existence of a non-conventional lowest-lying scalar nonet containing the a0(980). Then the a0(1450) and also the K0*(1430) are likely candidates to belong to a conventional p-wave q \bar q nonet. However a comparison of their properties with those expected on this basis reveals a number of puzzling features. It is pointed out that these puzzles can be resolved in a natural and robust way by assuming a ``bare'' conventional p-wave scalar q \bar q nonet to mix with a lighter four quark qq \bar q \bar q scalar nonet to form new ``physical'' states. The essential …
Resolutions Of Subsets Of Finite Sets Of Points In Projective Space, Steven P. Diaz, Anthony V. Geramita, Juan C. Migliore
Resolutions Of Subsets Of Finite Sets Of Points In Projective Space, Steven P. Diaz, Anthony V. Geramita, Juan C. Migliore
Mathematics - All Scholarship
Given a finite set, X, of points in projective space for which the Hilbert function is known, a standard result says that there exists a subset of this finite set whose Hilbert function is "as big as possible'' inside X. Given a finite set of points in projective space for which the minimal free resolution of its homogeneous ideal is known, what can be said about possible resolutions of ideals of subsets of this finite set? We first give a maximal rank type description of the most generic possible resolution of a subset. Then we show that this generic resolution …
The Conformal Mode In 2d Simplicial Gravity, Simon Catterall, Emil Mottola
The Conformal Mode In 2d Simplicial Gravity, Simon Catterall, Emil Mottola
Physics - All Scholarship
We verify that summing 2D DT geometries correctly reproduces the Polyakov action for the conformal mode, including all ghost contributions, at large volumes. The Gaussian action is reproduced even for c=10, well into the branched polymer phase, which confirms the expectation that the DT measure is indeed correct in this regime as well.
On-Off Intermittency In Stochastically Driven Electrohydrodynamic Convection In Nematics, Thomas John, Ralf Stannarius, Ulrich Behn
On-Off Intermittency In Stochastically Driven Electrohydrodynamic Convection In Nematics, Thomas John, Ralf Stannarius, Ulrich Behn
Mathematics - All Scholarship
We report on-off intermittency in electroconvection of nematic liquid crystals driven by a dichotomous stochastic electric voltage. With increasing voltage amplitude we observe laminar phases of undistorted director state interrupted by shorter bursts of spatially regular stripes. Near a critical value of the amplitude the distribution of the duration of laminar phases is governed over several decades by a power law with exponent -3/2. The experimental findings agree with simulations of the linearized electrohydrodynamic equations near the sample stability threshold.
K-Inflation, Christian Armendariz-Picon, T. Damour, V. Mukhanov
K-Inflation, Christian Armendariz-Picon, T. Damour, V. Mukhanov
Physics - All Scholarship
It is shown that a large class of higher-order (i.e. non-quadratic) scalar kinetic terms can, without the help of potential terms, drive an inflationary evolution starting from rather generic initial conditions. In many models, this kinetically driven inflation (or "k-inflation" for short) rolls slowly from a high-curvature initial phase, down to a low-curvature phase and can exit inflation to end up being radiation-dominated, in a naturally graceful manner. We hope that this novel inflation mechanism might be useful in suggesting new ways of reconciling the string dilaton with inflation
Monomer-Dimer Equilibrium Constants Of Rna In The Dimer Initiation Site Of Human Immunodeficiency Virus Type 1, Michael F. Shubsda, Mark P. Mcpike, Jerry Goodisman, James C. Dabrowiak
Monomer-Dimer Equilibrium Constants Of Rna In The Dimer Initiation Site Of Human Immunodeficiency Virus Type 1, Michael F. Shubsda, Mark P. Mcpike, Jerry Goodisman, James C. Dabrowiak
Chemistry - All Scholarship
The genome of the human immunodeficiency virus (HIV) exists as a dimer of two identical RNA molecules hydrogen bonded to each other near their 5' ends. The dimer, known to be important for viral infectivity, is formed by two monomers interacting through a stem-loop structure called the dimer initiation site (DIS). An initially formed intermediate, the "kissing" dimer, is unstable and rearranges to the stable, duplex form. In this report we use nondenaturing polyacrylamide gel electrophoresis to measure the monomer-dimer equilibrium constant of three RNA sequences, 41-, 27-, and 19-mers, located in the DIS of the MAL isolate of HIV-1. …
The Cleo-Iii Rich Detector And Beam Test Results, Raymond Mountain, J.C. Wang, Marina Artuso, R. Ayad
The Cleo-Iii Rich Detector And Beam Test Results, Raymond Mountain, J.C. Wang, Marina Artuso, R. Ayad
Physics - All Scholarship
We are constructing a Ring Imaging Cherenkov detector (RICH) for the CLEO III upgrade for precision charged hadron identification. The RICH uses plane and sawtooth LiF crystals as radiators, MWPCs as photon detectors with TEA as the photo-sensitive material, and low-noise Viking readout electronics. Results of a beam test of the first two out of total 30 sectors are presented.
The Cleo-Iii Ring Imaging Cherenkov Detector, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar
The Cleo-Iii Ring Imaging Cherenkov Detector, Raymond Mountain, Marina Artuso, R. Ayad, F. Azfar
Physics - All Scholarship
The CLEO-III Detector upgrade for charged particle identification is discussed. The RICH design uses solid LiF crystal radiators coupled with multi-wire chamber photon detectors, using TEA as the photosensor, and low-noise Viking readout electronics. Results from our beam test at Fermilab are presented.
Computational Complexity Of Determining The Barriers To Interface Motion In Random Systems, Alan Middleton
Computational Complexity Of Determining The Barriers To Interface Motion In Random Systems, Alan Middleton
Physics - All Scholarship
The low-temperature driven or thermally activated motion of several condensed matter systems is often modeled by the dynamics of interfaces (co-dimension-1 elastic manifolds) subject to a random potential. Two characteristic quantitative features of the energy landscape of such a many-degree-of-freedom system are the ground-state energy and the magnitude of the energy barriers between given configurations. While the numerical determination of the former can be accomplished in time polynomial in the system size, it is shown here that the problem of determining the latter quantity is NP-complete. Exact computation of barriers is therefore (almost certainly) much more difficult than determining the …
Recurrence And Ergodicity Of Interacting Particle Systems, J. Theodore Cox, Achim Klenke
Recurrence And Ergodicity Of Interacting Particle Systems, J. Theodore Cox, Achim Klenke
Mathematics - All Scholarship
Many interacting particle systems with short range interactions are not ergodic, but converge weakly towards a mixture of their ergodic invariant measures. The question arises whether a.s. the process eventually stays close to one of these ergodic states, or if it changes between the attainable ergodic states infinitely often ("recurrence"). Under the assumption that there exists a convergence--determining class of distributions that is (strongly) preserved under the dynamics, we show that the system is in fact recurrent in the above sense. We apply our method to several interacting particle systems, obtaining new or improved recurrence results. In addition, we answer …
Java’S Insecure Parallelism, Per Brinch Hansen
Java’S Insecure Parallelism, Per Brinch Hansen
College of Engineering and Computer Science - Former Departments, Centers, Institutes and Projects
The author examines the synchronization features of Java and finds that they are insecure variants of his earliest ideas in parallel programming published in 1972-73. The claim that Java supports monitors is shown to be false. The author concludes that Java ignores the last twenty-five years of research in parallel programming languages.
Mpijava: An Object-Oriented Java Interface To Mpi, Mark Baker, Bryan Carpenter, Geoffrey C. Fox, Sung Hoon Ko
Mpijava: An Object-Oriented Java Interface To Mpi, Mark Baker, Bryan Carpenter, Geoffrey C. Fox, Sung Hoon Ko
Northeast Parallel Architecture Center
A basic prerequisite for parallel programming is a good communication API. The recent interest in using Java for scientific and engineering application has led to several international efforts to produce a message passing interface to support parallel computation. In this paper we describe and then discuss the syntax, functionality and performance of one such interface, mpiJava, an object-oriented Java interface to MPI. We first discuss the design of the mpiJava API and the issues associated with its development. We then move on to briefly outline the steps necessary to 'port' mpiJava onto a range of operating systems, including Windows NT, …
The Gateway System: Uniform Web Based Access To Remote Resources, Tomasz Haupt, Erol Akarsu, Geoffrey C. Fox, Alexey Kalinichenko
The Gateway System: Uniform Web Based Access To Remote Resources, Tomasz Haupt, Erol Akarsu, Geoffrey C. Fox, Alexey Kalinichenko
Northeast Parallel Architecture Center
Exploiting our experience developing the WebFlow system, we designed the Gateway system to provide seamless and secure access to computational resources at ASC MSRC. The Gateway follows our commodity components strategy, and it is implemented as a modern three-tier system. Tier 1 is a high-level front-end for visual programming, steering, run-time data analysis and visualization, built on top of the Web and OO commodity standards. Distributed object-based, scalable, and reusable Web server and Object broker middleware forms Tier 2. Back-end services comprise Tier 3. In particular, access to high performance computational resources is provided by implementing the emerging standard for …
Building Distributed Systems For The Pragmatic Object Web, Geoffrey C. Fox, Wojtek Furmanski, Tomasz Haupt
Building Distributed Systems For The Pragmatic Object Web, Geoffrey C. Fox, Wojtek Furmanski, Tomasz Haupt
Northeast Parallel Architecture Center
We review the growing power and capability of commodity computing and communication technologies largely driven by commercial distributed information systems. These systems are built from CORBA, Microsoft's COM, JavaBeans, and rapidly advancing Web approaches. One can abstract these to a three-tier model with largely independent clients connected to a distributed network of servers. The latter host various services including object and relational databases and of course parallel and sequential computing. High performance can be obtained by combining concurrency at the middle server tier with optimized parallel back end services. The resultant system combines the needed performance for large-scale HPCC applications …
Thoughts On The Structure Of An Mpj Reference Implementation, Mark Baker, Bryan Carpenter
Thoughts On The Structure Of An Mpj Reference Implementation, Mark Baker, Bryan Carpenter
Northeast Parallel Architecture Center
We sketch a proposed reference implementation for MPJ, the Java Grande Forum's MPI-like message-passing API [9, 3]. The proposal relies heavily on RMI and Jini for finding computational resources, creating slave processes, and handling failures. User-level communication is implemented efficiently directly on top of Java sockets.
The Gateway System: Uniform Web Based Access To Remote Resources, Geoffrey C. Fox, Tomasz Haupt, Erol Akarsu, Alexey Kalinichenko, Kang-Seok Kim
The Gateway System: Uniform Web Based Access To Remote Resources, Geoffrey C. Fox, Tomasz Haupt, Erol Akarsu, Alexey Kalinichenko, Kang-Seok Kim
Northeast Parallel Architecture Center
Exploiting our experience developing the WebFlow system, we designed the Gateway system to provide seamless and secure access to computational resources at ASC MSRC. The Gateway follows our commodity components strategy, and it is implemented as a modern three-tier system. Tier 1 is a high-level front end for visual programming, steering, run-time data analysis and visualization that is built on top of the Web and OO commodity standards. Distributed object-based, scalable, and reusable Web server and Object broker middleware forms Tier 2. Back-end services comprise Tier 3. In particular, access to high-performance computational resources is provided by implementing the emerging …
Mpijava 1.2: Api Specification, Bryan Carpenter, Geoffrey C. Fox, Sung-Hoon Ko, Sang Lim
Mpijava 1.2: Api Specification, Bryan Carpenter, Geoffrey C. Fox, Sung-Hoon Ko, Sang Lim
Northeast Parallel Architecture Center
This document defines the API of mpiJava, a Java language binding for MPI 1.1. The document is not a standalone specification of the behaviour of MPI--it is meant to be read in conjunction with the MPI standard document [2]. Subsections are laid out in the same way as in the standard document, to allow cross-referencing. Where the mpiJava binding makes no significant change to a particular section of the standard document, we will just note here that there are no special issues for the Java binding. This does not mean that the corresponding section of the standard is irrelevant to …
Using Webhla To Integrate Hpc Fms Modules With Web/Commodity Based Distributed Object Technologies Of Corba, Java, Com And Xml, Geoffrey C. Fox, Wojtek Furmanski, Ganesh Krishnamurthy, Hasan T. Ozdemir, Zeynep Odcikin-Ozdemir, Tom A. Pulikal, Krishnan Rangarajan, Ankur Sood
Using Webhla To Integrate Hpc Fms Modules With Web/Commodity Based Distributed Object Technologies Of Corba, Java, Com And Xml, Geoffrey C. Fox, Wojtek Furmanski, Ganesh Krishnamurthy, Hasan T. Ozdemir, Zeynep Odcikin-Ozdemir, Tom A. Pulikal, Krishnan Rangarajan, Ankur Sood
Northeast Parallel Architecture Center
HLA standards for interoperability between various DoD Modeling and Simulation paradigms are being enforced in parallel with the rapid onset of new Object Web / Commodity standards for distributed objects and componentware, emergent at the crossroads of CORBA, COM, Java, and XML technologies. WebHLA explores synergies between and integrates both trends by offering Object Web based implementation of the HLA framework. Our goal is to deliver a uniform platform that facilitates conversion of legacy codes to and development of new codes in compliance with HLA, HPC and Object Web standards. We outline here the overall design of WebHLA, we summarize …
Webhla - An Interactive Multiplayer Environment For High Performance Distributed Modeling And Simulation, Geoffrey C. Fox, Wojtek Furmanski, Subhash Nair, Hasan T. Ozdemir, Zeynep Odcikin-Ozdemir, Tom A. Pulikal
Webhla - An Interactive Multiplayer Environment For High Performance Distributed Modeling And Simulation, Geoffrey C. Fox, Wojtek Furmanski, Subhash Nair, Hasan T. Ozdemir, Zeynep Odcikin-Ozdemir, Tom A. Pulikal
Northeast Parallel Architecture Center
The process of integrating DoD Modeling and Simulation paradigms around the new HLA/RTI standards proceeds in parallel with the onset of new Object Web standards for distributed objects and componentware, emergent at the crossroads of CORBA, DCOM, Java, and XML based distributed object technologies. We describe here our WebHLA approach which integrates both trends by offering Object Web based implementation of the HLA framework. WebHLA follows a three-tier architecture including: a) Web / Commodity based interactive simulation authoring and runtime front-ends given by Java applets or DirectX multiplayers; b) software bus in the middleware, given by Object Web RTI i.e. …
Internetics: Technologies, Applications And Academic Field, Or, Parallel Computing And Computational Science Do Not Quite Work, Geoffrey C. Fox
Internetics: Technologies, Applications And Academic Field, Or, Parallel Computing And Computational Science Do Not Quite Work, Geoffrey C. Fox
Northeast Parallel Architecture Center
Ten years ago, we were all sure that parallel computing technology and the interdisciplinary academic field of computational science would be center pieces of both academic and economic growth. We show that this insight was, in principle, correct but was an incomplete vision for large-scale computation implies both increased computer power and increasing numbers of users and applications. Parallel computing undoubtedly works on essentially all problems, but we were unable to produce deployable software systems. Further, few industries could achieve adequate return to justify investment in parallel computers, except in a few areas such as databases. Computational science is the …
Benchmarks And Standards For The Evaluation Of Parallel Job Schedulers, Steve J. Chapin, Walfredo Cirne, Dror G. Feitelson, James Patton Jones
Benchmarks And Standards For The Evaluation Of Parallel Job Schedulers, Steve J. Chapin, Walfredo Cirne, Dror G. Feitelson, James Patton Jones
Electrical Engineering and Computer Science - All Scholarship
The evaluation of parallel job schedulers hinges on the workloads used. It is suggested that this be standardized, in terms of both format and content, so as to ease the evaluation and comparison of different systems. The question remains whether this can encompass both traditional parallel systems and metacomputing systems. This paper is based on a panel on this subject that was held at the workshop, and the ensuing discussion; its authors are both the panel members and participants from the audience. Naturally, not all of us agree with all the opinions expressed here...
Performance Analysis Of Csma And Btma Protocols In Multihop Networks: Part Ii - Multiple Channel Case, Lin Wu, Pramod K. Varshney
Performance Analysis Of Csma And Btma Protocols In Multihop Networks: Part Ii - Multiple Channel Case, Lin Wu, Pramod K. Varshney
Electrical Engineering and Computer Science - All Scholarship
Busy tone multiple access protocols have been used in multihop networks to reduce the effect of the hidden terminal problem. This paper demonstrates another approach to reduce the effect of the hidden terminal problem namely the use of multiple channel schemes. A protocol that uses both the busy tone and the multiple channel techniques achieves the best performance. Using a Markov chain model and an approximation, the throughput performance of the multiple channel nonpersistent CSMA protocol and the multiple channel conservative BTMA protocol in a large network is evaluated and compared. The results show that the multichannel CSMA and BTMA …