Dyson conducts SpaceDRUMS OPS

NASA Image and Video Library

2010-04-28

ISS023-E-028754 (28 April 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 23 flight engineer, services the SpaceDRUMS/Space Dynamically Responding Ultrasonic Matrix (SDRM) hardware in the Kibo laboratory of the International Space Station.

Polynomial functors and combinatorial Dyson-Schwinger equations

NASA Astrophysics Data System (ADS)

Kock, Joachim

2017-04-01

We present a general abstract framework for combinatorial Dyson-Schwinger equations, in which combinatorial identities are lifted to explicit bijections of sets, and more generally equivalences of groupoids. Key features of combinatorial Dyson-Schwinger equations are revealed to follow from general categorical constructions and universal properties. Rather than beginning with an equation inside a given Hopf algebra and referring to given Hochschild 1-cocycles, our starting point is an abstract fixpoint equation in groupoids, shown canonically to generate all the algebraic structures. Precisely, for any finitary polynomial endofunctor P defined over groupoids, the system of combinatorial Dyson-Schwinger equations X = 1 + P(X) has a universal solution, namely the groupoid of P-trees. The isoclasses of P-trees generate naturally a Connes-Kreimer-like bialgebra, in which the abstract Dyson-Schwinger equation can be internalised in terms of canonical B+-operators. The solution to this equation is a series (the Green function), which always enjoys a Faà di Bruno formula, and hence generates a sub-bialgebra isomorphic to the Faà di Bruno bialgebra. Varying P yields different bialgebras, and cartesian natural transformations between various P yield bialgebra homomorphisms and sub-bialgebras, corresponding for example to truncation of Dyson-Schwinger equations. Finally, all constructions can be pushed inside the classical Connes-Kreimer Hopf algebra of trees by the operation of taking core of P-trees. A byproduct of the theory is an interpretation of combinatorial Green functions as inductive data types in the sense of Martin-Löf type theory (expounded elsewhere).

Numerical Solution of Dyson Brownian Motion and a Sampling Scheme for Invariant Matrix Ensembles

NASA Astrophysics Data System (ADS)

Li, Xingjie Helen; Menon, Govind

2013-12-01

The Dyson Brownian Motion (DBM) describes the stochastic evolution of N points on the line driven by an applied potential, a Coulombic repulsion and identical, independent Brownian forcing at each point. We use an explicit tamed Euler scheme to numerically solve the Dyson Brownian motion and sample the equilibrium measure for non-quadratic potentials. The Coulomb repulsion is too singular for the SDE to satisfy the hypotheses of rigorous convergence proofs for tamed Euler schemes (Hutzenthaler et al. in Ann. Appl. Probab. 22(4):1611-1641, 2012). Nevertheless, in practice the scheme is observed to be stable for time steps of O(1/ N 2) and to relax exponentially fast to the equilibrium measure with a rate constant of O(1) independent of N. Further, this convergence rate appears to improve with N in accordance with O(1/ N) relaxation of local statistics of the Dyson Brownian motion. This allows us to use the Dyson Brownian motion to sample N× N Hermitian matrices from the invariant ensembles. The computational cost of generating M independent samples is O( MN 4) with a naive scheme, and O( MN 3log N) when a fast multipole method is used to evaluate the Coulomb interaction.

Probing electronic wave functions of sodium-doped clusters: Dyson orbitals, anisotropy parameters, and ionization cross-sections

DOE PAGES

Gunina, Anastasia O.; Krylov, Anna I.

2016-11-14

We apply high-level ab initio methods to describe the electronic structure of small clusters of ammonia and dimethylether (DME) doped with sodium, which provide a model for solvated electrons. We investigate the effect of the solvent and cluster size on the electronic states. We consider both energies and properties, with a focus on the shape of the electronic wave function and the related experimental observables such as photoelectron angular distributions. The central quantity in modeling photoionization experiments is the Dyson orbital, which describes the difference between the initial N-electron and final (N-1)-electron states of a system. Dyson orbitals enter themore » expression of the photoelectron matrix element, which determines total and partial photoionization cross-sections. We compute Dyson orbitals for the Na(NH3)n and Na(DME)m clusters using correlated wave functions (obtained with equation-of-motion coupled-cluster model for electron attachment with single and double substitutions) and compare them with more approximate Hartree-Fock and Kohn-Sham orbitals. As a result, we also analyze the effect of correlation and basis sets on the shapes of Dyson orbitals and the experimental observables.« less

Dyson works with IVGEN Experiment Payload in Columbus MSG

NASA Image and Video Library

2010-05-03

ISS023-E-030740 (3 May 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 23 flight engineer, works with experiment hardware in the Microgravity Science Glovebox (MSG) located in the Columbus laboratory of the International Space Station.

TECHNOS Interview: Esther Dyson.

ERIC Educational Resources Information Center

Raney, Mardell

1997-01-01

This interview with Esther Dyson, who is president and owner of EDventure Holdings which focuses on emerging information technology worldwide, discusses personal responsibility for technology; government's role; content ownership and intellectual property; Internet development; education and computers; parents' role in education; teacher…

FE Caldwell Dyson works with the MERLIN in the US Lab

NASA Image and Video Library

2010-07-18

ISS024-E-008590 (18 July 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, works with the Microgravity Experiment Research Locker/Incubator (MERLIN) on Express rack 6 in the Destiny laboratory of the International Space Station.

Quark scalar, axial and tensor charges in the Schwinger-Dyson formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamanaka, Nodoka

2016-01-22

The quark scalar, axial and tensor charges of nucleon are calculated in the Schwinger-Dyson formalism. We first calculate these charges in the rainbow-ladder truncation using the IR cut quark-gluon vertex, and show that the result is in agreement with the known data. We then perform the same calculation with the phenomenological IR singular quark-gluon vertex. In this case, the Schwinger-Dyson equation does not converge. We show that this result suggests the requirement of additional corrections to the rainbow-ladder truncation, due to the interaction between quark and gluons in the deep IR region.

Nucleon PDFs and TMDs from Continuum QCD

NASA Astrophysics Data System (ADS)

Bednar, Kyle; Cloet, Ian; Tandy, Peter

2017-09-01

The parton structure of the nucleon is investigated in an approach based upon QCD's Dyson-Schwinger equations. The method accommodates a variety of QCD's dynamical outcomes including: the running mass of quark propagators and formation of non-pointlike di-quark correlations. All needed elements, including the nucleon wave function solution from a Poincaré covariant Faddeev equation, are encoded in spectral-type representations in the Nakanishi style to facilitate Feynman integral procedures and allow insight into key underlying mechanisms. Results will be presented for spin-independent PDFs and TMDs arising from a truncation to allow only scalar di-quark correlations. The influence of axial-vector di-quark correlations may be discussed if results are available. Supported by NSF Grant No. PHY-1516138.

Towards a model of pion generalized parton distributions from Dyson-Schwinger equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moutarde, H.

2015-04-10

We compute the pion quark Generalized Parton Distribution H{sup q} and Double Distributions F{sup q} and G{sup q} in a coupled Bethe-Salpeter and Dyson-Schwinger approach. We use simple algebraic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We derive analytic expressions for the pion Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compares very well to experimental pion form factor or parton distribution function data.

Electron propagator calculations on the ionization energies of CrH -, MnH - and FeH -

NASA Astrophysics Data System (ADS)

Lin, Jyh-Shing; Ortiz, J. V.

1990-08-01

Electron propagator calculations with unrestricted Hartree-Fock reference states yield the ionization energies of the title anions. Spin contamination in the anionic reference state is small, enabling the use of second-and third-order self-energies in the Dyson equation. Feynman-Dyson amplitudes for these ionizations are essentially identical to canonical spin-orbitals. For most of the final states, these consist of an antibonding combination of an sp metal hybrid, polarized away from the hydrogen, and hydroegen s functions. In one case, the Feynman-Dyson amplitude consists of nonbonding d functions. Calculated ionization energies are within 0.5 eV of experiment.

Esther Dyson's Vision of the Future.

ERIC Educational Resources Information Center

Runyan, Andy

1999-01-01

Discusses a vision of the future based on Esther Dyson's views of the proliferation of the Internet. Topics include the Internet as a communication medium; electronic commerce; the role of education, including the role of teachers; intellectual property rights; and friction freedom in a new digital economy relating to pricing. (LRW)

How gauge covariance of the fermion and boson propagators in QED constrain the effective fermion-boson vertex

DOE PAGES

Jia, Shaoyang; Pennington, M. R.

2016-12-12

In this paper, we derive the gauge covariance requirement imposed on the QED fermion-photon three-point function within the framework of a spectral representation for fermion propagators. When satisfied, such requirement ensures solutions to the fermion propagator Schwinger-Dyson equation (SDE) in any covariant gauge with arbitrary numbers of spacetime dimensions to be consistent with the Landau-Khalatnikov-Fradkin transformation (LKFT). The general result has been verified by the special cases of three and four dimensions. Additionally, we present the condition that ensures the vacuum polarization is independent of the gauge parameter. Finally, as an illustration, we show how the gauge technique dimensionally regularizedmore » in four dimensions does not satisfy the covariance requirement.« less

HELAC-PHEGAS: A generator for all parton level processes

NASA Astrophysics Data System (ADS)

Cafarella, Alessandro; Papadopoulos, Costas G.; Worek, Malgorzata

2009-10-01

The updated version of the HELAC-PHEGAS event generator is presented. The matrix elements are calculated through Dyson-Schwinger recursive equations using color connection representation. Phase-space generation is based on a multichannel approach, including optimization. HELAC-PHEGAS generates parton level events with all necessary information, in the most recent Les Houches Accord format, for the study of any process within the Standard Model in hadron and lepton colliders. New version program summaryProgram title: HELAC-PHEGAS Catalogue identifier: ADMS_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADMS_v2_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 35 986 No. of bytes in distributed program, including test data, etc.: 380 214 Distribution format: tar.gz Programming language: Fortran Computer: All Operating system: Linux Classification: 11.1, 11.2 External routines: Optionally Les Houches Accord (LHA) PDF Interface library ( http://projects.hepforge.org/lhapdf/) Catalogue identifier of previous version: ADMS_v1_0 Journal reference of previous version: Comput. Phys. Comm. 132 (2000) 306 Does the new version supersede the previous version?: Yes, partly Nature of problem: One of the most striking features of final states in current and future colliders is the large number of events with several jets. Being able to predict their features is essential. To achieve this, the calculations need to describe as accurately as possible the full matrix elements for the underlying hard processes. Even at leading order, perturbation theory based on Feynman graphs runs into computational problems, since the number of graphs contributing to the amplitude grows as n!. Solution method: Recursive algorithms based on Dyson-Schwinger equations have been developed recently in order to overcome the computational obstacles. The calculation of the amplitude, using Dyson-Schwinger recursive equations, results in a computational cost growing asymptotically as 3 n, where n is the number of particles involved in the process. Off-shell subamplitudes are introduced, for which a recursion relation has been obtained allowing to express an n-particle amplitude in terms of subamplitudes, with 1-, 2-, … up to (n-1) particles. The color connection representation is used in order to treat amplitudes involving colored particles. In the present version HELAC-PHEGAS can be used to efficiently obtain helicity amplitudes, total cross sections, parton-level event samples in LHA format, for arbitrary multiparticle processes in the Standard Model in leptonic, pp¯ and pp collisions. Reasons for new version: Substantial improvements, major functionality upgrade. Summary of revisions: Color connection representation, efficient integration over PDF via the PARNI algorithm, interface to LHAPDF, parton level events generated in the most recent LHA format, k reweighting for Parton Shower matching, numerical predictions for amplitudes for arbitrary processes for phase-space points provided by the user, new user interface and the possibility to run over computer clusters. Running time: Depending on the process studied. Usually from seconds to hours. References:A. Kanaki, C.G. Papadopoulos, Comput. Phys. Comm. 132 (2000) 306. C.G. Papadopoulos, Comput. Phys. Comm. 137 (2001) 247. URL: http://www.cern.ch/helac-phegas.

A Noted Physicist's Contrarian View of Global Warming

ERIC Educational Resources Information Center

Goldstein, Evan R., Comp.

2008-01-01

According to Freeman Dyson, an emeritus professor of physics at the Institute for Advanced Study, the debate about global warming has become too narrow and opinions have become too entrenched. Relying on a computer model designed by the Yale University economist William D. Nordhaus, Dyson compared the effectiveness and economic feasibility of…

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson performs the traditional door signing Friday, April 2, 2010 at the Cosmonaut Hotel in Baikonur, Kazakhstan. Caldwell Dyson was launched onboard the Soyuz rocket later that day with Expedition 23 Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko on a mission to the International Space Station (ISS). Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

Mary Ellen Caldwell, center, speaks to her daughter NASA Flight Engineer Tracy Caldwell Dyson onboard the International Space Station from the Russian Mission Control Center, Korolev, Russia, Sunday, April 4, 2010. The Soyuz TMA-18 docked to the International Space Station carrying Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, left, speaks during the State Commission meeting at the Cosmonaut Hotel while her colleagues Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko, right, listen on Thursday, April 1, 2010 in Baikonur, Kazakhstan. The State Commission meeting approves the Soyuz launch of Caldwell Dyson, Skvortsov and Kornienko to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 Flight Engineer Tracy Caldwell Dyson says a few words during the State Commission meeting to approve the Soyuz launch of Caldwell Dyson, Expedition 23 Soyuz Commander Alexander Skvortsov and Expedition 23 Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010 in Baikonur, Kazakhstan. The crew is kept in a separate room with a glass window in order to help maintain their health. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 crew members, from left, NASA's Tracy Caldwell Dyson, Russian Alexander Skvortsov and Russian Mikhail Kornienko are seen during the State Commission meeting to approve the Soyuz launch of Skvortsov, Caldwell Dyson and Mikhail Kornienko on Thursday, April 1, 2010 in Baikonur, Kazakhstan. The crew is kept in a separate room with a glass window in order to help maintain their health. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 Soyuz Commander Alexander Skvortsov, center, holds up a poster of the Expedition 23 crew while Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko, right, smile during the State Commission meeting held at the Cosmonaut Hotel, Thursday, April 1, 2010 in Baikonur, Kazakhstan. The State Commission meeting approves the Soyuz launch of Caldwell Dyson, Skvortsov and Kornienko to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

Non-Unitary Boson Mapping and Its Application to Nuclear Collective Motions

NASA Astrophysics Data System (ADS)

Takada, K.

First, the general theory of boson mapping for even-number many-fermion systems is surveyed. In order to overcome the confusion concerning the so-called unphysical or spurious states in the boson mapping, the correct concept of the unphysical states is precisely given in a clear-cut way. Next, a method to apply the boson mapping to a truncated many-fermion Hilbert space consisting of collective phonons is proposed, by putting special emphasis on the Dyson-type non-unitary boson mapping. On the basis of this method, it becomes possible for the first time to apply the Dyson-type boson mapping to analyses of collective motions in realistic nuclei. This method is also extended to be applicable to odd-number-fermion systems. As known well, the Dyson-type boson mapping is a non-unitary transformation and it gives a non-Hermitian boson Hamiltonian. It is not easy (but not impossible) to solve the eigenstates of the non-Hermitian Hamiltonian. A Hermitian treatment of this non-Hermitian eigenvalue problem is discussed and it is shown that this treatment is a very good approximation. Using this Hermitian treatment, we can obtain the normal-ordered Holstein-Primakoff-type boson expansion in the multi-collective-phonon subspace. Thereby the convergence of the boson expansion can be tested. Some examples of application of the Dyson-type non-unitary boson mapping to simplified models and realistic nuclei are also shown, and we can see that it is quite useful for analysis of the collective motions in realistic nuclei. In contrast to the above-mentioned ordinary type of boson mapping, which may be called a ``static'' boson mapping, the Dyson-type non-unitary selfconsistent-collective-coordinate method is discussed. The latter is, so to speak, a ``dynamical'' boson mapping, which is a dynamical extension of the ordinary boson mapping to be capable to include the coupling effects from the non-collective degrees of freedom selfconsistently. Thus all of the Dyson-type non-unitary boson mapping from A to Z is summarized in this paper.

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson of the U.S. prepares to have her Russian Sokol suit pressure checked at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Caldwell Dyson and fellow Expedition 23 crewmembers Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko of Russia launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, left, Soyuz Commander Alexander Skvortsov or Russia, and Flight Engineer Mikhail Kornienko of the Russia, right, have their Russian Sokol suits prepared for launch by a technicians at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Caldwell Dyson, Skvortsov and Kornienko and launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

Expedition 23 Flight Engineer Tracy Caldwell Dyson answers a reporters' question during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan on Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Collecting, Preserving, and Interpreting the History of Electronic Games: An Interview with Jon-Paul C. Dyson

ERIC Educational Resources Information Center

American Journal of Play, 2017

2017-01-01

Jon-Paul C. Dyson is vice president for exhibits and director of the International Center for the History of Electronic Games (ICHEG) at The Strong. Trained as a cultural and intellectual historian, he joined The Strong in 1998 and has worked on and supervised the development of dozens of exhibits on play and video games. He initiated the museum's…

Women's History Month at NASA

NASA Image and Video Library

2011-03-14

NASA Astronaut and Expeditions 23 and 24 Flight Engineer, Tracy Caldwell Dyson, speaks at a Women's History Month event at NASA Headquarters, Wednesday, March 16, 2011 in Washington. The event entitled Women Inspiring the Next Generation to Reveal the Unknown is a joint venture with NASA and the White House Council on Women and Girls. Caldwell Dyson recently returned from a six-month stay aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson of the U.S. has her Russian Sokol suit prepared for launch by a technician at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Caldwell Dyson and fellow Expedition 23 crew members Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko of Russia launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of Russia, top, NASA Flight Engineer Tracy Caldwell Dyson of the U.S. and Soyuz Commander Alexander Skvortsov of Russia, bottom, wave farewell from the bottom of the Soyuz rocket at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko, Caldwell Dyson and Skvortsov launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 at 10:04 a.m. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

NASA's Tracy Caldwell Dyson, left, looks on as Expedition 23 Soyuz Commander Alexander Skvortsov answers a reporters' question during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan on Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 prime and backup crew members, from left, NASA's Tracy Caldwell Dyson, Russian Aleksander Skvortsov, Russian Mikhail Kornienko, NASA's Scott Kelly, Russian Alexander Samokutyayev, and Russian Andrei Borisenko are seen during the State Commission meeting to approve the Soyuz launch of Caldwell Dyson, Skvortsov and Kornienko, Thursday, April 1, 2010 in Baikonur, Kazakhstan. The crew is kept in a separate room with a glass window in order to help maintain their health. Photo Credit: (NASA/Bill Ingalls)

T-38 A- AIRCRAFT (NASA 924)

NASA Image and Video Library

1983-12-07

S82-33032 (30 June 1982) --- This scene shows activity at the spacecraft communicator and flight activities officer consoles in the mission operations control room (MOCR) in the Johnson Space Center?s mission control center (MCC). Astronaut Brewster H. Shaw Jr., right, Astronaut Roy D. Bridges Jr. and Marianne J. Dyson are pictured during STS-4?s Day 4 activity. Shaw and Bridges are spacecraft communicators and Dyson is a flight activities officer on the entry team.

Women's History Month at NASA

NASA Image and Video Library

2011-03-14

NASA Astronaut and Expeditions 23 and 24 Flight Engineer, Tracy Caldwell Dyson, far left, speaks at a Women's History Month event at NASA Headquarters, Wednesday, March 16, 2011 in Washington. The event entitled Women Inspiring the Next Generation to Reveal the Unknown is a joint venture with NASA and the White House Council on Women and Girls. Caldwell Dyson recently returned from a six-month stay aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

Wilson loop from a Dyson equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pak, M.; Reinhardt, H.

2009-12-15

The Dyson equation proposed for planar temporal Wilson loops in the context of supersymmetric gauge theories is critically analyzed thereby exhibiting its ingredients and approximations involved. We reveal its limitations and identify its range of applicability in nonsupersymmetric gauge theories. In particular, we show that this equation is applicable only to strongly asymmetric planar Wilson loops (consisting of a long and a short pair of loop segments) and as a consequence the Wilsonian potential can be extracted only up to intermediate distances. By this equation the Wilson loop is exclusively determined by the gluon propagator. We solve the Dyson equationmore » in Coulomb gauge for the temporal Wilson loop with the instantaneous part of the gluon propagator and for the spatial Wilson loop with the static gluon propagator obtained in the Hamiltonian approach to continuum Yang-Mills theory and on the lattice. In both cases we find a linearly rising color potential.« less

PREFACE: International Conference on Dynamics of Systems on the Nanoscale (DySoN 2012)

NASA Astrophysics Data System (ADS)

Solov'yov, Andrey V.

2013-06-01

Conference logo The Second International Conference 'Dynamics of Systems on the Nanoscale' (DySoN 2012) took place in Saint Petersburg, Russia between 30 September and 4 October 2012. The venue was the Courtyard by Marriott St Petersburg Vasilievsky Hotel, 2nd line of Vasilievsky Island 61/30A, 199178. The conference was organized by the Frankfurt Institute for Advanced Studies - Goethe University, A F Ioffe Physical-Technical Institute and Saint Petersburg State Polytechnic University. This DySoN conference has been built upon a series of International Symposia 'Atomic Cluster Collisions: structure and dynamics from the nuclear to the biological scale' (ISACC 2003, ISACC 2007, ISACC 2008, ISACC 2009 and ISACC 2011). During these meetings it has become clear that there is a need for an interdisciplinary conference covering a broader range of topics than just atomic cluster collisions, related to the Dynamics of Systems on a Nanoscale. Therefore, in 2010 it was decided to launch a new conference series under the title 'Dynamics of Systems on the Nanoscale'. The first DySoN conference took place at the National Research Council, Rome, Italy in 2010. The DySoN 2012 is the second conference in this series. The DySoN 2012 Conference promoted the growth and exchange of interdisciplinary scientific information on the structure, formation and dynamics of animate and inanimate matter on the nanometer scale. There are many examples of complex many-body systems of micro- and nanometer scale size exhibiting unique features, properties and functions. These systems may have very different nature and origin, e.g. atomic and molecular clusters, nanoobjects, ensembles of nanoparticles, nanostructures, biomolecules, biomolecular and mesoscopic systems. A detailed understanding of the structure and dynamics of these systems on the nanometer scale is an important fundamental task, the solution of which is necessary in numerous applications of nano- and biotechnology, material science and medicine. Although mesoscopic, nano- and biomolecular systems differ in their nature and origin, a number of fundamental problems are common to all of them: what are the underlying principles of self-organization and self-assembly of matter on the micro- and nanoscale? Are these principles classical or quantum? How does function emerge on the nano- and the mesoscale in systems of different origin? What criteria govern the stability of these systems? How do their properties change as a function of size and composition? How are their properties altered by their environment? Seeking answers to these questions is at the core of a new interdisciplinary field that lies at the intersection of physics, chemistry and biology, a field called Meso-Bio-Nano (MBN) Science. Both experimental and theoretical aspects of the mentioned problems were discussed at the DySoN 2012 Conference. Particular attention was devoted to dynamical phenomena and many-body effects taking place in various MBN systems, which include problems of structure formation, fusion and fission, collision and fragmentation, collective electron excitations, reactivity, nanoscale phase transitions, nanoscale insights into biodamage, channeling phenomena and many more. This volume is a collection of the contributions received from the participants of the DySoN 2012 Conference. It provides an overview of the topics, new results and ideas that have been discussed at the conference. I would like to thank all the authors of these proceedings, as well as all the participants of the conference for making it so successful. The third DySoN Conference will be held in Edinburgh in May 2014. A V Solov'yov Frankfurt Institute for Advanced Studies, Ruth-Moufang Str. 1, 60438, Frankfurt am Main, Germany On leave from A F Ioffe Physical-Technical Institute, Polytechnicheskaya 26, 194021, St. Petersburg, Russia E-mail: solovyov@fias.uni-frankfurt.de The PDF contains further information about the conference. Conference photograph Picture

US EVA 16 EMU Prep

NASA Image and Video Library

2010-08-11

ISS024-E-011673 (11 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, attired in her Extravehicular Mobility Unit (EMU) spacesuit, is pictured in the Quest airlock of the International Space Station as the second of three planned spacewalks to remove and replace an ammonia pump module that failed July 31 draws to a close. NASA astronaut Shannon Walker and Russian cosmonaut Fyodor Yurchikhin, both flight engineers, assist Caldwell Dyson with the doffing of her spacesuit.

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

Expedition 23 crew members NASA’s Tracy Caldwell Dyson (second from left), Russian Alexander Skvortsov and Russian Mikhail Kornienko (right) pose for photographers during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan, Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of Russia, top, NASA Flight Engineer Tracy Caldwell Dyson of the U.S. and Soyuz Commander Alexander Skvortsov of Russia, bottom, wave farewell from the bottom of the Soyuz rocket at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko, Caldwell Dyson and Skvortsov launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 at 10:04 a.m. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

Expedition 23 crew members, from left, NASA’s Tracy Caldwell Dyson, Russian Alexander Skvortsov and Russian Mikhail Kornienko pose for photographers during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan, Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

Expedition 23 crew members, from left, NASA’s Tracy Caldwell Dyson, Russian Alexander Skvortsov and Russian Mikhail Kornienko are seen during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan, Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Expedition 24 Soyuz Landing

NASA Image and Video Library

2010-09-24

Russian search and rescue teams arrive at the landing site seconds after the Soyuz TMA-18 spacecraft touched down with Expedition 24 Commander Alexander Skvortsov and Flight Engineers Tracy Caldwell Dyson and Mikhail Kornienko near the town of Arkalyk, Kazakhstan on Saturday, Sept. 25, 2010. Russian Cosmonauts Skvortsov and Kornienko and NASA Astronaut Caldwell Dyson, are returning from six months onboard the International Space Station where they served as members of the Expedition 23 and 24 crews. Photo Credit: (NASA/Bill Ingalls)

Expedition 24 Soyuz Landing

NASA Image and Video Library

2010-09-24

Expedition 24 Commander Alexander Skvortsov laughs after being given fresh fruit and vegetables shortly after landing in the Soyuz TMA-18 spacecraft with fellow crew members Tracy Caldwell Dyson and Mikhail Kornienko near the town of Arkalyk, Kazakhstan on Saturday, Sept. 25, 2010. Russian Cosmonauts Skvortsov and Kornienko and NASA Astronaut Caldwell Dyson, are returning from six months onboard the International Space Station where they served as members of the Expedition 23 and 24 crews. Photo Credit: (NASA/Bill Ingalls)

Expedition 24 Soyuz Landing

NASA Image and Video Library

2010-09-24

Russian search and rescue personnel and engineers prepare to extract the crew from the Soyuz TMA-18 moments after it landed with Expedition 24 Commander Alexander Skvortsov and Flight Engineers Tracy Caldwell Dyson and Mikhail Kornienko near the town of Arkalyk, Kazakhstan on Saturday, Sept. 25, 2010. Russian Cosmonauts Skvortsov and Kornienko and NASA Astronaut Caldwell Dyson, are returning from six months onboard the International Space Station where they served as members of the Expedition 23 and 24 crews. Photo Credit: (NASA/Bill Ingalls)

Expedition 24 Soyuz Landing

NASA Image and Video Library

2010-09-24

Girls in traditional Kazakhstan dress await the arrival of the Soyuz TMA-18 crew at the Karaganda airport in Kazakhstan. The Soyuz TMA-18 spacecraft, carrying Expedition 24 Commander Alexander Skvortsov and Flight Engineers Tracy Caldwell Dyson and Mikhail Kornienko, landed, near the town of Arkalyk, Kazakhstan on Saturday, Sept. 25, 2010. Russian Cosmonauts Skvortsov and Kornienko and NASA Astronaut Caldwell Dyson, are returning from six months onboard the International Space Station where they served as members of the Expedition 23 and 24 crews. Photo Credit: (NASA/Bill Ingalls)

Are the Dyson rings around pulsars detectable?

NASA Astrophysics Data System (ADS)

Osmanov, Z.

2018-04-01

In the previous paper ring (Osmanov 2016) (henceforth Paper-I) we have extended the idea of Freeman Dyson and have shown that a supercivilization has to use ring-like megastructures around pulsars instead of a spherical shell. In this work we reexamine the same problem in the observational context and we show that facilities of modern infrared (IR) telescopes (Very Large Telescope Interferometer and Wide-field Infrared Survey Explorer (WISE)) might efficiently monitor the nearby zone of the solar system and search for the IR Dyson-rings up to distances of the order of 0.2 kpc, corresponding to the current highest achievable angular resolution, 0.001 mas. In this case the total number of pulsars in the observationally reachable area is about 64 +/- 21. We show that pulsars from the distance of the order of ~ 1 kpc are still visible for WISE as point-like sources but in order to confirm that the object is the neutron star, one has to use the ultraviolet telescopes, which at this moment cannot provide enough sensitivity.

On the search for artificial Dyson-like structures around pulsars

NASA Astrophysics Data System (ADS)

Osmanov, Z.

2016-04-01

Assuming the possibility of existence of a supercivilization we extend the idea of Freeman Dyson considering pulsars instead of stars. It is shown that instead of a spherical shell the supercivilization must use ring-like constructions. We have found that a size of the `ring' should be of the order of (10-4-10-1) AU with temperature interval (300-600) K for relatively slowly rotating pulsars and (10-350) AU with temperature interval (300-700) K for rapidly spinning neutron stars, respectively. Although for the latter the Dyson construction is unrealistically massive and cannot be considered seriously. Analyzing the stresses in terms of the radiation and wind flows it has been argued that they cannot significantly affect the ring construction. On the other hand, the ring in-plane unstable equilibrium can be restored by the energy which is small compared with the energy extracted from the star. This indicates that the search for infrared ring-like sources close to slowly rotating pulsars seems to be quite promising.

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

The crew of Expedition 23 are seen on a large TV screen in the Russian Mission Control Center in Korolev, Russia, Sunday, April 4, 2010, shortly after the Soyuz TMA-18 spacecraft docked to the International Space Station and delivered Expedition 23 Flight Engineers Alexander Skvortsov, Mikhail Kornienko and Tracy Caldwell Dyson. Clockwise from top right are NASA astronaut TJ Creamer, NASA astronaut Tracy Caldwell Dyson, Russian cosmonaut Alexander Skvortsov, Russian cosmonaut Mikhail Kornienko, JAXA (Japan Aerospace Exploration Agency) astronaut Soichi Noguchi and Expedition 23 commander Russian cosmonaut Oleg Kotov . Photo Credit: (NASA/Carla Cioffi)

Inverse participation ratios in the XX spin chain

NASA Astrophysics Data System (ADS)

Tsukerman, Emmanuel

2017-03-01

We continue the study of the inverse participation ratios (IPRs) of the XXZ Heisenberg spin chain initiated by Stéphan, Furukawa, Misguich, and Pasquier (2009) and continued by Misguich, Pasquier, and Luck (2016) by focusing on the case of the XX Heisenberg spin chain. For the ground state, Stéphan et al. note that calculating the IPR is equivalent to Dyson's constant term ex-conjecture. We express the IPRs of excited states as an apparently new "discrete" Hall inner product. We analyze this inner product using the theory of symmetric functions (Jack polynomials, Schur polynomials, the standard Hall inner product, and ωq ,t) to determine some exact expressions and asymptotics for IPRs. We show that IPRs can be indexed by partitions, and asymptotically the IPR of a partition is equal to that of the conjugate partition. We relate the IPRs to two other models from physics, namely, the circular symplectic ensemble of Dyson and the Dyson-Gaudin two-dimensional Coulomb lattice gas. Finally, we provide a description of the IPRs in terms of a signed count of diagonals of permutohedra.

Tensorial Gross-Neveu models

NASA Astrophysics Data System (ADS)

Benedetti, Dario; Carrozza, Sylvain; Gurau, Razvan; Sfondrini, Alessandro

2018-01-01

We define and study various tensorial generalizations of the Gross-Neveu model in two dimensions, that is, models with four-fermion interactions and G 3 symmetry, where we take either G = U( N) or G = O( N). Such models can also be viewed as two-dimensional generalizations of the Sachdev-Ye-Kitaev model, or more precisely of its tensorial counterpart introduced by Klebanov and Tarnopolsky, which is in part our motivation for studying them. Using the Schwinger-Dyson equations at large- N, we discuss the phenomenon of dynamical mass generation and possible combinations of couplings to avoid it. For the case G = U( N),we introduce an intermediate field representation and perform a stability analysis of the vacua. It turns out that the only apparently viable combination of couplings that avoids mass generation corresponds to an unstable vacuum. The stable vacuum breaks U( N)3 invariance, in contradiction with the Coleman-Mermin-Wagner theorem, but this is an artifact of the large- N expansion, similar to the breaking of continuous chiral symmetry in the chiral Gross-Neveu model.

Three ways to solve critical ϕ4 theory on 4 ‑ 𝜖 dimensional real projective space: Perturbation, bootstrap, and Schwinger-Dyson equation

NASA Astrophysics Data System (ADS)

Hasegawa, Chika; Nakayama, Yu

2018-03-01

In this paper, we solve the two-point function of the lowest dimensional scalar operator in the critical ϕ4 theory on 4 ‑ 𝜖 dimensional real projective space in three different methods. The first is to use the conventional perturbation theory, and the second is to impose the cross-cap bootstrap equation, and the third is to solve the Schwinger-Dyson equation under the assumption of conformal invariance. We find that the three methods lead to mutually consistent results but each has its own advantage.

Quantum control and the challenge of non-Hermitian model-building

NASA Astrophysics Data System (ADS)

Znojil, Miloslav

2015-06-01

In a way inspired by the brief 2002 note “The challenge of nonhermitian structures in physics” by Ramirez and Mielnik (with the text most easily available via arXiv:quant- ph/0211048) the situation in the theory is briefly summarized here as it looks twelve years later. Our text has three parts. In the first one we briefly mention the pre-history (dating back to the Freeman Dyson's proposal of the non-Hermitian-Hamiltonian method in 1956 and to its subsequent successful “interacting boson model” applications in nuclear physics) and, first of all, the amazing recent progress reached, in the stationary case, using, in essence, an inversion of the Dyson's approach. The impact on the latter idea upon abstract quantum physics is sampled, first of all, by the reference to papers by Bender et al. (who made the non-Hermitian model-building popular under the nickname of parity-times-time-reflection- symmetric alias PT-symmetric quantum mechanics) and by Mostafazadeh (who reinterpreted PT-symmetry as P-pseudo-Hermiticity). In the second part of our review the emphasis is shifted to the newest, non-stationary upgrade of the formalism which we proposed in the year 2009 and which is characterized by the simultaneous participation of a triplet of Hilbert spaces H in the representation of a single quantum system. In the third part of the review we finally emphasize that the majority of applications of our three-Hilbert-space (THS) recipe is still ahead of us because the enhancement of the flexibility is necessarily accompanied by an enhancement of the technical difficulties. An escape out of the technical trap is proposed to be sought in a restriction of attention to quantum models living in finite-dimensional Hilbert spaces H. As long as the use of such spaces is so typical for the quantum-control considerations, we conclude with conjecture that the THS formalism should start searching for implementations in the field of quantum control.

Two-flavor hybrid stars with the Dyson-Schwinger quark model

NASA Astrophysics Data System (ADS)

Wei, J. B.; Chen, H.; Schulze, H.-J.

2017-11-01

We study the properties of two-flavor quark matter in the Dyson-Schwinger model and investigate the possible consequences for hybrid neutron stars, with particular regard to the two-solar-mass limit. We find that with some extreme values of the model parameters, the mass fraction of two-flavor quark matter in heavy neutron stars can be as high as 30 percent and the possible energy release during the conversion from nucleonic neutron stars to hybrid stars can reach 1052 erg. Supported by NSFC (11305144, 11475149, 11303023), Central Universities (CUGL 140609) in China, “NewCompStar,” COST Action MP1304

Photoionization of furan from the ground and excited electronic states.

PubMed

Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

2016-02-28

Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

Solvable two-dimensional time-dependent non-Hermitian quantum systems with infinite dimensional Hilbert space in the broken PT-regime

NASA Astrophysics Data System (ADS)

Fring, Andreas; Frith, Thomas

2018-06-01

We provide exact analytical solutions for a two-dimensional explicitly time-dependent non-Hermitian quantum system. While the time-independent variant of the model studied is in the broken PT-symmetric phase for the entire range of the model parameters, and has therefore a partially complex energy eigenspectrum, its time-dependent version has real energy expectation values at all times. In our solution procedure we compare the two equivalent approaches of directly solving the time-dependent Dyson equation with one employing the Lewis–Riesenfeld method of invariants. We conclude that the latter approach simplifies the solution procedure due to the fact that the invariants of the non-Hermitian and Hermitian system are related to each other in a pseudo-Hermitian fashion, which in turn does not hold for their corresponding time-dependent Hamiltonians. Thus constructing invariants and subsequently using the pseudo-Hermiticity relation between them allows to compute the Dyson map and to solve the Dyson equation indirectly. In this way one can bypass to solve nonlinear differential equations, such as the dissipative Ermakov–Pinney equation emerging in our and many other systems.

CrasyDSE: A framework for solving Dyson-Schwinger equations.

PubMed

Huber, Markus Q; Mitter, Mario

2012-11-01

Dyson-Schwinger equations are important tools for non-perturbative analyses of quantum field theories. For example, they are very useful for investigations in quantum chromodynamics and related theories. However, sometimes progress is impeded by the complexity of the equations. Thus automating parts of the calculations will certainly be helpful in future investigations. In this article we present a framework for such an automation based on a C++ code that can deal with a large number of Green functions. Since also the creation of the expressions for the integrals of the Dyson-Schwinger equations needs to be automated, we defer this task to a Mathematica notebook. We illustrate the complete workflow with an example from Yang-Mills theory coupled to a fundamental scalar field that has been investigated recently. As a second example we calculate the propagators of pure Yang-Mills theory. Our code can serve as a basis for many further investigations where the equations are too complicated to tackle by hand. It also can easily be combined with DoFun , a program for the derivation of Dyson-Schwinger equations. Program title : CrasyDSE Catalogue identifier : AEMY _v1_0 Program summary URL : http://cpc.cs.qub.ac.uk/summaries/AEMY_v1_0.html Program obtainable from : CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions : Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc. : 49030 No. of bytes in distributed program, including test data, etc. : 303958 Distribution format : tar.gz Programming language : Mathematica 8 and higher, C++ . Computer : All on which Mathematica and C++ are available. Operating system : All on which Mathematica and C++ are available (Windows, Unix, Mac OS). Classification : 11.1, 11.4, 11.5, 11.6. Nature of problem : Solve (large) systems of Dyson-Schwinger equations numerically. Solution method : Create C++ functions in Mathematica to be used for the numeric code in C++ . This code uses structures to handle large numbers of Green functions. Unusual features : Provides a tool to convert Mathematica expressions into C++ expressions including conversion of function names. Running time : Depending on the complexity of the investigated system solving the equations numerically can take seconds on a desktop PC to hours on a cluster.

CrasyDSE: A framework for solving Dyson-Schwinger equations

NASA Astrophysics Data System (ADS)

Huber, Markus Q.; Mitter, Mario

2012-11-01

Dyson-Schwinger equations are important tools for non-perturbative analyses of quantum field theories. For example, they are very useful for investigations in quantum chromodynamics and related theories. However, sometimes progress is impeded by the complexity of the equations. Thus automating parts of the calculations will certainly be helpful in future investigations. In this article we present a framework for such an automation based on a C++ code that can deal with a large number of Green functions. Since also the creation of the expressions for the integrals of the Dyson-Schwinger equations needs to be automated, we defer this task to a Mathematica notebook. We illustrate the complete workflow with an example from Yang-Mills theory coupled to a fundamental scalar field that has been investigated recently. As a second example we calculate the propagators of pure Yang-Mills theory. Our code can serve as a basis for many further investigations where the equations are too complicated to tackle by hand. It also can easily be combined with DoFun, a program for the derivation of Dyson-Schwinger equations.

Random functions via Dyson Brownian Motion: progress and problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Gaoyuan; Battefeld, Thorsten

2016-09-05

We develope a computationally efficient extension of the Dyson Brownian Motion (DBM) algorithm to generate random function in C{sup 2} locally. We further explain that random functions generated via DBM show an unstable growth as the traversed distance increases. This feature restricts the use of such functions considerably if they are to be used to model globally defined ones. The latter is the case if one uses random functions to model landscapes in string theory. We provide a concrete example, based on a simple axionic potential often used in cosmology, to highlight this problem and also offer an ad hocmore » modification of DBM that suppresses this growth to some degree.« less

Expedition 19 Crew Training

NASA Image and Video Library

2009-03-20

Expedition 19 Flight Engineer Michael R. Barratt and backup spaceflight participant Esther Dyson exercise at the Cosmonaut Hotel, Saturday, March 21, 2009 in Baikonur, Kazakhstan. (Photo Credit: NASA/Bill Ingalls)

Photoelectron wave function in photoionization: plane wave or Coulomb wave?

PubMed

Gozem, Samer; Gunina, Anastasia O; Ichino, Takatoshi; Osborn, David L; Stanton, John F; Krylov, Anna I

2015-11-19

The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectron wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. The results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.

Leading-order calculation of hadronic contributions to the Muon g-2 using the Dyson-Schwinger approach

NASA Astrophysics Data System (ADS)

Goecke, Tobias; Fischer, Christian S.; Williams, Richard

2011-10-01

We present a calculation of the hadronic vacuum polarisation (HVP) tensor within the framework of Dyson-Schwinger equations. To this end we use a well-established phenomenological model for the quark-gluon interaction with parameters fixed to reproduce hadronic observables. From the HVP tensor we compute both the Adler function and the HVP contribution to the anomalous magnetic moment of the muon, aμ. We find aμHVP = 6760 ×10-11 which deviates about two percent from the value extracted from experiment. Additionally, we make comparison with a recent lattice determination of aμHVP and find good agreement within our approach. We also discuss the implications of our result for a corresponding calculation of the hadronic light-by-light scattering contribution to aμ.

Hadronic contribution to the muon g-2: A Dyson-Schwinger perspective

NASA Astrophysics Data System (ADS)

Goecke, T.; Fischer, C. S.; Williams, R.

2012-04-01

We summarize our results for hadronic contributions to the anomalous magnetic moment of the muon (aμ), the one from hadronic vacuum-polarization (HVP) and the light-by-light scattering contribution (LBL), obtained from the Dyson-Schwinger equations (DSEs) of QCD. In the case of HVP we find good agreement with model independent determinations from dispersion relations for aμHV P as well as for the Adler function with deviations well below the ten percent level. From this we conclude that the DSE approach should be capable of describing aμLBL with similar accuracy. We also present results for LBL using a resonance expansion of the quark-anti-quark T-matrix. Our preliminary value is aμLBL=(217±91)×10-11.

Quark Propagator with electroweak interactions in the Dyson-Schwinger approach

NASA Astrophysics Data System (ADS)

Mian, Walid Ahmed; Maas, Axel

2017-03-01

Motivated by the non-negligible dynamical backcoupling of the electroweak interactions with the strong interaction during neutron star mergers, we study the effects of the explicit breaking of C, P and flavor symmetry on the strong sector. The quark propagator is the simplest object which encodes the consequences of these breakings. To asses the impact, we study the influence of especially parity violation on the propagator for various masses. For this purpose the functional methods in form of Dyson-Schwinger-Equations are employed. We find that explicit isospin breaking leads to a qualitative change of behavior even for a slight explicit breaking, which is in contrast to the expectations from perturbation theory. Our results thus suggest that non-perturbative backcoupling effects could be larger than expected.

Velocity statistics for interacting edge dislocations in one dimension from Dyson's Coulomb gas model.

PubMed

Jafarpour, Farshid; Angheluta, Luiza; Goldenfeld, Nigel

2013-10-01

The dynamics of edge dislocations with parallel Burgers vectors, moving in the same slip plane, is mapped onto Dyson's model of a two-dimensional Coulomb gas confined in one dimension. We show that the tail distribution of the velocity of dislocations is power law in form, as a consequence of the pair interaction of nearest neighbors in one dimension. In two dimensions, we show the presence of a pairing phase transition in a system of interacting dislocations with parallel Burgers vectors. The scaling exponent of the velocity distribution at effective temperatures well below this pairing transition temperature can be derived from the nearest-neighbor interaction, while near the transition temperature, the distribution deviates from the form predicted by the nearest-neighbor interaction, suggesting the presence of collective effects.

ARED Pulley and Rope

NASA Image and Video Library

2010-09-09

ISS024-E-014009 (9 Sept. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, works with the advanced Resistive Exercise Device (aRED) in the Tranquility node of the International Space Station.

GLACIER Express Rack Setup

NASA Image and Video Library

2010-09-01

ISS024-E-012995 (1 Sept. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.

Similarity-transformed dyson mapping and SDG-interacting boson hamiltonian

NASA Astrophysics Data System (ADS)

Navrátil, P.; Dobeš, J.

1991-10-01

The sdg-interacting boson hamiltonian is constructed from the fermion shell-model input. The seniority boson mapping as given by the similarity-transformed Dyson boson mapping is used. The s, d, and g collective boson amplitudes are determined consistently from the mapped hamiltonian. Influence of the starting shell-model parameters is discussed. Calculations for the Sm isotopic chain and for the 148Sm, 150Nd, and 196Pt nuclei are presented. Calculated energy levels as well as E2 and E4 properties agree rather well with experimental ones. To obtain such agreement, the input shell-model parameters cannot be fixed at a constant set for several nuclei but have to be somewhat varied, especially in the deformed region. Possible reasons for this variation are discussed. Effects of the explicit g-boson consideration are shown.

Irreversibility and entanglement spectrum statistics in quantum circuits

NASA Astrophysics Data System (ADS)

Shaffer, Daniel; Chamon, Claudio; Hamma, Alioscia; Mucciolo, Eduardo R.

2014-12-01

We show that in a quantum system evolving unitarily under a stochastic quantum circuit the notions of irreversibility, universality of computation, and entanglement are closely related. As the state evolves from an initial product state, it gets asymptotically maximally entangled. We define irreversibility as the failure of searching for a disentangling circuit using a Metropolis-like algorithm. We show that irreversibility corresponds to Wigner-Dyson statistics in the level spacing of the entanglement eigenvalues, and that this is obtained from a quantum circuit made from a set of universal gates for quantum computation. If, on the other hand, the system is evolved with a non-universal set of gates, the statistics of the entanglement level spacing deviates from Wigner-Dyson and the disentangling algorithm succeeds. These results open a new way to characterize irreversibility in quantum systems.

Is interstellar archeology possible?

NASA Astrophysics Data System (ADS)

Carrigan, Richard A.

2012-09-01

Searching for signatures of cosmic-scale archeological artifacts such as Dyson spheres is an interesting alternative to conventional radio SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archeology or sometimes cosmic archeology. A variety of interstellar archeology signatures is discussed including non-natural planetary atmospheric constituents, stellar doping, Dyson spheres, as well as signatures of stellar, and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is reviewed in the discussion of galactic signatures. These potential interstellar archeological signatures are classified using the Kardashev scale. A modified Drake equation is introduced. With few exceptions interstellar archeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.

Photoelectron wave function in photoionization: Plane wave or Coulomb wave? [Does photoionization of neutral targets produce Coulomb or plane waves?

DOE PAGES

Gozem, Samer; Gunina, Anastasia O.; Ichino, Takatoshi; ...

2015-10-28

The calculation of absolute total cross sections requires accurate wave functions of the photoelectron and of the initial and final states of the system. The essential information contained in the latter two can be condensed into a Dyson orbital. We employ correlated Dyson orbitals and test approximate treatments of the photoelectron wave function, that is, plane and Coulomb waves, by comparing computed and experimental photoionization and photodetachment spectra. We find that in anions, a plane wave treatment of the photoelectron provides a good description of photodetachment spectra. For photoionization of neutral atoms or molecules with one heavy atom, the photoelectronmore » wave function must be treated as a Coulomb wave to account for the interaction of the photoelectron with the +1 charge of the ionized core. For larger molecules, the best agreement with experiment is often achieved by using a Coulomb wave with a partial (effective) charge smaller than unity. This likely derives from the fact that the effective charge at the centroid of the Dyson orbital, which serves as the origin of the spherical wave expansion, is smaller than the total charge of a polyatomic cation. Finally, the results suggest that accurate molecular photoionization cross sections can be computed with a modified central potential model that accounts for the nonspherical charge distribution of the core by adjusting the charge in the center of the expansion.« less

Coupled-cluster Green's function: Analysis of properties originating in the exponential parametrization of the ground-state wave function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Bo; Kowalski, Karol

In this paper we derive basic properties of the Green’s function matrix elements stemming from the exponential coupled cluster (CC) parametrization of the ground-state wave function. We demon- strate that all intermediates used to express retarded (or equivalently, ionized) part of the Green’s function in the ω-representation can be expressed through connected diagrams only. Similar proper- ties are also shared by the first order ω-derivatives of the retarded part of the CC Green’s function. This property can be extended to any order ω-derivatives of the Green’s function. Through the Dyson equation of CC Green’s function, the derivatives of corresponding CCmore » self-energy can be evaluated analytically. In analogy to the CC Green’s function, the corresponding CC self-energy is expressed in terms of connected diagrams only. Moreover, the ionized part of the CC Green’s func- tion satisfies the non-homogeneous linear system of ordinary differential equations, whose solution may be represented in the exponential form. Our analysis can be easily generalized to the advanced part of the CC Green’s function.« less

Compact Infrared Spectrometers

NASA Technical Reports Server (NTRS)

Mouroulis, Pantazis

2009-01-01

Concentric spectrometer forms are advantageous for constructing a variety of systems spanning the entire visible to infrared range. Spectrometer examples are given, including broadband or high resolution forms. Some issues associated with the Dyson catadioptric type are also discussed.

Dynamical mass generation in unquenched QED using the Dyson-Schwinger equations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kızılersü, Ayse; Sizer, Tom; Pennington, Michael R.

We present a comprehensive numerical study of dynamical mass generation for unquenched QED in four dimensions, in the absence of four-fermion interactions, using the Dyson-Schwinger approach. We begin with an overview of previous investigations of criticality in the quenched approximation. To this we add an analysis using a new fermion-antifermion-boson interaction ansatz, the Kizilersu-Pennington (KP) vertex, developed for an unquenched treatment. After surveying criticality in previous unquenched studies, we investigate the performance of the KP vertex in dynamical mass generation using a renormalized fully unquenched system of equations. This we compare with the results for two hybrid vertices incorporating themore » Curtis-Pennington vertex in the fermion equation. We conclude that the KP vertex is as yet incomplete, and its relative gauge-variance is due to its lack of massive transverse components in its design.« less

Entanglement complexity in quantum many-body dynamics, thermalization, and localization

NASA Astrophysics Data System (ADS)

Yang, Zhi-Cheng; Hamma, Alioscia; Giampaolo, Salvatore M.; Mucciolo, Eduardo R.; Chamon, Claudio

2017-07-01

Entanglement is usually quantified by von Neumann entropy, but its properties are much more complex than what can be expressed with a single number. We show that the three distinct dynamical phases known as thermalization, Anderson localization, and many-body localization are marked by different patterns of the spectrum of the reduced density matrix for a state evolved after a quantum quench. While the entanglement spectrum displays Poisson statistics for the case of Anderson localization, it displays universal Wigner-Dyson statistics for both the cases of many-body localization and thermalization, albeit the universal distribution is asymptotically reached within very different time scales in these two cases. We further show that the complexity of entanglement, revealed by the possibility of disentangling the state through a Metropolis-like algorithm, is signaled by whether the entanglement spectrum level spacing is Poisson or Wigner-Dyson distributed.

Alien calculus and a Schwinger-Dyson equation: two-point function with a nonperturbative mass scale

NASA Astrophysics Data System (ADS)

Bellon, Marc P.; Clavier, Pierre J.

2018-02-01

Starting from the Schwinger-Dyson equation and the renormalization group equation for the massless Wess-Zumino model, we compute the dominant nonperturbative contributions to the anomalous dimension of the theory, which are related by alien calculus to singularities of the Borel transform on integer points. The sum of these dominant contributions has an analytic expression. When applied to the two-point function, this analysis gives a tame evolution in the deep euclidean domain at this approximation level, making doubtful the arguments on the triviality of the quantum field theory with positive β -function. On the other side, we have a singularity of the propagator for timelike momenta of the order of the renormalization group invariant scale of the theory, which has a nonperturbative relationship with the renormalization point of the theory. All these results do not seem to have an interpretation in terms of semiclassical analysis of a Feynman path integral.

Dynamical mass generation in unquenched QED using the Dyson-Schwinger equations

DOE PAGES

Kızılersü, Ayse; Sizer, Tom; Pennington, Michael R.; ...

2015-03-13

We present a comprehensive numerical study of dynamical mass generation for unquenched QED in four dimensions, in the absence of four-fermion interactions, using the Dyson-Schwinger approach. We begin with an overview of previous investigations of criticality in the quenched approximation. To this we add an analysis using a new fermion-antifermion-boson interaction ansatz, the Kizilersu-Pennington (KP) vertex, developed for an unquenched treatment. After surveying criticality in previous unquenched studies, we investigate the performance of the KP vertex in dynamical mass generation using a renormalized fully unquenched system of equations. This we compare with the results for two hybrid vertices incorporating themore » Curtis-Pennington vertex in the fermion equation. We conclude that the KP vertex is as yet incomplete, and its relative gauge-variance is due to its lack of massive transverse components in its design.« less

Low-momentum ghost dressing function and the gluon mass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boucaud, Ph.; Leroy, J. P.; Le Yaouanc, A.

2010-09-01

We study the low-momentum ghost propagator Dyson-Schwinger equation in the Landau gauge, assuming for the truncation a constant ghost-gluon vertex, as it is extensively done, and a simple model for a massive gluon propagator. Then, regular Dyson-Schwinger equation solutions (the zero-momentum ghost dressing function not diverging) appear to emerge, and we show the ghost propagator to be described by an asymptotic expression reliable up to the order O(q{sup 2}). That expression, depending on the gluon mass and the zero-momentum Taylor-scheme effective charge, is proven to fit pretty well some low-momentum ghost propagator data [I. L. Bogolubsky, E. M. Ilgenfritz, M.more » Muller-Preussker, and A. Sternbeck, Phys. Lett. B 676, 69 (2009); Proc. Sci., LAT2007 (2007) 290] from big-volume lattice simulations where the so-called ''simulated annealing algorithm'' is applied to fix the Landau gauge.« less

Bending space-time: a commentary on Dyson, Eddington and Davidson (1920) 'A determination of the deflection of light by the Sun's gravitational field'.

PubMed

Longair, Malcolm

2015-04-13

The famous eclipse expedition of 1919 to Sobral, Brazil, and the island of Principe, in the Gulf of Guinea, led by Dyson, Eddington and Davidson was a turning point in the history of relativity, not only because of its importance as a test of Einstein's General Theory of Relativity, but also because of the intense public interest which was aroused by the success of the expedition. The dramatic sequence of events which occurred is reviewed, as well as the long-term impact of its success. The gravitational bending of electromagnetic waves by massive bodies is a subject of the greatest importance for contemporary and future astronomy, astrophysics and cosmology. Examples of the potential impact of this key tool of modern observational astronomy are presented. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society.

Similarity-transformed equation-of-motion vibrational coupled-cluster theory.

PubMed

Faucheaux, Jacob A; Nooijen, Marcel; Hirata, So

2018-02-07

A similarity-transformed equation-of-motion vibrational coupled-cluster (STEOM-XVCC) method is introduced as a one-mode theory with an effective vibrational Hamiltonian, which is similarity transformed twice so that its lower-order operators are dressed with higher-order anharmonic effects. The first transformation uses an exponential excitation operator, defining the equation-of-motion vibrational coupled-cluster (EOM-XVCC) method, and the second uses an exponential excitation-deexcitation operator. From diagonalization of this doubly similarity-transformed Hamiltonian in the small one-mode excitation space, the method simultaneously computes accurate anharmonic vibrational frequencies of all fundamentals, which have unique significance in vibrational analyses. We establish a diagrammatic method of deriving the working equations of STEOM-XVCC and prove their connectedness and thus size-consistency as well as the exact equality of its frequencies with the corresponding roots of EOM-XVCC. We furthermore elucidate the similarities and differences between electronic and vibrational STEOM methods and between STEOM-XVCC and vibrational many-body Green's function theory based on the Dyson equation, which is also an anharmonic one-mode theory. The latter comparison inspires three approximate STEOM-XVCC methods utilizing the common approximations made in the Dyson equation: the diagonal approximation, a perturbative expansion of the Dyson self-energy, and the frequency-independent approximation. The STEOM-XVCC method including up to the simultaneous four-mode excitation operator in a quartic force field and its three approximate variants are formulated and implemented in computer codes with the aid of computer algebra, and they are applied to small test cases with varied degrees of anharmonicity.

Similarity-transformed equation-of-motion vibrational coupled-cluster theory

NASA Astrophysics Data System (ADS)

Faucheaux, Jacob A.; Nooijen, Marcel; Hirata, So

2018-02-01

A similarity-transformed equation-of-motion vibrational coupled-cluster (STEOM-XVCC) method is introduced as a one-mode theory with an effective vibrational Hamiltonian, which is similarity transformed twice so that its lower-order operators are dressed with higher-order anharmonic effects. The first transformation uses an exponential excitation operator, defining the equation-of-motion vibrational coupled-cluster (EOM-XVCC) method, and the second uses an exponential excitation-deexcitation operator. From diagonalization of this doubly similarity-transformed Hamiltonian in the small one-mode excitation space, the method simultaneously computes accurate anharmonic vibrational frequencies of all fundamentals, which have unique significance in vibrational analyses. We establish a diagrammatic method of deriving the working equations of STEOM-XVCC and prove their connectedness and thus size-consistency as well as the exact equality of its frequencies with the corresponding roots of EOM-XVCC. We furthermore elucidate the similarities and differences between electronic and vibrational STEOM methods and between STEOM-XVCC and vibrational many-body Green's function theory based on the Dyson equation, which is also an anharmonic one-mode theory. The latter comparison inspires three approximate STEOM-XVCC methods utilizing the common approximations made in the Dyson equation: the diagonal approximation, a perturbative expansion of the Dyson self-energy, and the frequency-independent approximation. The STEOM-XVCC method including up to the simultaneous four-mode excitation operator in a quartic force field and its three approximate variants are formulated and implemented in computer codes with the aid of computer algebra, and they are applied to small test cases with varied degrees of anharmonicity.

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson waves farewell to well wishers as she departs the Cosmonaut Hotel on the morning of the Soyuz launch to the International Space Station on Friday, April 2, 2010 in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Strong Coupling Continuum QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pennington, M. R.

2011-05-23

The Schwinger-Dyson, Bethe-Salpeter system of equations are the link between coloured quarks and gluons, and colourless hadrons and their properties. This talk reviews some aspects of these studies from the infrared behaviour of ghosts to the prediction of electromagnetic form-factors.

Strong Coupling Continuum QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael Pennington

2011-05-01

The Schwinger-Dyson, Bethe-Salpeter system of equations are the link between coloured quarks and gluons, and colourless hadrons and their properties. This talk reviews some aspects of these studies from the infrared behaviour of ghosts to the prediction of electromagnetic form-factors.

StationLIFE_ Let’s Get Physical

NASA Image and Video Library

2015-05-08

Every month on StationLIFE, we’ll focus on a scientific area where the International Space Station is conducting groundbreaking research. This month, astronaut Tracy Dyson hosts a focus on how the station is a unique environment for physical sciences.

Vascular Blood Collection stowage in MELFI

NASA Image and Video Library

2010-08-26

ISS024-E-012555 (26 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, replaces a dewar tray containing biological samples in the Minus Eighty Laboratory Freezer for ISS (MELFI-1) in the Kibo laboratory of the International Space Station.

Vascular Blood Collection stowage in MELFI

NASA Image and Video Library

2010-08-26

ISS024-E-012553 (26 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, replaces a dewar tray containing biological samples in the Minus Eighty Laboratory Freezer for ISS (MELFI-1) in the Kibo laboratory of the International Space Station.

Kids in Space Water Absorption Flight Procedures #40 Demo

NASA Image and Video Library

2010-09-15

ISS024-E-014988 (15 Sept. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, conducts a demonstration for the "Kids in Space" session for Water Absorption Flight Procedures #40 in the Columbus laboratory of the International Space Station.

Kids in Space Water Absorption Flight Procedures 40 Demo

NASA Image and Video Library

2010-09-15

ISS024-E-014993 (15 Sept. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, conducts a demonstration for the "Kids in Space" session for Water Absorption Flight Procedures #40 in the Columbus laboratory of the International Space Station.

OGS Maintenance

NASA Image and Video Library

2010-07-21

ISS024-E-009246 (21 July 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, is pictured during troubleshooting operations of the Oxygen Generator System (OGS) hardware and replacement of an H2 (hydrogen) Dome Orbit Replaceable Unit (ORU) in the Destiny laboratory of the International Space Station.

Expeditions 23, 24 & 25 HQ Presentation

NASA Image and Video Library

2011-03-16

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011.

Vascular Blood Collection stowage in MELFI

NASA Image and Video Library

2010-08-26

ISS024-E-012546 (26 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, prepares to insert biological samples in a dewar tray in the Minus Eighty Laboratory Freezer for ISS (MELFI-1) in the Kibo laboratory of the International Space Station.

Vascular Blood Collection stowage in MELFI

NASA Image and Video Library

2010-08-26

ISS024-E-012548 (26 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, prepares to insert biological samples in a dewar tray in the Minus Eighty Laboratory Freezer for ISS (MELFI-1) in the Kibo laboratory of the International Space Station.

The robustness of zero-determinant strategies in Iterated Prisoner's Dilemma games.

PubMed

Chen, Jing; Zinger, Aleksey

2014-09-21

Press and Dyson (2012) discovered a special set of strategies in two-player Iterated Prisoner's Dilemma games, the zero-determinant (ZD) strategies. Surprisingly, a player using such strategies can unilaterally enforce a linear relation between the payoffs of the two players. In particular, with a subclass of such strategies, the extortionate strategies, the former player obtains an advantageous share of the total payoff of the players, and the other player׳s best response is to always cooperate, by doing which he maximizes the payoff of the extortioner as well. When an extortionate player faces a player who is not aware of the theory of ZD strategies and improves his own payoff by adaptively changing his strategy following some unknown dynamics, Press and Dyson conjecture that there always exist adapting paths for the latter leading to the maximum possible scores for both players. In this work we confirm their conjecture in a very strong sense, not just for extortionate strategies, but for all ZD strategies that impose positive correlations between the players' payoffs. We show that not only the conjectured adapting paths always exist, but that actually every adapting path leads to the maximum possible scores, although some paths may not lead to the unconditional cooperation by the adapting player. This is true even in the rare cases where the setup of Press and Dyson is not directly applicable. Our result shows that ZD strategies are even more powerful than as pointed out by their discoverers. Given our result, the player using ZD strategies is assured that she will receive the maximum payoff attainable under the desired payoff relation she imposes, without knowing how the other player will evolve. This makes the use of ZD strategies even more desirable for sentient players. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modeling Photoelectron Spectra of CuO, Cu2O, and CuO2 Anions with Equation-of-Motion Coupled-Cluster Methods: An Adventure in Fock Space.

PubMed

Orms, Natalie; Krylov, Anna I

2018-04-12

The experimental photoelectron spectra of di- and triatomic copper oxide anions have been reported previously. We present an analysis of the experimental spectra of the CuO - , Cu 2 O - , and CuO 2 - anions using equation-of-motion coupled-cluster (EOM-CC) methods. The open-shell electronic structure of each molecule demands a unique combination of EOM-CC methods to achieve an accurate and balanced representation of the multiconfigurational anionic- and neutral-state manifolds. Analysis of the Dyson orbitals associated with photodetachment from CuO - reveals the strong non-Koopmans character of the CuO states. For the lowest detachment energy, a good agreement between theoretical and experimental values is obtained with CCSD(T) (coupled-cluster with single and double excitations and perturbative account of triple excitations). The (T) correction is particularly important for Cu 2 O - . Use of a relativistic pseudopotential and matching basis set improves the quality of results in most cases. EOM-DIP-CCSD analysis of the low-lying states of CuO 2 - reveals multiple singlet and triplet anionic states near the triplet ground state, adding an extra layer of complexity to the interpretation of the experimental CuO 2 - photoelectron spectrum.

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson, left, and Soyuz Commander Alexander Skvortsov wave farewell to well wishers as they depart the Cosmonaut Hotel on the morning of their Soyuz launch to the International Space Station on Friday, April 2, 2010 in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Kirk Shireman, NASA's deputy ISS program manager, speaks during the State Commission meeting to approve the Soyuz launch of Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Commemorating John Dyson

NASA Astrophysics Data System (ADS)

Pittard, Julian M.

2015-03-01

John Dyson was born on the 7th January 1941 in Meltham Mills, West Yorkshire, England, and later grew up in Harrogate and Leeds. The proudest moment of John's early life was meeting Freddie Trueman, who became one of the greatest fast bowlers of English cricket. John used a state scholarship to study at Kings College London, after hearing a radio lecture by D. M. McKay. He received a first class BSc Special Honours Degree in Physics in 1962, and began a Ph.D. at the University of Manchester Department of Astronomy after being attracted to astronomy by an article of Zdenek Kopal in the semi-popular journal New Scientist. John soon started work with Franz Kahn, and studied the possibility that the broad emission lines seen from the Orion Nebula were due to flows driven by the photoevaporation of neutral globules embedded in a HII region. John's thesis was entitled ``The Age and Dynamics of the Orion Nebula`` and he passed his oral examination on 28th February 1966.

Coulomb gauge ghost Dyson-Schwinger equation

NASA Astrophysics Data System (ADS)

Watson, P.; Reinhardt, H.

2010-12-01

A numerical study of the ghost Dyson-Schwinger equation in Coulomb gauge is performed and solutions for the ghost propagator found. As input, lattice results for the spatial gluon propagator are used. It is shown that in order to solve completely, the equation must be supplemented by a nonperturbative boundary condition (the value of the inverse ghost propagator dressing function at zero momentum), which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to low momenta until forced to freeze out in the infrared to the value of the boundary condition. The renormalization is shown to be largely independent of the boundary condition. The boundary condition and the pattern of the solutions can be interpreted in terms of the Gribov gauge-fixing ambiguity. The connection to the temporal gluon propagator and the infrared slavery picture of confinement is explored.

Thermal Infrared Spectral Imager for Airborne Science Applications

NASA Technical Reports Server (NTRS)

Johnson, William R.; Hook, Simon J.; Mouroulis, Pantazis; Wilson, Daniel W.; Gunapala, Sarath D.; Hill, Cory J.; Mumolo, Jason M.; Eng, Bjorn T.

2009-01-01

An airborne thermal hyperspectral imager is under development which utilizes the compact Dyson optical configuration and quantum well infrared photo detector (QWIP) focal plane array. The Dyson configuration uses a single monolithic prism-like grating design which allows for a high throughput instrument (F/1.6) with minimal ghosting, stray-light and large swath width. The configuration has the potential to be the optimal imaging spectroscopy solution for lighter-than-air (LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The planned instrument specifications are discussed as well as design trade-offs. Calibration testing results (noise equivalent temperature difference, spectral linearity and spectral bandwidth) and laboratory emissivity plots from samples are shown using an operational testbed unit which has similar specifications as the final airborne system. Field testing of the testbed unit was performed to acquire plots of apparent emissivity for various known standard minerals (such as quartz). A comparison is made using data from the ASTER spectral library.

Bending space–time: a commentary on Dyson, Eddington and Davidson (1920) ‘A determination of the deflection of light by the Sun's gravitational field’

PubMed Central

Longair, Malcolm

2015-01-01

The famous eclipse expedition of 1919 to Sobral, Brazil, and the island of Principe, in the Gulf of Guinea, led by Dyson, Eddington and Davidson was a turning point in the history of relativity, not only because of its importance as a test of Einstein's General Theory of Relativity, but also because of the intense public interest which was aroused by the success of the expedition. The dramatic sequence of events which occurred is reviewed, as well as the long-term impact of its success. The gravitational bending of electromagnetic waves by massive bodies is a subject of the greatest importance for contemporary and future astronomy, astrophysics and cosmology. Examples of the potential impact of this key tool of modern observational astronomy are presented. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750149

Dynamical chiral symmetry breaking and confinement with an infrared-vanishing gluon propagator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawes, F.T.; Roberts, C.D.; Williams, A.G.

1994-05-01

We study a model Dyson-Schwinger equation for the quark propagator closed using an [ital Ansatz] for the gluon propagator of the form [ital D]([ital q])[similar to][ital q][sup 2]/[([ital q][sup 2])[sup 2]+[ital b][sup 4

Expedition 23, 24, 25 HQ Visit

NASA Image and Video Library

2011-03-16

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011. (NASA/Paul E. Alers)

Expeditions 23, 24 & 25 HQ Presentation

NASA Image and Video Library

2011-03-16

Astronauts Tracy Caldwell Dyson, flight engineer on Expeditions 23 and 24, left, and Doug Wheelock, Expedition 24 flight engineer and commander of Expedition 25, discuss their mission to the International Space Station during a visit to NASA Headquarters in Washington, Wednesday, March 16, 2011. (NASA/Paul E. Alers)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Anatoly Perminov, head of the Russian Federal Space Agency (ROSCOSMOS), speaks during the State Commission meeting to approve the Soyuz launch of Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

US EVA 15 EMU Prep

NASA Image and Video Library

2010-08-07

ISS024-E-011561 (7 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, dons her Extravehicular Mobility Unit (EMU) spacesuit in the Quest airlock of the International Space Station in preparation for the first of three planned spacewalks to remove and replace an ammonia pump module that failed July 31.

Chiral symmetry breaking in quenched massive strong-coupling four-dimensional QED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawes, F.T.; Williams, A.G.

1995-03-15

We present results from a study of subtractive renormalization of the fermion propagator Dyson-Schwinger equation (DSE) in massive strong-coupling quenched four-dimensional QED. The results are compared for three different fermion-photon proper vertex [ital Ansa]$[ital uml---tze]: bare [gamma][sup [mu

Laboratory for Computer Science Progress Report 18, July 1980-June 1981,

DTIC Science & Technology

1983-04-01

group in collaboration with Rolf Landauer of IBM Research. Some of the most conspicuous participants: Dyson, Feynman, Wheeler Landauer, Keyes, Bennett...Sheldon A. Data Model Equivalence, December 1978, AD A062-753 TM-119 Shamir, Adi and Richard E. Zippel On the Security of the Merkle -Hellman

Expedition 23 Soyuz Launch

NASA Image and Video Library

2010-04-01

The Soyuz TMA-18 rocket launches from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 carrying Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. to the International Space Station. (Photo Credit: NASA/Bill Ingalls)

Expedition 23 Soyuz Launch

NASA Image and Video Library

2010-04-01

The Soyuz TMA-18 rocket launches from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 carrying Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. to the International Space Station. (Photo Credit: NASA/Carla Cioffi)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Sergei Krikalev, Chief, State Organization, Gagarin Research and Test Cosmonaut Training Center speaks during the State Commission meeting to approve the Soyuz launch of Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Anatoly Perminov, head of the Russian Federal Space Agency (ROSCOSMOS), second from left, speaks during the State Commission meeting to approve the Soyuz launch of Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Soyuz Launch

NASA Image and Video Library

2010-04-01

The Soyuz TMA-18 rocket launches from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 carrying Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. to the International Space Station. (Photo Credit: NASA/Bill Ingalls/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson talks with family and colleagues from behind glass prior to her launch onboard a Soyuz rocket with Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko of Russia to the International Space Station (ISS), Friday April 2, 2010 in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 crew members NASA Flight Engineer Tracy Caldwell Dyson, left, Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko, right, leave the Cosmonaut Hotel on the morning of their launch on a Soyuz rocket to the International Space Station, Friday, April 2, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Bill Ingalls)

An iconoclast's career

NASA Astrophysics Data System (ADS)

Anderson, Philip

2013-03-01

The "maverick genius" referred to in the title of Phillip Schewe's book is Freeman Dyson: a truly great mathematical physicist, bestselling author, longest-serving member of the US military's JASON advisory group, and occupant of the "fourth chair" when the Nobel Prize for Physics was awarded for quantum electrodynamics (QED) - among many other distinctions.

Investigating Cultural Collision: Educators' Perceptions of Hip-Hop Culture

ERIC Educational Resources Information Center

Beachum, Floyd D.

2013-01-01

Hip-hop music has been embraced worldwide by youth, pummeled in the media for supposedly increasing social misery and hailed as a significant musical breakthrough. Hip-hop culture has transcended musical boundaries and now impacts speech, clothing, mannerisms, movies, websites, television programming, magazines, and energy drinks (Dyson, 2007;…

Perceptions and Understanding of Games Creation: Teacher Candidates Perspective

ERIC Educational Resources Information Center

Treadwell, Sheri M.; Smith, Mark A.; Pratt, Erica

2014-01-01

Games Creation (GC) is an instructional strategy that encourages students to develop problem-solving and critical thinking skills. Children who experience GC have the potential to construct knowledge and a deeper understanding of game play (Rovegno & Bandhauer, 1994) and positive outcomes in motor skill development (Dyson, 2001; LaFont,…

BISE Experiment

NASA Image and Video Library

2010-08-30

ISS024-E-012668 (30 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, uses Neurospat hardware to perform the Bodies in the Space Environment (BISE) experiment in the Destiny laboratory of the International Space Station. The Canadian Space Agency-sponsored BISE experiment studies how astronauts perceive up and down in microgravity.

BISE Experiment

NASA Image and Video Library

2010-08-30

ISS024-E-012670 (30 Aug. 2010) --- NASA astronaut Tracy Caldwell Dyson, Expedition 24 flight engineer, uses Neurospat hardware to perform the Bodies in the Space Environment (BISE) experiment in the Destiny laboratory of the International Space Station. The Canadian Space Agency-sponsored BISE experiment studies how astronauts perceive up and down in microgravity.

Learning to Read in the Wake of Reform: Young Children's Experiences with Scientifically Based Reading Curriculum

ERIC Educational Resources Information Center

Spencer, Tamara

2011-01-01

In recent years, researchers have called into question the efficacy of prescribed commercial curricula in early childhood classrooms (Genishi & Dyson, 2009). Despite these concerns, federally funded initiatives and such findings as those presented in the Report of the National Early Literacy Panel continue to promote scientifically based…

Cultural Literacy Assimilation: The Literacy Experiences of Children of Immigrants

ERIC Educational Resources Information Center

Rosen, Dana

2014-01-01

Although students' literacy practices are influenced by a variety of sources, including texts, teachers, peers, the media, and their home culture (Dyson, 1993), the process of becoming literate is truly grounded in their cultural beliefs (Ferdman, 1990). Literacy skills are embedded in cultural practice, and cultural practice is learned implicitly…

Perspective on rainbow-ladder truncation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eichmann, G.; Institut fuer Physik, Karl-Franzens-Universitaet Graz, A-8010 Graz; Alkofer, R.

2008-04-15

Prima facie the systematic implementation of corrections to the rainbow-ladder truncation of QCD's Dyson-Schwinger equations will uniformly reduce in magnitude those calculated mass-dimensioned results for pseudoscalar and vector meson properties that are not tightly constrained by symmetries. The aim and interpretation of studies employing rainbow-ladder truncation are reconsidered in this light.

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson, left, Expedition 23 Soyuz Commander Alexander Skvortsov and Expedition 23 Flight Engineer Mikhail Kornienko, right, talk with family and colleagues from behind glass prior to their launch onboard a Soyuz rocket to the International Space Station (ISS), Friday, April 2, 2010 in Baikonur, Kazakhstan. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Soyuz Launch

NASA Image and Video Library

2010-04-01

Photographers capture the Soyuz TMA-18 rocket as it launches from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010 carrying Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. to the International Space Station. (Photo Credit: NASA/Bill Ingalls)

Perspective on rainbow-ladder truncation

NASA Astrophysics Data System (ADS)

Eichmann, G.; Alkofer, R.; Cloët, I. C.; Krassnigg, A.; Roberts, C. D.

2008-04-01

Prima facie the systematic implementation of corrections to the rainbow-ladder truncation of QCD's Dyson-Schwinger equations will uniformly reduce in magnitude those calculated mass-dimensioned results for pseudoscalar and vector meson properties that are not tightly constrained by symmetries. The aim and interpretation of studies employing rainbow-ladder truncation are reconsidered in this light.

On the subsystem formulation of linear-response time-dependent DFT.

PubMed

Pavanello, Michele

2013-05-28

A new and thorough derivation of linear-response subsystem time-dependent density functional theory (TD-DFT) is presented and analyzed in detail. Two equivalent derivations are presented and naturally yield self-consistent subsystem TD-DFT equations. One reduces to the subsystem TD-DFT formalism of Neugebauer [J. Chem. Phys. 126, 134116 (2007)]. The other yields Dyson type equations involving three types of subsystem response functions: coupled, uncoupled, and Kohn-Sham. The Dyson type equations for subsystem TD-DFT are derived here for the first time. The response function formalism reveals previously hidden qualities and complications of subsystem TD-DFT compared with the regular TD-DFT of the supersystem. For example, analysis of the pole structure of the subsystem response functions shows that each function contains information about the electronic spectrum of the entire supersystem. In addition, comparison of the subsystem and supersystem response functions shows that, while the correlated response is subsystem additive, the Kohn-Sham response is not. Comparison with the non-subjective partition DFT theory shows that this non-additivity is largely an artifact introduced by the subjective nature of the density partitioning in subsystem DFT.

Automatic numerical evaluation of vacancy-mediated transport for arbitrary crystals: Onsager coefficients in the dilute limit using a Green function approach

NASA Astrophysics Data System (ADS)

Trinkle, Dallas R.

2017-10-01

A general solution for vacancy-mediated diffusion in the dilute-vacancy/dilute-solute limit for arbitrary crystal structures is derived from the master equation. A general numerical approach to the vacancy lattice Green function reduces to the sum of a few analytic functions and numerical integration of a smooth function over the Brillouin zone for arbitrary crystals. The Dyson equation solves for the Green function in the presence of a solute with arbitrary but finite interaction range to compute the transport coefficients accurately, efficiently and automatically, including cases with very large differences in solute-vacancy exchange rates. The methodology takes advantage of the space group symmetry of a crystal to reduce the complexity of the matrix inversion in the Dyson equation. An open-source implementation of the algorithm is available, and numerical results are presented for the convergence of the integration error of the bare vacancy Green function, and tracer correlation factors for a variety of crystals including wurtzite (hexagonal diamond) and garnet.

Expedition 19 State Commission

NASA Image and Video Library

2009-03-24

Spaceflight Participant Charles Simonyi, left, Expedition 19 Commander Gennady I. Padalka, Flight Engineer Michael R. Barratt, third from left, backup Expedition 19 flight engineer Maxim Suraev, backup commander Jeffrey Williams and backup spaceflight participant Esther Dyson, far right, are seen in quarantine behind glass during the State Commission meeting on Wednesday, March 25, 2009 in Baikonur, Kazakhstan. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

The Soyuz TMA-18 spacecraft is seen at sunrise prior to its launch at 10:04am, Friday, April 2, 2010 in Baikonur, Kazakhstan. The Soyuz spacecraft will carry Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson to the International Space Station. Photo Credit: (NASA/Bill Ingalls)

Living the Transition--The Great Mortality Change through the Lives of the Country Doctors

ERIC Educational Resources Information Center

Lundberg, Anna

2003-01-01

This paper works alongside other studies claiming the need for further elaboration of the theory of the demographic transition. A number of perspectives on the transition, some of them related to gender, democracy, education, and labour has, according to Tim Dyson, been insufficiently researched by social scientists. The most recently introduced…

Women's History Month at NASA

NASA Image and Video Library

2011-03-14

NASA Administrator Lori Garver listens to astronaut Tracy Caldwell Dyson (off camera) at a Women's History Month event at NASA Headquarters, Wednesday, March 16, 2011 in Washington. The event entitled Women Inspiring the Next Generation to Reveal the Unknown is a joint venture with NASA and the White House Council on Women and Girls. Photo Credit: (NASA/Carla Cioffi)

Children, Language, and Literacy: Diverse Learners in Diverse Times. Language & Literacy Series

ERIC Educational Resources Information Center

Genishi, Celia; Dyson, Anne Haas

2009-01-01

In their new collaboration, Celia Genishi and Anne Haas Dyson celebrate the genius of young children as they learn language and literacy in our diverse times. Despite burgeoning sociocultural diversity, many early childhood classrooms (pre-K to grade 2) offer a one-size-fits-all curriculum in which learning is too often assessed by standardized…

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

View from the balcony of the Russian Mission Control Center in Korolev, Russia as the Soyuz TMA-18 docks to the International Space Station on Sunday, April 4, 2010. The Soyuz TMA-18 docked to the International Space Station carrying Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

Kirk Shireman, NASA's deputy ISS program manager, answers reporter’s questions during a Soyuz post-docking press conference at the Russian Mission Control Center in Korolev, Russia on Sunday, April 4, 2010. The Soyuz TMA-18 docked to the International Space Station carrying Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of Russia has his Russian Sokol suit pressure checked at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko and fellow Expedition 23 crewmembers Soyuz Commander Alexander Skvortsov and NASA Flight Engineer Tracy Caldwell Dyson launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

Alexei Krasnov, Director of Manned Space Programs Department, Roscosmos, listens to reporter’s questions during a Soyuz post-docking press conference at the Russian mission Control Center in Korolev, Russia on Sunday, April 4, 2010. The Soyuz TMA-18 docked to the International Space Station carrying Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 Soyuz Commander Alexander Skvortsov says a few words during the State Commission meeting to approve the Soyuz launch of Skvortsov, Expedition 23 Flight Engineer Tracy Caldwell Dyson and Flight Engineer Mikhail Kornienko on Thursday, April 1, 2010 in Baikonur, Kazakhstan. The crew is kept in a separate room with a glass window in order to help maintain their health. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

Kirk Shireman, right, NASA's deputy ISS program manager, answers reporter’s questions during a Soyuz post-docking press conference at the Russian Mission Control Center in Korolev, Russia on Sunday, April 4, 2010. The Soyuz TMA-18 docked to the International Space Station carrying Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Docking

NASA Image and Video Library

2010-04-03

A large TV screen in Russian Mission Control Center in Korolev, Russia shows Expedition 23 Commander Oleg Kotov, right, welcoming NASA astronaut and Flight Engineer Tracy Caldwell Dyson onboard the International Space Station after she and fellow crew members Expedition 23 Soyuz Commander Alexander Skvortsov and Flight Engineer Mikhail Kornienko docked their Soyuz TMA-18 spacecraft on Sunday, April 4, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Soyuz Commander Alexander Skvortsov has his Russian Sokol suit pressure checked at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Skvortsov and fellow Expedition 23 crew members Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of Russia has his Russian Sokol suit pressure checked at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko and fellow Expedition 23 crewmembers Soyuz Commander Alexander Skvortsov and NASA Flight Engineer Tracy Caldwell Dyson launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Bill Ingalls)

Security Strategy of the Bureau of Diplomatic Security.

DTIC Science & Technology

2011-06-10

Williams, M.A. , Member John A. Dyson, MBA , Member Gregory Scott Hospodor, Ph.D Accepted this 10th day of June 2011 by...ACRONYMS AAR After Action Review ASOS Advance Security Overseas Seminar ATA Antiterrorism Assistance Program BRSO Regional Security Officer Course ...BSAC Basic Special Agent Course DS Bureau of Diplomatic Security FACT Foreign Affairs Counter Threat FAH Foreign Affairs Handbook FAM Foreign

STS_135_MaxQ

NASA Image and Video Library

2011-05-05

JSC2011-E-059375 (4 May 2011) --- NASA astronaut Chris Ferguson, STS-135 commander, plays the drums with the all-astronaut band known as Max Q as the group performs on Innovation Day at NASA?s Johnson Space Center in Houston May 4, 2011. Vocalist Tracy Caldwell Dyson is at left. Guitarist Drew Feustel is at right. Photo credit: NASA Photo/Houston Chronicle, Smiley N. Pool

Retrieval Capabilities of Hierarchical Networks: From Dyson to Hopfield

NASA Astrophysics Data System (ADS)

Agliari, Elena; Barra, Adriano; Galluzzi, Andrea; Guerra, Francesco; Tantari, Daniele; Tavani, Flavia

2015-01-01

We consider statistical-mechanics models for spin systems built on hierarchical structures, which provide a simple example of non-mean-field framework. We show that the coupling decay with spin distance can give rise to peculiar features and phase diagrams much richer than their mean-field counterpart. In particular, we consider the Dyson model, mimicking ferromagnetism in lattices, and we prove the existence of a number of metastabilities, beyond the ordered state, which become stable in the thermodynamic limit. Such a feature is retained when the hierarchical structure is coupled with the Hebb rule for learning, hence mimicking the modular architecture of neurons, and gives rise to an associative network able to perform single pattern retrieval as well as multiple-pattern retrieval, depending crucially on the external stimuli and on the rate of interaction decay with distance; however, those emergent multitasking features reduce the network capacity with respect to the mean-field counterpart. The analysis is accomplished through statistical mechanics, Markov chain theory, signal-to-noise ratio technique, and numerical simulations in full consistency. Our results shed light on the biological complexity shown by real networks, and suggest future directions for understanding more realistic models.

Infrared analysis of Dyson-Schwinger equations taking into account the Gribov horizon in Landau gauge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huber, M. Q.; Alkofer, R.; Sorella, S. P.

2010-03-15

The low momentum behavior of the Landau gauge Gribov-Zwanziger action is investigated using the respective Dyson-Schwinger equations. Because of the mixing of the gluon and the auxiliary fields four scenarios can be distinguished for the infrared behavior. Two of them lead to inconsistencies and can be discarded. Another one corresponds to the case where the auxiliary fields behave exactly like the Faddeev-Popov ghosts and the same scaling relation as in standard Landau gauge, {kappa}{sub A}+2{kappa}{sub c}=0, is valid. Even the parameter {kappa} is found to be the same, 0.595. The mixed propagators, which appear, are suppressed in all loops, andmore » their anomalous infrared exponent can also be determined. A fourth case provides an even stricter scaling relation that includes also the mixed propagators, but possesses the same qualitative feature, i.e. the propagators of the Faddeev-Popov ghost and the auxiliary fields are infrared enhanced and the mixed and the gluon propagators are infrared suppressed. In this case the system of equations to obtain the parameter {kappa} is nonlinear in all variables.« less

Starry Messages - Searching for Signatures of Interstellar Archaeology

NASA Astrophysics Data System (ADS)

Carrigan, R. A., Jr.

Searching for signatures of cosmic-scale archaeological artefacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the originating civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology . The detection of intelligence elsewhere in the Universe with interstellar archaeology or SETI would have broad implications for science. For example, the constraints of the anthropic principle would have to be loosened if a different type of intelligence was discovered elsewhere. A variety of interstellar archaeology signatures are discussed including non-natural planetary atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson spheres, as well as signatures of stellar and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is introduced in the discussion of galactic signatures. These potential interstellar archaeological signatures are classified using the Kardashev scale. A modified Drake equation is used to evaluate the relative challenges of finding various sources. With few exceptions interstellar archaeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.

An experimental study on the near-source region of lazy turbulent plumes

NASA Astrophysics Data System (ADS)

Ciriello, Francesco; Hunt, Gary R.

2017-11-01

The near-source region of a `lazy' turbulent buoyant plume issuing from a circular source is examined for source Richardson numbers in the range of 101 to 107. New data is acquired for the radial contraction and streamwise variation of volume flux through an experimental programme of dye visualisations and particle image velocimetry. This data reveals the limited applicability of traditional entrainment laws used in integral modelling approaches for the description of the near-source region for these source Richardson numbers. A revised entrainment function is proposed, based on which we introduce a classification of plume behaviour whereby the degree of `laziness' may be expressed in terms of the excess dilution that occurs compared to a `pure' constant Richardson number plume. The increased entrainment measured in lazy plumes is attributed to Rayleigh-Taylor instabilities developing along the contraction of the plume which promote the additional engulfment of ambient fluid into the plume. This work was funded by an EPSRC Industial Case Award sponsored by Dyson Technology Ltd. Special thanks go to the members of the Dyson Environmental Control Group that regularly visit us in Cambridge for discussions about our work.

Starry messages: Searching for signatures of interstellar archaeology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrigan, Richard A., Jr.; /Fermilab

2009-12-01

Searching for signatures of cosmic-scale archaeological artifacts such as Dyson spheres or Kardashev civilizations is an interesting alternative to conventional SETI. Uncovering such an artifact does not require the intentional transmission of a signal on the part of the original civilization. This type of search is called interstellar archaeology or sometimes cosmic archaeology. The detection of intelligence elsewhere in the Universe with interstellar archaeology or SETI would have broad implications for science. For example, the constraints of the anthropic principle would have to be loosened if a different type of intelligence was discovered elsewhere. A variety of interstellar archaeology signaturesmore » are discussed including non-natural planetary atmospheric constituents, stellar doping with isotopes of nuclear wastes, Dyson spheres, as well as signatures of stellar and galactic-scale engineering. The concept of a Fermi bubble due to interstellar migration is introduced in the discussion of galactic signatures. These potential interstellar archaeological signatures are classified using the Kardashev scale. A modified Drake equation is used to evaluate the relative challenges of finding various sources. With few exceptions interstellar archaeological signatures are clouded and beyond current technological capabilities. However SETI for so-called cultural transmissions and planetary atmosphere signatures are within reach.« less

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The Soyuz TMA-18 spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 State Commission

NASA Image and Video Library

2010-03-31

Expedition 23 Flight Engineer Mikhail Kornienko says a few words during the State Commission meeting to approve the Soyuz launch of Kornienko, Expedition 23 Soyuz Commander Alexander Skvortsov and Expedition 23 Flight Engineer Tracy Caldwell Dyson on Thursday, April 1, 2010 in Baikonur, Kazakhstan. The crew is kept in a separate room with a glass window in order to help maintain their health. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, left, Expedition 23 Soyuz Commander Alexander Skvortsov and Expedition 23 Flight Engineer Mikhail Kornienko, third from left, walk out to salute Head of the Russian Federal Space Agency Anatoly Perminov, third from right, prior to their launch onboard the Soyuz TMA-18 to the International Space Station (ISS), Friday, April 2, 2010 in Baikonur, Kazakhstan. Photo Credit: (NASA/Victor Zelentsov)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-31

The Soyuz TMA-18 spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The Soyuz TMA-18 spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Russian cosmonaut Expedition 23 Flight Engineer Mikhail Kornienko smiles as he awaits to have his Sokol suit pressure checked prior to launch, Friday, April 2, 2010, in Baikonur, Kazakhstan. Kornienko and fellow Expedition 23 crew members Soyuz Commander Alexander Skvortsov and NASA Flight Engineer Tracy Caldwell Dyson launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 NASA Flight Engineer Tracy Caldwell Dyson, left, talks with Soyuz Commander Alexander Skvortsov of Russia, while Flight Engineer Mikhail Kornienko of Russia has his Russian Sokol suit prepared for launch at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. The Expedition 23 crew members launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. (Photo Credit: NASA/Bill Ingalls)

Expedition 23 Prelaunch Press Conference

NASA Image and Video Library

2010-03-31

Expedition 23 Flight Engineer Mikhail Kornienko answers a reporters' question during a press conference held at the Cosmonaut Hotel in Baikonur, Kazakhstan on Thursday, April 1, 2010. The launch of the Soyuz spacecraft with Expedition 23 NASA Flight Engineer Mikhail Kornienko, Soyuz Commander Alexander Skvortsov and Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Bill Ingalls)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of Russia prepares to have his Russian Sokol suit pressure checked at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko and fellow Expedition 23 crewmembers Soyuz Commander Alexander Skvortsov and NASA Flight Engineer Tracy Caldwell Dyson launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 preflight

NASA Image and Video Library

2010-03-31

The launch pad at the Baikonur Cosmodrome in Kazakhstan is illuminated at sunrise in the Central Asian desert as it awaits the arrival of the Soyuz TMA-18 vehicle March 31, 2010 which was transported from its assembly hangar to the pad by railcar at dawn. Expedition 23 crewmates Alexander Skvortsov, Mikhail Kornienko and Tracy Caldwell Dyson will launch from Baikonur April 2 en route to the International Space Station.

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Mikhail Kornienko of the Russia has his Russian Sokol suit prepared for launch by a technician at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Kornienko and fellow Expedition 23 crewmembers Soyuz Commander Alexander Skvortsov and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Soyuz Commander Alexander Skvortsov has his Russian Sokol suit prepared for launch by a technician at the Baikonur Cosmodrome in Baikonur, Kazakhstan, Friday, April 2, 2010. Skvortsov and fellow Expedition 23 crewmembers Flight Engineer Mikhail Kornienko of the Russia and NASA Flight Engineer Tracy Caldwell Dyson of the U.S. launched in their Soyuz TMA-18 rocket from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, 2010. Photo Credit: (NASA/Carla Cioffi)

Nonperturbative confinement in quantum chromodynamics. I. Study of an approximate equation of Mandelstam

NASA Astrophysics Data System (ADS)

Atkinson, D.; Drohm, J. K.; Johnson, P. W.; Stam, K.

1981-11-01

An approximated form of the Dyson-Schwinger equation for the gluon propagator in quarkless QCD is subjected to nonlinear functional and numerical analysis. It is found that solutions exist, and that these have a double pole at the origin of the square of the propagator momentum, together with an accumulation of soft branch points. This analytic structure is strongly suggestive of confinement by infrared slavery.

From quarks and gluons to baryon form factors.

PubMed

Eichmann, Gernot

2012-04-01

I briefly summarize recent results for nucleon and [Formula: see text] electromagnetic, axial and transition form factors in the Dyson-Schwinger approach. The calculation of the current diagrams from the quark-gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects.

Multiscale Models of Melting Arctic Sea Ice

DTIC Science & Technology

2014-09-30

from weakly to highly correlated, or Poissonian toward Wigner -Dyson, as a function of system connectedness. This provides a mechanism for explaining...eluded us. Court Strong found such a method. It creates an optimal fit of a hyperbolic tangent model for the fractal dimension as a function of log A...actual melt pond images, and have made significant advances in the underlying functional and numerical analysis needed for these computations

50th Anniversary of the Civil Rights Act of 1964

NASA Image and Video Library

2014-06-23

Dr. Michael Eric Dyson, a professor of sociology at Georgetown University, speaks as part of a panel discussion at an event celebrating the 50th Anniversary of the Civil Rights Act of 1964 on Monday, June 23, 2014 in the James E. Webb Auditorium at NASA Headquarters in Washington, DC. The event highlighted the influence of the Civil Rights Act on NASA. Photo Credit: (NASA/Joel Kowsky)

Ethnicity and Healthcare Practice - A Guide for the Primary Care Team Dyson Simon Culley Lorraine Ethnicity and Healthcare Practice - A Guide for the Primary Care Team 150 Quay Books 9781856423663 1856423662 [Formula: see text].

PubMed

2010-06-02

How could a book exploring culture and ethnicity not interest a nurse? Chapters cover ethnicity, the diversity of UK ethnic groups, managing diversity in health care, communication, the effects of disease on family and community, mental health, substance misuse and refugees and asylum seekers.

HyTES: Thermal Imaging Spectrometer Development

NASA Technical Reports Server (NTRS)

Johnson, William R.; Hook, Simon J.; Mouroulis, Pantazis; Wilson, Daniel W.; Gunapala, Sarath D.; Realmuto, Vincent; Lamborn, Andy; Paine, Chris; Mumolo, Jason M.; Eng, Bjorn T.

2011-01-01

The Jet Propulsion Laboratory has developed the Hyperspectral Thermal Emission Spectrometer (HyTES). It is an airborne pushbroom imaging spectrometer based on the Dyson optical configuration. First low altitude test flights are scheduled for later this year. HyTES uses a compact 7.5-12 micrometer m hyperspectral grating spectrometer in combination with a Quantum Well Infrared Photodetector (QWIP) and grating based spectrometer. The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal science-grade imaging spectroscopy solution for high altitude, lighter-than-air (HAA, LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP sensor allows for optimum spatial and spectral uniformity and provides adequate responsivity which allows for near 100mK noise equivalent temperature difference (NEDT) operation across the LWIR passband. The QWIP's repeatability and uniformity will be helpful for data integrity since currently an onboard calibrator is not planned. A calibration will be done before and after eight hour flights to gage any inconsistencies. This has been demonstrated with lab testing. Further test results show adequate NEDT, linearity as well as applicable earth science emissivity target results (Silicates, water) measured in direct sunlight.

A strategic 'viewfinder' for SETI research

NASA Astrophysics Data System (ADS)

Teodorani, Massimo

2014-12-01

One of the most important reasons why unsuccessful results have been obtained so far by the SETI Project is due to the fact that no sure targets to aim at have been available up-to the present state of research. All-sky surveys, even if very accurate and complete, might result to be time-consuming. SETI needs at least one effective 'viewfinder' in order that a true targeted research is carried out with a possible success. The best foundation to get this can be identified with the search for the evidence of extraterrestrial astro-engineering activity in form of the Dyson spheres predicted by theory. The existence of such stellar objects can be ascertained by finding the evidence of two main signatures in stars of solar spectral type: infrared excess and anomalous light curves due to transiting artificial objects. These are probably the most powerful viewfinders in order to allow SETI techniques for intelligent signal search to be aimed at more appropriate targets. This paper is not intended to be a research paper but rather a review paper whose goal is not to present calculations and/or operational research but rather to be a research proposal for a more focused research in SETI just using Dyson Spheres as crucial markers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, C. D.; Schmidt, S. M.; Physics

Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions; and the transition to, and properties of, a quark gluon plasma. We provide a contemporary perspective, couched primarily in terms of the Dyson-Schwinger equations but also making comparisons with other approaches and models. Our discourse provides a practitioners' guide to features of the Dyson-Schwinger equations [such as confinement and dynamical chiral symmetry breaking] and canvasses phenomenological applications to light meson and baryon properties in cold, sparse QCD.more » These provide the foundation for an extension to hot, dense QCD, which is probed via the introduction of the intensive thermodynamic variables: chemical potential and temperature. We describe order parameters whose evolution signals deconfinement and chiral symmetry restoration, and chronicle their use in demarcating the quark gluon plasma phase boundary and characterizing the plasma's properties. Hadron traits change in an equilibrated plasma. We exemplify this and discuss putative signals of the effects. Finally, since plasma formation is not an equilibrium process, we discuss recent developments in kinetic theory and its application to describing the evolution from a relativistic heavy ion collision to an equilibrated quark gluon plasma.« less

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The Soyuz TMA-18 spacecraft is raised into position shortly after it was rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Carla Cioffi)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

Pad technicians secure the Soyuz TMA-18 spacecraft shortly after it was rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The Soyuz TMA-18 spacecraft is raised into position shortly after it was rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-31

Pad technicians prepare to raise the Soyuz TMA-18 spacecraft shortly after it was rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

A Russian security officer stands guard as the Soyuz TMA-18 spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

NASA Day in Montgomery, Feb. 22, 2018

NASA Image and Video Library

2018-02-22

Officials from Marshall Space Flight Center discussed the state's role in leading America back to the Moon and on to Mars with elected officials, industry leaders, students and the public during the Aerospace States Association’s Alabama Aerospace Week in Montgomery, Ala. NASA was honored by the Alabama legislature with a resolution and proclamation from Gov. Kay Ivey recognizing the agency's achievements. Astronaut Tracy Dyson speaks to legislators in Alabama House of Representatives

NASA Day in Montgomery, Feb. 22, 2018

NASA Image and Video Library

2018-02-22

Officials from Marshall Space Flight Center discussed the state's role in leading America back to the Moon and on to Mars with elected officials, industry leaders, students and the public during the Aerospace States Association’s Alabama Aerospace Week in Montgomery, Ala. NASA was honored by the Alabama legislature with a resolution and proclamation from Gov. Kay Ivey recognizing the agency's achievements. MSFC Director Todd May and Astronaut Tracy Dyson chat with Alabama Governor Kay Ivey.

NASA Day in Montgomery, Feb. 22, 2018

NASA Image and Video Library

2018-02-22

Officials from Marshall Space Flight Center discussed the state's role in leading America back to the Moon and on to Mars with elected officials, industry leaders, students and the public during the Aerospace States Association’s Alabama Aerospace Week in Montgomery, Ala. NASA was honored by the Alabama legislature with a resolution and proclamation from Gov. Kay Ivey recognizing the agency's achievements. MSFC Director Todd May and Astronaut Tracy Dyson speak to the Alabama State Senate.

50th Anniversary of the Civil Rights Act of 1964

NASA Image and Video Library

2014-06-23

Members of the audience listen as Dr. Michael Eric Dyson, a professor of sociology at Georgetown University, answers a question during a panel discussion at an event celebrating the 50th Anniversary of the Civil Rights Act of 1964 on Monday, June 23, 2014 in the James E. Webb Auditorium at NASA Headquarters in Washington, DC. The event highlighted the influence of the Civil Rights Act on NASA. Photo Credit: (NASA/Joel Kowsky)

On Pfaffian Random Point Fields

NASA Astrophysics Data System (ADS)

Kargin, V.

2014-02-01

We study Pfaffian random point fields by using the Moore-Dyson quaternion determinants. First, we give sufficient conditions that ensure that a self-dual quaternion kernel defines a valid random point field, and then we prove a CLT for Pfaffian point fields. The proofs are based on a new quaternion extension of the Cauchy-Binet determinantal identity. In addition, we derive the Fredholm determinantal formulas for the Pfaffian point fields which use the quaternion determinant.

Dirac Magnons in Honeycomb Ferromagnets

NASA Astrophysics Data System (ADS)

Pershoguba, Sergey S.; Banerjee, Saikat; Lashley, J. C.; Park, Jihwey; Ågren, Hans; Aeppli, Gabriel; Balatsky, Alexander V.

2018-01-01

The discovery of the Dirac electron dispersion in graphene [A. H. Castro Neto, et al., The Electronic Properties of Graphene, Rev. Mod. Phys. 81, 109 (2009), 10.1103/RevModPhys.81.109] led to the question of the Dirac cone stability with respect to interactions. Coulomb interactions between electrons were shown to induce a logarithmic renormalization of the Dirac dispersion. With a rapid expansion of the list of compounds and quasiparticle bands with linear band touching [T. O. Wehling, et al., Dirac Materials, Adv. Phys. 63, 1 (2014), 10.1080/00018732.2014.927109], the concept of bosonic Dirac materials has emerged. We consider a specific case of ferromagnets consisting of van der Waals-bonded stacks of honeycomb layers, e.g., chromium trihalides CrX3 (X =F , Cl, Br and I), that display two spin wave modes with energy dispersion similar to that for the electrons in graphene. At the single-particle level, these materials resemble their fermionic counterparts. However, how different particle statistics and interactions affect the stability of Dirac cones has yet to be determined. To address the role of interacting Dirac magnons, we expand the theory of ferromagnets beyond the standard Dyson theory [F. J. Dyson, General Theory of Spin-Wave Interactions, Phys. Rev. 102, 1217 (1956), 10.1103/PhysRev.102.1217, F. J. Dyson, Thermodynamic Behavior of an Ideal Ferromagnet, Phys. Rev. 102, 1230 (1956), 10.1103/PhysRev.102.1230] to the case of non-Bravais honeycomb layers. We demonstrate that magnon-magnon interactions lead to a significant momentum-dependent renormalization of the bare band structure in addition to strongly momentum-dependent magnon lifetimes. We show that our theory qualitatively accounts for hitherto unexplained anomalies in nearly half-century-old magnetic neutron-scattering data for CrBr3 [W. B. Yelon and R. Silberglitt, Renormalization of Large-Wave-Vector Magnons in Ferromagnetic CrBr3 Studied by Inelastic Neutron Scattering: Spin-Wave Correlation Effects, Phys. Rev. B 4, 2280 (1971), 10.1103/PhysRevB.4.2280, E. J. Samuelsen, et al., Spin Waves in Ferromagnetic CrBr3 Studied by Inelastic Neutron Scattering, Phys. Rev. B 3, 157 (1971), 10.1103/PhysRevB.3.157]. We also show that honeycomb ferromagnets display dispersive surface and edge states, unlike their electronic analogs.

Qwest and HyTES: Two New Hyperspectral Thermal Infrared Imaging Spectrometers for Earth Science

DTIC Science & Technology

2009-10-01

and QWIP focal plane arrays. The long wave infrared ( LWIR ) is typically expressed as the wavelength range between 7 and 14 µm. Our current...recently recommended by the National Research Council in their Decadal Survey. The LWIR component of the HyspIRI mission will address science...but extends the Dyson design to work optimally with the LWIR . The savings in physical size for similar F/# systems is dramatic as shown in Figure

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The sun rises behind the Soyuz launch pad shortly before the Soyuz TMA-18 spacecraft is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

The sun rises behind the Soyuz launch pad shortly before the Soyuz TMA-18 spacecraft is rolled out by the train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 321, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit: (NASA/Carla Cioffi)

Expedition 23 Launch Day

NASA Image and Video Library

2010-04-01

Expedition 23 Flight Engineer Tracy Caldwell Dyson, front left, Expedition 23 Soyuz Commander Alexander Skvortsov, front center, and Expedition 23 Flight Engineer Mikhail Kornienko pose with backup crewmembers NASA Flight Engineer Scott Kelly of the U.S., back left, Flight Engineer Alexander Samokutyayev of Russia, back center, and Flight Engineer Andrei Borisenko of Russia, prior to the crews’ launch onboard a Soyuz rocket to the International Space Station on Friday, April 2, 2010, in Baikonur, Kazakhstan. Photo Credit: (NASA/Carla Cioffi)

A supersymmetric SYK-like tensor model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Cheng; Spradlin, Marcus; Volovich, Anastasia

2017-05-11

We consider a supersymmetric SYK-like model without quenched disorder that is built by coupling two kinds of fermionic Ν = 1 tensor-valued superfields, ''quarks'' and ''mesons''. We prove that the model has a well-defined large-N limit in which the (s)quark 2-point functions are dominated by mesonic ''melon'' diagrams. We sum these diagrams to obtain the Schwinger-Dyson equations and show that in the IR, the solution agrees with that of the supersymmetric SYK model.

Women's History Month at NASA

NASA Image and Video Library

2011-03-14

NASA Deputy Administrator Lori Garver, far left at table, answers a students question at a Women's History Month event at NASA Headquarters, Wednesday, March 16, 2011 in Washington. Garver is joined on the panel by NASA astronaut Tracy Caldwell Dyson, center, and NASA Aerospace Engineer Sabrina Thompson. The event entitled Women Inspiring the Next Generation to Reveal the Unknown is a joint venture with NASA and the White House Council on Women and Girls. Photo Credit: (NASA/Carla Cioffi)

Crew Meal in Node 1 Unity

NASA Image and Video Library

2010-04-14

S131-E-010222 (14 April 2010) --- A fish-eye lens attached to an electronic still camera was used to capture this image of STS-131 and Expedition 23 crew members in the Unity node of the International Space Station while space shuttle Discovery remains docked with the station. Pictured are NASA astronauts Rick Mastracchio, Tracy Caldwell Dyson, Clayton Anderson and T.J. Creamer; along with Russian cosmonaut Oleg Kotov and Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi.

A fresh look at the photoelectron spectrum of bromobenzene: A third-order non-Dyson electron propagator study.

PubMed

Schneider, M; Soshnikov, D Yu; Holland, D M P; Powis, I; Antonsson, E; Patanen, M; Nicolas, C; Miron, C; Wormit, M; Dreuw, A; Trofimov, A B

2015-10-14

The valence-shell ionization spectrum of bromobenzene, as a representative halogen substituted aromatic, was studied using the non-Dyson third-order algebraic-diagrammatic construction [nD-ADC(3)] approximation for the electron propagator. This method, also referred to as IP-ADC(3), was implemented as a part of the Q-Chem program and enables large-scale calculations of the ionization spectra, where the computational effort scales as n(5) with respect to the number of molecular orbitals n. The IP-ADC(3) scheme is ideally suited for investigating low-lying ionization transitions, so fresh insight could be gained into the cationic state manifold of bromobenzene. In particular, the present IP-ADC(3) calculations with the cc-pVTZ basis reveal a whole class of low-lying low-intensity two-hole-one-particle (2h-1p) doublet and quartet states, which are relevant to various photoionization processes. The good qualitative agreement between the theoretical spectral profile for the valence-shell ionization transitions generated with the smaller cc-pVDZ basis set and the experimental photoelectron spectrum measured at a photon energy of 80 eV on the PLÉIADES beamline at the Soleil synchrotron radiation source allowed all the main features to be assigned. Some theoretical aspects of the ionization energy calculations concerning the use of various approximation schemes and basis sets are discussed.

A fresh look at the photoelectron spectrum of bromobenzene: A third-order non-Dyson electron propagator study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, M.; Wormit, M.; Dreuw, A.

2015-10-14

The valence-shell ionization spectrum of bromobenzene, as a representative halogen substituted aromatic, was studied using the non-Dyson third-order algebraic-diagrammatic construction [nD-ADC(3)] approximation for the electron propagator. This method, also referred to as IP-ADC(3), was implemented as a part of the Q-Chem program and enables large-scale calculations of the ionization spectra, where the computational effort scales as n{sup 5} with respect to the number of molecular orbitals n. The IP-ADC(3) scheme is ideally suited for investigating low-lying ionization transitions, so fresh insight could be gained into the cationic state manifold of bromobenzene. In particular, the present IP-ADC(3) calculations with the cc-pVTZmore » basis reveal a whole class of low-lying low-intensity two-hole-one-particle (2h-1p) doublet and quartet states, which are relevant to various photoionization processes. The good qualitative agreement between the theoretical spectral profile for the valence-shell ionization transitions generated with the smaller cc-pVDZ basis set and the experimental photoelectron spectrum measured at a photon energy of 80 eV on the PLÉIADES beamline at the Soleil synchrotron radiation source allowed all the main features to be assigned. Some theoretical aspects of the ionization energy calculations concerning the use of various approximation schemes and basis sets are discussed.« less

Review of high fidelity imaging spectrometer design for remote sensing

NASA Astrophysics Data System (ADS)

Mouroulis, Pantazis; Green, Robert O.

2018-04-01

We review the design and assessment techniques that underlie a number of successfully deployed space and airborne imaging spectrometers that have been demonstrated to achieve demanding specifications in terms of throughput and response uniformity. The principles are illustrated with telescope designs as well as spectrometer examples from the Offner and Dyson families. We also show how the design space can be extended with the use of freeform surfaces and provide additional design examples with grating as well as prism dispersive elements.

The United States Air Force Summary, FY 1988/1989 (Amended). Fourteenth Edition

DTIC Science & Technology

1988-05-15

UNClASSIFIEDI ,••o MARIANA ISLS ....••. 8 GUAM ..o ANDERSEI AFB o () II ,. BONIN ISLSo II • .... to t D ~, # # ()0KAOENA AB i ’or • o USAF MAJOR...Leath, Marvin (TX) McCurdy, Dave (OK) Foglietta, T. M. (PA) Dyson, Roy (MD) Hertel, Dennis M. (MI) Lloyd, Marilyn B. (TN) Sisisky, Norman (VA) Ray...1988) House Research and Development Subcommittee Democrats Price, Melvin (IL) Chmn. Aspin, Les (WI) Schroeder, Patricia (CO) McCurdy, Dave (OK) Hertel

STS-132 crew during their MSS/SIMP EVA3 OPS 4 training

NASA Image and Video Library

2010-01-28

JSC2010-E-014953 (28 Jan. 2010) --- NASA astronauts Piers Sellers, STS-132 mission specialist; and Tracy Caldwell Dyson, Expedition 23/24 flight engineer, use the virtual reality lab in the Space Vehicle Mock-up Facility at NASA's Johnson Space Center to train for some of their duties aboard the space shuttle and space station. This type of computer interface, paired with virtual reality training hardware and software, helps to prepare crew members for dealing with space station elements.

STS-132 crew during their MSS/SIMP EVA3 OPS 4 training

NASA Image and Video Library

2010-01-28

JSC2010-E-014949 (28 Jan. 2010) --- NASA astronauts Piers Sellers, STS-132 mission specialist; and Tracy Caldwell Dyson, Expedition 23/24 flight engineer, use the virtual reality lab in the Space Vehicle Mock-up Facility at NASA's Johnson Space Center to train for some of their duties aboard the space shuttle and space station. This type of computer interface, paired with virtual reality training hardware and software, helps to prepare crew members for dealing with space station elements.

Mean dyadic Green's function for a two layer random medium

NASA Technical Reports Server (NTRS)

Zuniga, M. A.

1981-01-01

The mean dyadic Green's function for a two-layer random medium with arbitrary three-dimensional correlation functions has been obtained with the zeroth-order solution to the Dyson equation by applying the nonlinear approximation. The propagation of the coherent wave in the random medium is similar to that in an anisotropic medium with different propagation constants for the characteristic transverse electric and transverse magnetic polarizations. In the limit of a laminar structure, two propagation constants for each polarization are found to exist.

NASA Johnson Style_ Gangnam Style Parody

NASA Image and Video Library

2012-12-14

NASA Johnson Style is a volunteer outreach video project created by the students of NASA's Johnson Space Center. It was created as an educational parody of Psy's Gangnam Style. The lyrics and scenes in the video have been re-imagined in order to inform the public about the amazing work going on at NASA and the Johnson Space Center. Special thanks to astronauts Tracy Caldwell Dyson, Mike Massimino and Clay Anderson Special thanks to Mr. Mike Coats, Dr. Ellen Ochoa, and all supporting senior staff members

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-31

The flags of the United States, Russia and Kazakhstan are seen at the launch pad after the Soyuz TMA-18 spacecraft was rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

Instanton approach to large N Harish-Chandra-Itzykson-Zuber integrals.

PubMed

Bun, J; Bouchaud, J P; Majumdar, S N; Potters, M

2014-08-15

We reconsider the large N asymptotics of Harish-Chandra-Itzykson-Zuber integrals. We provide, using Dyson's Brownian motion and the method of instantons, an alternative, transparent derivation of the Matytsin formalism for the unitary case. Our method is easily generalized to the orthogonal and symplectic ensembles. We obtain an explicit solution of Matytsin's equations in the case of Wigner matrices, as well as a general expansion method in the dilute limit, when the spectrum of eigenvalues spreads over very wide regions.

Expedition 23 Soyuz Rollout

NASA Image and Video Library

2010-03-30

Russian security officers and their dog patrol the railroad track ahead of the Soyuz TMA-18 spacecraft as it is rolled out by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov of Russia, Flight Engineer Mikhail Kornienko of Russia, and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 10:04 a.m. Kazakhstan time. Photo Credit (NASA/Bill Ingalls)

NASA Day in Montgomery, Feb. 22, 2018

NASA Image and Video Library

2018-02-22

Officials from Marshall Space Flight Center discussed the state's role in leading America back to the Moon and on to Mars with elected officials, industry leaders, students and the public during the Aerospace States Association’s Alabama Aerospace Week in Montgomery, Ala. NASA was honored by the Alabama legislature with a resolution and proclamation from Gov. Kay Ivey recognizing the agency's achievements. Astronaut Tracy Dyson, Alabama Governor Kay Ivey, and MSFC Director pose with proclamation signed by Governor Ivey declaring February 22, 2108, as NASA Day

Callan-Symanzik equations for infrared Yang-Mills theory

NASA Astrophysics Data System (ADS)

Weber, Axel; Dall'Olio, Pietro

2017-12-01

Dyson-Schwinger equations have been successful in determining the correlation functions in Yang-Mills theory in the Landau gauge, in the infrared regime. We argue that similar results can be obtained, in a technically simpler way, with Callan-Symanzik renormalization group equations. We present generalizations of the infrared safe renormalization scheme proposed by Tissier and Wschebor in 2011, and show how the renormalization scheme dependence can be used to improve the matching to the existing lattice data for the gluon and ghost propagators.

Inversion of Ionospheric Backscatter Radar Data in Order to Map and Model the Ionosphere

DTIC Science & Technology

2006-08-17

M., Wild, J . A., Lester, M., Yeoman, T . K., Milan, S. E., Ye, H., Devlin, J . C., Frey, H. U., and Kikuchi, T ., Interhemispheric asymmetries in the...Devlin, J . and Salim, T ., Evaluation of Digital Generation and Phasing Techniques for Transmitter Signals of the TIGER N.Z. Radar. WARS02 (Workshop on...17. Conde, M. and Dyson, P. L., Thermospheric Vertical Winds Above Mawson , Antarctica, J . Atmos. Terr. Phys., Vol. 57, 589-596, 1995. 18. Conde, M

Experimental determination of the effective strong coupling constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexandre Deur; Volker Burkert; Jian-Ping Chen

2007-07-01

We extract an effective strong coupling constant from low Q{sup 2} data on the Bjorken sum. Using sum rules, we establish its Q{sup 2}-behavior over the complete Q{sup 2}-range. The result is compared to effective coupling constants extracted from different processes and to calculations based on Schwinger-Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constant and the calculations is not clear, the results agree surprisingly well.

Electronic structure calculation by nonlinear optimization: Application to metals

NASA Astrophysics Data System (ADS)

Benedek, R.; Min, B. I.; Woodward, C.; Garner, J.

1988-04-01

There is considerable interest in the development of novel algorithms for the calculation of electronic structure (e.g., at the level of the local-density approximation of density-functional theory). In this paper we consider a first-order equation-of-motion method. Two methods of solution are described, one proposed by Williams and Soler, and the other base on a Born-Dyson series expansion. The extension of the approach to metallic systems is outlined and preliminary numerical calculations for Zintl-phase NaTl are presented.

The optimistic heretic

NASA Astrophysics Data System (ADS)

Dyson, Freeman

2008-01-01

The Oxford English Dictionary defines the word “heretic” as “the holder of an unorthodox opinion”. By his own admission, physicist Freeman Dyson has most definitely not been a heretic as far as his contributions to science are concerned, having carried out significant research on quantum electrodynamics and the stability of bulk matter. However, he certainly has unorthodox views when it comes to social issues related to science, which he has discussed at length in a number of books over the last two decades.

Scientific Eschatology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyes, H

2005-03-18

The future evolution of the universe suggested by the cosmological model proposed earlier at this meeting by the authors is explored. The fundamental role played by the positive ''cosmological constant'' is emphasized. Dyson's 1979 paper entitled ''Time Without End'' is briefly reviewed. His most optimistic scenario requires that the universe be geometrically open and that biology is structural in the sense that the current complexity of human society can be reproduced by scaling up its (quantum mechanical) structure to arbitrary size. If the recently measured ''cosmological constant'' is indeed a fundamental constant of nature, then Dyson's scenario is, for variousmore » reasons, ruled out by the finite (De Sitter) horizon due to exponential expansion of the resulting space. However, the finite temperature of that horizon does open other interesting options. If, as is suggested by the cosmology under consideration, the current exponential expansion of the universe is due to a phase transition which fixes a physical boundary condition during the early radiation dominated era, the behavior of the universe after the relevant scale factor crosses the De Sitter radius opens up still other possibilities. The relevance of Martin Rees' apocalyptic eschatology recently presented in his book ''Our Final Hour'' is mentioned. It is concluded that even for the far future, whether or not cultural and scientific descendants of the current epoch will play a role in it, an understanding (sadly, currently lacking) of community and political evolution and control is essential for a preliminary treatment of what could be even vaguely called scientific eschatology.« less

Critical flavor number of the Thirring model in three dimensions

NASA Astrophysics Data System (ADS)

Wellegehausen, Björn H.; Schmidt, Daniel; Wipf, Andreas

2017-11-01

The Thirring model is a four-fermion theory with a current-current interaction and U (2 N ) chiral symmetry. It is closely related to three-dimensional QED and other models used to describe properties of graphene. In addition, it serves as a toy model to study chiral symmetry breaking. In the limit of flavor number N →1 /2 it is equivalent to the Gross-Neveu model, which shows a parity-breaking discrete phase transition. The model was already studied with different methods, including Dyson-Schwinger equations, functional renormalization group methods, and lattice simulations. Most studies agree that there is a phase transition from a symmetric phase to a spontaneously broken phase for a small number of fermion flavors, but no symmetry breaking for large N . But there is no consensus on the critical flavor number Ncr above which there is no phase transition anymore and on further details of the critical behavior. Values of N found in the literature vary between 2 and 7. All earlier lattice studies were performed with staggered fermions. Thus it is questionable if in the continuum limit the lattice model recovers the internal symmetries of the continuum model. We present new results from lattice Monte Carlo simulations of the Thirring model with SLAC fermions which exactly implement all internal symmetries of the continuum model even at finite lattice spacing. If we reformulate the model in an irreducible representation of the Clifford algebra, we find, in contradiction to earlier results, that the behavior for even and odd flavor numbers is very different: for even flavor numbers, chiral and parity symmetry are always unbroken; for odd flavor numbers, parity symmetry is spontaneously broken below the critical flavor number Nircr=9 , while chiral symmetry is still unbroken.

SDG Fermion-Pair Algebraic SO(12) and Sp(10) Models and Their Boson Realizations

NASA Astrophysics Data System (ADS)

Navratil, P.; Geyer, H. B.; Dobes, J.; Dobaczewski, J.

1995-11-01

It is shown how the boson mapping formalism may be applied as a useful many-body tool to solve a fermion problem. This is done in the context of generalized Ginocchio models for which we introduce S-, D-, and G-pairs of fermions and subsequently construct the sdg-boson realizations of the generalized Dyson type. The constructed SO(12) and Sp(10) fermion models are solved beyond the explicit symmetry limits. Phase transitions to rotational structures are obtained also in situations where there is no underlying SU(3) symmetry.

United States Air Force Statistical Digest (Abridged), Fiscal Year 1991 Estimate

DTIC Science & Technology

1990-01-01

AS OF: 30 APRIL 1990 0 USAF ACTIVE INSTALLATIONS m I.I.l IV FIGURE E-6 •..•o , ••o MARIANA ISLS 8 GUAM c.e ANDERSEN AFB o o o ,. BONIN ISLS o o o...Byron, Beverly B. (MD) Mavroules, Nicholas (MA) Hutto, Earl D. (Fl) Skelton, Ike (MO) leath, Marvin (TX) McCurdy, Dave (OK) Foglletta, T.M. (PA) Dyson...34 ’: :..:;"’, :.;..: ’ "".:.:..’:.::.’. DEMOCRATS Dellums, Ronald (CA) Chmn. McCurdy, Dave (OK) Foglletta, Thomas (PA) Hertel, Dennis (MI) Darden, George

A Coupled Creep Plasticity Model for Residual Stress Relaxation of a Shot-Peened Nickel-Base Superalloy (Postprint)

DTIC Science & Technology

2010-01-01

McLean and Dyson." The basic model is adapted to incorporate the effects of prior plastic strain and coupling to the plasticity model. The 10...Creep Problems in Stroctural Members (New’tbrk: American Elsevier Publishing Co., 1969), p.137. 13. J.L. Chaboche, J Applied Machanics , 55 (March...1988), p~ 59-64. 14. J.L. Chaboche, J Applied Machanics , 55 (March 1988), p~ 65-72. 15. D.R. Sande .. (Ph.D. thesis, Texas A&M University, 1988

Rainbow tensor model with enhanced symmetry and extreme melonic dominance

NASA Astrophysics Data System (ADS)

Itoyama, H.; Mironov, A.; Morozov, A.

2017-08-01

We introduce and briefly analyze the rainbow tensor model where all planar diagrams are melonic. This leads to considerable simplification of the large N limit as compared to that of the matrix model: in particular, what are dressed in this limit are propagators only, which leads to an oversimplified closed set of Schwinger-Dyson equations for multi-point correlators. We briefly touch upon the Ward identities, the substitute of the spectral curve and the AMM/EO topological recursion and their possible connections to Connes-Kreimer theory and forest formulas.

NASA Day in Montgomery, Feb. 22, 2018

NASA Image and Video Library

2018-02-22

Officials from Marshall Space Flight Center discussed the state's role in leading America back to the Moon and on to Mars with elected officials, industry leaders, students and the public during the Aerospace States Association’s Alabama Aerospace Week in Montgomery, Ala. NASA was honored by the Alabama legislature with a resolution and proclamation from Gov. Kay Ivey recognizing the agency's achievements. Dr. Quentin T. Ross, Jr., President, Alabama State University, Astronaut Tracy Dyson, and MSFC Director Todd May talk to members of the media at Alabama State University.

Non-quasiparticle states in a half-metallic ferromagnet with antiferromagnetic s-d(f) interaction.

PubMed

Irkhin, V Yu

2015-04-22

Non-quasiparticle (incoherent) states which play an important role in the electronic structure of half-metallic ferromagnets (HMF) are investigated consistently in the case of antiferromagnetic s-d(f) exchange interaction. Their appropriate description in the limit of strong correlations requires a rearrangement of perturbation series in comparison with the usual Dyson equation. This consideration provides a solution of the Kondo problem in the HMF case and can be important for first-principle HMF calculations performed earlier for ferromagnetic s-d(f) interaction.

TOPICAL REVIEW: Nonlinear aspects of the renormalization group flows of Dyson's hierarchical model

NASA Astrophysics Data System (ADS)

Meurice, Y.

2007-06-01

We review recent results concerning the renormalization group (RG) transformation of Dyson's hierarchical model (HM). This model can be seen as an approximation of a scalar field theory on a lattice. We introduce the HM and show that its large group of symmetry simplifies drastically the blockspinning procedure. Several equivalent forms of the recursion formula are presented with unified notations. Rigourous and numerical results concerning the recursion formula are summarized. It is pointed out that the recursion formula of the HM is inequivalent to both Wilson's approximate recursion formula and Polchinski's equation in the local potential approximation (despite the very small difference with the exponents of the latter). We draw a comparison between the RG of the HM and functional RG equations in the local potential approximation. The construction of the linear and nonlinear scaling variables is discussed in an operational way. We describe the calculation of non-universal critical amplitudes in terms of the scaling variables of two fixed points. This question appears as a problem of interpolation between these fixed points. Universal amplitude ratios are calculated. We discuss the large-N limit and the complex singularities of the critical potential calculable in this limit. The interpolation between the HM and more conventional lattice models is presented as a symmetry breaking problem. We briefly introduce models with an approximate supersymmetry. One important goal of this review is to present a configuration space counterpart, suitable for lattice formulations, of functional RG equations formulated in momentum space (often called exact RG equations and abbreviated ERGE).

Resumming the large-N approximation for time evolving quantum systems

NASA Astrophysics Data System (ADS)

Mihaila, Bogdan; Dawson, John F.; Cooper, Fred

2001-05-01

In this paper we discuss two methods of resumming the leading and next to leading order in 1/N diagrams for the quartic O(N) model. These two approaches have the property that they preserve both boundedness and positivity for expectation values of operators in our numerical simulations. These approximations can be understood either in terms of a truncation to the infinitely coupled Schwinger-Dyson hierarchy of equations, or by choosing a particular two-particle irreducible vacuum energy graph in the effective action of the Cornwall-Jackiw-Tomboulis formalism. We confine our discussion to the case of quantum mechanics where the Lagrangian is L(x,ẋ)=(12)∑Ni=1x˙2i-(g/8N)[∑Ni=1x2i- r20]2. The key to these approximations is to treat both the x propagator and the x2 propagator on similar footing which leads to a theory whose graphs have the same topology as QED with the x2 propagator playing the role of the photon. The bare vertex approximation is obtained by replacing the exact vertex function by the bare one in the exact Schwinger-Dyson equations for the one and two point functions. The second approximation, which we call the dynamic Debye screening approximation, makes the further approximation of replacing the exact x2 propagator by its value at leading order in the 1/N expansion. These two approximations are compared with exact numerical simulations for the quantum roll problem. The bare vertex approximation captures the physics at large and modest N better than the dynamic Debye screening approximation.

The Hyperspectral Thermal Emission Spectrometer (HyTES): Preliminary Results

NASA Technical Reports Server (NTRS)

Hook, Simon; Johnson, William R.; Eng, Bjorn T.; Gunapala, Sarah D.; Lamborn, Andrew U.; Mouroulis, Pantazis, Z.; Mouroulis, Pantazis, Z.; Paine, Christopher G.; Soibel, Alexander; Wilson, Daniel W.

2011-01-01

The Hyperspectral Thermal Emission Spectrometer (HyTES) is being developed as part of the risk reduction activities associated with the Hyperspectral Infrared Imager (HyspIRI). HyspIRI is one of the Tier 2 Decadal Survey Missions. HyTES will provide information on how to place the filters on the HyspIRI Thermal Infrared Instrument (TIR) as well as provide antecedent science data. The pushbroom design has 512 spatial pixels over a 50-degree field of view and 256 spectral channels between 7.5 micrometers to 12 micrometers. HyTES includes many key enabling state-of-the-art technologies including a high performance convex diffraction grating, a quantum well infrared photodetector (QWIP) focal plane array, and a compact Dyson-inspired optical design. The Dyson optical design allows for a very compact and optically fast system (F/1.6). It also minimizes cooling requirements due to the fact it has a single monolithic prism-like grating design which allows baffling for stray light suppression. The monolithic configuration eases mechanical tolerancing requirements which are a concern since the complete optical assembly is operated at cryogenic temperatures ((is) approximately 100K). The QWIP allows for optimum spatial and spectral uniformity and provides adequate responsivity or D-star to allow 200mK noise equivalent temperature difference (NEDT) operation across the LWIR passband. Assembly of the system is nearly complete. After completion, alignment results will be presented which show low keystone and smile distortion. This is required to minimize spatial-spectral mixing between adjacent spectral channels and spatial positions. Predictions show the system will have adequate signal to noise for laboratory calibration targets.

Upgrade of a UV-VIS-NIR imaging spectrometer for the coastal ocean observation: concept, design, fabrication, and test of prototype.

PubMed

Yu, Lei

2017-06-26

A novel UV-VIS-NIR imaging spectrometer prototype has been presented for the remote sensing of the coastal ocean by air. The concept is proposed for the needs of the observation. An advanced design has been demonstrated based on the Dyson spectrometer in details. The analysis and tests present excellent optical performances in the spectral broadband, easy and low cost fabrication and alignment, low inherent stray light, and high signal to noise ratio. The research provides an easy method for the coastal ocean observation.

Exact solution of matricial Φ23 quantum field theory

NASA Astrophysics Data System (ADS)

Grosse, Harald; Sako, Akifumi; Wulkenhaar, Raimar

2017-12-01

We apply a recently developed method to exactly solve the Φ3 matrix model with covariance of a two-dimensional theory, also known as regularised Kontsevich model. Its correlation functions collectively describe graphs on a multi-punctured 2-sphere. We show how Ward-Takahashi identities and Schwinger-Dyson equations lead in a special large- N limit to integral equations that we solve exactly for all correlation functions. The solved model arises from noncommutative field theory in a special limit of strong deformation parameter. The limit defines ordinary 2D Schwinger functions which, however, do not satisfy reflection positivity.

Refining the detection of the zero crossing for the three-gluon vertex in symmetric and asymmetric momentum subtraction schemes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boucaud, Ph.; De Soto, F.; Rodriguez-Quintero, J.

This article reports on the detailed study of the three-gluon vertex in four-dimensional $SU(3)$ Yang-Mills theory employing lattice simulations with large physical volumes and high statistics. A meticulous scrutiny of the so-called symmetric and asymmetric kinematical configurations is performed and it is shown that the associated form-factor changes sign at a given range of momenta. Here, the lattice results are compared to the model independent predictions of Schwinger-Dyson equations and a very good agreement among the two is found.

Refining the detection of the zero crossing for the three-gluon vertex in symmetric and asymmetric momentum subtraction schemes

DOE PAGES

Boucaud, Ph.; De Soto, F.; Rodriguez-Quintero, J.; ...

2017-06-14

This article reports on the detailed study of the three-gluon vertex in four-dimensional $SU(3)$ Yang-Mills theory employing lattice simulations with large physical volumes and high statistics. A meticulous scrutiny of the so-called symmetric and asymmetric kinematical configurations is performed and it is shown that the associated form-factor changes sign at a given range of momenta. Here, the lattice results are compared to the model independent predictions of Schwinger-Dyson equations and a very good agreement among the two is found.

Intermediate quantum maps for quantum computation

NASA Astrophysics Data System (ADS)

Giraud, O.; Georgeot, B.

2005-10-01

We study quantum maps displaying spectral statistics intermediate between Poisson and Wigner-Dyson. It is shown that they can be simulated on a quantum computer with a small number of gates, and efficiently yield information about fidelity decay or spectral statistics. We study their matrix elements and entanglement production and show that they converge with time to distributions which differ from random matrix predictions. A randomized version of these maps can be implemented even more economically and yields pseudorandom operators with original properties, enabling, for example, one to produce fractal random vectors. These algorithms are within reach of present-day quantum computers.

Footprints of alien technology

NASA Astrophysics Data System (ADS)

Davies, P. C. W.

2012-04-01

If alien civilizations do, or did, exist, their technology will impact their environment. Some consideration has been given to the detection of large-scale astro-engineering, such as Dyson spheres. However, a very advanced technology might leave more subtle footprints requiring sophisticated scientific methods to uncover. We must not overlook the possibility that alien technology has impacted our immediate astronomical environment, even Earth itself, but probably a very long time ago. This raises the question of what traces, if anything, might remain today. I shall consider the possibilities of biological, geological and physical traces, and suggest ways that we might search for them.

Landau ghost pole problem in quantum field theory: From 50th of last century to the present day

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jafarov, Rauf G., E-mail: rauf-jafarov@hotmail.com; Mutallimov, Mutallim M.

2016-03-25

In this paper we present our results of the investigation of asymptotical behavior of amplitude at short distances in four-dimensional scalar field theory with ϕ{sup 4} interaction. To formulate of our calculating model – two-particle approximation of the mean-field expansion we have used an Rochev’s iteration scheme of solution of the Schwinger-Dyson equations with the fermion bilocal source. We have considered the nonlinear integral equations in deep-inelastic region of momenta. As result we have a non-trivial behavior of amplitude at large momenta.

Analytic few-photon scattering in waveguide QED

NASA Astrophysics Data System (ADS)

Hurst, David L.; Kok, Pieter

2018-04-01

We develop an approach to light-matter coupling in waveguide QED based upon scattering amplitudes evaluated via Dyson series. For optical states containing more than single photons, terms in this series become increasingly complex, and we provide a diagrammatic recipe for their evaluation, which is capable of yielding analytic results. Our method fully specifies a combined emitter-optical state that permits investigation of light-matter entanglement generation protocols. We use our expressions to study two-photon scattering from a Λ -system and find that the pole structure of the transition amplitude is dramatically altered as the two ground states are tuned from degeneracy.

Cluster perturbation theory for calculation of electronic properties of ensembles of metal nanoclusters

NASA Astrophysics Data System (ADS)

Zhumagulov, Yaroslav V.; Krasavin, Andrey V.; Kashurnikov, Vladimir A.

2018-05-01

The method is developed for calculation of electronic properties of an ensemble of metal nanoclusters with the use of cluster perturbation theory. This method is applied to the system of gold nanoclusters. The Greens function of single nanocluster is obtained by ab initio calculations within the framework of the density functional theory, and then is used in Dyson equation to group nanoclusters together and to compute the Greens function as well as the electron density of states of the whole ensemble. The transition from insulator state of a single nanocluster to metallic state of bulk gold is observed.

Exact mean-energy expansion of Ginibre's gas for coupling constants Γ =2 ×(oddinteger)

NASA Astrophysics Data System (ADS)

Salazar, R.; Téllez, G.

2017-12-01

Using the approach of a Vandermonde determinant to the power Γ =Q2/kBT expansion on monomial functions, a way to find the excess energy Uexc of the two-dimensional one-component plasma (2DOCP) on hard and soft disks (or a Dyson gas) for odd values of Γ /2 is provided. At Γ =2 , the present study not only corroborates the result for the particle-particle energy contribution of the Dyson gas found by Shakirov [Shakirov, Phys. Lett. A 375, 984 (2011), 10.1016/j.physleta.2011.01.004] by using an alternative approach, but also provides the exact N -finite expansion of the excess energy of the 2DOCP on the hard disk. The excess energy is fitted to the ansatz of the form Uexc=K1N +K2√{N }+K3+K4/N +O (1 /N2) to study the finite-size correction, with Ki coefficients and N the number of particles. In particular, the bulk term of the excess energy is in agreement with the well known result of Jancovici for the hard disk in the thermodynamic limit [Jancovici, Phys. Rev. Lett. 46, 386 (1981), 10.1103/PhysRevLett.46.386]. Finally, an expression is found for the pair correlation function which still keeps a link with the random matrix theory via the kernel in the Ginibre ensemble [Ginibre, J. Math. Phys. 6, 440 (1965), 10.1063/1.1704292] for odd values of Γ /2 . A comparison between the analytical two-body density function and histograms obtained with Monte Carlo simulations for small systems and Γ =2 ,6 ,10 ,... shows that the approach described in this paper may be used to study analytically the crossover behavior from systems in the fluid phase to small crystals.

Justifying quasiparticle self-consistent schemes via gradient optimization in Baym-Kadanoff theory.

PubMed

Ismail-Beigi, Sohrab

2017-09-27

The question of which non-interacting Green's function 'best' describes an interacting many-body electronic system is both of fundamental interest as well as of practical importance in describing electronic properties of materials in a realistic manner. Here, we study this question within the framework of Baym-Kadanoff theory, an approach where one locates the stationary point of a total energy functional of the one-particle Green's function in order to find the total ground-state energy as well as all one-particle properties such as the density matrix, chemical potential, or the quasiparticle energy spectrum and quasiparticle wave functions. For the case of the Klein functional, our basic finding is that minimizing the length of the gradient of the total energy functional over non-interacting Green's functions yields a set of self-consistent equations for quasiparticles that is identical to those of the quasiparticle self-consistent GW (QSGW) (van Schilfgaarde et al 2006 Phys. Rev. Lett. 96 226402-4) approach, thereby providing an a priori justification for such an approach to electronic structure calculations. In fact, this result is general, applies to any self-energy operator, and is not restricted to any particular approximation, e.g., the GW approximation for the self-energy. The approach also shows that, when working in the basis of quasiparticle states, solving the diagonal part of the self-consistent Dyson equation is of primary importance while the off-diagonals are of secondary importance, a common observation in the electronic structure literature of self-energy calculations. Finally, numerical tests and analytical arguments show that when the Dyson equation produces multiple quasiparticle solutions corresponding to a single non-interacting state, minimizing the length of the gradient translates into choosing the solution with largest quasiparticle weight.

Mean field dynamics of some open quantum systems

NASA Astrophysics Data System (ADS)

Merkli, Marco; Rafiyi, Alireza

2018-04-01

We consider a large number N of quantum particles coupled via a mean field interaction to another quantum system (reservoir). Our main result is an expansion for the averages of observables, both of the particles and of the reservoir, in inverse powers of √{N }. The analysis is based directly on the Dyson series expansion of the propagator. We analyse the dynamics, in the limit N →∞ , of observables of a fixed number n of particles, of extensive particle observables and their fluctuations, as well as of reservoir observables. We illustrate our results on the infinite mode Dicke model and on various energy-conserving models.

A Mathematical Account of the NEGF Formalism

NASA Astrophysics Data System (ADS)

Cornean, Horia D.; Moldoveanu, Valeriu; Pillet, Claude-Alain

2018-02-01

The main goal of this paper is to put on solid mathematical grounds the so-called Non-Equilibrium Green's Function (NEGF) transport formalism for open systems. In particular, we derive the Jauho-Meir-Wingreen formula for the time-dependent current through an interacting sample coupled to non-interacting leads. Our proof is non-perturbative and uses neither complex-time Keldysh contours, nor Langreth rules of 'analytic continuation'. We also discuss other technical identities (Langreth, Keldysh) involving various many body Green's functions. Finally, we study the Dyson equation for the advanced/retarded interacting Green's function and we rigorously construct its (irreducible) self-energy, using the theory of Volterra operators.

Phase Diagram of Planar Matrix Quantum Mechanics, Tensor, and Sachdev-Ye-Kitaev Models.

PubMed

Azeyanagi, Tatsuo; Ferrari, Frank; Massolo, Fidel I Schaposnik

2018-02-09

We study the Schwinger-Dyson equations of a fermionic planar matrix quantum mechanics [or tensor and Sachdev-Ye-Kitaev (SYK) models] at leading melonic order. We find two solutions describing a high entropy, SYK black-hole-like phase and a low entropy one with trivial IR behavior. There is a line of first order phase transitions that terminates at a new critical point. Critical exponents are nonmean field and differ on the two sides of the transition. Interesting phenomena are also found in unstable and stable bosonic models, including Kazakov critical points and inconsistency of SYK-like solutions of the IR limit.

View of Expedition 24 Crew Members in the MRM2

NASA Image and Video Library

2010-09-24

ISS024-E-015327 (24 Sept. 2010) --- Russian cosmonaut Alexander Skvortsov (right), Expedition 24 commander; NASA astronaut Tracy Caldwell Dyson and Russian cosmonaut Mikhail Kornienko, both flight engineers, pose for a photo during final preparations for their departure in the Soyuz TMA-18 docked to the Poisk Mini-Research Module 2 (MRM2) of the International Space Station. Originally scheduled for Sept. 23, the Soyuz undocked a day later due to a Poisk-side hatch sensor problem, which prevented hooks on the Poisk side of the docking interface from opening. The Soyuz undocked at 10:02 p.m. (EDT) on Sept. 24, 2010.

Mean field dynamics of some open quantum systems.

PubMed

Merkli, Marco; Rafiyi, Alireza

2018-04-01

We consider a large number N of quantum particles coupled via a mean field interaction to another quantum system (reservoir). Our main result is an expansion for the averages of observables, both of the particles and of the reservoir, in inverse powers of [Formula: see text]. The analysis is based directly on the Dyson series expansion of the propagator. We analyse the dynamics, in the limit [Formula: see text], of observables of a fixed number n of particles, of extensive particle observables and their fluctuations, as well as of reservoir observables. We illustrate our results on the infinite mode Dicke model and on various energy-conserving models.

Crew Meal in Node 1 Unity

NASA Image and Video Library

2010-04-09

S131-E-008304 (9 April 2010) --- With 13 astronauts and cosmonauts onboard the station at one time, activities around the galley in the Unity node get rather busy at meal time. Over half the 13 are seen in this flight day five aggregation. NASA astronaut James P. Dutton Jr., STS-131 pilot, prepares part of his meal at left. Also pictured clockwise (from the right) are JAXA astronaut Soichi Noguchi and NASA astronaut Tracy Caldwell Dyson, both Expedition 23 flight engineers; NASA astronauts Stephanie Wilson and Clayton Anderson, both STS-131 mission specialists; along with Russian cosmonauts Oleg Kotov and Mikhail Kornienko, Expedition 23 commander and flight engineer, respectively.

On the Asymptotic Behavior of a Log Gas in the Bulk Scaling Limit in the Presence of a Varying External Potential I

NASA Astrophysics Data System (ADS)

Bothner, Thomas; Deift, Percy; Its, Alexander; Krasovsky, Igor

2015-08-01

We study the determinant , of the integrable Fredholm operator K s acting on the interval (-1, 1) with kernel . This determinant arises in the analysis of a log-gas of interacting particles in the bulk-scaling limit, at inverse temperature , in the presence of an external potential supported on an interval of length . We evaluate, in particular, the double scaling limit of as and , in the region , for any fixed . This problem was first considered by Dyson (Chen Ning Yang: A Great Physicist of the Twentieth Century. International Press, Cambridge, pp. 131-146, 1995).

Dynamics of systems on the nanoscale

NASA Astrophysics Data System (ADS)

Korol, Andrei V.; Solov'yov, Andrey V.

2017-12-01

Various aspects of the structure formation and dynamics of animate and inanimate matter on the nanoscale is a highly interdisciplinary field of rapidly emerging research interest by both experimentalists and theorists. The International Conference on Dynamics of Systems on the Nanoscale (DySoN) is the premier forum to present cutting-edge research in this field. It was established in 2010 and the most recent conference was held in Bad Ems, Germany in October of 2016. This Topical Issue presents original research results from some of the participants, who attended this conference. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

Gravitational lensing: a unique probe of dark matter and dark energy.

PubMed

Ellis, Richard S

2010-03-13

I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe-the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects.

On the Tracy-Widomβ Distribution for β=6

NASA Astrophysics Data System (ADS)

Grava, Tamara; Its, Alexander; Kapaev, Andrei; Mezzadri, Francesco

2016-11-01

We study the Tracy-Widom distribution function for Dyson's β-ensemble with β = 6. The starting point of our analysis is the recent work of I. Rumanov where he produces a Lax-pair representation for the Bloemendal-Virág equation. The latter is a linear PDE which describes the Tracy-Widom functions corresponding to general values of β. Using his Lax pair, Rumanov derives an explicit formula for the Tracy-Widom β=6 function in terms of the second Painlevé transcendent and the solution of an auxiliary ODE. Rumanov also shows that this formula allows him to derive formally the asymptotic expansion of the Tracy-Widom function. Our goal is to make Rumanov's approach and hence the asymptotic analysis it provides rigorous. In this paper, the first one in a sequel, we show that Rumanov's Lax-pair can be interpreted as a certain gauge transformation of the standard Lax pair for the second Painlevé equation. This gauge transformation though contains functional parameters which are defined via some auxiliary nonlinear ODE which is equivalent to the auxiliary ODE of Rumanov's formula. The gauge-interpretation of Rumanov's Lax-pair allows us to highlight the steps of the original Rumanov's method which needs rigorous justifications in order to make the method complete. We provide a rigorous justification of one of these steps. Namely, we prove that the Painlevé function involved in Rumanov's formula is indeed, as it has been suggested by Rumanov, the Hastings-McLeod solution of the second Painlevé equation. The key issue which we also discuss and which is still open is the question of integrability of the auxiliary ODE in Rumanov's formula. We note that this question is crucial for the rigorous asymptotic analysis of the Tracy-Widom function. We also notice that our work is a partial answer to one of the problems related to the β-ensembles formulated by Percy Deift during the June 2015 Montreal Conference on integrable systems.

Emergent Irreversibility and Entanglement Spectrum Statistics

NASA Astrophysics Data System (ADS)

Chamon, Claudio; Hamma, Alioscia; Mucciolo, Eduardo R.

2014-06-01

We study the problem of irreversibility when the dynamical evolution of a many-body system is described by a stochastic quantum circuit. Such evolution is more general than a Hamiltonian one, and since energy levels are not well defined, the well-established connection between the statistical fluctuations of the energy spectrum and irreversibility cannot be made. We show that the entanglement spectrum provides a more general connection. Irreversibility is marked by a failure of a disentangling algorithm and is preceded by the appearance of Wigner-Dyson statistical fluctuations in the entanglement spectrum. This analysis can be done at the wave-function level and offers an alternative route to study quantum chaos and quantum integrability.

Chiral symmetry restoration at finite temperature and chemical potential in the improved ladder approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taniguchi, Y.; Yoshida, Y.

1997-02-01

The chiral symmetry of QCD is studied at finite temperature and chemical potential using the Schwinger-Dyson equation in the improved ladder approximation. We calculate three order parameters: the vacuum expectation value of the quark bilinear operator, the pion decay constant, and the quark mass gap. We have a second order phase transition at the temperature T{sub c}=169 MeV along the zero chemical potential line, and a first order phase transition at the chemical potential {mu}{sub c}=598 MeV along the zero temperature line. We also calculate the critical exponents of the three order parameters. {copyright} {ital 1997} {ital The American Physicalmore » Society}« less

Scale-setting, flavor dependence, and chiral symmetry restoration

DOE PAGES

Binosi, D; Roberts, Craig D.; Rodriguez-Quintero, J.

2017-06-13

Here, we determine the flavor dependence of the renormalization-group-invariant running interaction through judicious use of both unquenched Dyson-Schwinger equation and lattice results for QCD’s gauge-sector two-point functions. An important step is the introduction of a physical scale setting procedure that enables a realistic expression of the effect of different numbers of active quark flavours on the interaction. Using this running interaction in concert with a well constrained class of dressed–gluon-quark vertices, we estimate the critical number of active lighter-quarks above which dynamical chiral symmetry breaking becomes impossible: n cr f ≈ 9; and hence in whose neighborhood QCD is plausiblymore » a conformal theory.« less

N-point functions in rolling tachyon background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jokela, Niko; Keski-Vakkuri, Esko; Department of Physics, P.O. Box 64, FIN-00014, University of Helsinki

2009-04-15

We study n-point boundary correlation functions in timelike boundary Liouville theory, relevant for open string multiproduction by a decaying unstable D brane. We give an exact result for the one-point function of the tachyon vertex operator and show that it is consistent with a previously proposed relation to a conserved charge in string theory. We also discuss when the one-point amplitude vanishes. Using a straightforward perturbative expansion, we find an explicit expression for a tachyon n-point amplitude for all n, however the result is still a toy model. The calculation uses a new asymptotic approximation for Toeplitz determinants, derived bymore » relating the system to a Dyson gas at finite temperature.« less

Quasi-normal modes from non-commutative matrix dynamics

NASA Astrophysics Data System (ADS)

Aprile, Francesco; Sanfilippo, Francesco

2017-09-01

We explore similarities between the process of relaxation in the BMN matrix model and the physics of black holes in AdS/CFT. Focusing on Dyson-fluid solutions of the matrix model, we perform numerical simulations of the real time dynamics of the system. By quenching the equilibrium distribution we study quasi-normal oscillations of scalar single trace observables, we isolate the lowest quasi-normal mode, and we determine its frequencies as function of the energy. Considering the BMN matrix model as a truncation of N=4 SYM, we also compute the frequencies of the quasi-normal modes of the dual scalar fields in the AdS5-Schwarzschild background. We compare the results, and we finda surprising similarity.

Spontaneous PT-Symmetry Breaking for Systems of Noncommutative Euclidean Lie Algebraic Type

NASA Astrophysics Data System (ADS)

Dey, Sanjib; Fring, Andreas; Mathanaranjan, Thilagarajah

2015-11-01

We propose a noncommutative version of the Euclidean Lie algebra E 2. Several types of non-Hermitian Hamiltonian systems expressed in terms of generic combinations of the generators of this algebra are investigated. Using the breakdown of the explicitly constructed Dyson maps as a criterium, we identify the domains in the parameter space in which the Hamiltonians have real energy spectra and determine the exceptional points signifying the crossover into the different types of spontaneously broken PT-symmetric regions with pairs of complex conjugate eigenvalues. We find exceptional points which remain invariant under the deformation as well as exceptional points becoming dependent on the deformation parameter of the algebra.

From Bethe–Salpeter Wave functions to Generalised Parton Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.

2016-06-06

We review recent works on the modelling of Generalised Parton Distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. A specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within thismore » framework, in a two-body approximation« less

MgH Rydberg series: Transition energies from electron propagator theory and oscillator strengths from the molecular quantum defect orbital method

NASA Astrophysics Data System (ADS)

Corzo, H. H.; Velasco, A. M.; Lavín, C.; Ortiz, J. V.

2018-02-01

Vertical excitation energies belonging to several Rydberg series of MgH have been inferred from 3+ electron-propagator calculations of the electron affinities of MgH+ and are in close agreement with experiment. Many electronically excited states with n > 3 are reported for the first time and new insight is given on the assignment of several Rydberg series. Valence and Rydberg excited states of MgH are distinguished respectively by high and low pole strengths corresponding to Dyson orbitals of electron attachment to the cation. By applying the Molecular Quantum Defect Orbital method, oscillator strengths for electronic transitions involving Rydberg states also have been determined.

Exact Extremal Statistics in the Classical 1D Coulomb Gas

NASA Astrophysics Data System (ADS)

Dhar, Abhishek; Kundu, Anupam; Majumdar, Satya N.; Sabhapandit, Sanjib; Schehr, Grégory

2017-08-01

We consider a one-dimensional classical Coulomb gas of N -like charges in a harmonic potential—also known as the one-dimensional one-component plasma. We compute, analytically, the probability distribution of the position xmax of the rightmost charge in the limit of large N . We show that the typical fluctuations of xmax around its mean are described by a nontrivial scaling function, with asymmetric tails. This distribution is different from the Tracy-Widom distribution of xmax for Dyson's log gas. We also compute the large deviation functions of xmax explicitly and show that the system exhibits a third-order phase transition, as in the log gas. Our theoretical predictions are verified numerically.

Efficiency trial of 80% thiophanate-methyl and 72% streptomycin against konjac bacterial soft rot

NASA Astrophysics Data System (ADS)

Lin, Tianxing; Gong, Mingfu; Guan, Qinlan; Tan, Chunyan

2018-04-01

Amorphophallus konjac soft rot can cause severe yield losses, and the effects agent to prevent the disease had not been found currently in production. In this dissertation, inhibition on konjac soft rot bacteria of seven agricultural fungicides, as benzene ring yl ether, methyl thiophanate, streptomycin sulfate, methane frost hymexazol, bismerthiazol WP, gray mold and Dyson Mn-Zn, was determined by antagonistic petri dish method. The results indicated that: the tested fungicide s had certain inhibition on konjac soft rot bacteria, and the inhibitory effect of different fungicides was significant difference. 80% thiophanate-methyl and 72% streptomycin sulfate had a good inhibitory effect on konjac soft rot disease bacteria.

Gravitational lensing: a unique probe of dark matter and dark energy

PubMed Central

Ellis, Richard S.

2010-01-01

I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe—the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects. PMID:20123743

50th Anniversary of the Civil Rights Act of 1964

NASA Image and Video Library

2014-06-23

Members of the audience listen as U.S. Representative Eddie Bernice Johnson, of Texas; Dr. Harriet Jenkins, Former Assistant Administrator for Equal Opportunity Programs at NASA; Dr. Roger Launius, Associate Director of Collections and Curatorial Affairs at the Smithsonian National Air and Space Museum; and Dr. Michael Eric Dyson, a professor of sociology at Georgetown University; speak on a panel moderated by Suzanne Malveaux, of CNN, at an event celebrating the 50th Anniversary of the Civil Rights Act of 1964 on Monday, June 23, 2014 in the James E. Webb Auditorium at NASA Headquarters in Washington, DC. The event highlighted the influence of the Civil Rights Act on NASA. Photo Credit: (NASA/Joel Kowsky)

Stochastic many-body perturbation theory for anharmonic molecular vibrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermes, Matthew R.; Hirata, So, E-mail: sohirata@illinois.edu; CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012

2014-08-28

A new quantum Monte Carlo (QMC) method for anharmonic vibrational zero-point energies and transition frequencies is developed, which combines the diagrammatic vibrational many-body perturbation theory based on the Dyson equation with Monte Carlo integration. The infinite sums of the diagrammatic and thus size-consistent first- and second-order anharmonic corrections to the energy and self-energy are expressed as sums of a few m- or 2m-dimensional integrals of wave functions and a potential energy surface (PES) (m is the vibrational degrees of freedom). Each of these integrals is computed as the integrand (including the value of the PES) divided by the value ofmore » a judiciously chosen weight function evaluated on demand at geometries distributed randomly but according to the weight function via the Metropolis algorithm. In this way, the method completely avoids cumbersome evaluation and storage of high-order force constants necessary in the original formulation of the vibrational perturbation theory; it furthermore allows even higher-order force constants essentially up to an infinite order to be taken into account in a scalable, memory-efficient algorithm. The diagrammatic contributions to the frequency-dependent self-energies that are stochastically evaluated at discrete frequencies can be reliably interpolated, allowing the self-consistent solutions to the Dyson equation to be obtained. This method, therefore, can compute directly and stochastically the transition frequencies of fundamentals and overtones as well as their relative intensities as pole strengths, without fixed-node errors that plague some QMC. It is shown that, for an identical PES, the new method reproduces the correct deterministic values of the energies and frequencies within a few cm{sup −1} and pole strengths within a few thousandths. With the values of a PES evaluated on the fly at random geometries, the new method captures a noticeably greater proportion of anharmonic effects.« less

MESIC GROUP AND CONSERVATION OF PARITY (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petermann, A.; Ruegg, H.

1960-01-01

A principle of invariance under a continuous local group of transformations, the mesic group, is investigated. This principle has the following influences: 1. For the pseudoscslar Yukawa interaction of two Fermiore with the pseudoscalar pi -meson it entails PC invariance. 2. If the Fermions have equal bare masses with respect to electromagnetic interaction (a hypothesis which is plausible for the nucleons), the principle imposes, for the ps interaction with pi , the conservation of isotopic spin and separate P and C invariance. 3. For the Fermi interactions of the pairs (pn), nonconservation of parity. Arguments leading to this principle aremore » based on a generalization of the demonstration of the Dyson-Foldy equivalence theorem as given by Stueckelberg and Petermann. (auth)« less

X-ray Raman scattering from molecules and solids in the framework of the Mahan-Nozières-De Dominicis model

NASA Astrophysics Data System (ADS)

Privalov, Timofei; Gel'mukhanov, Faris; Ågren, Hans

2001-10-01

We have developed a formulation of resonant x-ray Raman scattering of molecules and solids based on the Mahan-Nozières-De Dominicis model. A key step in the formulation is given by a reduction of the Keldysh-Dyson equations for the Green's function to a set of linear algebraic equations. This gave way for a tractable scheme that can be used to analyze the resonant x-ray scattering in the whole time domain. The formalism is used to investigate the role of core-hole relaxation, interference, band filling, detuning, and size of the scattering target. Numerical applications are performed with a one-dimensional tight-binding model.

Finite-range Coulomb gas models of banded random matrices and quantum kicked rotors

NASA Astrophysics Data System (ADS)

Pandey, Akhilesh; Kumar, Avanish; Puri, Sanjay

2017-11-01

Dyson demonstrated an equivalence between infinite-range Coulomb gas models and classical random matrix ensembles for the study of eigenvalue statistics. We introduce finite-range Coulomb gas (FRCG) models via a Brownian matrix process, and study them analytically and by Monte Carlo simulations. These models yield new universality classes, and provide a theoretical framework for the study of banded random matrices (BRMs) and quantum kicked rotors (QKRs). We demonstrate that, for a BRM of bandwidth b and a QKR of chaos parameter α , the appropriate FRCG model has the effective range d =b2/N =α2/N , for large N matrix dimensionality. As d increases, there is a transition from Poisson to classical random matrix statistics.

Chimera distribution amplitudes for the pion and the longitudinally polarized ρ-meson

NASA Astrophysics Data System (ADS)

Stefanis, N. G.; Pimikov, A. V.

2016-01-01

Using QCD sum rules with nonlocal condensates, we show that the distribution amplitude of the longitudinally polarized ρ-meson may have a shorttailed platykurtic profile in close analogy to our recently proposed platykurtic distribution amplitude for the pion. Such a chimera distribution de facto amalgamates the broad unimodal profile of the distribution amplitude, obtained with a Dyson-Schwinger equations-based computational scheme, with the suppressed tails characterizing the bimodal distribution amplitudes derived from QCD sum rules with nonlocal condensates. We argue that pattern formation, emerging from the collective synchronization of coupled oscillators, can provide a single theoretical scaffolding to study unimodal and bimodal distribution amplitudes of light mesons without recourse to particular computational schemes and the reasons for them.

Ground and excited states of CaSH through electron propagator calculations

NASA Astrophysics Data System (ADS)

Ortiz, J. V.

1990-05-01

Electron propagator calculations of electron affinities of CaSH + produce ground and excited state energies at the optimized, C s minimum of the neutral ground state and at a C ∞v geometry. Feynman-Dyson amplitudes (FDAs) describe the distribution of the least bound electron in various states. The neutral ground state differs from the cation by the occupation of a one-electron state dominated by Ca s functions. Described by FDAs with Ca-S π pseudosymmetry, corresponding excited states have unpaired electrons in orbitals displaying interference between Ca p and d functions. Above these lies a σ pseudosymmetry FDA with principal contributions from Ca d functions. Two FDAs with σ pseudosymmetry follow. Higher excited states exhibit considerable delocalization onto S.

Finite-range Coulomb gas models of banded random matrices and quantum kicked rotors.

PubMed

Pandey, Akhilesh; Kumar, Avanish; Puri, Sanjay

2017-11-01

Dyson demonstrated an equivalence between infinite-range Coulomb gas models and classical random matrix ensembles for the study of eigenvalue statistics. We introduce finite-range Coulomb gas (FRCG) models via a Brownian matrix process, and study them analytically and by Monte Carlo simulations. These models yield new universality classes, and provide a theoretical framework for the study of banded random matrices (BRMs) and quantum kicked rotors (QKRs). We demonstrate that, for a BRM of bandwidth b and a QKR of chaos parameter α, the appropriate FRCG model has the effective range d=b^{2}/N=α^{2}/N, for large N matrix dimensionality. As d increases, there is a transition from Poisson to classical random matrix statistics.

FAST TRACK COMMUNICATION: Freezing and extreme-value statistics in a random energy model with logarithmically correlated potential

NASA Astrophysics Data System (ADS)

Fyodorov, Yan V.; Bouchaud, Jean-Philippe

2008-09-01

We investigate some implications of the freezing scenario proposed by Carpentier and Le Doussal (CLD) for a random energy model (REM) with logarithmically correlated random potential. We introduce a particular (circular) variant of the model, and show that the integer moments of the partition function in the high-temperature phase are given by the well-known Dyson Coulomb gas integrals. The CLD freezing scenario allows one to use those moments for extracting the distribution of the free energy in both high- and low-temperature phases. In particular, it yields the full distribution of the minimal value in the potential sequence. This provides an explicit new class of extreme-value statistics for strongly correlated variables, manifestly different from the standard Gumbel class.

On the zero-crossing of the three-gluon Green's function from lattice simulations

NASA Astrophysics Data System (ADS)

Athenodorou, Andreas; Boucaud, Philippe; de Soto, Feliciano; Rodríguez-Quintero, José; Zafeiropoulos, Savvas

2018-03-01

We report on some efforts recently made in order to gain a better understanding of some IR properties of the 3-point gluon Green's function by exploiting results from large-volume quenched lattice simulations. These lattice results have been obtained by using both tree-level Symanzik and the standard Wilson action, in the aim of assessing the possible impact of effects presumably resulting from a particular choice for the discretization of the action. The main resulting feature is the existence of a negative log-aritmic divergence at zero-momentum, which pulls the 3-gluon form factors down at low momenta and, consequently, yields a zero-crossing at a given deep IR momentum. The results can be correctly explained by analyzing the relevant Dyson-Schwinger equations and appropriate truncation schemes.

Serendipity, Punctuated

NASA Astrophysics Data System (ADS)

Asmus, John F.

Laser divestment entered the field of art conservation through a nonlinear sequence of positive accidental events (serendipity) that involved the cinema industry, the invention of spread-spectrum and frequency-hopping communications, nuclear space propulsion, and oceanography. The unlikely chain of events began with the invention of a secure military communications system by a Viennese motion picture actress (1942). A first evaluation of the novel communications concept took place during a high-altitude nuclear test (TEAK) over the Pacific Ocean in 1958. The secure radio link proved to be a failure; however, analyses of the backscattered electromagnetic radiation contributed to the realization that nuclear-explosion plasmas need not be spherically symmetrical. Nobel Laureate Freeman Dyson exploited this nuclear option to guide in the design and prototype development of the ORION spaceship that was to rendezvous with the planet Saturn in 1970.

Galaxy Gadgeteers: Architects in Space

NASA Astrophysics Data System (ADS)

Morris, M. S.

This essay explores interdisciplinary themes finding links between architecture, science and science fiction. A character from Douglas Adams' Hitchhiker's Guide series is presented as an archetypical architect charged with designing planets. The author offers diverse examples of other architectural projects dealing with vast planetary and interplanetary scales. The design of space colonies within Dyson Spheres and Torus Rings is examined with an eye to precedents from architectural history. Speculative space colony designs pursued by NASA are critiqued as awkward assemblages of futuristic fantasy and nostalgia. Contemporary architectural projects are presented, revealing the scalar adaptability or looseness of certain architects with strong stylistic tendencies. The paper concludes by examining partly unrealized designs for an Enlightenment utopian town and how themes inspired by the image of the solar system move from spatial and formal arrangements to pictorial and metaphorical depictions.

Multiloop functional renormalization group for general models

NASA Astrophysics Data System (ADS)

Kugler, Fabian B.; von Delft, Jan

2018-02-01

We present multiloop flow equations in the functional renormalization group (fRG) framework for the four-point vertex and self-energy, formulated for a general fermionic many-body problem. This generalizes the previously introduced vertex flow [F. B. Kugler and J. von Delft, Phys. Rev. Lett. 120, 057403 (2018), 10.1103/PhysRevLett.120.057403] and provides the necessary corrections to the self-energy flow in order to complete the derivative of all diagrams involved in the truncated fRG flow. Due to its iterative one-loop structure, the multiloop flow is well suited for numerical algorithms, enabling improvement of many fRG computations. We demonstrate its equivalence to a solution of the (first-order) parquet equations in conjunction with the Schwinger-Dyson equation for the self-energy.

50th Anniversary of the Civil Rights Act of 1964

NASA Image and Video Library

2014-06-23

Dr. Michael Eric Dyson, a professor of sociology at Georgetown University, left; speaks as part of a panel discussion at an event celebrating the 50th Anniversary of the Civil Rights Act of 1964 on Monday, June 23, 2014 in the James E. Webb Auditorium at NASA Headquarters in Washington, DC. The panel was moderated by Suzanne Malveaux, a correspondent with CNN, left; and also included U.S. Representative Eddie Bernice Johnson, of Texas, second from left; Dr. Harriet Jenkins, Former Assistant Administrator for Equal Opportunity Programs at NASA, third from left; and Dr. Roger Launius, Associate Director of Collections and Curatorial Affairs at the Smithsonian National Air and Space Museum, second from right. The event highlighted the influence of the Civil Rights Act on NASA. Photo Credit: (NASA/Joel Kowsky)

50th Anniversary of the Civil Rights Act of 1964

NASA Image and Video Library

2014-06-23

From left: Robert Lightroot. NASA Associate Administrator; Dr. Roger Launius, Associate Director of Collections and Curatorial Affairs at the Smithsonian National Air and Space Museum; Dr. Harriett Jenkins, Former Assistant Administrator for Equal Opportunity Programs at NASA; Brenda Manuel, Associate Administrator for Diversity and Equal Opportunity at NASA; Suzanne Malveaux, CNN Correspondent and panel moderator; U.S. Representative Eddie Bernice Johnson, of Texas; Dr. Michael Eric Dyson, professor of sociology at Georgetown University; and Charles Bolden, NASA Administrator; pose for a picture following an event celebrating the 50th Anniversary of the Civil Rights Act of 1964 on Monday, June 23, 2014 in the James E. Webb Auditorium at NASA Headquarters in Washington, DC. The event highlighted the influence of the Civil Rights Act on NASA. Photo Credit: (NASA/Joel Kowsky)

Intermediate-coupling theory of the spin polaron in the {ital t}-{ital J} model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barentzen, H.

1996-03-01

The spin polaron in the {ital t-J} model, i.e., a hole dressed by a cloud of virtual magnons of the antiferromagnetic spin background, is treated within the framework of intermediate-coupling theory. The original {ital t}-{ital J} model is first reformulated in terms of spinless fermions and bosons by means of the generalized Dyson-Maleev representation (DMR). The latter may be regarded as the natural extension of the ordinary DMR of pure (undoped) spin systems to the case where holes are present, and is similar to the one originally proposed by Schmitt-Rink, Varma, and Ruckenstein. The reformulated {ital t}-{ital J} model, whichmore » is reminiscent of the Fr{umlt o}hlich Hamiltonian, is then subjected to a series of unitary transformations, analogous to those employed by Lee, Low, and Pines in their treatment of the Fr{umlt o}hlich polaron. Our approach yields an approximate quasiparticle energy {ital E}({ital k}{bold )} as well as the corresponding eigenvector. To explore the range of validity of our theory, the analytic expressions are then further analyzed for intermediate ({ital J}/{ital t}=0.4) and strong ({ital J}/{ital t}=0.08) coupling, where special attention is paid to the quasiparticle bandwidth {ital W}. The intermediate-coupling result for {ital E}({ital k}{bold )} is in excellent agreement with the dispersion curve recently obtained by Dagotto and co-workers by means of a Green function Monte Carlo method. Even in the strong-coupling range the bandshape remains qualitatively correct. The bandwidth {ital W} is rather accurate for weak coupling ({ital J}/{ital t}{approx_gt}3), and still reasonable in the intermediate range 0.4{approx_lt}{ital J}/{ital t}{le}3, where it deviates from the correct values by some 10-20%. Our theory fails, however, to describe the proper behavior of {ital W} in the strong-coupling regime. This shows that the limitations of our approach manifest themselves in the bandwidths rather than in the shapes of the dispersion curves.« less

Out of the Shadows

NASA Astrophysics Data System (ADS)

Byers, Nina; Williams, Gary

2006-08-01

Foreword Freeman J. Dyson; Introduction Nina Byers; 1. Hertha Aryton 1854-1923 Joan Mason; 2. Margaret Maltby 1860-1944 Peggy Kidwell; 3. Agnes Pockels 1862-1935 Gary A. Williams; 4. Marie Curie 1867-1934 A. Pais; 5. Henrietta Leavitt 1868-1921 Jean L. Turner; 6. Harriet Brooks 1876-1933 C. W. Wong; 7. Lise Meitner 1878-1968 Ruth Lewin Sime; 8. Emmy Noether 1882-1935 Nina Byers; 9. Inge Lehmann 1888-1993 Bruce A. Bolt; 10. Marietta Blau 1894-1970 Leopold Halpern and Maurice M. Shapiro; 11. Hertha Sponer 1895-1968 Helmut Rechenberg; 12. Irene Joliot-Curie 1897-1956 Hélène Langevin-Joliot and Pierre Radvanyi; 13. Katherine Burr Blodgett 1898-1979 Gary A. Williams; 14. Cecilia Payne Gaposchkin 1900-1979 Vera C. Rubin; 15. Mary Cartwright 1900-1998 Freeman J. Dyson; 16. Bertha Jeffreys 1903-1999 Ruth M. Williams; 17. Kathleen Yardley Lonsdale1903-1971 Judith Milledge; 18. Maria Goeppert Mayer 1906-1972 Steven A. Moszkowski; 19. Helen Megaw 1907-2002 A. Michael Glazer and Christine Kelsey; 20. Yvette Cauchois 1908-1999 Christiane Bonnelle; 21. Marguerite Perey 1909-1975 Jean-Pierre Adloff and George B. Kauffman; 22. Dorothy Crowfoot Hodgkin 1910-1994 Jenny P. Glusker; 23. Gertrude Scharff Goldhaber 1911-1998 Alfred Scharff Goldhaber; 24. Chien Shiung Wu 1912-1997 Noemie Bencze-Koller; 25. Margaret E. Burbidge 1919 Virginia Trimble; 26. Phyllis Freier 1921-1992 Cecil J. Waddington; 27. Rosalyn S. Yalow 1921 M. S. Dresselhaus and F. A. Stahl; 28. Esther Conwell 1922 Lewis Rothberg; 29. Cecile Dewitt-Morette 1922 Bryce DeWitt; 30. Yvonne Choquet-Bruhat 1923 James W. York Jr.; 31. Vera Rubin 1928 Robert J. Rubin; 32. Mildred S. Dresselhaus 1930 G. Dresselhaus and F. A. Stahl; 33. Myriam Sarachik 1933 Jonathan R. Friedman; 34. Juliet Lee-Franzini 1933 Paolo Franzini; 35. Helen T. Edwards 1936 John Peoples; 36. Mary K. Gaillard 1939 Andreszej Buras; 37. Renata Kallosh 1943 Andrei Linde and Michael Gutperle; 38. Jocelyn Bell Burnell 1943 Ferdinand V. Coroniti and Gary A. Williams; 39. Gail G. Hanson 1947 David G. Cassel; 40. San Lan Wu David B. Cline.

Out of the Shadows

NASA Astrophysics Data System (ADS)

Byers, Nina; Williams, Gary

2010-12-01

Foreword Freeman J. Dyson; Introduction Nina Byers; 1. Hertha Aryton 1854-1923 Joan Mason; 2. Margaret Maltby 1860-1944 Peggy Kidwell; 3. Agnes Pockels 1862-1935 Gary A. Williams; 4. Marie Curie 1867-1934 A. Pais; 5. Henrietta Leavitt 1868-1921 Jean L. Turner; 6. Harriet Brooks 1876-1933 C. W. Wong; 7. Lise Meitner 1878-1968 Ruth Lewin Sime; 8. Emmy Noether 1882-1935 Nina Byers; 9. Inge Lehmann 1888-1993 Bruce A. Bolt; 10. Marietta Blau 1894-1970 Leopold Halpern and Maurice M. Shapiro; 11. Hertha Sponer 1895-1968 Helmut Rechenberg; 12. Irene Joliot-Curie 1897-1956 Hélène Langevin-Joliot and Pierre Radvanyi; 13. Katherine Burr Blodgett 1898-1979 Gary A. Williams; 14. Cecilia Payne Gaposchkin 1900-1979 Vera C. Rubin; 15. Mary Cartwright 1900-1998 Freeman J. Dyson; 16. Bertha Jeffreys 1903-1999 Ruth M. Williams; 17. Kathleen Yardley Lonsdale1903-1971 Judith Milledge; 18. Maria Goeppert Mayer 1906-1972 Steven A. Moszkowski; 19. Helen Megaw 1907-2002 A. Michael Glazer and Christine Kelsey; 20. Yvette Cauchois 1908-1999 Christiane Bonnelle; 21. Marguerite Perey 1909-1975 Jean-Pierre Adloff and George B. Kauffman; 22. Dorothy Crowfoot Hodgkin 1910-1994 Jenny P. Glusker; 23. Gertrude Scharff Goldhaber 1911-1998 Alfred Scharff Goldhaber; 24. Chien Shiung Wu 1912-1997 Noemie Bencze-Koller; 25. Margaret E. Burbidge 1919 Virginia Trimble; 26. Phyllis Freier 1921-1992 Cecil J. Waddington; 27. Rosalyn S. Yalow 1921 M. S. Dresselhaus and F. A. Stahl; 28. Esther Conwell 1922 Lewis Rothberg; 29. Cecile Dewitt-Morette 1922 Bryce DeWitt; 30. Yvonne Choquet-Bruhat 1923 James W. York Jr.; 31. Vera Rubin 1928 Robert J. Rubin; 32. Mildred S. Dresselhaus 1930 G. Dresselhaus and F. A. Stahl; 33. Myriam Sarachik 1933 Jonathan R. Friedman; 34. Juliet Lee-Franzini 1933 Paolo Franzini; 35. Helen T. Edwards 1936 John Peoples; 36. Mary K. Gaillard 1939 Andreszej Buras; 37. Renata Kallosh 1943 Andrei Linde and Michael Gutperle; 38. Jocelyn Bell Burnell 1943 Ferdinand V. Coroniti and Gary A. Williams; 39. Gail G. Hanson 1947 David G. Cassel; 40. San Lan Wu David B. Cline.

Couplings between the ρ and D and D * mesons

DOE PAGES

El-Bennich, Bruno; Paracha, M. Ali; Roberts, Craig D.; ...

2017-02-27

In this paper, we compute couplings between the ρ-meson and D and D* mesons—D(*)ρD(*)—that are relevant to phenomenological meson-exchange models used to analyze nucleon–D-meson scattering and explore the possibility of exotic charmed nuclei. Our framework is built from elements constrained by Dyson-Schwinger equation studies in QCD, and therefore expresses a simultaneous description of light- and heavy-quarks and the states they constitute. We find that all interactions, including the three independent D*ρD* couplings, differ markedly amongst themselves in strength and also in range, as measured by their evolution with ρ-meson virtuality. As a consequence, it appears that one should be cautiousmore » in using a single coupling strength or parametrization for the study of interactions between D(*) mesons and matter.« less

On the zero-crossing of the three-gluon Green's function from lattice simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Athenodorou, Andreas; Boucaud, Philippe; de Soto, Feliciano

We report on some efforts recently made in order to gain a better understanding of some IR properties of the 3-point gluon Green’s function by exploiting results from large-volume quenched lattice simulations. These lattice results have been obtained by using both tree-level Symanzik and the standard Wilson action, in the aim of assessing the possible impact of effects presumably resulting from a particular choice for the discretization of the action. The main resulting feature is the existence of a negative log-aritmic divergence at zero-momentum, which pulls the 3-gluon form factors down at low momenta and, consequently, yields a zero-crossing atmore » a given deep IR momentum. The results can be correctly explained by analyzing the relevant Dyson-Schwinger equations and appropriate truncation schemes.« less

Dynamical photoionization observables of the CS molecule: The role of electron correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ponzi, Aurora; Coriani, Sonia; Decleva, Piero

2014-05-28

Highly correlated calculations are performed on the primary ionic states and the prominent satellite present in the outer valence photoelectron spectrum of carbon monosulfide (CS). Dyson orbitals are coupled to accurate one particle continuum orbitals to provide a correlated description of energy dependent cross sections, asymmetry parameters, branching ratios, and molecular frame photoelectron angular distributions. The comparison with results obtained at the Hartree-Fock and Density Functional Theory level shows the strong sensitivity of these observables to details of the correlation in the bound states. The behaviour of the well characterized satellite state is analyzed in detail, and shows differences frommore » the relevant primary states, revealing the limitations of a simple intensity borrowing mechanism. The results resolve the intensity disagreement with experiment obtained at the level of the sudden approximation.« less

Critical Exponents, Scaling Law, Universality and Renormalization Group Flow in Strong Coupling QED

NASA Astrophysics Data System (ADS)

Kondo, Kei-Ichi

The critical behavior of strongly coupled QED with a chiral-invariant four-fermion interaction (gauged Nambu-Jona-Lasinio model) is investigated through the unquenched Schwinger-Dyson equation including the fermion loop effect at the one-loop level. It is shown that the critical exponents satisfy the (hyper)scaling relations as in the quenched case. However, the respective critical exponent takes the classical mean-field value, and consequently unquenched QED belongs to the same universality class as the zero-charge model. On the other hand, it is pointed out that quenched QED violates not only universality but also weak universality, due to continuously varying critical exponents. Furthermore, the renormalization group flow of constant renormalized charge is given. All the results are consistent with triviality of QED and the gauged Nambu-Jona-Lasinio model in the unquenched case.

Couplings between the ρ and D and D * mesons

DOE Office of Scientific and Technical Information (OSTI.GOV)

El-Bennich, Bruno; Paracha, M. Ali; Roberts, Craig D.

In this paper, we compute couplings between the ρ-meson and D and D* mesons—D(*)ρD(*)—that are relevant to phenomenological meson-exchange models used to analyze nucleon–D-meson scattering and explore the possibility of exotic charmed nuclei. Our framework is built from elements constrained by Dyson-Schwinger equation studies in QCD, and therefore expresses a simultaneous description of light- and heavy-quarks and the states they constitute. We find that all interactions, including the three independent D*ρD* couplings, differ markedly amongst themselves in strength and also in range, as measured by their evolution with ρ-meson virtuality. As a consequence, it appears that one should be cautiousmore » in using a single coupling strength or parametrization for the study of interactions between D(*) mesons and matter.« less

Organizing symmetry-protected topological phases by layering and symmetry reduction: A minimalist perspective

NASA Astrophysics Data System (ADS)

Xiong, Charles Zhaoxi; Alexandradinata, A.

2018-03-01

It is demonstrated that fermionic/bosonic symmetry-protected topological (SPT) phases across different dimensions and symmetry classes can be organized using geometric constructions that increase dimensions and symmetry-reduction maps that change symmetry groups. Specifically, it is shown that the interacting classifications of SPT phases with and without glide symmetry fit into a short exact sequence, so that the classification with glide is constrained to be a direct sum of cyclic groups of order 2 or 4. Applied to fermionic SPT phases in the Wigner-Dyson class AII, this implies that the complete interacting classification in the presence of glide is Z4⊕Z2⊕Z2 in three dimensions. In particular, the hourglass-fermion phase recently realized in the band insulator KHgSb must be robust to interactions. Generalizations to spatiotemporal glide symmetries are discussed.

Emergent irreversibility and entanglement spectrum statistics

NASA Astrophysics Data System (ADS)

Mucciolo, Eduardo; Chamon, Claudio; Hamma, Alioscia

2014-03-01

We study the problem of irreversibility when the dynamical evolution of a many-body system is described by a stochastic quantum circuit. Such evolution is more general than Hamitonian, and since energy levels are not well defined, the well-established connection between the statistical fluctuations of the energy spectrum and irreversibility cannot be made. We show that the entanglement spectrum provides a more general connection. Irreversibility is marked by a failure of a disentangling algorithm and is preceded by the appearance of Wigner-Dyson statistical fluctuations in the entanglement spectrum. This analysis can be done at the wavefunction level and offers a new route to study quantum chaos and quantum integrability. We acknowledge financial support from the U.S. National Science Foundation through grants CCF 1116590 and CCF 1117241, from the National Basic Research Program of China through grants 2011CBA00300 and 2011CBA00301, and from the National Natural Science Fo.

Domain wall network as QCD vacuum: confinement, chiral symmetry, hadronization

NASA Astrophysics Data System (ADS)

Nedelko, Sergei N.; Voronin, Vladimir V.

2017-03-01

An approach to QCD vacuum as a medium describable in terms of statistical ensemble of almost everywhere homogeneous Abelian (anti-)self-dual gluon fields is reviewed. These fields play the role of the confining medium for color charged fields as well as underline the mechanism of realization of chiral SUL(Nf) × SUR(Nf) and UA(1) symmetries. Hadronization formalism based on this ensemble leads to manifestly defined quantum effective meson action. Strong, electromagnetic and weak interactions of mesons are represented in the action in terms of nonlocal n-point interaction vertices given by the quark-gluon loops averaged over the background ensemble. Systematic results for the mass spectrum and decay constants of radially excited light, heavy-light mesons and heavy quarkonia are presented. Relationship of this approach to the results of functional renormalization group and Dyson-Schwinger equations, and the picture of harmonic confinement is briefly outlined.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forrester, Peter J., E-mail: p.forrester@ms.unimelb.edu.au; Thompson, Colin J.

The Golden-Thompson inequality, Tr (e{sup A+B}) ⩽ Tr (e{sup A}e{sup B}) for A, B Hermitian matrices, appeared in independent works by Golden and Thompson published in 1965. Both of these were motivated by considerations in statistical mechanics. In recent years the Golden-Thompson inequality has found applications to random matrix theory. In this article, we detail some historical aspects relating to Thompson's work, giving in particular a hitherto unpublished proof due to Dyson, and correspondence with Pólya. We show too how the 2 × 2 case relates to hyperbolic geometry, and how the original inequality holds true with the trace operation replaced bymore » any unitarily invariant norm. In relation to the random matrix applications, we review its use in the derivation of concentration type lemmas for sums of random matrices due to Ahlswede-Winter, and Oliveira, generalizing various classical results.« less

The ghost propagator in Coulomb gauge

NASA Astrophysics Data System (ADS)

Watson, P.; Reinhardt, H.

2011-05-01

We present results for a numerical study of the ghost propagator in Coulomb gauge whereby lattice results for the spatial gluon propagator are used as input to solving the ghost Dyson-Schwinger equation. We show that in order to solve completely, the ghost equation must be supplemented by a boundary condition (the value of the inverse ghost propagator dressing function at zero momentum) which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to low momenta until `forced' to freeze out in the infrared to the value of the boundary condition. The boundary condition can be interpreted in terms of the Gribov gauge-fixing ambiguity; we also demonstrate that this is not connected to the renormalization. Further, the connection to the temporal gluon propagator and the infrared slavery picture of confinement is discussed.

Determining partial differential cross sections for low-energy electron photodetachment involving conical intersections using the solution of a Lippmann-Schwinger equation constructed with standard electronic structure techniques.

PubMed

Han, Seungsuk; Yarkony, David R

2011-05-07

A method for obtaining partial differential cross sections for low energy electron photodetachment in which the electronic states of the residual molecule are strongly coupled by conical intersections is reported. The method is based on the iterative solution to a Lippmann-Schwinger equation, using a zeroth order Hamiltonian consisting of the bound nonadiabatically coupled residual molecule and a free electron. The solution to the Lippmann-Schwinger equation involves only standard electronic structure techniques and a standard three-dimensional free particle Green's function quadrature for which fast techniques exist. The transition dipole moment for electron photodetachment, is a sum of matrix elements each involving one nonorthogonal orbital obtained from the solution to the Lippmann-Schwinger equation. An expression for the electron photodetachment transition dipole matrix element in terms of Dyson orbitals, which does not make the usual orthogonality assumptions, is derived.

Description of quasiparticle and satellite properties via cumulant expansions of the retarded one-particle Green's function

DOE PAGES

Mayers, Matthew Z.; Hybertsen, Mark S.; Reichman, David R.

2016-08-22

A cumulant-based GW approximation for the retarded one-particle Green's function is proposed, motivated by an exact relation between the improper Dyson self-energy and the cumulant generating function. We explore qualitative aspects of this method within a simple one-electron independent phonon model, where it is seen that the method preserves the energy moment of the spectral weight while also reproducing the exact Green's function in the weak-coupling limit. For the three-dimensional electron gas, this method predicts multiple satellites at the bottom of the band, albeit with inaccurate peak spacing. But, its quasiparticle properties and correlation energies are more accurate than bothmore » previous cumulant methods and standard G0W0. These results point to features that may be exploited within the framework of cumulant-based methods and suggest promising directions for future exploration and improvements of cumulant-based GW approaches.« less

O'Connell's process as a vicious Brownian motion.

PubMed

Katori, Makoto

2011-12-01

Vicious Brownian motion is a diffusion scaling limit of Fisher's vicious walk model, which is a system of Brownian particles in one dimension such that if two motions meet they kill each other. We consider the vicious Brownian motions conditioned never to collide with each other and call it noncolliding Brownian motion. This conditional diffusion process is equivalent to the eigenvalue process of the Hermitian-matrix-valued Brownian motion studied by Dyson [J. Math. Phys. 3, 1191 (1962)]. Recently, O'Connell [Ann. Probab. (to be published)] introduced a generalization of the noncolliding Brownian motion by using the eigenfunctions (the Whittaker functions) of the quantum Toda lattice in order to analyze a directed polymer model in 1 + 1 dimensions. We consider a system of one-dimensional Brownian motions with a long-ranged killing term as a generalization of the vicious Brownian motion and construct the O'Connell process as a conditional process of the killing Brownian motions to survive forever.

Weyl nodes in Andreev spectra of multiterminal Josephson junctions: Chern numbers, conductances, and supercurrents

NASA Astrophysics Data System (ADS)

Xie, Hong-Yi; Vavilov, Maxim G.; Levchenko, Alex

2018-02-01

We consider mesoscopic four-terminal Josephson junctions and study emergent topological properties of the Andreev subgap bands. We use symmetry-constrained analysis for Wigner-Dyson classes of scattering matrices to derive band dispersions. When the scattering matrix of the normal region connecting superconducting leads is energy independent, the determinant formula for Andreev spectrum can be reduced to a palindromic equation that admits a complete analytical solution. Band topology manifests with an appearance of the Weyl nodes which serve as monopoles of finite Berry curvature. The corresponding fluxes are quantified by Chern numbers that translate into a quantized nonlocal conductance that we compute explicitly for the time-reversal-symmetric scattering matrix. The topological regime can also be identified by supercurrents as Josephson current-phase relationships exhibit pronounced nonanalytic behavior and discontinuities near Weyl points that can be controllably accessed in experiments.

Structure of hadron resonances with a nearby zero of the amplitude

NASA Astrophysics Data System (ADS)

Kamiya, Yuki; Hyodo, Tetsuo

2018-03-01

We discuss the relation between the analytic structure of the scattering amplitude and the origin of an eigenstate represented by a pole of the amplitude. If the eigenstate is not dynamically generated by the interaction in the channel of interest, the residue of the pole vanishes in the zero coupling limit. Based on the topological nature of the phase of the scattering amplitude, we show that the pole must encounter with the Castillejo-Dalitz-Dyson (CDD) zero in this limit. It is concluded that the dynamical component of the eigenstate is small if a CDD zero exists near the eigenstate pole. We show that the line shape of the resonance is distorted from the Breit-Wigner form as an observable consequence of the nearby CDD zero. Finally, studying the positions of poles and CDD zeros of the K ¯ N -π Σ amplitude, we discuss the origin of the eigenstates in the Λ (1405 ) region.

Pion distribution amplitude from lattice QCD.

PubMed

Cloët, I C; Chang, L; Roberts, C D; Schmidt, S M; Tandy, P C

2013-08-30

A method is explained through which a pointwise accurate approximation to the pion's valence-quark distribution amplitude (PDA) may be obtained from a limited number of moments. In connection with the single nontrivial moment accessible in contemporary simulations of lattice-regularized QCD, the method yields a PDA that is a broad concave function whose pointwise form agrees with that predicted by Dyson-Schwinger equation analyses of the pion. Under leading-order evolution, the PDA remains broad to energy scales in excess of 100 GeV, a feature which signals persistence of the influence of dynamical chiral symmetry breaking. Consequently, the asymptotic distribution φπ(asy)(x) is a poor approximation to the pion's PDA at all such scales that are either currently accessible or foreseeable in experiments on pion elastic and transition form factors. Thus, related expectations based on φ φπ(asy)(x) should be revised.

Aspects of Quantum Theory

NASA Astrophysics Data System (ADS)

Salam, Abdus; Wigner, E. P.

2010-03-01

Preface; List of contributors; Bibliography of P. A. M. Dirac; 1. Dirac in Cambridge R. J. Eden and J. C. Polkinghorne; 2. Travels with Dirac in the Rockies J. H. Van Vleck; 3. 'The golden age of theoretical physics': P. A. M. Dirac's scientific work from 1924 to 1933 Jagdish Mehra; 4. Foundation of quantum field theory Res Jost; 5. The early history of the theory of electron: 1897-1947 A. Pais; 6. The Dirac equation A. S. Wightman; 7. Fermi-Dirac statistics Rudolph Peierls; 8. Indefinite metric in state space W. Heisenberg; 9. On bras and kets J. M. Jauch; 10. The Poisson bracket C. Lanczos; 11. La 'fonction' et les noyaux L. Schwartz; 12. On the Dirac magnetic poles Edoardo Amadli and Nicola Cabibbo; 13. The fundamental constants and their time variation Freeman J. Dyson; 14. On the time-energy uncertainty relation Eugene P. Wigner; 15. The path-integral quantisation of gravity Abdus Salam and J. Strathdee; Index; Plates.

Are the dressed gluon and ghost propagators in the Landau gauge presently determined in the confinement regime of QCD?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pennington, M. R.; Wilson, D. J.

2011-11-01

The gluon and ghost propagators in Landau gauge QCD are investigated using the Schwinger-Dyson equation approach. Working in Euclidean spacetime, we solve for these propagators using a selection of vertex inputs, initially for the ghost equation alone and then for both propagators simultaneously. The results are shown to be highly sensitive to the choices of vertices. We favor the infrared finite ghost solution from studying the ghost equation alone where we argue for a specific unique solution. In order to solve this simultaneously with the gluon using a dressed-one-loop truncation, we find that a nontrivial full ghost-gluon vertex is requiredmore » in the vanishing gluon momentum limit. The self-consistent solutions we obtain correspond to having a masslike term in the gluon propagator dressing, in agreement with similar studies supporting the long-held proposal of Cornwall.« less

High-energy anomalies in covalent high-Tc cuprates with large Hubbard Ud on copper

NASA Astrophysics Data System (ADS)

Barišić, O. S.; Barišić, S.

2015-03-01

A large Ud theory is constructed for the metallic state of high-Tc cuprates. The Emery three-band model, extended with Ox-Oy hopping tpp, and with Ud → ∞, is mapped on slave fermions. The Dyson time-dependent diagrammatic theory in terms of the Cu-O hopping tpd, starting from the nondegenerate unperturbed ground state, is translationally and asymptotically locally gauge invariant. The small parameter of the theory is the average hole occupation of Cu sites nd. The lowest order of the theory generates the single particle propagators of the hybridized pdp- and dpd-fermions with the exact covalent three band structure. The leading many-body effect is band narrowing, accompanied by Landau-like damping of the single particle propagation, due to incoherent local charge Cu-O fluctuations. The corresponding continuum is found below and above the Fermi level.

Extortion can outperform generosity in the iterated prisoner's dilemma

PubMed Central

Wang, Zhijian; Zhou, Yanran; Lien, Jaimie W.; Zheng, Jie; Xu, Bin

2016-01-01

Zero-determinant (ZD) strategies, as discovered by Press and Dyson, can enforce a linear relationship between a pair of players' scores in the iterated prisoner's dilemma. Particularly, the extortionate ZD strategies can enforce and exploit cooperation, providing a player with a score advantage, and consequently higher scores than those from either mutual cooperation or generous ZD strategies. In laboratory experiments in which human subjects were paired with computer co-players, we demonstrate that both the generous and the extortionate ZD strategies indeed enforce a unilateral control of the reward. When the experimental setting is sufficiently long and the computerized nature of the opponent is known to human subjects, the extortionate strategy outperforms the generous strategy. Human subjects' cooperation rates when playing against extortionate and generous ZD strategies are similar after learning has occurred. More than half of extortionate strategists finally obtain an average score higher than that from mutual cooperation. PMID:27067513

The Scientific Papers of the Honourable Henry Cavendish, F. R. S. 2 Volume Set

NASA Astrophysics Data System (ADS)

Cavendish, Henry; Clerk Maxwell, James; Thorpe, Edward, , Sir; Larmor, Joseph, , Sir

2011-02-01

Volume 1: Preface Sir Joseph Larmor; Introduction; First published paper on electricity, 1771; Preliminary propositions; Appendix; Thoughts concerning electricity; Account of the experiments; Second published paper on electricity, 1776; Experiments in 1771; Experiments in 1772; Experiments in 1773; Measurers; Experiments with the artificial torpedo; Resistance to electricity; Results of comparisons of charges; Results on resistance; Notes by the editor, 1879 James Clerk Maxwell; Life of Cavendish Thomas Young; Index to Cavendish Manuscripts. Volume 2: Introduction; Reprint of papers communicated by Cavendish to the Royal Society and published in the Philosophical Transactions; Unpublished papers from the original manuscripts in the possession of the Duke of Devonshire, K. G., LL. D., F. R. S.; Cavendish's mathematical and dynamical manuscripts Sir Joseph Larmor; Cavendish as a geologist Sir Archibald Geikie; Cavendish's astronomical manuscripts Sir Frank W. Dyson; Cavendish's magnetic work Charles Chree; Index.

Theory of Stochastic Laplacian Growth

NASA Astrophysics Data System (ADS)

Alekseev, Oleg; Mineev-Weinstein, Mark

2017-07-01

We generalize the diffusion-limited aggregation by issuing many randomly-walking particles, which stick to a cluster at the discrete time unit providing its growth. Using simple combinatorial arguments we determine probabilities of different growth scenarios and prove that the most probable evolution is governed by the deterministic Laplacian growth equation. A potential-theoretical analysis of the growth probabilities reveals connections with the tau-function of the integrable dispersionless limit of the two-dimensional Toda hierarchy, normal matrix ensembles, and the two-dimensional Dyson gas confined in a non-uniform magnetic field. We introduce the time-dependent Hamiltonian, which generates transitions between different classes of equivalence of closed curves, and prove the Hamiltonian structure of the interface dynamics. Finally, we propose a relation between probabilities of growth scenarios and the semi-classical limit of certain correlation functions of "light" exponential operators in the Liouville conformal field theory on a pseudosphere.

Applications of Coherent Radiation from Electrons traversing Crystals

NASA Astrophysics Data System (ADS)

Überall, H.

2000-04-01

Historically, the first types of coherent radiation from electrons traversing crystals studied were coherent bremsstrahlung (CB: Dyson and Überall 1955; Überall 1956, 1962) and channeling radiation (CR: Kumakhov, 1976) which produce quasimonochromatic X-rays and γ-rays, as well as parametric X-rays (Baryshevsky and Feranchuk, 1983). Related non-crystal sources are transition radiation and synchrotron radiation. We here present a comparison of radiation types from these sources, and we discuss a series of their possible applications, namely (a) CR: X-ray lithography, angiography, structure analysis of macromolecules, and trace element analysis, and (b) for CB: Radiography, use as a neutron source, elemental analysis, radiation therapy, and radioisotope production for commercial or medical use. CR and CB are very intense sources, needing only low-energy, moderately-priced electron linacs for their generation, hence competing with (or surpassing) more conventional X-ray sources intensity-wise and from a cost standpoint.

Inflation with a graceful exit in a random landscape

NASA Astrophysics Data System (ADS)

Pedro, F. G.; Westphal, A.

2017-03-01

We develop a stochastic description of small-field inflationary histories with a graceful exit in a random potential whose Hessian is a Gaussian random matrix as a model of the unstructured part of the string landscape. The dynamical evolution in such a random potential from a small-field inflation region towards a viable late-time de Sitter (dS) minimum maps to the dynamics of Dyson Brownian motion describing the relaxation of non-equilibrium eigenvalue spectra in random matrix theory. We analytically compute the relaxation probability in a saddle point approximation of the partition function of the eigenvalue distribution of the Wigner ensemble describing the mass matrices of the critical points. When applied to small-field inflation in the landscape, this leads to an exponentially strong bias against small-field ranges and an upper bound N ≪ 10 on the number of light fields N participating during inflation from the non-observation of negative spatial curvature.

Electron Waiting Times in Mesoscopic Conductors

NASA Astrophysics Data System (ADS)

Albert, Mathias; Haack, Géraldine; Flindt, Christian; Büttiker, Markus

2012-05-01

Electron transport in mesoscopic conductors has traditionally involved investigations of the mean current and the fluctuations of the current. A complementary view on charge transport is provided by the distribution of waiting times between charge carriers, but a proper theoretical framework for coherent electronic systems has so far been lacking. Here we develop a quantum theory of electron waiting times in mesoscopic conductors expressed by a compact determinant formula. We illustrate our methodology by calculating the waiting time distribution for a quantum point contact and find a crossover from Wigner-Dyson statistics at full transmission to Poisson statistics close to pinch-off. Even when the low-frequency transport is noiseless, the electrons are not equally spaced in time due to their inherent wave nature. We discuss the implications for renewal theory in mesoscopic systems and point out several analogies with level spacing statistics and random matrix theory.

Universality for 1d Random Band Matrices: Sigma-Model Approximation

NASA Astrophysics Data System (ADS)

Shcherbina, Mariya; Shcherbina, Tatyana

2018-02-01

The paper continues the development of the rigorous supersymmetric transfer matrix approach to the random band matrices started in (J Stat Phys 164:1233-1260, 2016; Commun Math Phys 351:1009-1044, 2017). We consider random Hermitian block band matrices consisting of W× W random Gaussian blocks (parametrized by j,k \\in Λ =[1,n]^d\\cap Z^d ) with a fixed entry's variance J_{jk}=δ _{j,k}W^{-1}+β Δ _{j,k}W^{-2} , β >0 in each block. Taking the limit W→ ∞ with fixed n and β , we derive the sigma-model approximation of the second correlation function similar to Efetov's one. Then, considering the limit β , n→ ∞, we prove that in the dimension d=1 the behaviour of the sigma-model approximation in the bulk of the spectrum, as β ≫ n , is determined by the classical Wigner-Dyson statistics.

Photon-Z mixing the Weinberg-Salam model: Effective charges and the a = -3 gauge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baulieu, L.; Coquereaux, R.

1982-04-15

We study some properties of the Weinberg-Salam model connected with the photon-Z mixing. We solve the linear Dyson-Schwinger equations between full and 1PI boson propagators. The task is made easier, by the two-point function Ward identities that we derive to all orders and in any gauge. Some aspects of the renormalization of the model are also discussed. We display the exact mass-dependent one-loop two-point functions involving the photon and Z field in any linear xi-gauge. The special gauge a = xi/sup -1/ = -3 is shown to play a peculiar role. In this gauge, the Z field is multiplicatively renormalizablemore » (at the one-loop level), and one can construct both electric and weak effective charges of the theory from the photon and Z propagators, with a very simple expression similar to that of the QED Petermann, Stueckelberg, Gell-Mann and Low charge.« less

Baryon Spectroscopy at ELSA and at MAMI - selected results

NASA Astrophysics Data System (ADS)

Krusche, B.

2014-05-01

Spectroscopy of baryons and their excited states plays a key role for our understanding of the strong interaction in the non-perturbative regime. Both, in theory and in experiment, large progress has been made during the last few years. The rapid developments in lattice gauge calculations and the application of the Dyson-Schwinger equation to QCD have opened new perspectives for the interpretation of the excitation spectrum of the nucleon. In parallel, large efforts have been undertaken world-wide, and are still running, to investigate excited nucleon states experimentally, in particular with photon-induced production of mesons. In the present contribution we discuss such experimental programs conducted at the tagged photon beams of the electron accelerators ELSA in Bonn and MAMI in Mainz. These programs are diverse. They include the measurement of cross sections, single- and double polarization observables for single meson production and production of meson pairs off free protons as well as of quasi-free nucleons bound in the deuteron (and sometimes other light nuclei).

Modifications to the Patient Rule-Induction Method that utilize non-additive combinations of genetic and environmental effects to define partitions that predict ischemic heart disease.

PubMed

Dyson, Greg; Frikke-Schmidt, Ruth; Nordestgaard, Børge G; Tybjaerg-Hansen, Anne; Sing, Charles F

2009-05-01

This article extends the Patient Rule-Induction Method (PRIM) for modeling cumulative incidence of disease developed by Dyson et al. (Genet Epidemiol 31:515-527) to include the simultaneous consideration of non-additive combinations of predictor variables, a significance test of each combination, an adjustment for multiple testing and a confidence interval for the estimate of the cumulative incidence of disease in each partition. We employ the partitioning algorithm component of the Combinatorial Partitioning Method to construct combinations of predictors, permutation testing to assess the significance of each combination, theoretical arguments for incorporating a multiple testing adjustment and bootstrap resampling to produce the confidence intervals. An illustration of this revised PRIM utilizing a sample of 2,258 European male participants from the Copenhagen City Heart Study is presented that assesses the utility of genetic variants in predicting the presence of ischemic heart disease beyond the established risk factors.

Modifications to the Patient Rule-Induction Method that utilize non-additive combinations of genetic and environmental effects to define partitions that predict ischemic heart disease

PubMed Central

Dyson, Greg; Frikke-Schmidt, Ruth; Nordestgaard, Børge G.; Tybjærg-Hansen, Anne; Sing, Charles F.

2009-01-01

This paper extends the Patient Rule-Induction Method (PRIM) for modeling cumulative incidence of disease developed by Dyson et al. (2007) to include the simultaneous consideration of non-additive combinations of predictor variables, a significance test of each combination, an adjustment for multiple testing and a confidence interval for the estimate of the cumulative incidence of disease in each partition. We employ the partitioning algorithm component of the Combinatorial Partitioning Method (CPM) to construct combinations of predictors, permutation testing to assess the significance of each combination, theoretical arguments for incorporating a multiple testing adjustment and bootstrap resampling to produce the confidence intervals. An illustration of this revised PRIM utilizing a sample of 2258 European male participants from the Copenhagen City Heart Study is presented that assesses the utility of genetic variants in predicting the presence of ischemic heart disease beyond the established risk factors. PMID:19025787

SETV: an Extension of SETI?

NASA Astrophysics Data System (ADS)

Teodorani, M.

2003-02-01

In the ambit of the SETI Project, a new branch named SETV (Search for Extraterrestrial Visitation) was born very recently due to the international effort of some engineers, astronomers and other researchers, and it is now in a development phase with several monitoring projects. SETV is aimed at investigating, by using well-tested means of physical and technological sciences, the possible evidence of extraterrestrial visitations inside our solar system. On the basis of statistical calculations of galactic migration, and of models coming from standard stellar evolution, Dyson theory and advanced possibilities invoked by theoretical physics, the historical excursus which turned the SETA hypothesis (Search for Extraterrestrial Artifacts), developed in the 80', into the present SETV definition, is presented in detail. The possibility that extraterrestrial intelligences are present inside our solar system with inhabited and/or robotic probes is discussed, including the possibility that our planet is one of their targets. A proposal concerning instrumented multi-wavelength surveys and identification of such exogenous probes is presented.

Radiometric and spectral stray light correction for the portable remote imaging spectrometer (PRISM) coastal ocean sensor

NASA Astrophysics Data System (ADS)

Haag, Justin M.; Van Gorp, Byron E.; Mouroulis, Pantazis; Thompson, David R.

2017-09-01

The airborne Portable Remote Imaging Spectrometer (PRISM) instrument is based on a fast (F/1.8) Dyson spectrometer operating at 350-1050 nm and a two-mirror telescope combined with a Teledyne HyViSI 6604A detector array. Raw PRISM data contain electronic and optical artifacts that must be removed prior to radiometric calibration. We provide an overview of the process transforming raw digital numbers to calibrated radiance values. Electronic panel artifacts are first corrected using empirical relationships developed from laboratory data. The instrument spectral response functions (SRF) are reconstructed using a measurement-based optimization technique. Removal of SRF effects from the data improves retrieval of true spectra, particularly in the typically low-signal near-ultraviolet and near-infrared regions. As a final step, radiometric calibration is performed using corrected measurements of an object of known radiance. Implementation of the complete calibration procedure maximizes data quality in preparation for subsequent processing steps, such as atmospheric removal and spectral signature classification.

Towards an exact correlated orbital theory for electrons

NASA Astrophysics Data System (ADS)

Bartlett, Rodney J.

2009-12-01

The formal and computational attraction of effective one-particle theories like Hartree-Fock and density functional theory raise the question of how far such approaches can be taken to offer exact results for selected properties of electrons in atoms, molecules, and solids. Some properties can be exactly described within an effective one-particle theory, like principal ionization potentials and electron affinities. This fact can be used to develop equations for a correlated orbital theory (COT) that guarantees a correct one-particle energy spectrum. They are built upon a coupled-cluster based frequency independent self-energy operator presented here, which distinguishes the approach from Dyson theory. The COT also offers an alternative to Kohn-Sham density functional theory (DFT), whose objective is to represent the electronic density exactly as a single determinant, while paying less attention to the energy spectrum. For any estimate of two-electron terms COT offers a litmus test of its accuracy for principal Ip's and Ea's. This feature for approximating the COT equations is illustrated numerically.

Ghost-gluon vertex in the presence of the Gribov horizon

NASA Astrophysics Data System (ADS)

Mintz, B. W.; Palhares, L. F.; Sorella, S. P.; Pereira, A. D.

2018-02-01

We consider Yang-Mills theories quantized in the Landau gauge in the presence of the Gribov horizon via the refined Gribov-Zwanziger (RGZ) framework. As the restriction of the gauge path integral to the Gribov region is taken into account, the resulting gauge field propagators display a nontrivial infrared behavior, being very close to the ones observed in lattice gauge field theory simulations. In this work, we explore a higher correlation function in the refined Gribov-Zwanziger theory: the ghost-gluon interaction vertex, at one-loop level. We show explicit compatibility with kinematical constraints, as required by the Ward identities of the theory, and obtain analytical expressions in the limit of vanishing gluon momentum. We find that the RGZ results are nontrivial in the infrared regime, being compatible with lattice Yang-Mills simulations in both SU(2) and SU(3), as well as with solutions from Schwinger-Dyson equations in different truncation schemes, Functional Renormalization Group analysis, and the renormalization group-improved Curci-Ferrari model.

Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling.

PubMed

Grell, Gilbert; Bokarev, Sergey I; Winter, Bernd; Seidel, Robert; Aziz, Emad F; Aziz, Saadullah G; Kühn, Oliver

2015-08-21

X-ray photoelectron spectra provide a wealth of information on the electronic structure. The extraction of molecular details requires adequate theoretical methods, which in case of transition metal complexes has to account for effects due to the multi-configurational and spin-mixed nature of the many-electron wave function. Here, the restricted active space self-consistent field method including spin-orbit coupling is used to cope with this challenge and to calculate valence- and core-level photoelectron spectra. The intensities are estimated within the frameworks of the Dyson orbital formalism and the sudden approximation. Thereby, we utilize an efficient computational algorithm that is based on a biorthonormal basis transformation. The approach is applied to the valence photoionization of the gas phase water molecule and to the core ionization spectrum of the [Fe(H2O)6](2+) complex. The results show good agreement with the experimental data obtained in this work, whereas the sudden approximation demonstrates distinct deviations from experiments.

The ghost propagator in Coulomb gauge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, P.; Reinhardt, H.

2011-05-23

We present results for a numerical study of the ghost propagator in Coulomb gauge whereby lattice results for the spatial gluon propagator are used as input to solving the ghost Dyson-Schwinger equation. We show that in order to solve completely, the ghost equation must be supplemented by a boundary condition (the value of the inverse ghost propagator dressing function at zero momentum) which determines if the solution is critical (zero value for the boundary condition) or subcritical (finite value). The various solutions exhibit a characteristic behavior where all curves follow the same (critical) solution when going from high to lowmore » momenta until 'forced' to freeze out in the infrared to the value of the boundary condition. The boundary condition can be interpreted in terms of the Gribov gauge-fixing ambiguity; we also demonstrate that this is not connected to the renormalization. Further, the connection to the temporal gluon propagator and the infrared slavery picture of confinement is discussed.« less

Dysonian Approach to SETI: A Fruitful Middle Ground?

NASA Astrophysics Data System (ADS)

Bradbury, R. J.; Cirkovic, M. M.; Dvorsky, G.

We critically assess the prevailing currents in the Search for Extraterrestrial Intelligence (SETI), embodied in the notion of radio-searches for intentional artificial signals as envisioned by pioneers such as Frank Drake, Philip Morrison, Michael Papagiannis and others. In particular, we emphasize (1) the necessity of integrating SETI into a wider astrobiological and future studies context, (2) the relevance of and lessons to be learnt from the anti-SETI arguments, in particular Fermi's paradox, and (3) a need for complementary approach which we dub the Dysonian SETI. It is meaningfully derived from the inventive and visionary ideas of Freeman J. Dyson and his imaginative precursors, like Konstantin E. Tsiolkovsky, Olaf Stapledon, Nikola Tesla or John B. S. Haldane, who suggested macro-engineering projects as the focal points in the context of extrapolations about the future of humanity and, by analogy, other intelligent species. We consider practical ramifications of the Dysonian SETI and indicate some of the promising directions for future work.

Inclusion of particle-vibration coupling in the Fayans functional: Odd-even mass differences of semimagic nuclei

NASA Astrophysics Data System (ADS)

Saperstein, E. E.; Baldo, M.; Pankratov, S. S.; Tolokonnikov, S. V.

2018-05-01

A method is presented to evaluate the particle-phonon coupling (PC) corrections to the single-particle energies in semimagic nuclei, based on the direct solution of the Dyson equation with PC-corrected mass operator. It is used for finding the odd-even mass difference between even Pb and Sn isotopes and their odd-proton neighbors. The Fayans energy density functional DF3-a is used, which gives rather highly accurate predictions for these mass differences already at the mean-field level. In the case of the lead chain, account for the PC corrections induced by the low-lying phonons 21+ and 31- makes agreement of the theory with the experimental data significantly better. For the tin chain, the situation is not so definite. In this case, the PC corrections make agreement better in the case of the addition mode but they spoil the agreement for the removal mode. We discuss the reason for such a discrepancy.

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

NASA Astrophysics Data System (ADS)

Seridonio, A. C.; Walmsley, L.

2001-04-01

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d≤δ (d being the thickness of the sample and δ the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method.

Phonon-particle coupling effects in odd-even mass differences of semi-magic nuclei

NASA Astrophysics Data System (ADS)

Saperstein, E. E.; Baldo, M.; Pankratov, S. S.; Tolokonnikov, S. V.

2017-11-01

A method to evaluate the particle-phonon coupling (PC) corrections to the single-particle energies in semi-magic nuclei, based on a direct solving the Dyson equation with PC corrected mass operator, is used for finding the odd-even mass difference between 18 even Pb isotopes and their odd-proton neighbors. The Fayans energy density functional (EDF) DF3-a is used which gives rather high accuracy of the predictions for these mass differences already on the mean-field level, with the average deviation from the existing experimental data equal to 0.389 MeV. It is only a bit worse than the corresponding value of 0.333 MeV for the Skyrme EDF HFB-17, which belongs to a family of Skyrme EDFs with the highest overall accuracy in describing the nuclear masses. Account for the PC corrections induced by the low-laying phonons 2 1 + and 3 1 - significantly diminishes the deviation of the theory from the data till 0.218 MeV.

Communication: The description of strong correlation within self-consistent Green's function second-order perturbation theory

NASA Astrophysics Data System (ADS)

Phillips, Jordan J.; Zgid, Dominika

2014-06-01

We report an implementation of self-consistent Green's function many-body theory within a second-order approximation (GF2) for application with molecular systems. This is done by iterative solution of the Dyson equation expressed in matrix form in an atomic orbital basis, where the Green's function and self-energy are built on the imaginary frequency and imaginary time domain, respectively, and fast Fourier transform is used to efficiently transform these quantities as needed. We apply this method to several archetypical examples of strong correlation, such as a H32 finite lattice that displays a highly multireference electronic ground state even at equilibrium lattice spacing. In all cases, GF2 gives a physically meaningful description of the metal to insulator transition in these systems, without resorting to spin-symmetry breaking. Our results show that self-consistent Green's function many-body theory offers a viable route to describing strong correlations while remaining within a computationally tractable single-particle formalism.

O'Connell's process as a vicious Brownian motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katori, Makoto

Vicious Brownian motion is a diffusion scaling limit of Fisher's vicious walk model, which is a system of Brownian particles in one dimension such that if two motions meet they kill each other. We consider the vicious Brownian motions conditioned never to collide with each other and call it noncolliding Brownian motion. This conditional diffusion process is equivalent to the eigenvalue process of the Hermitian-matrix-valued Brownian motion studied by Dyson [J. Math. Phys. 3, 1191 (1962)]. Recently, O'Connell [Ann. Probab. (to be published)] introduced a generalization of the noncolliding Brownian motion by using the eigenfunctions (the Whittaker functions) of themore » quantum Toda lattice in order to analyze a directed polymer model in 1 + 1 dimensions. We consider a system of one-dimensional Brownian motions with a long-ranged killing term as a generalization of the vicious Brownian motion and construct the O'Connell process as a conditional process of the killing Brownian motions to survive forever.« less

Sound waves and flexural mode dynamics in two-dimensional crystals

NASA Astrophysics Data System (ADS)

Michel, K. H.; Scuracchio, P.; Peeters, F. M.

2017-09-01

Starting from a Hamiltonian with anharmonic coupling between in-plane acoustic displacements and out-of-plane (flexural) modes, we derived coupled equations of motion for in-plane displacements correlations and flexural mode density fluctuations. Linear response theory and time-dependent thermal Green's functions techniques are applied in order to obtain different response functions. As external perturbations we allow for stresses and thermal heat sources. The displacement correlations are described by a Dyson equation where the flexural density distribution enters as an additional perturbation. The flexural density distribution satisfies a kinetic equation where the in-plane lattice displacements act as a perturbation. In the hydrodynamic limit this system of coupled equations is at the basis of a unified description of elastic and thermal phenomena, such as isothermal versus adiabatic sound motion and thermal conductivity versus second sound. The general theory is formulated in view of application to graphene, two-dimensional h-BN, and 2H-transition metal dichalcogenides and oxides.

Coupled dynamics in gluon mass generation and the impact of the three-gluon vertex

NASA Astrophysics Data System (ADS)

Binosi, Daniele; Papavassiliou, Joannis

2018-03-01

We present a detailed study of the subtle interplay transpiring at the level of two integral equations that are instrumental for the dynamical generation of a gluon mass in pure Yang-Mills theories. The main novelty is the joint treatment of the Schwinger-Dyson equation governing the infrared behavior of the gluon propagator and of the integral equation that controls the formation of massless bound-state excitations, whose inclusion is instrumental for obtaining massive solutions from the former equation. The self-consistency of the entire approach imposes the requirement of using a single value for the gauge coupling entering in the two key equations; its fulfilment depends crucially on the details of the three-gluon vertex, which contributes to both of them, but with different weight. In particular, the characteristic suppression of this vertex at intermediate and low energies enables the convergence of the iteration procedure to a single gauge coupling, whose value is reasonably close to that extracted from related lattice simulations.

How do agents represent?

NASA Astrophysics Data System (ADS)

Ryan, Alex

Representation is inherent to the concept of an agent, but its importance in complex systems has not yet been widely recognised. In this paper I introduce Peirce's theory of signs, which facilitates a definition of representation in general. In summary, representation means that for some agent, a model is used to stand in for another entity in a way that shapes the behaviour of the agent with respect to that entity. Representation in general is then related to the theories of representation that have developed within different disciplines. I compare theories of representation from metaphysics, military theory and systems theory. Additional complications arise in explaining the special case of mental representations, which is the focus of cognitive science. I consider the dominant theory of cognition — that the brain is a representational device — as well as the sceptical anti-representational response. Finally, I argue that representation distinguishes agents from non-representational objects: agents are objects capable of representation.

Students' Representational Fluency at University: A Cross-Sectional Measure of How Multiple Representations Are Used by Physics Students Using the Representational Fluency Survey

ERIC Educational Resources Information Center

Hill, Matthew; Sharma, Manjula Devi

2015-01-01

To succeed within scientific disciplines, using representations, including those based on words, graphs, equations, and diagrams, is important. Research indicates that the use of discipline specific representations (sometimes referred to as expert generated representations), as well as multi-representational use, is critical for problem solving…

Mothers' and fathers' attachment and caregiving representations during transition to parenthood: an actor-partner approach.

PubMed

Fonseca, Ana; Nazaré, Bárbara; Canavarro, Maria Cristina

2018-07-01

This study aimed to investigate the effect of one's attachment representations on one's and the partner's caregiving representations. According to attachment theory, individual differences in parenting and caregiving behaviours may be a function of parents' caregiving representations of the self as caregiver, and of others as worthy of care, which are rooted on parents' attachment representations. Furthermore, the care-seeking and caregiving interactions that occur within the couple relationship may also shape individuals' caregiving representations. The sample comprised 286 cohabiting couples who were assessed during pregnancy (attachment representations) and one month post-birth (caregiving representations). Path analyses were used to examine effects among variables. Results showed that for mothers and fathers, their own more insecure attachment representations predicted their less positive caregiving representations of the self as caregiver and of others as worthy of help and more self-focused motivations for caregiving. Moreover, fathers' attachment representations were found to predict mothers' caregiving representations of themselves as caregivers. Secure attachment representations of both members of the couple seem to be an inner resource promoting parents' positive representations of caregiving, and should be assessed and fostered during the transition to parenthood in both members of the couple.

Representation Elements of Spatial Thinking

NASA Astrophysics Data System (ADS)

Fiantika, F. R.

2017-04-01

This paper aims to add a reference in revealing spatial thinking. There several definitions of spatial thinking but it is not easy to defining it. We can start to discuss the concept, its basic a forming representation. Initially, the five sense catch the natural phenomenon and forward it to memory for processing. Abstraction plays a role in processing information into a concept. There are two types of representation, namely internal representation and external representation. The internal representation is also known as mental representation; this representation is in the human mind. The external representation may include images, auditory and kinesthetic which can be used to describe, explain and communicate the structure, operation, the function of the object as well as relationships. There are two main elements, representations properties and object relationships. These elements play a role in forming a representation.

Primary Teachers' Representational Practices: From Competency to Fluency

ERIC Educational Resources Information Center

Nichols, Kim; Stevenson, Michael; Hedberg, John; Gillies, Robyn Margaret

2016-01-01

Eighteen primary teachers across three conditions (Representational Fluency, Representational Agency, Comparison) received two days of training around an inquiry unit on plate tectonics replete with representations. The Representational Agency group also received training around the semiotic and material affordances of representations while the…

Mesons in strong magnetic fields: (I) General analyses

DOE PAGES

Hattori, Koichi; Kojo, Toru; Su, Nan

2016-03-21

Here, we study properties of neutral and charged mesons in strong magnetic fields |eB| >> Λ 2 QCD with Λ QCD being the QCD renormalization scale. Assuming long-range interactions, we examine magnetic-field dependences of various quantities such as the constituent quark mass, chiral condensate, meson spectra, and meson wavefunctions by analyzing the Schwinger–Dyson and Bethe–Salpeter equations. Based on the density of states obtained from these analyses, we extend the hadron resonance gas (HRG) model to investigate thermodynamics at large B. As B increases the meson energy behaves as a slowly growing function of the meson's transverse momenta, and thus amore » large number of meson states is accommodated in the low energy domain; the density of states at low temperature is proportional to B 2. This extended transverse phase space in the infrared regime significantly enhances the HRG pressure at finite temperature, so that the system reaches the percolation or chiral restoration regime at lower temperature compared to the case without a magnetic field; this simple picture would offer a gauge invariant and intuitive explanation of the inverse magnetic catalysis.« less

Theory of Friedel oscillations in monolayer graphene and group-VI dichalcogenides in a magnetic field

NASA Astrophysics Data System (ADS)

Rusin, Tomasz M.; Zawadzki, Wlodek

2018-05-01

Friedel oscillations (FO) of electron density caused by a deltalike neutral impurity in two-dimensional (2D) systems in a magnetic field are calculated. Three 2D cases are considered: free electron gas, monolayer graphene, and group-VI dichalcogenides. An exact form of the renormalized Green's function is used in the calculations, as obtained by a summation of the infinite Dyson series and regularization procedure. Final results are valid for large ranges of potential strengths V0, electron densities ne, magnetic fields B , and distances from the impurity r . Realistic models for the impurities are used. The first FO of induced density in WS2 are described by the relation Δ n (r ) ∝sin(2 π r /TFO) /r2 , where TFO∝1 /√{EF} . For weak impurity potentials, the amplitudes of FO are proportional to V0. For attractive potentials and high fields, the total electron density remains positive for all r . On the other hand, for low fields, repulsive potentials and small r , the total electron density may become negative, so that many-body effects should be taken into account.

Hessian eigenvalue distribution in a random Gaussian landscape

NASA Astrophysics Data System (ADS)

Yamada, Masaki; Vilenkin, Alexander

2018-03-01

The energy landscape of multiverse cosmology is often modeled by a multi-dimensional random Gaussian potential. The physical predictions of such models crucially depend on the eigenvalue distribution of the Hessian matrix at potential minima. In particular, the stability of vacua and the dynamics of slow-roll inflation are sensitive to the magnitude of the smallest eigenvalues. The Hessian eigenvalue distribution has been studied earlier, using the saddle point approximation, in the leading order of 1/ N expansion, where N is the dimensionality of the landscape. This approximation, however, is insufficient for the small eigenvalue end of the spectrum, where sub-leading terms play a significant role. We extend the saddle point method to account for the sub-leading contributions. We also develop a new approach, where the eigenvalue distribution is found as an equilibrium distribution at the endpoint of a stochastic process (Dyson Brownian motion). The results of the two approaches are consistent in cases where both methods are applicable. We discuss the implications of our results for vacuum stability and slow-roll inflation in the landscape.

Infrared singularities in Landau gauge Yang-Mills theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alkofer, Reinhard; Huber, Markus Q.; Schwenzer, Kai

2010-05-15

We present a more detailed picture of the infrared regime of Landau-gauge Yang-Mills theory. This is done within a novel framework that allows one to take into account the influence of finite scales within an infrared power counting analysis. We find that there are two qualitatively different infrared fixed points of the full system of Dyson-Schwinger equations. The first extends the known scaling solution, where the ghost dynamics is dominant and gluon propagation is strongly suppressed. It features in addition to the strong divergences of gluonic vertex functions in the previously considered uniform scaling limit, when all external momenta tendmore » to zero, also weaker kinematic divergences, when only some of the external momenta vanish. The second solution represents the recently proposed decoupling scenario where the gluons become massive and the ghosts remain bare. In this case we find that none of the vertex functions is enhanced, so that the infrared dynamics is entirely suppressed. Our analysis also provides a strict argument why the Landau-gauge gluon dressing function cannot be infrared divergent.« less

Eternity in six hours: Intergalactic spreading of intelligent life and sharpening the Fermi paradox

NASA Astrophysics Data System (ADS)

Armstrong, Stuart; Sandberg, Anders

2013-08-01

The Fermi paradox is the discrepancy between the strong likelihood of alien intelligent life emerging (under a wide variety of assumptions) and the absence of any visible evidence for such emergence. In this paper, we extend the Fermi paradox to not only life in this galaxy, but to other galaxies as well. We do this by demonstrating that travelling between galaxies - indeed even launching a colonisation project for the entire reachable universe - is a relatively simple task for a star-spanning civilisation, requiring modest amounts of energy and resources. We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to. Given certain technological assumptions, such as improved automation, the task of constructing Dyson spheres, designing replicating probes, and launching them at distant galaxies, become quite feasible. We extensively analyse the dynamics of such a project, including issues of deceleration and collision with particles in space. Using similar methods, there are millions of galaxies that could have reached us by now. This results in a considerable sharpening of the Fermi paradox.

Variational Principles, Occam Razor and Simplicity Paradox

NASA Astrophysics Data System (ADS)

Berezin, Alexander A.

2004-05-01

Variational minimum principles (VMP) refer to energy (statics, Thomson and Earnshaw theorems in electrostatics), action (Maupertuis, Euler, Lagrange, Hamilton), light (Fermat), quantum paths (Feynman), etc. Historically, VMP appeal to some economy in nature, similarly to Occam Razor Parsimony (ORP) principle. Version of ORP are "best world" (Leibniz), Panglossianism (Voltaire), and "most interesting world" (Dyson). Conceptually, VMP exemplify curious fact that infinite set is often simpler than its subsets (e.g., set of all integers is simpler than set of primes). Algorithmically very simple number 0.1234567... (Champernowne constant) contains Library of Babel of "all books" (Borges) and codes (infinitely many times) everything countably possible. Likewise, full Megaverse (Everett, Deutsch, Guth, Linde) is simpler than our specific ("Big Bang") universe. Dynamically, VMP imply memory effects akin to hysteresis. Similar ideas are "water memory" (Benveniste, Josephson) and isotopic biology (Berezin). Paradoxically, while ORP calls for economy (simplicity), unfolding of ORP in VMP seemingly works in the opposite direction allowing for complexity emergence (e.g., symmetry breaking in Jahn-Teller effect). Metaphysical extrapolation of this complimentarity may lead to "it-from-bit" (Wheeler) reflection of why there is something rather than nothing.

Mirror Numbers and Wigner's ``Unreasonable Effectiveness''

NASA Astrophysics Data System (ADS)

Berezin, Alexander

2006-04-01

Wigner's ``unreasonable effectiveness of mathematics in physics'' can be augmented by concept of mirror number (MN). It is defined as digital string infinite in both directions. Example is ()5141327182() where first 5 digits is Pi ``spelled'' backward (``mirrored'') and last 5 digits is the beginning of decimal exp1 string. Let MN be constructed from two different transcendental (or algebraically irrational) numbers, set of such MNs is Cantor-uncountable. Most MNs have contain any finite digital sequence repeated infinitely many times. In spirit of ``Contact'' (C.Sagan) each normal MN contains ``Library of Babel'' of all possible texts and patterns (J.L.Borges). Infinite at both ends, MN do not have any numerical values and, contrary to numbers written in positional systems, all digits in MNs have equal weight -- sort of ``numerological democracy''. In Pythagorean-Platonic models (space-time and physical world originating from pure numbers) idea of MN resolves paradox of ``beginning'' (or ``end'') of time. Because in MNs all digits have equal status, (quantum) randomness leads to more uniform and fully ergodic phase trajectories (cf. F.Dyson, Infinite in All Directions) .

Quark-mass dependence of the H dibaryon in Λ Λ scattering

NASA Astrophysics Data System (ADS)

Yamaguchi, Yasuhiro; Hyodo, Tetsuo

2016-12-01

We study the quark mass dependence of the H dibaryon in the strangeness S =-2 baryon-baryon scattering. A low-energy effective field theory is used to describe the coupled-channel scattering, in which the quark mass dependence is incorporated so as to reproduce the lattice QCD data by the HAL QCD collaboration in the SU(3) limit. We point out the existence of the Castillejo-Dalitz-Dyson pole in the Λ Λ scattering amplitude below the threshold in the SU(3) limit, which may cause the Ramsauer-Townsend effect near the N Ξ threshold at the physical point. The H dibaryon is unbound at the physical point, and a resonance appears just below the N Ξ threshold. As a consequence of the coupled-channel dynamics, the pole associated with the resonance is not continuously connected to the bound state in the SU(3) limit. Through the extrapolation in quark masses, we show that the unitary limit of the Λ Λ scattering is achieved between the physical point and the SU(3) limit. We discuss the possible realization of the "H matter" in the unphysical quark mass region.

Self-consistent Green's function embedding for advanced electronic structure methods based on a dynamical mean-field concept

NASA Astrophysics Data System (ADS)

Chibani, Wael; Ren, Xinguo; Scheffler, Matthias; Rinke, Patrick

2016-04-01

We present an embedding scheme for periodic systems that facilitates the treatment of the physically important part (here a unit cell or a supercell) with advanced electronic structure methods, that are computationally too expensive for periodic systems. The rest of the periodic system is treated with computationally less demanding approaches, e.g., Kohn-Sham density-functional theory, in a self-consistent manner. Our scheme is based on the concept of dynamical mean-field theory formulated in terms of Green's functions. Our real-space dynamical mean-field embedding scheme features two nested Dyson equations, one for the embedded cluster and another for the periodic surrounding. The total energy is computed from the resulting Green's functions. The performance of our scheme is demonstrated by treating the embedded region with hybrid functionals and many-body perturbation theory in the GW approach for simple bulk systems. The total energy and the density of states converge rapidly with respect to the computational parameters and approach their bulk limit with increasing cluster (i.e., computational supercell) size.

Magnons in a honeycomb ferromagnet

NASA Astrophysics Data System (ADS)

Banerjee, Saikat

The original discovery of the Dirac electron dispersion in graphene led naturally to the question of Dirac cone stability with respect to interactions, and the Coulomb interaction between electrons was shown to induce a logarithmic renormalization of the Dirac dispersion. With the rapid expansion of the list of Dirac fermion compounds, the concept of bosonic Dirac materials has emerged. At the single particle level, these materials closely resemble the fermionic counterparts. However, the changed particle statistics affects the stability of Dirac cones differently. Here we study the effect of interactions focusing on the honeycomb ferromagnet - where the quasi-particles are magnetic spin waves (magnons). We demonstrate that magnon-magnon interactions lead to a significant renormalization of the bare band structure. We also address the question of the edge and surface states for a finite system. We applied these results to ferromagnetic CrBr3, where the Cr3+ atoms are arranged in weakly coupled honeycomb layers. Our theory qualitatively accounts for the unexplained anomalies in neutron scattering data from 40 years ago for CrBr3 and hereby expand the theory of ferromagnets beyond the standard Dyson theory.

Thermalization dynamics of two correlated bosonic quantum wires after a split

NASA Astrophysics Data System (ADS)

Huber, Sebastian; Buchhold, Michael; Schmiedmayer, Jörg; Diehl, Sebastian

2018-04-01

Cherently splitting a one-dimensional Bose gas provides an attractive, experimentally established platform to investigate many-body quantum dynamics. At short enough times, the dynamics is dominated by the dephasing of single quasiparticles, and well described by the relaxation towards a generalized Gibbs ensemble corresponding to the free Luttinger theory. At later times on the other hand, the approach to a thermal Gibbs ensemble is expected for a generic, interacting quantum system. Here, we go one step beyond the quadratic Luttinger theory and include the leading phonon-phonon interactions. By applying kinetic theory and nonequilibrium Dyson-Schwinger equations, we analyze the full relaxation dynamics beyond dephasing and determine the asymptotic thermalization process in the two-wire system for a symmetric splitting protocol. The major observables are the different phonon occupation functions and the experimentally accessible coherence factor, as well as the phase correlations between the two wires. We demonstrate that, depending on the splitting protocol, the presence of phonon collisions can have significant influence on the asymptotic evolution of these observables, which makes the corresponding thermalization dynamics experimentally accessible.

The G-HAT Search for Advanced Extraterrestrial Civilizations: The Reddest Extended WISE Sources

NASA Astrophysics Data System (ADS)

Maldonado, Jessica; Povich, Matthew S.; Wright, Jason; Griffith, Roger; Sigurdsson, Steinn; Mullan, Brendan L.

2015-01-01

Freeman Dyson (1960) theorized how to identify possible signatures of advanced extra-terrestrial civilizations by their waste heat, an inevitable byproduct of a civilization using a significant fraction of the luminosity from their host star. If a civilizations could tap the starlight throughout their host galaxy their waste heat would be easily detectable by recent infrared surveys. The Glimpsing Heat from Alien Technologies (G-HAT) pilot project aims to place limits on the existence of extraterrestrial civilizations at pan-galactic scales. We present results from the G-HAT cleaned catalog of 563 extremely red, extended high Galactic latitude (|b| ≥ 10) sources from the WISE All-Sky Catalog. Our catalog includes sources new to the scientific literature along with well-studied objects (e.g. starburst galaxies, AGN, and planetary nebulae) that exemplify extreme WISE colors. Objects of particular interest include a supergiant Be star (48 Librae) surrounded by a resolved, mid-infrared nebula, possibly indicating dust in the stellar wind ejecta, and a curious cluster of seven extremely red WISE sources (associated with IRAS 04287+6444) that have no optical counterparts.

Color Superconductivity and Charge Neutrality in Yukawa Theory

NASA Astrophysics Data System (ADS)

Alford, Mark G.; Pangeni, Kamal; Windisch, Andreas

2018-02-01

It is generally believed that when Cooper pairing occurs between two different species of fermions, their Fermi surfaces become locked together so that the resultant state remains "neutral," with equal number densities of the two species, even when subjected to a chemical potential that couples to the difference in number densities. This belief is based on mean-field calculations in models with a zero-range interaction, where the anomalous self-energy is independent of energy and momentum. Following up on an early report of a deviation from neutrality in a Dyson-Schwinger calculation of color-flavor-locked quark matter, we investigate the neutrality of a two-species condensate using a Yukawa model which has a finite-range interaction. In a mean field calculation we obtain the full energy-momentum dependence of the self-energy and find that the energy dependence leads to a population imbalance in the Cooper-paired phase when it is stressed by a species-dependent chemical potential. This gives some support to the suggestion that the color-flavor-locked phase of quark matter might not be an insulator.

Random matrix models, double-time Painlevé equations, and wireless relaying

NASA Astrophysics Data System (ADS)

Chen, Yang; Haq, Nazmus S.; McKay, Matthew R.

2013-06-01

This paper gives an in-depth study of a multiple-antenna wireless communication scenario in which a weak signal received at an intermediate relay station is amplified and then forwarded to the final destination. The key quantity determining system performance is the statistical properties of the signal-to-noise ratio (SNR) γ at the destination. Under certain assumptions on the encoding structure, recent work has characterized the SNR distribution through its moment generating function, in terms of a certain Hankel determinant generated via a deformed Laguerre weight. Here, we employ two different methods to describe the Hankel determinant. First, we make use of ladder operators satisfied by orthogonal polynomials to give an exact characterization in terms of a "double-time" Painlevé differential equation, which reduces to Painlevé V under certain limits. Second, we employ Dyson's Coulomb fluid method to derive a closed form approximation for the Hankel determinant. The two characterizations are used to derive closed-form expressions for the cumulants of γ, and to compute performance quantities of engineering interest.

Representational geometry: integrating cognition, computation, and the brain

PubMed Central

Kriegeskorte, Nikolaus; Kievit, Rogier A.

2013-01-01

The cognitive concept of representation plays a key role in theories of brain information processing. However, linking neuronal activity to representational content and cognitive theory remains challenging. Recent studies have characterized the representational geometry of neural population codes by means of representational distance matrices, enabling researchers to compare representations across stages of processing and to test cognitive and computational theories. Representational geometry provides a useful intermediate level of description, capturing both the information represented in a neuronal population code and the format in which it is represented. We review recent insights gained with this approach in perception, memory, cognition, and action. Analyses of representational geometry can compare representations between models and the brain, and promise to explain brain computation as transformation of representational similarity structure. PMID:23876494

Contacts de langues et representations (Language Contacts and Representations).

ERIC Educational Resources Information Center

Matthey, Marinette, Ed.

1997-01-01

Essays on language contact and the image of language, entirely in French, include: "Representations 'du' contexte et representations 'en' contexte? Eleves et enseignants face a l'apprentissage de la langue" ("Representations 'of' Context or Representations 'in' Context? Students and Teachers Facing Language Learning" (Laurent…

Qualitative aspects of representational competence among college chemistry students: Multiple representations and their role in the understanding of ideal gases

NASA Astrophysics Data System (ADS)

Madden, Sean Patrick

This study examined the role of multiple representations of chemical phenomena, specifically, the temperature-pressure relationship of ideal gases, in the problem solving strategies of college chemistry students. Volunteers included students enrolled in a first semester general chemistry course at a western university. Two additional volunteers from the same university were asked to participate and serve as models of greater sophistication. One was a senior chemistry major; another was a junior science writing major. Volunteers completed an initial screening task involving multiple representations of concentration and dilution concepts. Based on the results of this screening instrument a smaller set of subjects were asked to complete a think aloud session involving multiple representations of the temperature-pressure relationship. Data consisted of the written work of the volunteers and transcripts from videotaped think aloud sessions. The data were evaluated by the researcher and two other graduate students in chemical education using a coding scheme (Kozma, Schank, Coppola, Michalchik, and Allen. 2000). This coding scheme was designed to identify essential features of representational competence and differences in uses of multiple representations. The results indicate that students tend to have a strong preference for one type of representation. Students scoring low on representational competence, as measured by the rubric, ignored important features of some representations or acknowledged them only superficially. Students scoring higher on representational competence made meaningful connections among representations. The more advanced students, those who rated highly on representational competence, tended to use their preferred representation in a heuristic manner to establish meaning for other representations. The more advanced students also reflected upon the problem at greater length before beginning work. Molecular level sketches seemed to be the most difficult type of representation for students to interpret. Most subjects scored higher on representational competence when engaged in creating graphs and sketches than when evaluating provided representations. This study suggests that students may benefit from an instruction that emphasizes heuristic use of multiple representations in chemistry problem solving. An instructional strategy that makes use of a variety of representations and requires students to create their own representations may have measurable benefits to chemistry students.

Representational geometry: integrating cognition, computation, and the brain.

PubMed

Kriegeskorte, Nikolaus; Kievit, Rogier A

2013-08-01

The cognitive concept of representation plays a key role in theories of brain information processing. However, linking neuronal activity to representational content and cognitive theory remains challenging. Recent studies have characterized the representational geometry of neural population codes by means of representational distance matrices, enabling researchers to compare representations across stages of processing and to test cognitive and computational theories. Representational geometry provides a useful intermediate level of description, capturing both the information represented in a neuronal population code and the format in which it is represented. We review recent insights gained with this approach in perception, memory, cognition, and action. Analyses of representational geometry can compare representations between models and the brain, and promise to explain brain computation as transformation of representational similarity structure. Copyright © 2013 Elsevier Ltd. All rights reserved.

Maternal and paternal infant representations: a comparison between parents of term and preterm infants.

PubMed

Tooten, Anneke; Hall, Ruby A S; Hoffenkamp, Hannah N; Braeken, Johan; Vingerhoets, Ad J J M; van Bakel, Hedwig J A

2014-08-01

Research on parental attachment representations after preterm birth is limited and inconclusive. The present study is the first in which maternal and paternal attachment representations after term, moderately and very preterm birth are compared. In addition, special attention was directed toward disrupted attachment representations. Mothers and fathers of term infants (≥ 37 weeks of gestational age, n=71), moderately preterm infants (≥ 32-37 weeks of gestational age, n=62) and very preterm infants (<32 weeks of gestational age, n=56) participated in the present study. Attachment representations (balanced, disengaged, distorted) about their infants were evaluated with the Working Model of the Child Interview (WMCI). To asses disrupted representations the coding of the WMCI was extended with the disrupted scale (WMCI-D). The three main classifications of attachment representations were not affected by preterm birth. In addition, there were no gender differences in the rate of balanced representations. In case of non-balanced representations however, maternal representations were more often distorted, whereas fathers showed more often disengaged representations. Results further revealed that maternal disrupted attachment representations were marked by role/boundary confusion or disorientation, whereas paternal disrupted attachment representations were characterized by withdrawal. Given the gender differences it is essential to tailor interventions according to the attachment representations of the parent, in order to be able to alter their non-balanced and/or disrupted attachment representations. Copyright © 2014 Elsevier Inc. All rights reserved.

System for conversion between the boundary representation model and a constructive solid geometry model of an object

DOEpatents

Christensen, Noel C.; Emery, James D.; Smith, Maurice L.

1988-04-05

A system converts from the boundary representation of an object to the constructive solid geometry representation thereof. The system converts the boundary representation of the object into elemental atomic geometrical units or I-bodies which are in the shape of stock primitives or regularized intersections of stock primitives. These elemental atomic geometrical units are then represented in symbolic form. The symbolic representations of the elemental atomic geometrical units are then assembled heuristically to form a constructive solid geometry representation of the object usable for manufacturing thereof. Artificial intelligence is used to determine the best constructive solid geometry representation from the boundary representation of the object. Heuristic criteria are adapted to the manufacturing environment for which the device is to be utilized. The surface finish, tolerance, and other information associated with each surface of the boundary representation of the object are mapped onto the constructive solid geometry representation of the object to produce an enhanced solid geometry representation, particularly useful for computer-aided manufacture of the object.

Negotiated Representational Mediators: How Young Children Decide What to Include in Their Science Representations

ERIC Educational Resources Information Center

Danish, Joshua A.; Enyedy, Noel

2007-01-01

In this paper, we synthesize two bodies of work related to students' representational activities: the notions of meta-representational competence and representation as a form of practice. We report on video analyses of kindergarten and first-grade students as they create representations of pollination in a science classroom, as well as summarize…

The Past Is Present: Representations of Parents, Friends, and Romantic Partners Predict Subsequent Romantic Representations.

PubMed

Furman, Wyndol; Collibee, Charlene

2018-01-01

This study examined how representations of parent-child relationships, friendships, and past romantic relationships are related to subsequent romantic representations. Two-hundred 10th graders (100 female; M age  = 15.87 years) from diverse neighborhoods in a Western U.S. city were administered questionnaires and were interviewed to assess avoidant and anxious representations of their relationships with parents, friends, and romantic partners. Participants then completed similar questionnaires and interviews about their romantic representations six more times over the next 7.5 years. Growth curve analyses revealed that representations of relationships with parents, friends, and romantic partners each uniquely predicted subsequent romantic representations across development. Consistent with attachment and behavioral systems theory, representations of romantic relationships are revised by representations and experiences in other relationships. © 2016 The Authors. Child Development © 2016 Society for Research in Child Development, Inc.

Building Hierarchical Representations for Oracle Character and Sketch Recognition.

PubMed

Jun Guo; Changhu Wang; Roman-Rangel, Edgar; Hongyang Chao; Yong Rui

2016-01-01

In this paper, we study oracle character recognition and general sketch recognition. First, a data set of oracle characters, which are the oldest hieroglyphs in China yet remain a part of modern Chinese characters, is collected for analysis. Second, typical visual representations in shape- and sketch-related works are evaluated. We analyze the problems suffered when addressing these representations and determine several representation design criteria. Based on the analysis, we propose a novel hierarchical representation that combines a Gabor-related low-level representation and a sparse-encoder-related mid-level representation. Extensive experiments show the effectiveness of the proposed representation in both oracle character recognition and general sketch recognition. The proposed representation is also complementary to convolutional neural network (CNN)-based models. We introduce a solution to combine the proposed representation with CNN-based models, and achieve better performances over both approaches. This solution has beaten humans at recognizing general sketches.

Representational Competence in Chemistry: A Comparison between Students with Different Levels of Understanding of Basic Chemical Concepts and Chemical Representations

ERIC Educational Resources Information Center

Sim, Joong Hiong; Daniel, Esther Gnanamalar Sarojini

2014-01-01

Representational competence is defined as "skills in interpreting and using representations". This study attempted to compare students' of high, medium, and low levels of understanding of (1) basic chemical concepts, and (2) chemical representations, in their representational competence. A total of 411 Form 4 science students (mean age =…

Specialized mechanisms for theory of mind: are mental representations special because they are mental or because they are representations?

PubMed

Cohen, Adam S; Sasaki, Joni Y; German, Tamsin C

2015-03-01

Does theory of mind depend on a capacity to reason about representations generally or on mechanisms selective for the processing of mental state representations? In four experiments, participants reasoned about beliefs (mental representations) and notes (non-mental, linguistic representations), which according to two prominent theories are closely matched representations because both are represented propositionally. Reaction times were faster and accuracies higher when participants endorsed or rejected statements about false beliefs than about false notes (Experiment 1), even when statements emphasized representational format (Experiment 2), which should have favored the activation of representation concepts. Experiments 3 and 4 ruled out a counterhypothesis that differences in task demands were responsible for the advantage in belief processing. These results demonstrate for the first time that understanding of mental and linguistic representations can be dissociated even though both may carry propositional content, supporting the theory that mechanisms governing theory of mind reasoning are narrowly specialized to process mental states, not representations more broadly. Extending this theory, we discuss whether less efficient processing of non-mental representations may be a by-product of mechanisms specialized for processing mental states. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Narrative representations of caregivers and emotion dysregulation as predictors of maltreated children's rejection by peers.

PubMed

Shields, A; Ryan, R M; Cicchetti, D

2001-05-01

This study examined whether maltreated children were more likely than nonmaltreated children to develop poor-quality representations of caregivers and whether these representations predicted children's rejection by peers. A narrative task assessing representations of mothers and fathers was administered to 76 maltreated and 45 nonmaltreated boys and girls (8-12 years old). Maltreated children's representations were more negative/constricted and less positive/coherent than those of nonmaltreated children. Maladaptive representations were associated with emotion dysregulation, aggression, and peer rejection, whereas positive/coherent representations were related to prosocial behavior and peer preference. Representations mediated maltreatment's effects on peer rejection in part by undermining emotion regulation. Findings suggest that representations of caregivers serve an important regulatory function in the peer relationships of at-risk children.

Identifying Representational Competence with Multi-Representational Displays

ERIC Educational Resources Information Center

Stieff, Mike; Hegarty, Mary; Deslongchamps, Ghislain

2011-01-01

Increasingly, multi-representational educational technologies are being deployed in science classrooms to support science learning and the development of representational competence. Several studies have indicated that students experience significant challenges working with these multi-representational displays and prefer to use only one…

Multimodal Literacies in Science: Currency, Coherence and Focus

NASA Astrophysics Data System (ADS)

Klein, Perry D.; Kirkpatrick, Lori C.

2010-01-01

Since the 1990s, researchers have increasingly drawn attention to the multiplicity of representations used in science. This issue of RISE advances this line of research by placing such representations at the centre of science teaching and learning. The authors show that representations do not simply transmit scientific information; they are integral to reasoning about scientific phenomena. This focus on thinking with representations mediates between well-resolved representations and formal reasoning of disciplinary science, and the capacity-limited, perceptually-driven nature of human cognition. The teaching practices described here build on three key principles: Each representation is interpreted through others; natural language is a sign system that is used to interpret a variety of other kinds of representations; and this chain of signs or representations is ultimately grounded in bodily experiences of perception and action. In these papers, the researchers provide examples and analysis of teachers scaffolding students in using representations to construct new knowledge, and in constructing new representations to express and develop their knowledge. The result is a new delineation of the power and the challenges of teaching science with multiple representations.

System for conversion between the boundary representation model and a constructive solid geometry model of an object

DOEpatents

Christensen, N.C.; Emery, J.D.; Smith, M.L.

1985-04-29

A system converts from the boundary representation of an object to the constructive solid geometry representation thereof. The system converts the boundary representation of the object into elemental atomic geometrical units or I-bodies which are in the shape of stock primitives or regularized intersections of stock primitives. These elemental atomic geometrical units are then represented in symbolic form. The symbolic representations of the elemental atomic geometrical units are then assembled heuristically to form a constructive solid geometry representation of the object usable for manufacturing thereof. Artificial intelligence is used to determine the best constructive solid geometry representation from the boundary representation of the object. Heuristic criteria are adapted to the manufacturing environment for which the device is to be utilized. The surface finish, tolerance, and other information associated with each surface of the boundary representation of the object are mapped onto the constructive solid geometry representation of the object to produce an enhanced solid geometry representation, particularly useful for computer-aided manufacture of the object. 19 figs.

Learning Sparse Feature Representations using Probabilistic Quadtrees and Deep Belief Nets

DTIC Science & Technology

2015-04-24

Feature Representations usingProbabilistic Quadtrees and Deep Belief Nets Learning sparse feature representations is a useful instru- ment for solving an...novel framework for the classifi cation of handwritten digits that learns sparse representations using probabilistic quadtrees and Deep Belief Nets... Learning Sparse Feature Representations usingProbabilistic Quadtrees and Deep Belief Nets Report Title Learning sparse feature representations is a useful

Characterizing representational learning: A combined simulation and tutorial on perturbation theory

NASA Astrophysics Data System (ADS)

Kohnle, Antje; Passante, Gina

2017-12-01

Analyzing, constructing, and translating between graphical, pictorial, and mathematical representations of physics ideas and reasoning flexibly through them ("representational competence") is a key characteristic of expertise in physics but is a challenge for learners to develop. Interactive computer simulations and University of Washington style tutorials both have affordances to support representational learning. This article describes work to characterize students' spontaneous use of representations before and after working with a combined simulation and tutorial on first-order energy corrections in the context of quantum-mechanical time-independent perturbation theory. Data were collected from two institutions using pre-, mid-, and post-tests to assess short- and long-term gains. A representational competence level framework was adapted to devise level descriptors for the assessment items. The results indicate an increase in the number of representations used by students and the consistency between them following the combined simulation tutorial. The distributions of representational competence levels suggest a shift from perceptual to semantic use of representations based on their underlying meaning. In terms of activity design, this study illustrates the need to support students in making sense of the representations shown in a simulation and in learning to choose the most appropriate representation for a given task. In terms of characterizing representational abilities, this study illustrates the usefulness of a framework focusing on perceptual, syntactic, and semantic use of representations.

Standard model of knowledge representation

NASA Astrophysics Data System (ADS)

Yin, Wensheng

2016-09-01

Knowledge representation is the core of artificial intelligence research. Knowledge representation methods include predicate logic, semantic network, computer programming language, database, mathematical model, graphics language, natural language, etc. To establish the intrinsic link between various knowledge representation methods, a unified knowledge representation model is necessary. According to ontology, system theory, and control theory, a standard model of knowledge representation that reflects the change of the objective world is proposed. The model is composed of input, processing, and output. This knowledge representation method is not a contradiction to the traditional knowledge representation method. It can express knowledge in terms of multivariate and multidimensional. It can also express process knowledge, and at the same time, it has a strong ability to solve problems. In addition, the standard model of knowledge representation provides a way to solve problems of non-precision and inconsistent knowledge.

Distinguishing Representations as Origin and Representations as Input: Roles for Individual Neurons.

PubMed

Edwards, Jonathan C W

2016-01-01

It is widely perceived that there is a problem in giving a naturalistic account of mental representation that deals adequately with the issue of meaning, interpretation, or significance (semantic content). It is suggested here that this problem may arise partly from the conflation of two vernacular senses of representation: representation-as-origin and representation-as-input. The flash of a neon sign may in one sense represent a popular drink, but to function as a representation it must provide an input to a 'consumer' in the street. The arguments presented draw on two principles - the neuron doctrine and the need for a venue for 'presentation' or 'reception' of a representation at a specified site, consistent with the locality principle. It is also argued that domains of representation cannot be defined by signal traffic, since they can be expected to include 'null' elements based on non-firing cells. In this analysis, mental representations-as-origin are distributed patterns of cell firing. Each firing cell is given semantic value in its own right - some form of atomic propositional significance - since different axonal branches may contribute to integration with different populations of signals at different downstream sites. Representations-as-input are patterns of local co-arrival of signals in the form of synaptic potentials in dendrites. Meaning then draws on the relationships between active and null inputs, forming 'scenarios' comprising a molecular combination of 'premises' from which a new output with atomic propositional significance is generated. In both types of representation, meaning, interpretation or significance pivots on events in an individual cell. (This analysis only applies to 'occurrent' representations based on current neural activity.) The concept of representations-as-input emphasizes the need for an internal 'consumer' of a representation and the dependence of meaning on the co-relationships involved in an input interaction between signals and consumer. The acceptance of this necessity provides a basis for resolving the problem that representations appear both as distributed (representation-as-origin) and as local (representation-as-input). The key implications are that representations in the brain are massively multiple both in series and in parallel, and that individual cells play specific semantic roles. These roles are discussed in relation to traditional concepts of 'gnostic' cell types.

Distinguishing Representations as Origin and Representations as Input: Roles for Individual Neurons

PubMed Central

Edwards, Jonathan C. W.

2016-01-01

It is widely perceived that there is a problem in giving a naturalistic account of mental representation that deals adequately with the issue of meaning, interpretation, or significance (semantic content). It is suggested here that this problem may arise partly from the conflation of two vernacular senses of representation: representation-as-origin and representation-as-input. The flash of a neon sign may in one sense represent a popular drink, but to function as a representation it must provide an input to a ‘consumer’ in the street. The arguments presented draw on two principles – the neuron doctrine and the need for a venue for ‘presentation’ or ‘reception’ of a representation at a specified site, consistent with the locality principle. It is also argued that domains of representation cannot be defined by signal traffic, since they can be expected to include ‘null’ elements based on non-firing cells. In this analysis, mental representations-as-origin are distributed patterns of cell firing. Each firing cell is given semantic value in its own right – some form of atomic propositional significance – since different axonal branches may contribute to integration with different populations of signals at different downstream sites. Representations-as-input are patterns of local co-arrival of signals in the form of synaptic potentials in dendrites. Meaning then draws on the relationships between active and null inputs, forming ‘scenarios’ comprising a molecular combination of ‘premises’ from which a new output with atomic propositional significance is generated. In both types of representation, meaning, interpretation or significance pivots on events in an individual cell. (This analysis only applies to ‘occurrent’ representations based on current neural activity.) The concept of representations-as-input emphasizes the need for an internal ‘consumer’ of a representation and the dependence of meaning on the co-relationships involved in an input interaction between signals and consumer. The acceptance of this necessity provides a basis for resolving the problem that representations appear both as distributed (representation-as-origin) and as local (representation-as-input). The key implications are that representations in the brain are massively multiple both in series and in parallel, and that individual cells play specific semantic roles. These roles are discussed in relation to traditional concepts of ‘gnostic’ cell types. PMID:27746760

Data Representations for Geographic Information Systems.

ERIC Educational Resources Information Center

Shaffer, Clifford A.

1992-01-01

Surveys the field and literature of geographic information systems (GIS) and spatial data representation as it relates to GIS. Highlights include GIS terms, data types, and operations; vector representations and raster, or grid, representations; spatial indexing; elevation data representations; large spatial databases; and problem areas and future…

4 CFR 28.113 - Contents of representation petitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 4 Accounts 1 2014-01-01 2013-01-01 true Contents of representation petitions. 28.113 Section 28... ACCOUNTABILITY OFFICE Special Procedures; Representation Proceedings § 28.113 Contents of representation petitions. (a) The contents of representation petitions filed under § 28.112(a)(1) (by a labor organization...

4 CFR 28.113 - Contents of representation petitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 4 Accounts 1 2011-01-01 2011-01-01 false Contents of representation petitions. 28.113 Section 28... ACCOUNTABILITY OFFICE Special Procedures; Representation Proceedings § 28.113 Contents of representation petitions. (a) The contents of representation petitions filed under § 28.112(a)(1) (by a labor organization...

4 CFR 28.113 - Contents of representation petitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 4 Accounts 1 2013-01-01 2013-01-01 false Contents of representation petitions. 28.113 Section 28... ACCOUNTABILITY OFFICE Special Procedures; Representation Proceedings § 28.113 Contents of representation petitions. (a) The contents of representation petitions filed under § 28.112(a)(1) (by a labor organization...

4 CFR 28.113 - Contents of representation petitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 4 Accounts 1 2012-01-01 2012-01-01 false Contents of representation petitions. 28.113 Section 28... ACCOUNTABILITY OFFICE Special Procedures; Representation Proceedings § 28.113 Contents of representation petitions. (a) The contents of representation petitions filed under § 28.112(a)(1) (by a labor organization...

Optimization of digital designs

NASA Technical Reports Server (NTRS)

Miles, Lowell H. (Inventor); Whitaker, Sterling R. (Inventor)

2009-01-01

An application specific integrated circuit is optimized by translating a first representation of its digital design to a second representation. The second representation includes multiple syntactic expressions that admit a representation of a higher-order function of base Boolean values. The syntactic expressions are manipulated to form a third representation of the digital design.

Taxonomy development and knowledge representation of nurses' personal cognitive artifacts.

PubMed

McLane, Sharon; Turley, James P

2009-11-14

Nurses prepare knowledge representations, or summaries of patient clinical data, each shift. These knowledge representations serve multiple purposes, including support of working memory, workload organization and prioritization, critical thinking, and reflection. This summary is integral to internal knowledge representations, working memory, and decision-making. Study of this nurse knowledge representation resulted in development of a taxonomy of knowledge representations necessary to nursing practice.This paper describes the methods used to elicit the knowledge representations and structures necessary for the work of clinical nurses, described the development of a taxonomy of this knowledge representation, and discusses translation of this methodology to the cognitive artifacts of other disciplines. Understanding the development and purpose of practitioner's knowledge representations provides important direction to informaticists seeking to create information technology alternatives. The outcome of this paper is to suggest a process template for transition of cognitive artifacts to an information system.

Quasiprobability Representations of Quantum Mechanics with Minimal Negativity

NASA Astrophysics Data System (ADS)

Zhu, Huangjun

2016-09-01

Quasiprobability representations, such as the Wigner function, play an important role in various research areas. The inevitable appearance of negativity in such representations is often regarded as a signature of nonclassicality, which has profound implications for quantum computation. However, little is known about the minimal negativity that is necessary in general quasiprobability representations. Here we focus on a natural class of quasiprobability representations that is distinguished by simplicity and economy. We introduce three measures of negativity concerning the representations of quantum states, unitary transformations, and quantum channels, respectively. Quite surprisingly, all three measures lead to the same representations with minimal negativity, which are in one-to-one correspondence with the elusive symmetric informationally complete measurements. In addition, most representations with minimal negativity are automatically covariant with respect to the Heisenberg-Weyl groups. Furthermore, our study reveals an interesting tradeoff between negativity and symmetry in quasiprobability representations.

Children's representations of multiple family relationships: organizational structure and development in early childhood.

PubMed

Schermerhorn, Alice C; Cummings, E Mark; Davies, Patrick T

2008-02-01

The authors examine mutual family influence processes at the level of children's representations of multiple family relationships, as well as the structure of those representations. From a community sample with 3 waves, each spaced 1 year apart, kindergarten-age children (105 boys and 127 girls) completed a story-stem completion task, tapping representations of multiple family relationships. Structural equation modeling with autoregressive controls indicated that representational processes involving different family relationships were interrelated over time, including links between children's representations of marital conflict and reactions to conflict, between representations of security about marital conflict and parent-child relationships, and between representations of security in father-child and mother-child relationships. Mixed support was found for notions of increasing stability in representations during this developmental period. Results are discussed in terms of notions of transactional family dynamics, including family-wide perspectives on mutual influence processes attributable to multiple family relationships.

When this means that: the role of working memory and inhibitory control in children's understanding of representations.

PubMed

Astle, Andrea; Kamawar, Deepthi; Vendetti, Corrie; Podjarny, Gal

2013-10-01

We investigated cognitive skills that contribute to 4-year-olds' understanding of representations. In our main task, children used representations on a perspective line drawing to find stickers hidden in a model room. To compare the contributions made by various cognitive skills with children's understanding of different types of representations, we manipulated the resemblance between the representations and their referents. Our results indicate that when representations are iconic (i.e., look like their referents), children have very little difficulty with the task. Controlling for performance on this baseline version of the task, we found that specific cognitive skills are differentially predictive of performance when using arbitrary and conflicting representations (i.e., symbols). When the representation was arbitrarily linked to the sticker, performance was related to phonological and visuospatial working memory. When the representation matched the color of an alternate sticker (thereby conflicting with the desired sticker), performance was related to phonological working memory and inhibitory control. We discuss the role that different cognitive skills play in representational understanding as a function of the nature of the representation-referent relation. Copyright © 2013 Elsevier Inc. All rights reserved.

Neglecting the Left Side of a City Square but Not the Left Side of Its Clock: Prevalence and Characteristics of Representational Neglect

PubMed Central

Guariglia, Cecilia; Palermo, Liana; Piccardi, Laura; Iaria, Giuseppe; Incoccia, Chiara

2013-01-01

Representational neglect, which is characterized by the failure to report left-sided details of a mental image from memory, can occur after a right hemisphere lesion. In this study, we set out to verify the hypothesis that two distinct forms of representational neglect exist, one involving object representation and the other environmental representation. As representational neglect is considered rare, we also evaluated the prevalence and frequency of its association with perceptual neglect. We submitted a group of 96 unselected, consecutive, chronic, right brain-damaged patients to an extensive neuropsychological evaluation that included two representational neglect tests: the Familiar Square Description Test and the O'Clock Test. Representational neglect, as well as perceptual neglect, was present in about one-third of the sample. Most patients neglected the left side of imagined familiar squares but not the left side of imagined clocks. The present data show that representational neglect is not a rare disorder and also support the hypothesis that two different types of mental representations (i.e. topological and non-topological images) may be selectively damaged in representational neglect. PMID:23874416

Commonalities between Perception and Cognition.

PubMed

Tacca, Michela C

2011-01-01

Perception and cognition are highly interrelated. Given the influence that these systems exert on one another, it is important to explain how perceptual representations and cognitive representations interact. In this paper, I analyze the similarities between visual perceptual representations and cognitive representations in terms of their structural properties and content. Specifically, I argue that the spatial structure underlying visual object representation displays systematicity - a property that is considered to be characteristic of propositional cognitive representations. To this end, I propose a logical characterization of visual feature binding as described by Treisman's Feature Integration Theory and argue that systematicity is not only a property of language-like representations, but also of spatially organized visual representations. Furthermore, I argue that if systematicity is taken to be a criterion to distinguish between conceptual and non-conceptual representations, then visual representations, that display systematicity, might count as an early type of conceptual representations. Showing these analogies between visual perception and cognition is an important step toward understanding the interface between the two systems. The ideas here presented might also set the stage for new empirical studies that directly compare binding (and other relational operations) in visual perception and higher cognition.

Commonalities between Perception and Cognition

PubMed Central

Tacca, Michela C.

2011-01-01

Perception and cognition are highly interrelated. Given the influence that these systems exert on one another, it is important to explain how perceptual representations and cognitive representations interact. In this paper, I analyze the similarities between visual perceptual representations and cognitive representations in terms of their structural properties and content. Specifically, I argue that the spatial structure underlying visual object representation displays systematicity – a property that is considered to be characteristic of propositional cognitive representations. To this end, I propose a logical characterization of visual feature binding as described by Treisman’s Feature Integration Theory and argue that systematicity is not only a property of language-like representations, but also of spatially organized visual representations. Furthermore, I argue that if systematicity is taken to be a criterion to distinguish between conceptual and non-conceptual representations, then visual representations, that display systematicity, might count as an early type of conceptual representations. Showing these analogies between visual perception and cognition is an important step toward understanding the interface between the two systems. The ideas here presented might also set the stage for new empirical studies that directly compare binding (and other relational operations) in visual perception and higher cognition. PMID:22144974

Representing Nature of Science in a Science Textbook: Exploring author-editor-publisher interactions

NASA Astrophysics Data System (ADS)

DiGiuseppe, Maurice

2014-05-01

Current reforms in elementary and secondary science education call for students and teachers to develop more informed views of the nature of science (NOS)-a process in which science textbooks play a significant role. This paper reports on a case study of the development of representations of the NOS in a senior high school chemistry textbook by the book's author, editor, and publisher. The study examines the multiple discourses that arose as the developers reflected on their personal and shared understandings of NOS; squared these with mandated curricula, the educational needs of chemistry students and teachers, and the exigencies of large-scale commercial textbook publishing. As a result, the team developed and incorporated, in the textbook, representations of NOS they believed were the most pedagogically suitable. Analysis of the data in this study indicates that a number of factors significantly influenced the development of representations of NOS, including representational accuracy (the degree to which representations of NOS conformed to informed views of the NOS), representational consistency (the degree to which representations of NOS in different parts of the book conveyed the same meaning), representational appropriateness (the age-, grade-, and reading-level appropriateness of the NOS representations), representational alignment (the degree to which NOS representations aligned with mandated curriculum), representational marketability (the degree to which NOS representations would affect sales of the textbook), and 'Workplace Resources' factors including availability of time, relevant expertise, and opportunities for professional development.

Translating between Representations in a Social Context: A Study of Undergraduate Science Students' Representational Fluency

ERIC Educational Resources Information Center

Nichols, Kim; Ranasinghe, Muditha; Hanan, Jim

2013-01-01

Interacting with and translating across multiple representations is an essential characteristic of expertise and representational fluency. In this study, we explored the effect of interacting with and translating between representations in a computer simulation or in a paper-based assignment on scientific accuracy of undergraduate science…

Mathematical Representation Ability by Using Project Based Learning on the Topic of Statistics

NASA Astrophysics Data System (ADS)

Widakdo, W. A.

2017-09-01

Seeing the importance of the role of mathematics in everyday life, mastery of the subject areas of mathematics is a must. Representation ability is one of the fundamental ability that used in mathematics to make connection between abstract idea with logical thinking to understanding mathematics. Researcher see the lack of mathematical representation and try to find alternative solution to dolve it by using project based learning. This research use literature study from some books and articles in journals to see the importance of mathematical representation abiliy in mathemtics learning and how project based learning able to increase this mathematical representation ability on the topic of Statistics. The indicators for mathematical representation ability in this research classifies namely visual representation (picture, diagram, graph, or table); symbolize representation (mathematical statement. Mathematical notation, numerical/algebra symbol) and verbal representation (written text). This article explain about why project based learning able to influence student’s mathematical representation by using some theories in cognitive psychology, also showing the example of project based learning that able to use in teaching statistics, one of mathematics topic that very useful to analyze data.

Taking representation seriously: rethinking bioethics through Clint Eastwood's Million Dollar Baby.

PubMed

Braswell, Harold

2011-06-01

In this article, I propose a new model for understanding the function of representation in bioethics. Bioethicists have traditionally judged representations according to a mimetic paradigm, in which representations of bioethical dilemmas are assessed based on their correspondence to the "reality" of bioethics itself. In this article, I argue that this mimetic paradigm obscures the interaction between representation and reality and diverts bioethicists from analyzing the tensions in the representational object itself. I propose an anti-mimetic model of representation that is attuned to how representations can both maintain and potentially subvert dominant conceptions of bioethics. I illustrate this model through a case study of Clint Eastwood's film Million Dollar Baby. By focusing attention on the film's lack of adherence bioethical procedures and medical science, critics missed how an analysis of its representational logic provides a means of reimagining both bioethics and medical practice. In my conclusion, I build off this case study to assess how an incorporation of representational studies can deepen-and be deepened by-recent calls for interdisciplinarity in bioethics.

Representations of self and other in the narratives of neglected, physically abused, and sexually abused preschoolers.

PubMed

Toth, S L; Cicchetti, D; Macfie, J; Emde, R N

1997-01-01

The MacArthur Story Stem Battery was used to examine maternal and self-representations in neglected, physically abused, sexually abused, and nonmaltreated comparison preschool children. The narratives of maltreated children contained more negative maternal representations and more negative self-representations than did the narratives of nonmaltreated children. Maltreated children also were more controlling with and less responsive to the examiner. In examining the differential impact of maltreatment subtype differences on maternal and self-representations, physically abused children evidenced the most negative maternal representations; they also had more negative self-representations than nonmaltreated children. Sexually abused children manifested more positive self-representations than neglected children. Despite these differences in the nature of maternal and self-representations, physically and sexually abused children both were more controlling and less responsive to the examiner. The investigation adds to the corpus of knowledge regarding disturbances in the self-system functioning of maltreated children and provides support for relations between representational models of self and other and the self-organizing function that these models exert on children's lives.

Lexical is as lexical does: computational approaches to lexical representation

PubMed Central

Woollams, Anna M.

2015-01-01

In much of neuroimaging and neuropsychology, regions of the brain have been associated with ‘lexical representation’, with little consideration as to what this cognitive construct actually denotes. Within current computational models of word recognition, there are a number of different approaches to the representation of lexical knowledge. Structural lexical representations, found in original theories of word recognition, have been instantiated in modern localist models. However, such a representational scheme lacks neural plausibility in terms of economy and flexibility. Connectionist models have therefore adopted distributed representations of form and meaning. Semantic representations in connectionist models necessarily encode lexical knowledge. Yet when equipped with recurrent connections, connectionist models can also develop attractors for familiar forms that function as lexical representations. Current behavioural, neuropsychological and neuroimaging evidence shows a clear role for semantic information, but also suggests some modality- and task-specific lexical representations. A variety of connectionist architectures could implement these distributed functional representations, and further experimental and simulation work is required to discriminate between these alternatives. Future conceptualisations of lexical representations will therefore emerge from a synergy between modelling and neuroscience. PMID:25893204

Multi-representation based on scientific investigation for enhancing students’ representation skills

NASA Astrophysics Data System (ADS)

Siswanto, J.; Susantini, E.; Jatmiko, B.

2018-03-01

This research aims to implementation learning physics with multi-representation based on the scientific investigation for enhancing students’ representation skills, especially on the magnetic field subject. The research design is one group pretest-posttest. This research was conducted in the department of mathematics education, Universitas PGRI Semarang, with the sample is students of class 2F who take basic physics courses. The data were obtained by representation skills test and documentation of multi-representation worksheet. The Results show gain analysis value of .64 which means some medium improvements. The result of t-test (α = .05) is shows p-value = .001. This learning significantly improves students representation skills.

The effect of training methodology on knowledge representation in categorization.

PubMed

Hélie, Sébastien; Shamloo, Farzin; Ell, Shawn W

2017-01-01

Category representations can be broadly classified as containing within-category information or between-category information. Although such representational differences can have a profound impact on decision-making, relatively little is known about the factors contributing to the development and generalizability of different types of category representations. These issues are addressed by investigating the impact of training methodology and category structures using a traditional empirical approach as well as the novel adaptation of computational modeling techniques from the machine learning literature. Experiment 1 focused on rule-based (RB) category structures thought to promote between-category representations. Participants learned two sets of two categories during training and were subsequently tested on a novel categorization problem using the training categories. Classification training resulted in a bias toward between-category representations whereas concept training resulted in a bias toward within-category representations. Experiment 2 focused on information-integration (II) category structures thought to promote within-category representations. With II structures, there was a bias toward within-category representations regardless of training methodology. Furthermore, in both experiments, computational modeling suggests that only within-category representations could support generalization during the test phase. These data suggest that within-category representations may be dominant and more robust for supporting the reconfiguration of current knowledge to support generalization.

The effect of training methodology on knowledge representation in categorization

PubMed Central

Shamloo, Farzin; Ell, Shawn W.

2017-01-01

Category representations can be broadly classified as containing within–category information or between–category information. Although such representational differences can have a profound impact on decision–making, relatively little is known about the factors contributing to the development and generalizability of different types of category representations. These issues are addressed by investigating the impact of training methodology and category structures using a traditional empirical approach as well as the novel adaptation of computational modeling techniques from the machine learning literature. Experiment 1 focused on rule–based (RB) category structures thought to promote between–category representations. Participants learned two sets of two categories during training and were subsequently tested on a novel categorization problem using the training categories. Classification training resulted in a bias toward between–category representations whereas concept training resulted in a bias toward within–category representations. Experiment 2 focused on information-integration (II) category structures thought to promote within–category representations. With II structures, there was a bias toward within–category representations regardless of training methodology. Furthermore, in both experiments, computational modeling suggests that only within–category representations could support generalization during the test phase. These data suggest that within–category representations may be dominant and more robust for supporting the reconfiguration of current knowledge to support generalization. PMID:28846732

How Do Students Learn to See Concepts in Visualizations? Social Learning Mechanisms with Physical and Virtual Representations

ERIC Educational Resources Information Center

Rau, Martina A.

2017-01-01

STEM instruction often uses visual representations. To benefit from these, students need to understand how representations show domain-relevant concepts. Yet, this is difficult for students. Prior research shows that physical representations (objects that students manipulate by hand) and virtual representations (objects on a computer screen that…

Images as Representations: Visual Sources on Education and Childhood in the Past

ERIC Educational Resources Information Center

Dekker, Jeroen J.H.

2015-01-01

The challenge of using images for the history of education and childhood will be addressed in this article by looking at them as representations. Central is the relationship between representations and reality. The focus is on the power of paintings as representations of aspects of realities. First the meaning of representation for images as…

Analyse conversationnelle et representations sociales: Unite et diversite de L'image du bilinguisme (Conversational Analysis and Social Representations: Unity and Diversity in the Image of Bilingualism).

ERIC Educational Resources Information Center

Py, Bernard, Ed.

2000-01-01

Articles in this issue include the following: "Representations sociales et discours. Questions epistemologiques et methodologiques" (Social Representations and Discourse. Questions of Epistemology and Methodology); "Aspects theoretiques et methodologiques de la recherche sur le traitement discursif des representations sociales"…

A Graphical Exposition of the Link between Two Representations of the Excess Burden of Taxation

ERIC Educational Resources Information Center

Liu, Liqun; Rettenmaier, Andrew J.

2005-01-01

The excess burden of taxation typically has two graphical representations in undergraduate microeconomics and public finance textbooks: the IC/BC (indifference curve/budget constraint) representation and the demand/supply representation. The IC/BC representation has the advantage of showing the behavioral response to a distortionary tax and how a…

[The effect of goal framing on the activation of affective representations].

PubMed

Takehashi, Hiroki; Karasawa, Kaori

2007-10-01

Guided by regulatory focus theory, this study examined the effects of goal framing on the subjective experience of affect and the accessibility of affective representations. Study I examined lay persons' beliefs concerning the relationship between goal framing and certain kinds of affective experiences. The results indicated that a promotion focus was associated with happiness and disappointment, whereas a prevention focus was associated with relaxation and tension. Study 2 examined the effect of goal framing on the activation of affective representations, and found that a promotion focus activated both gain-related representations (happy and disappointment) and loss-related representations (relaxation and tension), whereas a prevention focus activated only loss-related representations. These results suggest that goal framing activates particular affective representations, and the activated affective representations may influence the interpretation of positive or negative experiences. The discussion considered the function of the activation of affective representations as a mediator between goal framing and its cognitive and behavioral consequences.

[Visual representation of natural scenes in flicker changes].

PubMed

Nakashima, Ryoichi; Yokosawa, Kazuhiko

2010-08-01

Coherence theory in scene perception (Rensink, 2002) assumes the retention of volatile object representations on which attention is not focused. On the other hand, visual memory theory in scene perception (Hollingworth & Henderson, 2002) assumes that robust object representations are retained. In this study, we hypothesized that the difference between these two theories is derived from the difference of the experimental tasks that they are based on. In order to verify this hypothesis, we examined the properties of visual representation by using a change detection and memory task in a flicker paradigm. We measured the representations when participants were instructed to search for a change in a scene, and compared them with the intentional memory representations. The visual representations were retained in visual long-term memory even in the flicker paradigm, and were as robust as the intentional memory representations. However, the results indicate that the representations are unavailable for explicitly localizing a scene change, but are available for answering the recognition test. This suggests that coherence theory and visual memory theory are compatible.

Deep Residual Network Predicts Cortical Representation and Organization of Visual Features for Rapid Categorization.

PubMed

Wen, Haiguang; Shi, Junxing; Chen, Wei; Liu, Zhongming

2018-02-28

The brain represents visual objects with topographic cortical patterns. To address how distributed visual representations enable object categorization, we established predictive encoding models based on a deep residual network, and trained them to predict cortical responses to natural movies. Using this predictive model, we mapped human cortical representations to 64,000 visual objects from 80 categories with high throughput and accuracy. Such representations covered both the ventral and dorsal pathways, reflected multiple levels of object features, and preserved semantic relationships between categories. In the entire visual cortex, object representations were organized into three clusters of categories: biological objects, non-biological objects, and background scenes. In a finer scale specific to each cluster, object representations revealed sub-clusters for further categorization. Such hierarchical clustering of category representations was mostly contributed by cortical representations of object features from middle to high levels. In summary, this study demonstrates a useful computational strategy to characterize the cortical organization and representations of visual features for rapid categorization.

The conventionality of pictorial representation in interstellar messages

NASA Astrophysics Data System (ADS)

Vakoch, D. A.

2000-06-01

Pictorial messages have previously been advocated for interstellar communication because such messages are presumed to be capable of presenting information in a non-arbitrary and easily intelligible manner. In contrast to this view, pictorial messages actually represent information in a partially conventional way. This point is demonstrated by examining pictorial representations of human beings from a range of cultures. While such representations may be understood quite readily by individuals familiar with the conventions of a particular culture, to the uninitiated outsider, such representations can be unintelligible. In spite of the partially arbitrary nature of pictorial representation, we may be able to construct messages that would teach extraterrestrial intelligence (ETI) some of the conventions by which we view pictures. One such approach is to pair numerical information about geometrical objects with pictorial representations of the same objects. Problems of conventionality can also be addressed in part through use of (1) multiple representations of the same object, (2) contextual cues, (3) three- and four-dimensional representations and (4) non-visual representations.

Body representation in patients after vascular brain injuries.

PubMed

Razmus, Magdalena

2017-11-01

Neuropsychological literature suggests that body representation is a multidimensional concept consisting of various types of representations. Previous studies have demonstrated dissociations between three types of body representation specified by the kind of data and processes, i.e. body schema, body structural description, and body semantics. The aim of the study was to describe the state of body representation in patients after vascular brain injuries and to provide evidence for the different types of body representation. The question about correlations between body representation deficits and neuropsychological dysfunctions was also investigated. Fifty patients after strokes and 50 control individuals participated in the study. They were examined with tasks referring to dynamic representation of body parts positions, topological body map, and lexical and semantic knowledge about the body. Data analysis showed that vascular brain injuries result in deficits of body representation, which may co-occur with cognitive dysfunctions, but the latter are a possible risk factor for body representation deficits rather than sufficient or imperative requisites for them. The study suggests that types of body representation may be separated on the basis not only of their content, but also of their relation with self. Principal component analysis revealed three factors, which explained over 66% of results variance. The factors, which may be interpreted as types or dimensions of mental model of a body, represent different degrees of connection with self. The results indicate another possibility of body representation types classification, which should be verified in future research.

Hyper-heuristic Evolution of Dispatching Rules: A Comparison of Rule Representations.

PubMed

Branke, Jürgen; Hildebrandt, Torsten; Scholz-Reiter, Bernd

2015-01-01

Dispatching rules are frequently used for real-time, online scheduling in complex manufacturing systems. Design of such rules is usually done by experts in a time consuming trial-and-error process. Recently, evolutionary algorithms have been proposed to automate the design process. There are several possibilities to represent rules for this hyper-heuristic search. Because the representation determines the search neighborhood and the complexity of the rules that can be evolved, a suitable choice of representation is key for a successful evolutionary algorithm. In this paper we empirically compare three different representations, both numeric and symbolic, for automated rule design: A linear combination of attributes, a representation based on artificial neural networks, and a tree representation. Using appropriate evolutionary algorithms (CMA-ES for the neural network and linear representations, genetic programming for the tree representation), we empirically investigate the suitability of each representation in a dynamic stochastic job shop scenario. We also examine the robustness of the evolved dispatching rules against variations in the underlying job shop scenario, and visualize what the rules do, in order to get an intuitive understanding of their inner workings. Results indicate that the tree representation using an improved version of genetic programming gives the best results if many candidate rules can be evaluated, closely followed by the neural network representation that already leads to good results for small to moderate computational budgets. The linear representation is found to be competitive only for extremely small computational budgets.

Reevaluating the two-representation model of numerical magnitude processing.

PubMed

Jiang, Ting; Zhang, Wenfeng; Wen, Wen; Zhu, Haiting; Du, Han; Zhu, Xiangru; Gao, Xuefei; Zhang, Hongchuan; Dong, Qi; Chen, Chuansheng

2016-01-01

One debate in mathematical cognition centers on the single-representation model versus the two-representation model. Using an improved number Stroop paradigm (i.e., systematically manipulating physical size distance), in the present study we tested the predictions of the two models for number magnitude processing. The results supported the single-representation model and, more importantly, explained how a design problem (failure to manipulate physical size distance) and an analytical problem (failure to consider the interaction between congruity and task-irrelevant numerical distance) might have contributed to the evidence used to support the two-representation model. This study, therefore, can help settle the debate between the single-representation and two-representation models.

When Does Changing Representation Improve Problem-Solving Performance?

NASA Technical Reports Server (NTRS)

Holte, Robert; Zimmer, Robert; MacDonald, Alan

1992-01-01

The aim of changing representation is the improvement of problem-solving efficiency. For the most widely studied family of methods of change of representation it is shown that the value of a single parameter, called the expulsion factor, is critical in determining (1) whether the change of representation will improve or degrade problem-solving efficiency and (2) whether the solutions produced using the change of representation will or will not be exponentially longer than the shortest solution. A method of computing the expansion factor for a given change of representation is sketched in general and described in detail for homomorphic changes of representation. The results are illustrated with homomorphic decompositions of the Towers of Hanoi problem.

Students' Understanding of External Representations of the Potassium Ion Channel Protein, Part I: Affordances and Limitations of Ribbon Diagrams, Vines, and Hydrophobic/Polar Representations

ERIC Educational Resources Information Center

Harle, Marissa; Towns, Marcy H.

2012-01-01

Research on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations. This project focuses on students' understanding of three external representations of the potassium ion channel protein. This is part I of a two-part study, which focuses on the affordances and…

Rank, Pay, and Representation of Women on the Faculty at the Urbana-Champaign Campus of the University of Illinois.

ERIC Educational Resources Information Center

Ferber, Marianne; Loeb, Jane

This report presents information on the employment status of women at the Urbana-Champaign campus of the University of Illinois. Discussed are: (1) the representation, rank, and pay of females on the faculty; (2) representation of women in administrative positions; (3) representation of women on the faculty versus representation in the labor…

MODELS FOR THE COMPLEX REPRESENTATIONS OF THE GROUPS \\mathrm{GL}(n,\\,q)

NASA Astrophysics Data System (ADS)

Klyachko, Alexander A.

1984-02-01

The main result of the paper consists in the construction of a model of the full linear group over a finite field, i.e. its representations such that each irreducible representation occurs as a component precisely once. The series of representations thus constructed has the well-known Gel'fand-Graev representation as first term.Bibliography: 12 titles.

Dependency-based Siamese long short-term memory network for learning sentence representations

PubMed Central

Zhu, Wenhao; Ni, Jianyue; Wei, Baogang; Lu, Zhiguo

2018-01-01

Textual representations play an important role in the field of natural language processing (NLP). The efficiency of NLP tasks, such as text comprehension and information extraction, can be significantly improved with proper textual representations. As neural networks are gradually applied to learn the representation of words and phrases, fairly efficient models of learning short text representations have been developed, such as the continuous bag of words (CBOW) and skip-gram models, and they have been extensively employed in a variety of NLP tasks. Because of the complex structure generated by the longer text lengths, such as sentences, algorithms appropriate for learning short textual representations are not applicable for learning long textual representations. One method of learning long textual representations is the Long Short-Term Memory (LSTM) network, which is suitable for processing sequences. However, the standard LSTM does not adequately address the primary sentence structure (subject, predicate and object), which is an important factor for producing appropriate sentence representations. To resolve this issue, this paper proposes the dependency-based LSTM model (D-LSTM). The D-LSTM divides a sentence representation into two parts: a basic component and a supporting component. The D-LSTM uses a pre-trained dependency parser to obtain the primary sentence information and generate supporting components, and it also uses a standard LSTM model to generate the basic sentence components. A weight factor that can adjust the ratio of the basic and supporting components in a sentence is introduced to generate the sentence representation. Compared with the representation learned by the standard LSTM, the sentence representation learned by the D-LSTM contains a greater amount of useful information. The experimental results show that the D-LSTM is superior to the standard LSTM for sentences involving compositional knowledge (SICK) data. PMID:29513748

37 CFR 11.101 - Competence.

Code of Federal Regulations, 2013 CFR

2013-07-01

... competent representation to a client. Competent representation requires the legal, scientific, and technical knowledge, skill, thoroughness and preparation reasonably necessary for the representation. ... COMMERCE REPRESENTATION OF OTHERS BEFORE THE UNITED STATES PATENT AND TRADEMARK OFFICE USPTO Rules of...

37 CFR 11.101 - Competence.

Code of Federal Regulations, 2014 CFR

2014-07-01

... competent representation to a client. Competent representation requires the legal, scientific, and technical knowledge, skill, thoroughness and preparation reasonably necessary for the representation. ... COMMERCE REPRESENTATION OF OTHERS BEFORE THE UNITED STATES PATENT AND TRADEMARK OFFICE USPTO Rules of...

Towards an Effective Theory of Reformulation. Part 1; Semantics

NASA Technical Reports Server (NTRS)

Benjamin, D. Paul

1992-01-01

This paper describes an investigation into the structure of representations of sets of actions, utilizing semigroup theory. The goals of this project are twofold: to shed light on the relationship between tasks and representations, leading to a classification of tasks according to the representations they admit; and to develop techniques for automatically transforming representations so as to improve problem-solving performance. A method is demonstrated for automatically generating serial algorithms for representations whose actions form a finite group. This method is then extended to representations whose actions form a finite inverse semigroup.

Differential involvement of knowledge representation and executive control in episodic memory performance in young and older adults.

PubMed

Bouazzaoui, Badiâa; Fay, Séverine; Taconnat, Laurence; Angel, Lucie; Vanneste, Sandrine; Isingrini, Michel

2013-06-01

Craik and Bialystok (2006, 2008) postulated that examining the evolution of knowledge representation and control processes across the life span could help in understanding age-related cognitive changes. The present study explored the hypothesis that knowledge representation and control processes are differentially involved in the episodic memory performance of young and older adults. Young and older adults were administered a cued-recall task and tests of crystallized knowledge and executive functioning to measure representation and control processes, respectively. Results replicate the classic finding that executive and cued-recall performance decline with age, but crystallized-knowledge performance does not. Factor analysis confirmed the independence of representation and control. Correlation analyses showed that the memory performance of younger adults was correlated with representation but not with control measures, whereas the memory performance of older adults was correlated with both representation and control measures. Regression analyses indicated that the control factor was the main predictor of episodic-memory performance for older adults, with the representation factor adding an independent contribution, but the representation factor was the sole predictor for young adults. This finding supports the view that factors sustaining episodic memory vary from young adulthood to old age; representation was shown to be important throughout adulthood, and control was also important for older adults. The results also indicated that control and representation modulate age-group-related variance in episodic memory.

Representations of control and psychological symptoms in couples dealing with cancer: a dyadic-regulation approach.

PubMed

Karademas, Evangelos C; Giannousi, Zoe

2013-01-01

The aim of this study was to examine the relation between illness representations of personal and treatment control and psychological symptoms (i.e. symptoms of anxiety and depression) in 72 married couples dealing with a recently diagnosed cancer. Patients were first-diagnosed with early stage (45.83%) or metastatic cancer (54.17%). Dyadic responses were examined with the actor-partner interdependence model. Also, in order to examine whether patients and spouses' representations of control moderate the relation of their partners' corresponding representations to psychological symptoms, we used the relevant bootstrapping framework developed by Hayes and Matthes [(2009). Computational procedures for probing interactions in OLS and logistic regression: SPSS and SAS implementations. Behavior Research Methods, 41, 924-936]. Patients' symptoms of anxiety and depression were associated with both partners' representations of control. Chi-square difference tests indicated that actor and partner effects were equal. Spouses' symptoms of anxiety and depression were related only to their own representations. Moreover, spouses' representations of personal control moderated the relation of patients' corresponding representations to depressive symptoms, whereas patients' representations of treatment control moderated the relation of their spouses' corresponding representations to both anxiety and depression. Findings suggest that both partners' representations of control are important for adaptation to illness. Moreover, they indicate that dyadic regulation may be equally important to self-regulation as far as adaptation to illness is concerned.

From phase space to integrable representations and level-rank duality

NASA Astrophysics Data System (ADS)

Chattopadhyay, Arghya; Dutta, Parikshit; Dutta, Suvankar

2018-05-01

We explicitly find representations for different large N phases of Chern-Simons matter theory on S 2 × S 1. These representations are characterised by Young diagrams. We show that no-gap and lower-gap phase of Chern-Simons-matter theory correspond to integrable representations of SU( N) k affine Lie algebra, where as upper-cap phase corresponds to integrable representations of SU( k - N) k affine Lie algebra. We use phase space description of [1] to obtain these representations and argue how putting a cap on eigenvalue distribution forces corresponding representations to be integrable. We also prove that the Young diagrams corresponding to lower-gap and upper-cap representations are related to each other by transposition under level-rank duality. Finally we draw phase space droplets for these phases and show how information about eigenvalue and Young diagram descriptions can be captured in topologies of these droplets in a unified way.

Volta-Based Cells Materials Chemical Multiple Representation to Improve Ability of Student Representation

NASA Astrophysics Data System (ADS)

Helsy, I.; Maryamah; Farida, I.; Ramdhani, M. A.

2017-09-01

This study aimed to describe the application of teaching materials, analyze the increase in the ability of students to connect the three levels of representation and student responses after application of multiple representations based teaching materials chemistry. The method used quasi one-group pretest-posttest design to 71 students. The results showed the application of teaching materials carried 88% with very good category. A significant increase ability to connect the three levels of representation of students after the application of multiple representations based teaching materials chemistry with t-value > t-crit (11.402 > 1.991). Recapitulation N-gain pretest and posttest showed relatively similar for all groups is 0.6 criterion being achievement. Students gave a positive response to the application of multiple representations based teaching materials chemistry. Students agree teaching materials used in teaching chemistry (88%), and agrees teaching materials to provide convenience in connecting the three levels of representation (95%).

Weighted Discriminative Dictionary Learning based on Low-rank Representation

NASA Astrophysics Data System (ADS)

Chang, Heyou; Zheng, Hao

2017-01-01

Low-rank representation has been widely used in the field of pattern classification, especially when both training and testing images are corrupted with large noise. Dictionary plays an important role in low-rank representation. With respect to the semantic dictionary, the optimal representation matrix should be block-diagonal. However, traditional low-rank representation based dictionary learning methods cannot effectively exploit the discriminative information between data and dictionary. To address this problem, this paper proposed weighted discriminative dictionary learning based on low-rank representation, where a weighted representation regularization term is constructed. The regularization associates label information of both training samples and dictionary atoms, and encourages to generate a discriminative representation with class-wise block-diagonal structure, which can further improve the classification performance where both training and testing images are corrupted with large noise. Experimental results demonstrate advantages of the proposed method over the state-of-the-art methods.

Bag of Lines (BoL) for Improved Aerial Scene Representation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sridharan, Harini; Cheriyadat, Anil M.

2014-09-22

Feature representation is a key step in automated visual content interpretation. In this letter, we present a robust feature representation technique, referred to as bag of lines (BoL), for high-resolution aerial scenes. The proposed technique involves extracting and compactly representing low-level line primitives from the scene. The compact scene representation is generated by counting the different types of lines representing various linear structures in the scene. Through extensive experiments, we show that the proposed scene representation is invariant to scale changes and scene conditions and can discriminate urban scene categories accurately. We compare the BoL representation with the popular scalemore » invariant feature transform (SIFT) and Gabor wavelets for their classification and clustering performance on an aerial scene database consisting of images acquired by sensors with different spatial resolutions. The proposed BoL representation outperforms the SIFT- and Gabor-based representations.« less

Generative Representations for Computer-Automated Design Systems

NASA Technical Reports Server (NTRS)

Hornby, Gregory S.

2004-01-01

With the increasing computational power of Computers, software design systems are progressing from being tools for architects and designers to express their ideas to tools capable of creating designs under human guidance. One of the main limitations for these computer-automated design programs is the representation with which they encode designs. If the representation cannot encode a certain design, then the design program cannot produce it. Similarly, a poor representation makes some types of designs extremely unlikely to be created. Here we define generative representations as those representations which can create and reuse organizational units within a design and argue that reuse is necessary for design systems to scale to more complex and interesting designs. To support our argument we describe GENRE, an evolutionary design program that uses both a generative and a non-generative representation, and compare the results of evolving designs with both types of representations.

Effective interactions in a quantum Bose-Bose mixture

NASA Astrophysics Data System (ADS)

Utesov, O. I.; Baglay, M. I.; Andreev, S. V.

2018-05-01

We generalize the Beliaev diagrammatic theory of an interacting spinless Bose-Einstein condensate to the case of a binary mixture. We derive a set of coupled Dyson equations and find analytically the Green's functions of the system. The elementary excitation spectrum consists of two branches, one of which takes the characteristic parabolic form ω ∝p2 in the limit of a spin-independent interaction. We observe renormalization of the magnon mass and the spin-wave velocity due to the Andreev-Bashkin entrainment effect. For a three-dimensional weakly interacting gas the spectrum can be obtained by applying the Bogoliubov transformation to a second-quantized Hamiltonian in which the microscopic two-body potentials in each channel are replaced by the corresponding off-shell scattering amplitudes. The superfluid drag density can be calculated by considering a mixture of phonons and magnons interacting via the effective potentials. We show that this problem is identical to the second-order perturbative treatment of a Bose polaron. In two dimensions the drag contributes to the magnon dispersion already in the first approximation. Our consideration provides a basis for systematic study of emergent phases in quantum degenerate Bose-Bose mixtures.

Anatomy of the magnetic catalysis by renormalization-group method

NASA Astrophysics Data System (ADS)

Hattori, Koichi; Itakura, Kazunori; Ozaki, Sho

2017-12-01

We first examine the scaling argument for a renormalization-group (RG) analysis applied to a system subject to the dimensional reduction in strong magnetic fields, and discuss the fact that a four-Fermi operator of the low-energy excitations is marginal irrespective of the strength of the coupling constant in underlying theories. We then construct a scale-dependent effective four-Fermi interaction as a result of screened photon exchanges at weak coupling, and establish the RG method appropriately including the screening effect, in which the RG evolution from ultraviolet to infrared scales is separated into two stages by the screening-mass scale. Based on a precise agreement between the dynamical mass gaps obtained from the solutions of the RG and Schwinger-Dyson equations, we discuss an equivalence between these two approaches. Focusing on QED and Nambu-Jona-Lasinio model, we clarify how the properties of the interactions manifest themselves in the mass gap, and point out an importance of respecting the intrinsic energy-scale dependences in underlying theories for the determination of the mass gap. These studies are expected to be useful for a diagnosis of the magnetic catalysis in QCD.

Anti-gravity: The key to 21st century physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyes, H.P.

1993-01-01

The masses coupling constants and cosmological parameters obtained using our discrete and combinatorial physics based on discrimination between bit-strings indicate that we can achieve the unification of quantum mechanics with relativity which had become the goal of twentieth century physics. To broaden our case we show that limitations on measurement of the position and velocity of an individual massive particle observed in a colliding beam scattering experiment imply real, rational commutation relations between position and velocity. Prior to this limit being pushed down to quantum effects, the lower bound is set by the available technology, but is otherwise scale invariant.more » Replacing force by force per unit mass and force per unit charge allows us to take over the Feynman-Dyson proof of the Maxwell Equations and extend it to weak gravity. The crossing symmetry of the individual scattering processes when one or more particles are replaced by anti-particles predicts both Coulomb attraction (for charged particles) and a Newtonian repulsion between any particle and its anti-particle. Previous quantum results remain intact, and predict the expected relativistic fine structure and spin dependencies. Experimental confirmation of this anti-gravity prediction would inaugurate the physics of the twenty-first century.« less

Anti-gravity: The key to 21st century physics

NASA Astrophysics Data System (ADS)

Noyes, H. P.

1993-01-01

The masses coupling constants and cosmological parameters obtained using our discrete and combinatorial physics based on discrimination between bit-strings indicate that we can achieve the unification of quantum mechanics with relativity which had become the goal of twentieth century physics. To broaden our case we show that limitations on measurement of the position and velocity of an individual massive particle observed in a colliding beam scattering experiment imply real, rational commutation relations between position and velocity. Prior to this limit being pushed down to quantum effects, the lower bound is set by the available technology, but is otherwise scale invariant. Replacing force by force per unit mass and force per unit charge allows us to take over the Feynman-Dyson proof of the Maxwell Equations and extend it to weak gravity. The crossing symmetry of the individual scattering processes when one or more particles are replaced by anti-particles predicts both Coulomb attraction (for charged particles) and a Newtonian repulsion between any particle and its anti-particle. Previous quantum results remain intact, and predict the expected relativistic fine structure and spin dependencies. Experimental confirmation of this anti-gravity prediction would inaugurate the physics of the twenty-first century.

Quantum chaos for nonstandard symmetry classes in the Feingold-Peres model of coupled tops

NASA Astrophysics Data System (ADS)

Fan, Yiyun; Gnutzmann, Sven; Liang, Yuqi

2017-12-01

We consider two coupled quantum tops with angular momentum vectors L and M . The coupling Hamiltonian defines the Feingold-Peres model, which is a known paradigm of quantum chaos. We show that this model has a nonstandard symmetry with respect to the Altland-Zirnbauer tenfold symmetry classification of quantum systems, which extends the well-known threefold way of Wigner and Dyson (referred to as "standard" symmetry classes here). We identify the nonstandard symmetry classes BD I0 (chiral orthogonal class with no zero modes), BD I1 (chiral orthogonal class with one zero mode), and C I (antichiral orthogonal class) as well as the standard symmetry class A I (orthogonal class). We numerically analyze the specific spectral quantum signatures of chaos related to the nonstandard symmetries. In the microscopic density of states and in the distribution of the lowest positive energy eigenvalue, we show that the Feingold-Peres model follows the predictions of the Gaussian ensembles of random-matrix theory in the appropriate symmetry class if the corresponding classical dynamics is chaotic. In a crossover to mixed and near-integrable classical dynamics, we show that these signatures disappear or strongly change.

Convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation and rate constants: Case study of the spin-boson model.

PubMed

Xu, Meng; Yan, Yaming; Liu, Yanying; Shi, Qiang

2018-04-28

The Nakajima-Zwanzig generalized master equation provides a formally exact framework to simulate quantum dynamics in condensed phases. Yet, the exact memory kernel is hard to obtain and calculations based on perturbative expansions are often employed. By using the spin-boson model as an example, we assess the convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation. The exact memory kernels are calculated by combining the hierarchical equation of motion approach and the Dyson expansion of the exact memory kernel. High order expansions of the memory kernels are obtained by extending our previous work to calculate perturbative expansions of open system quantum dynamics [M. Xu et al., J. Chem. Phys. 146, 064102 (2017)]. It is found that the high order expansions do not necessarily converge in certain parameter regimes where the exact kernel show a long memory time, especially in cases of slow bath, weak system-bath coupling, and low temperature. Effectiveness of the Padé and Landau-Zener resummation approaches is tested, and the convergence of higher order rate constants beyond Fermi's golden rule is investigated.

Convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation and rate constants: Case study of the spin-boson model

NASA Astrophysics Data System (ADS)

Xu, Meng; Yan, Yaming; Liu, Yanying; Shi, Qiang

2018-04-01

The Nakajima-Zwanzig generalized master equation provides a formally exact framework to simulate quantum dynamics in condensed phases. Yet, the exact memory kernel is hard to obtain and calculations based on perturbative expansions are often employed. By using the spin-boson model as an example, we assess the convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation. The exact memory kernels are calculated by combining the hierarchical equation of motion approach and the Dyson expansion of the exact memory kernel. High order expansions of the memory kernels are obtained by extending our previous work to calculate perturbative expansions of open system quantum dynamics [M. Xu et al., J. Chem. Phys. 146, 064102 (2017)]. It is found that the high order expansions do not necessarily converge in certain parameter regimes where the exact kernel show a long memory time, especially in cases of slow bath, weak system-bath coupling, and low temperature. Effectiveness of the Padé and Landau-Zener resummation approaches is tested, and the convergence of higher order rate constants beyond Fermi's golden rule is investigated.

the Ĝ infrared search for extraterrestrial civilizations with large energy supplies. II. Framework, strategy, and first result

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, J. T.; Griffith, R. L.; Sigurdsson, S.

We describe the framework and strategy of the Ĝ infrared search for extraterrestrial civilizations with large energy supplies, which will use the wide-field infrared surveys of WISE and Spitzer to search for these civilizations' waste heat. We develop a formalism for translating mid-infrared photometry into quantitative upper limits on extraterrestrial energy supplies. We discuss the likely sources of false positives, how dust can and will contaminate our search, and prospects for distinguishing dust from alien waste heat. We argue that galaxy-spanning civilizations may be easier to distinguish from natural sources than circumstellar civilizations (i.e., Dyson spheres), although GAIA will significantlymore » improve our capability to identify the latter. We present a zeroth order null result of our search based on the WISE all-sky catalog: we show, for the first time, that Kardashev Type III civilizations (as Kardashev originally defined them) are very rare in the local universe. More sophisticated searches can extend our methodology to smaller waste heat luminosities, and potentially entirely rule out (or detect) both Kardashev Type III civilizations and new physics that allows for unlimited 'free' energy generation.« less

Electronic transport close to semi-infinite 2D systems and their interfaces

NASA Astrophysics Data System (ADS)

Xia, Fanbing; Wang, Jian; Jian Wang's research Group Team

Transport properties of 2D materials especially close to their boundary has received much attention after the successful fabrication of Graphene. While most previous work is devoted to the conventional lead-device-lead setup with a finite size center area, this project investigates real space transport properties of infinite and semi-infinite 2D systems under the framework of Non-equilibrium Green's function. The commonly used method of calculating Green's function by inverting matrices in the real space can be unstable in dealing with large systems as sometimes it gives non-converging result. By transforming from the real space to momentum space, the author managed to replace the matrix inverting process by Brillouin Zone integral which can be greatly simplified by the application of contour integral. Combining this methodology with Dyson equations, we are able to calculate transport properties of semi-infinite graphene close to its zigzag boundary and its combination with other material including s-wave superconductor. Interference pattern of transmitted and reflected electrons, Graphene lensing effects and difference between Specular Andreev reflection and normal Andreev reflection are verified. We also generalize how to apply this method to a broad range of 2D materials. The University of Hong Kong.

Metric adjusted skew information

PubMed Central

Hansen, Frank

2008-01-01

We extend the concept of Wigner–Yanase–Dyson skew information to something we call “metric adjusted skew information” (of a state with respect to a conserved observable). This “skew information” is intended to be a non-negative quantity bounded by the variance (of an observable in a state) that vanishes for observables commuting with the state. We show that the skew information is a convex function on the manifold of states. It also satisfies other requirements, proposed by Wigner and Yanase, for an effective measure-of-information content of a state relative to a conserved observable. We establish a connection between the geometrical formulation of quantum statistics as proposed by Chentsov and Morozova and measures of quantum information as introduced by Wigner and Yanase and extended in this article. We show that the set of normalized Morozova–Chentsov functions describing the possible quantum statistics is a Bauer simplex and determine its extreme points. We determine a particularly simple skew information, the “λ-skew information,” parametrized by a λ ∈ (0, 1], and show that the convex cone this family generates coincides with the set of all metric adjusted skew informations. PMID:18635683

A systematic approach to sketch Bethe-Salpeter equation

NASA Astrophysics Data System (ADS)

Qin, Si-xue

2016-03-01

To study meson properties, one needs to solve the gap equation for the quark propagator and the Bethe-Salpeter (BS) equation for the meson wavefunction, self-consistently. The gluon propagator, the quark-gluon vertex, and the quark-anti-quark scattering kernel are key pieces to solve those equations. Predicted by lattice-QCD and Dyson-Schwinger analyses of QCD's gauge sector, gluons are non-perturbatively massive. In the matter sector, the modeled gluon propagator which can produce a veracious description of meson properties needs to possess a mass scale, accordingly. Solving the well-known longitudinal Ward-Green-Takahashi identities (WGTIs) and the less-known transverse counterparts together, one obtains a nontrivial solution which can shed light on the structure of the quark-gluon vertex. It is highlighted that the phenomenologically proposed anomalous chromomagnetic moment (ACM) vertex originates from the QCD Lagrangian symmetries and its strength is proportional to the magnitude of dynamical chiral symmetry breaking (DCSB). The color-singlet vector and axial-vector WGTIs can relate the BS kernel and the dressed quark-gluon vertex to each other. Using the relation, one can truncate the gap equation and the BS equation, systematically, without violating crucial symmetries, e.g., gauge symmetry and chiral symmetry.

Distribution of Schmidt-like eigenvalues for Gaussian ensembles of the random matrix theory

NASA Astrophysics Data System (ADS)

Pato, Mauricio P.; Oshanin, Gleb

2013-03-01

We study the probability distribution function P(β)n(w) of the Schmidt-like random variable w = x21/(∑j = 1nx2j/n), where xj, (j = 1, 2, …, n), are unordered eigenvalues of a given n × n β-Gaussian random matrix, β being the Dyson symmetry index. This variable, by definition, can be considered as a measure of how any individual (randomly chosen) eigenvalue deviates from the arithmetic mean value of all eigenvalues of a given random matrix, and its distribution is calculated with respect to the ensemble of such β-Gaussian random matrices. We show that in the asymptotic limit n → ∞ and for arbitrary β the distribution P(β)n(w) converges to the Marčenko-Pastur form, i.e. is defined as P_{n}^{( \\beta )}(w) \\sim \\sqrt{(4 - w)/w} for w ∈ [0, 4] and equals zero outside of the support, despite the fact that formally w is defined on the interval [0, n]. Furthermore, for Gaussian unitary ensembles (β = 2) we present exact explicit expressions for P(β = 2)n(w) which are valid for arbitrary n and analyse their behaviour.

Asymptotics for the Fredholm determinant of the sine kernel on a union of intervals

NASA Astrophysics Data System (ADS)

Widom, Harold

1995-07-01

In the bulk scaling limit of the Gaussian Unitary Ensemble of hermitian matrices the probability that an interval of length s contains no eigenvalues is the Fredholm determinant of the sine kernel{sin (x - y)}/{π (x - y)} over this interval. A formal asymptotic expansion for the determinant as s tends to infinity was obtained by Dyson. In this paper we replace a single interval of length s by sJ, where J is a union of m intervals and present a proof of the asymptotics up to second order. The logarithmic derivative with respect to s of the determinant equals a constant (expressible in terms of hyperelliptic integrals) times s, plus a bounded oscillatory function of s (zero if m=1, periodic if m=2, and in general expressible in terms of the solution of a Jacobi inversion problem), plus o(1). Also determined are the asymptotics of the trace of the resolvent operator, which is the ratio in the same model of the probability that the set contains exactly one eigenvalue to the probability that it contains none. The proofs use ideas from orthogonal polynomial theory.

Quantum chaos for nonstandard symmetry classes in the Feingold-Peres model of coupled tops.

PubMed

Fan, Yiyun; Gnutzmann, Sven; Liang, Yuqi

2017-12-01

We consider two coupled quantum tops with angular momentum vectors L and M. The coupling Hamiltonian defines the Feingold-Peres model, which is a known paradigm of quantum chaos. We show that this model has a nonstandard symmetry with respect to the Altland-Zirnbauer tenfold symmetry classification of quantum systems, which extends the well-known threefold way of Wigner and Dyson (referred to as "standard" symmetry classes here). We identify the nonstandard symmetry classes BDI_{0} (chiral orthogonal class with no zero modes), BDI_{1} (chiral orthogonal class with one zero mode), and CI (antichiral orthogonal class) as well as the standard symmetry class AI (orthogonal class). We numerically analyze the specific spectral quantum signatures of chaos related to the nonstandard symmetries. In the microscopic density of states and in the distribution of the lowest positive energy eigenvalue, we show that the Feingold-Peres model follows the predictions of the Gaussian ensembles of random-matrix theory in the appropriate symmetry class if the corresponding classical dynamics is chaotic. In a crossover to mixed and near-integrable classical dynamics, we show that these signatures disappear or strongly change.

Hydrostatic equilibrium of stars without electroneutrality constraint

NASA Astrophysics Data System (ADS)

Krivoruchenko, M. I.; Nadyozhin, D. K.; Yudin, A. V.

2018-04-01

The general solution of hydrostatic equilibrium equations for a two-component fluid of ions and electrons without a local electroneutrality constraint is found in the framework of Newtonian gravity theory. In agreement with the Poincaré theorem on analyticity and in the context of Dyson's argument, the general solution is demonstrated to possess a fixed (essential) singularity in the gravitational constant G at G =0 . The regular component of the general solution can be determined by perturbation theory in G starting from a locally neutral solution. The nonperturbative component obtained using the method of Wentzel, Kramers and Brillouin is exponentially small in the inner layers of the star and grows rapidly in the outward direction. Near the surface of the star, both components are comparable in magnitude, and their nonlinear interplay determines the properties of an electro- or ionosphere. The stellar charge varies within the limits of -0.1 to 150 C per solar mass. The properties of electro- and ionospheres are exponentially sensitive to variations of the fluid densities in the central regions of the star. The general solutions of two exactly solvable stellar models without a local electroneutrality constraint are also presented.

The Ĝ Infrared Search for Extraterrestrial Civilizations with Large Energy Supplies. II. Framework, Strategy, and First Result

NASA Astrophysics Data System (ADS)

Wright, J. T.; Griffith, R. L.; Sigurdsson, S.; Povich, M. S.; Mullan, B.

2014-09-01

We describe the framework and strategy of the Ĝ infrared search for extraterrestrial civilizations with large energy supplies, which will use the wide-field infrared surveys of WISE and Spitzer to search for these civilizations' waste heat. We develop a formalism for translating mid-infrared photometry into quantitative upper limits on extraterrestrial energy supplies. We discuss the likely sources of false positives, how dust can and will contaminate our search, and prospects for distinguishing dust from alien waste heat. We argue that galaxy-spanning civilizations may be easier to distinguish from natural sources than circumstellar civilizations (i.e., Dyson spheres), although GAIA will significantly improve our capability to identify the latter. We present a zeroth order null result of our search based on the WISE all-sky catalog: we show, for the first time, that Kardashev Type III civilizations (as Kardashev originally defined them) are very rare in the local universe. More sophisticated searches can extend our methodology to smaller waste heat luminosities, and potentially entirely rule out (or detect) both Kardashev Type III civilizations and new physics that allows for unlimited "free" energy generation.

STM images and STS for a rectangular quantum corral constructed with δ-function barriers and the effect of an adsorbed atom on STM images and STS

NASA Astrophysics Data System (ADS)

Mitsuoka, Shigenori; Tamura, Akira

2012-04-01

Assuming that an electron confined by double δ-function barriers is in a quasi-stationary state, we derived eigenfunctions and eigenenergies of the electron. Applying this point of view to the electron confined in a rectangular quantum corral (QC), we obtained scanning tunneling microscopic (STM) images and scanning tunneling spectrum (STS). Our results are consistent with experimental ones, which confirms validity of the present model. Comparing with the treatment in which the corral potential is chosen to be of square-barrier type, the present treatment has an advantage that the eigenvalue equations are simple and the number of parameters that specify the potential barrier is only one except the bottom of the potential well. On the basis of a Dyson equation for the Green function we calculated STM images and STS of the QC having an adsorbed atom inside. Our results are consistent with experimental STM images and STS. In contrast to a previous viewpoint that the STS profile is reversed with that of the empty QC, we concluded the STS peaks of the adsorbed QC are shifted downward from those of the empty QC.

Zero-Determinant Strategies in Iterated Public Goods Game

PubMed Central

Pan, Liming; Hao, Dong; Rong, Zhihai; Zhou, Tao

2015-01-01

Recently, Press and Dyson have proposed a new class of probabilistic and conditional strategies for the two-player iterated Prisoner’s Dilemma, so-called zero-determinant strategies. A player adopting zero-determinant strategies is able to pin the expected payoff of the opponents or to enforce a linear relationship between his own payoff and the opponents’ payoff, in a unilateral way. This paper considers zero-determinant strategies in the iterated public goods game, a representative multi-player game where in each round each player will choose whether or not to put his tokens into a public pot, and the tokens in this pot are multiplied by a factor larger than one and then evenly divided among all players. The analytical and numerical results exhibit a similar yet different scenario to the case of two-player games: (i) with small number of players or a small multiplication factor, a player is able to unilaterally pin the expected total payoff of all other players; (ii) a player is able to set the ratio between his payoff and the total payoff of all other players, but this ratio is limited by an upper bound if the multiplication factor exceeds a threshold that depends on the number of players. PMID:26293589

Stopping dynamics of ions passing through correlated honeycomb clusters

NASA Astrophysics Data System (ADS)

Balzer, Karsten; Schlünzen, Niclas; Bonitz, Michael

2016-12-01

A combined nonequilibrium Green functions-Ehrenfest dynamics approach is developed that allows for a time-dependent study of the energy loss of a charged particle penetrating a strongly correlated system at zero and finite temperatures. Numerical results are presented for finite inhomogeneous two-dimensional Fermi-Hubbard models, where the many-electron dynamics in the target are treated fully quantum mechanically and the motion of the projectile is treated classically. The simulations are based on the solution of the two-time Dyson (Keldysh-Kadanoff-Baym) equations using the second-order Born, third-order, and T -matrix approximations of the self-energy. As application, we consider protons and helium nuclei with a kinetic energy between 1 and 500 keV/u passing through planar fragments of the two-dimensional honeycomb lattice and, in particular, examine the influence of electron-electron correlations on the energy exchange between projectile and electron system. We investigate the time dependence of the projectile's kinetic energy (stopping power), the electron density, the double occupancy, and the photoemission spectrum. Finally, we show that, for a suitable choice of the Hubbard model parameters, the results for the stopping power are in fair agreement with ab initio simulations for particle irradiation of single-layer graphene.

Impact of WWI on Relativity and Other Sciences

NASA Astrophysics Data System (ADS)

Trimble, Virginia

2015-04-01

Custom calls WWII the physicists' war (radar, nuclear bombs, rockets) and WWI the chemists' war (nitrogen fixation and synthetic fuels as well as poison gases). In fact both wars affected all of science profoundly. For us, hostilities began with the capture of Erwin Freundlich's German eclipse expedition to the Crrimea in August 1914. Curioiusly they had gone there to measure deflection of starlight be the sun at the half-of-GR level predicted earlier by Einstein. The end came in 1919 with the founding of the IAU (Central Powers strictly excluded; indeed Germany did not join until after WWII) and the Eddington-Dyson-Crommelin eclipse expedition that did record the deflection. In between were many deaths (Moseley and Karl Schwarzschild perhaps best know), turning of observatory optical shops to making binoculars, periscopes, etc, and twisting of careers (including probably the origin of the Hubble-Shapley enmity, when the former volunteered and the latter went directly to a job at Mt. Wilson; Lemaitre is another interesting case). There will be a small prize for the first person to identify the gentleman who refereed my second thesis paper, who served the full four years, partly in the trenches, on the German side.

Elimination des constantes arbitraires dans la theorie relativiste des quanta [85

NASA Astrophysics Data System (ADS)

This article shows how the influence of the undetermined constants in the integral theory of collisions1)2)3)4) can be avoided. A rule is given by which the probability amplitudes (5[F]-matrix) may be calculated in terms of a given local action. The procedure of the integral method differs essentially from the differential method employed by Tomonaga6), Schwikger5), FÅÕímaí7) and Dyson8) in that the two sorts of diverging terms occuring in the formal solution of a Schroedinqer equation are avoided. These two divergencies are: 1) the well known «.self energy» divergencies which have been since corrected by methods of regularization (Rivikr1), Pattli and Villaks9)); 2) the more serious boundary divergencies (Stueckelberg4)) due to the sharp spatio-temporal limitation of the space-time region of evolution V in which the collisions occur. The convergent parts (anomalous g-factor of the electron and the Lamb-Rethekford shift) obtained by Schwinger are, in the present theory, the boundary independent amplitudes in fourth approximation. Üp to this approximation the rule eliminates the arbitrary constants from all conservative processes.

Reliability in the location of hindlimb motor representations in Fischer-344 rats: laboratory investigation.

PubMed

Frost, Shawn B; Iliakova, Maria; Dunham, Caleb; Barbay, Scott; Arnold, Paul; Nudo, Randolph J

2013-08-01

The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for reliably locating cortical motor representations of the hindlimb. Intracortical microstimulation techniques were used to derive detailed maps of the hindlimb motor representations in 6 adult Fischer-344 rats. The organization of the hindlimb movement representation, while variable across individual rats in topographic detail, displayed several commonalities. The hindlimb representation was positioned posterior to the forelimb motor representation and posterolateral to the motor trunk representation. The areal extent of the hindlimb representation across the cortical surface averaged 2.00 ± 0.50 mm(2). Superimposing individual maps revealed an overlapping area measuring 0.35 mm(2), indicating that the location of the hindlimb representation can be predicted reliably based on stereotactic coordinates. Across the sample of rats, the hindlimb representation was found 1.25-3.75 mm posterior to the bregma, with an average center location approximately 2.6 mm posterior to the bregma. Likewise, the hindlimb representation was found 1-3.25 mm lateral to the midline, with an average center location approximately 2 mm lateral to the midline. The location of the cortical hindlimb motor representation in Fischer-344 rats can be reliably located based on its stereotactic position posterior to the bregma and lateral to the longitudinal skull suture at midline. The ability to accurately predict the cortical localization of functional hindlimb territories in a rodent model is important, as such animal models are being increasingly used in the development of brain-computer interfaces for restoration of function after spinal cord injury.

Reliability in the Location of Hindlimb Motor Representations in Fischer-344 Rats

PubMed Central

Frost, Shawn B.; Iliakova, Maria; Dunham, Caleb; Barbay, Scott; Arnold, Paul; Nudo, Randolph J.

2014-01-01

Object The purpose of the present study was to determine the feasibility of using a common laboratory rat strain for locating cortical motor representations of the hindlimb reliably. Methods Intracortical Microstimulation (ICMS) techniques were used to derive detailed maps of the hindlimb motor representations in six adult Fischer-344 rats. Results The organization of the hindlimb movement representation, while variable across individuals in topographic detail, displayed several commonalities. The hindlimb representation was positioned posterior to the forelimb motor representation and postero-lateral to the motor trunk representation. The areal extent of the hindlimb representation across the cortical surface averaged 2.00 +/− 0.50 mm2. Superimposing individual maps revealed an overlapping area measuring 0.35 mm2, indicating that the location of the hindlimb representation can be predicted reliably based on stereotactic coordinates. Across the sample of rats, the hindlimb representation was found 1.25–3.75 mm posterior to Bregma, with an average center location ~ 2.6 mm posterior to Bregma. Likewise, the hindlimb representation was found 1–3.25 mm lateral to the midline, with an average center location ~ 2 mm lateral to midline. Conclusions The location of the cortical hindlimb motor representation in Fischer-344 rats can be reliably located based on its stereotactic position posterior to Bregma and lateral to the longitudinal skull suture at midline. The ability to accurately predict the cortical localization of functional hindlimb territories in a rodent model is important, as such animal models are being used increasingly in the development of brain-computer interfaces for restoration of function after spinal cord injury. PMID:23725395

The heterogeneity of mental representation: Ending the imagery debate.

PubMed

Pearson, Joel; Kosslyn, Stephen M

2015-08-18

The possible ways that information can be represented mentally have been discussed often over the past thousand years. However, this issue could not be addressed rigorously until late in the 20th century. Initial empirical findings spurred a debate about the heterogeneity of mental representation: Is all information stored in propositional, language-like, symbolic internal representations, or can humans use at least two different types of representations (and possibly many more)? Here, in historical context, we describe recent evidence that humans do not always rely on propositional internal representations but, instead, can also rely on at least one other format: depictive representation. We propose that the debate should now move on to characterizing all of the different forms of human mental representation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mozrzymas, Marek; Horodecki, Michał; Studziński, Michał

We consider the structure of algebra of operators, acting in n-fold tensor product space, which are partially transposed on the last term. Using purely algebraical methods we show that this algebra is semi-simple and then, considering its regular representation, we derive basic properties of the algebra. In particular, we describe all irreducible representations of the algebra of partially transposed operators and derive expressions for matrix elements of the representations. It appears that there are two kinds of irreducible representations of the algebra. The first one is strictly connected with the representations of the group S(n − 1) induced by irreduciblemore » representations of the group S(n − 2). The second kind is structurally connected with irreducible representations of the group S(n − 1)« less

Representation in Memory.

ERIC Educational Resources Information Center

Rumelhart, David E.; Norman, Donald A.

This paper reviews work on the representation of knowledge from within psychology and artificial intelligence. The work covers the nature of representation, the distinction between the represented world and the representing world, and significant issues concerned with propositional, analogical, and superpositional representations. Specific topics…

Behaviorally Relevant Abstract Object Identity Representation in the Human Parietal Cortex

PubMed Central

Jeong, Su Keun

2016-01-01

The representation of object identity is fundamental to human vision. Using fMRI and multivoxel pattern analysis, here we report the representation of highly abstract object identity information in human parietal cortex. Specifically, in superior intraparietal sulcus (IPS), a region previously shown to track visual short-term memory capacity, we found object identity representations for famous faces varying freely in viewpoint, hairstyle, facial expression, and age; and for well known cars embedded in different scenes, and shown from different viewpoints and sizes. Critically, these parietal identity representations were behaviorally relevant as they closely tracked the perceived face-identity similarity obtained in a behavioral task. Meanwhile, the task-activated regions in prefrontal and parietal cortices (excluding superior IPS) did not exhibit such abstract object identity representations. Unlike previous studies, we also failed to observe identity representations in posterior ventral and lateral visual object-processing regions, likely due to the greater amount of identity abstraction demanded by our stimulus manipulation here. Our MRI slice coverage precluded us from examining identity representation in anterior temporal lobe, a likely region for the computing of identity information in the ventral region. Overall, we show that human parietal cortex, part of the dorsal visual processing pathway, is capable of holding abstract and complex visual representations that are behaviorally relevant. These results argue against a “content-poor” view of the role of parietal cortex in attention. Instead, the human parietal cortex seems to be “content rich” and capable of directly participating in goal-driven visual information representation in the brain. SIGNIFICANCE STATEMENT The representation of object identity (including faces) is fundamental to human vision and shapes how we interact with the world. Although object representation has traditionally been associated with human occipital and temporal cortices, here we show, by measuring fMRI response patterns, that a region in the human parietal cortex can robustly represent task-relevant object identities. These representations are invariant to changes in a host of visual features, such as viewpoint, and reflect an abstract level of representation that has not previously been reported in the human parietal cortex. Critically, these neural representations are behaviorally relevant as they closely track the perceived object identities. Human parietal cortex thus participates in the moment-to-moment goal-directed visual information representation in the brain. PMID:26843642

Representation control increases task efficiency in complex graphical representations.

PubMed

Moritz, Julia; Meyerhoff, Hauke S; Meyer-Dernbecher, Claudia; Schwan, Stephan

2018-01-01

In complex graphical representations, the relevant information for a specific task is often distributed across multiple spatial locations. In such situations, understanding the representation requires internal transformation processes in order to extract the relevant information. However, digital technology enables observers to alter the spatial arrangement of depicted information and therefore to offload the transformation processes. The objective of this study was to investigate the use of such a representation control (i.e. the users' option to decide how information should be displayed) in order to accomplish an information extraction task in terms of solution time and accuracy. In the representation control condition, the participants were allowed to reorganize the graphical representation and reduce information density. In the control condition, no interactive features were offered. We observed that participants in the representation control condition solved tasks that required reorganization of the maps faster and more accurate than participants without representation control. The present findings demonstrate how processes of cognitive offloading, spatial contiguity, and information coherence interact in knowledge media intended for broad and diverse groups of recipients.

Protein Sub-Nuclear Localization Based on Effective Fusion Representations and Dimension Reduction Algorithm LDA.

PubMed

Wang, Shunfang; Liu, Shuhui

2015-12-19

An effective representation of a protein sequence plays a crucial role in protein sub-nuclear localization. The existing representations, such as dipeptide composition (DipC), pseudo-amino acid composition (PseAAC) and position specific scoring matrix (PSSM), are insufficient to represent protein sequence due to their single perspectives. Thus, this paper proposes two fusion feature representations of DipPSSM and PseAAPSSM to integrate PSSM with DipC and PseAAC, respectively. When constructing each fusion representation, we introduce the balance factors to value the importance of its components. The optimal values of the balance factors are sought by genetic algorithm. Due to the high dimensionality of the proposed representations, linear discriminant analysis (LDA) is used to find its important low dimensional structure, which is essential for classification and location prediction. The numerical experiments on two public datasets with KNN classifier and cross-validation tests showed that in terms of the common indexes of sensitivity, specificity, accuracy and MCC, the proposed fusing representations outperform the traditional representations in protein sub-nuclear localization, and the representation treated by LDA outperforms the untreated one.

Interparental conflict and adolescents' self-representations: The role of emotional insecurity.

PubMed

Silva, Carla Sofia; Calheiros, Maria Manuela; Carvalho, Helena

2016-10-01

Adolescents' signs of emotional insecurity in the context of interparental conflict (IC) - emotional reactivity, internal representations (i.e., constructive/destructive; spillover) and behavioral responses (i.e., withdrawal; inhibition; involvement) - were examined as mediators in the relation between IC and adolescents' self-representations. Self-reported measures were filled out by 221 Portuguese adolescents (59.3% girls; Mage = 12.91), attending public elementary and secondary schools. IC predicted less favorable self-representations. Adolescents' emotional reactivity and withdrawal mediated the relation between IC and emotional and physical appearance self-representations, while conflict spillover representations and constructive family representations mediated associations between IC and instrumental self-representations. This study emphasizes the importance of interparental conflict and adolescent emotional insecurity in the construction of their self-representations, having important theoretical and practical implications. It highlights the value of analyzing the specific role of several emotional insecurity dimensions, and informs practitioners' work aimed at promoting constructive conflict and adaptive emotional regulation skills. Copyright © 2016 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

Narrative, memory and social representations: a conversation between history and social psychology.

PubMed

Jovchelovitch, Sandra

2012-12-01

This paper explores relations between narrative, memory and social representations by examining how social representations express the ways in which communities deal with the historical past. Drawing on a case study of social representations of the Brazilian public sphere, it shows how a specific narrative of origins re-invents history as a useful mythological resource for defending identity, building inter-group solidarity and maintaining social cohesion. Produced by a time-travelling dialogue between multiple sources, this historical narrative is functional both to transform, to stabilise and give resilience to specific social representations of public life. The Brazilian case shows that historical narratives, which tend to be considered as part of the stable core of representational fields, are neither homogenous nor consensual but open polyphasic platforms for the construction of alternative, often contradictory, representations. These representations do not go away because they are ever changing and situated, recruit multiple ways of thinking and fulfil functions of identity, inter-group solidarity and social cohesion. In the disjunction between historiography and the past as social representation are the challenges and opportunities for the dialogue between historians and social psychologists.

Representation control increases task efficiency in complex graphical representations

PubMed Central

Meyerhoff, Hauke S.; Meyer-Dernbecher, Claudia; Schwan, Stephan

2018-01-01

In complex graphical representations, the relevant information for a specific task is often distributed across multiple spatial locations. In such situations, understanding the representation requires internal transformation processes in order to extract the relevant information. However, digital technology enables observers to alter the spatial arrangement of depicted information and therefore to offload the transformation processes. The objective of this study was to investigate the use of such a representation control (i.e. the users' option to decide how information should be displayed) in order to accomplish an information extraction task in terms of solution time and accuracy. In the representation control condition, the participants were allowed to reorganize the graphical representation and reduce information density. In the control condition, no interactive features were offered. We observed that participants in the representation control condition solved tasks that required reorganization of the maps faster and more accurate than participants without representation control. The present findings demonstrate how processes of cognitive offloading, spatial contiguity, and information coherence interact in knowledge media intended for broad and diverse groups of recipients. PMID:29698443

Protein Sub-Nuclear Localization Based on Effective Fusion Representations and Dimension Reduction Algorithm LDA

PubMed Central

Wang, Shunfang; Liu, Shuhui

2015-01-01

An effective representation of a protein sequence plays a crucial role in protein sub-nuclear localization. The existing representations, such as dipeptide composition (DipC), pseudo-amino acid composition (PseAAC) and position specific scoring matrix (PSSM), are insufficient to represent protein sequence due to their single perspectives. Thus, this paper proposes two fusion feature representations of DipPSSM and PseAAPSSM to integrate PSSM with DipC and PseAAC, respectively. When constructing each fusion representation, we introduce the balance factors to value the importance of its components. The optimal values of the balance factors are sought by genetic algorithm. Due to the high dimensionality of the proposed representations, linear discriminant analysis (LDA) is used to find its important low dimensional structure, which is essential for classification and location prediction. The numerical experiments on two public datasets with KNN classifier and cross-validation tests showed that in terms of the common indexes of sensitivity, specificity, accuracy and MCC, the proposed fusing representations outperform the traditional representations in protein sub-nuclear localization, and the representation treated by LDA outperforms the untreated one. PMID:26703574

Facilitating Mathematical Practices through Visual Representations

ERIC Educational Resources Information Center

Murata, Aki; Stewart, Chana

2017-01-01

Effective use of mathematical representation is key to supporting student learning. In "Principles to Actions: Ensuring Mathematical Success for All" (NCTM 2014), "use and connect mathematical representations" is one of the effective Mathematics Teaching Practices. By using different representations, students examine concepts…

Irreducible representations of finitely generated nilpotent groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beloshapka, I V; Gorchinskiy, S O

2016-01-31

We prove that irreducible complex representations of finitely generated nilpotent groups are monomial if and only if they have finite weight, which was conjectured by Parshin. Note that we consider (possibly infinite-dimensional) representations without any topological structure. In addition, we prove that for certain induced representations, irreducibility is implied by Schur irreducibility. Both results are obtained in a more general form for representations over an arbitrary field. Bibliography: 21 titles.

Cuntz-Krieger algebras representations from orbits of interval maps

NASA Astrophysics Data System (ADS)

Correia Ramos, C.; Martins, Nuno; Pinto, Paulo R.; Sousa Ramos, J.

2008-05-01

Let f be an expansive Markov interval map with finite transition matrix Af. Then for every point, we yield an irreducible representation of the Cuntz-Krieger algebra and show that two such representations are unitarily equivalent if and only if the points belong to the same generalized orbit. The restriction of each representation to the gauge part of is decomposed into irreducible representations, according to the decomposition of the orbit.

Motor memory is encoded as a gain-field combination of intrinsic and extrinsic action representations.

PubMed

Brayanov, Jordan B; Press, Daniel Z; Smith, Maurice A

2012-10-24

Actions can be planned in either an intrinsic (body-based) reference frame or an extrinsic (world-based) frame, and understanding how the internal representations associated with these frames contribute to the learning of motor actions is a key issue in motor control. We studied the internal representation of this learning in human subjects by analyzing generalization patterns across an array of different movement directions and workspaces after training a visuomotor rotation in a single movement direction in one workspace. This provided a dense sampling of the generalization function across intrinsic and extrinsic reference frames, which allowed us to dissociate intrinsic and extrinsic representations and determine the manner in which they contributed to the motor memory for a trained action. A first experiment showed that the generalization pattern reflected a memory that was intermediate between intrinsic and extrinsic representations. A second experiment showed that this intermediate representation could not arise from separate intrinsic and extrinsic learning. Instead, we find that the representation of learning is based on a gain-field combination of local representations in intrinsic and extrinsic coordinates. This gain-field representation generalizes between actions by effectively computing similarity based on the (Mahalanobis) distance across intrinsic and extrinsic coordinates and is in line with neural recordings showing mixed intrinsic-extrinsic representations in motor and parietal cortices.

A single-sided representation for the homogeneous Green's function of a unified scalar wave equation.

PubMed

Wapenaar, Kees

2017-06-01

A unified scalar wave equation is formulated, which covers three-dimensional (3D) acoustic waves, 2D horizontally-polarised shear waves, 2D transverse-electric EM waves, 2D transverse-magnetic EM waves, 3D quantum-mechanical waves and 2D flexural waves. The homogeneous Green's function of this wave equation is a combination of the causal Green's function and its time-reversal, such that their singularities at the source position cancel each other. A classical representation expresses this homogeneous Green's function as a closed boundary integral. This representation finds applications in holographic imaging, time-reversed wave propagation and Green's function retrieval by cross correlation. The main drawback of the classical representation in those applications is that it requires access to a closed boundary around the medium of interest, whereas in many practical situations the medium can be accessed from one side only. Therefore, a single-sided representation is derived for the homogeneous Green's function of the unified scalar wave equation. Like the classical representation, this single-sided representation fully accounts for multiple scattering. The single-sided representation has the same applications as the classical representation, but unlike the classical representation it is applicable in situations where the medium of interest is accessible from one side only.

Optical coherence tomography retinal image reconstruction via nonlocal weighted sparse representation

NASA Astrophysics Data System (ADS)

Abbasi, Ashkan; Monadjemi, Amirhassan; Fang, Leyuan; Rabbani, Hossein

2018-03-01

We present a nonlocal weighted sparse representation (NWSR) method for reconstruction of retinal optical coherence tomography (OCT) images. To reconstruct a high signal-to-noise ratio and high-resolution OCT images, utilization of efficient denoising and interpolation algorithms are necessary, especially when the original data were subsampled during acquisition. However, the OCT images suffer from the presence of a high level of noise, which makes the estimation of sparse representations a difficult task. Thus, the proposed NWSR method merges sparse representations of multiple similar noisy and denoised patches to better estimate a sparse representation for each patch. First, the sparse representation of each patch is independently computed over an overcomplete dictionary, and then a nonlocal weighted sparse coefficient is computed by averaging representations of similar patches. Since the sparsity can reveal relevant information from noisy patches, combining noisy and denoised patches' representations is beneficial to obtain a more robust estimate of the unknown sparse representation. The denoised patches are obtained by applying an off-the-shelf image denoising method and our method provides an efficient way to exploit information from noisy and denoised patches' representations. The experimental results on denoising and interpolation of spectral domain OCT images demonstrated the effectiveness of the proposed NWSR method over existing state-of-the-art methods.

Arrows as anchors: An analysis of the material features of electric field vector arrows

NASA Astrophysics Data System (ADS)

Gire, Elizabeth; Price, Edward

2014-12-01

Representations in physics possess both physical and conceptual aspects that are fundamentally intertwined and can interact to support or hinder sense making and computation. We use distributed cognition and the theory of conceptual blending with material anchors to interpret the roles of conceptual and material features of representations in students' use of representations for computation. We focus on the vector-arrows representation of electric fields and describe this representation as a conceptual blend of electric field concepts, physical space, and the material features of the representation (i.e., the physical writing and the surface upon which it is drawn). In this representation, spatial extent (e.g., distance on paper) is used to represent both distances in coordinate space and magnitudes of electric field vectors. In conceptual blending theory, this conflation is described as a clash between the input spaces in the blend. We explore the benefits and drawbacks of this clash, as well as other features of this representation. This analysis is illustrated with examples from clinical problem-solving interviews with upper-division physics majors. We see that while these intermediate physics students make a variety of errors using this representation, they also use the geometric features of the representation to add electric field contributions and to organize the problem situation productively.

Generative Representations for Automated Design of Robots

NASA Technical Reports Server (NTRS)

Homby, Gregory S.; Lipson, Hod; Pollack, Jordan B.

2007-01-01

A method of automated design of complex, modular robots involves an evolutionary process in which generative representations of designs are used. The term generative representations as used here signifies, loosely, representations that consist of or include algorithms, computer programs, and the like, wherein encoded designs can reuse elements of their encoding and thereby evolve toward greater complexity. Automated design of robots through synthetic evolutionary processes has already been demonstrated, but it is not clear whether genetically inspired search algorithms can yield designs that are sufficiently complex for practical engineering. The ultimate success of such algorithms as tools for automation of design depends on the scaling properties of representations of designs. A nongenerative representation (one in which each element of the encoded design is used at most once in translating to the design) scales linearly with the number of elements. Search algorithms that use nongenerative representations quickly become intractable (search times vary approximately exponentially with numbers of design elements), and thus are not amenable to scaling to complex designs. Generative representations are compact representations and were devised as means to circumvent the above-mentioned fundamental restriction on scalability. In the present method, a robot is defined by a compact programmatic form (its generative representation) and the evolutionary variation takes place on this form. The evolutionary process is an iterative one, wherein each cycle consists of the following steps: 1. Generative representations are generated in an evolutionary subprocess. 2. Each generative representation is a program that, when compiled, produces an assembly procedure. 3. In a computational simulation, a constructor executes an assembly procedure to generate a robot. 4. A physical-simulation program tests the performance of a simulated constructed robot, evaluating the performance according to a fitness criterion to yield a figure of merit that is fed back into the evolutionary subprocess of the next iteration. In comparison with prior approaches to automated evolutionary design of robots, the use of generative representations offers two advantages: First, a generative representation enables the reuse of components in regular and hierarchical ways and thereby serves a systematic means of creating more complex modules out of simpler ones. Second, the evolved generative representation may capture intrinsic properties of the design problem, so that variations in the representations move through the design space more effectively than do equivalent variations in a nongenerative representation. This method has been demonstrated by using it to design some robots that move, variously, by walking, rolling, or sliding. Some of the robots were built (see figure). Although these robots are very simple, in comparison with robots designed by humans, their structures are more regular, modular, hierarchical, and complex than are those of evolved designs of comparable functionality synthesized by use of nongenerative representations.

Unpacking Exoplanet Detection Using Pedagogical Discipline Representations (PDRs)

NASA Astrophysics Data System (ADS)

Prather, Edward E.; Chambers, Timothy G.; Wallace, Colin Scott; Brissenden, Gina

2017-01-01

Successful educators know the importance of using multiple representations to teach the content of their disciplines. We have all seen the moments of epiphany that can be inspired when engaging with just the right representation of a difficult concept. The formal study of the cognitive impact of different representations on learners is now an active area of education research. The affordances of a particular representation are defined as the elements of disciplinary knowledge that students are able to access and reason about using that representation. Instructors with expert pedagogical content knowledge teach each topic using representations with complementary affordances, maximizing their students’ opportunity to develop fluency with all aspects of the topic. The work presented here examines how we have applied the theory of affordances to the development of pedagogical discipline representation (PDR) in an effort to provide access to, and help non-science-majors engage in expert-like reasoning about, general relativity as applied to detection of exoplanets. We define a pedagogical discipline representation (PDR) as a representation that has been uniquely tailored for the purpose of teaching a specific topic within a discipline. PDRs can be simplified versions of expert representations or can be highly contextualized with features that purposefully help unpack specific reasoning or concepts, and engage learners’ pre-existing mental models while promoting and enabling critical discourse. Examples of PDRs used for instruction and assessment will be provided along with preliminary results documenting the effectiveness of their use in the classroom.

38 CFR 14.632 - Standards of conduct for persons providing representation before the Department

Code of Federal Regulations, 2013 CFR

2013-07-01

... the knowledge, skill, thoroughness, and preparation necessary for the representation. This includes... persons providing representation before the Department 14.632 Section 14.632 Pensions, Bonuses, and... Representation of Department of Veterans Affairs Claimants; Recognition of Organizations, Accredited...

38 CFR 14.632 - Standards of conduct for persons providing representation before the Department

Code of Federal Regulations, 2011 CFR

2011-07-01

... the knowledge, skill, thoroughness, and preparation necessary for the representation. This includes... persons providing representation before the Department 14.632 Section 14.632 Pensions, Bonuses, and... Representation of Department of Veterans Affairs Claimants; Recognition of Organizations, Accredited...

38 CFR 14.632 - Standards of conduct for persons providing representation before the Department

Code of Federal Regulations, 2014 CFR

2014-07-01

... the knowledge, skill, thoroughness, and preparation necessary for the representation. This includes... persons providing representation before the Department 14.632 Section 14.632 Pensions, Bonuses, and... Representation of Department of Veterans Affairs Claimants; Recognition of Organizations, Accredited...

38 CFR 14.632 - Standards of conduct for persons providing representation before the Department

Code of Federal Regulations, 2010 CFR

2010-07-01

... the knowledge, skill, thoroughness, and preparation necessary for the representation. This includes... persons providing representation before the Department 14.632 Section 14.632 Pensions, Bonuses, and... Representation of Department of Veterans Affairs Claimants; Recognition of Organizations, Accredited...

38 CFR 14.632 - Standards of conduct for persons providing representation before the Department

Code of Federal Regulations, 2012 CFR

2012-07-01

... the knowledge, skill, thoroughness, and preparation necessary for the representation. This includes... persons providing representation before the Department 14.632 Section 14.632 Pensions, Bonuses, and... Representation of Department of Veterans Affairs Claimants; Recognition of Organizations, Accredited...

Promoting Decimal Number Sense and Representational Fluency

ERIC Educational Resources Information Center

Suh, Jennifer M.; Johnston, Chris; Jamieson, Spencer; Mills, Michelle

2008-01-01

The abstract nature of mathematics requires the communication of mathematical ideas through multiple representations, such as words, symbols, pictures, objects, or actions. Building representational fluency involves using mathematical representations flexibly and being able to interpret and translate among these different models and mathematical…

Models as Feedback: Developing Representational Competence in Chemistry

ERIC Educational Resources Information Center

Padalkar, Shamin; Hegarty, Mary

2015-01-01

Spatial information in science is often expressed through representations such as diagrams and models. Learning the strengths and limitations of these representations and how to relate them are important aspects of developing scientific understanding, referred to as "representational competence." Diagram translation is particularly…

A polygon soup representation for free viewpoint video

NASA Astrophysics Data System (ADS)

Colleu, T.; Pateux, S.; Morin, L.; Labit, C.

2010-02-01

This paper presents a polygon soup representation for multiview data. Starting from a sequence of multi-view video plus depth (MVD) data, the proposed representation takes into account, in a unified manner, different issues such as compactness, compression, and intermediate view synthesis. The representation is built in two steps. First, a set of 3D quads is extracted using a quadtree decomposition of the depth maps. Second, a selective elimination of the quads is performed in order to reduce inter-view redundancies and thus provide a compact representation. Moreover, the proposed methodology for extracting the representation allows to reduce ghosting artifacts. Finally, an adapted compression technique is proposed that limits coding artifacts. The results presented on two real sequences show that the proposed representation provides a good trade-off between rendering quality and data compactness.

From Sensory Signals to Modality-Independent Conceptual Representations: A Probabilistic Language of Thought Approach

PubMed Central

Erdogan, Goker; Yildirim, Ilker; Jacobs, Robert A.

2015-01-01

People learn modality-independent, conceptual representations from modality-specific sensory signals. Here, we hypothesize that any system that accomplishes this feat will include three components: a representational language for characterizing modality-independent representations, a set of sensory-specific forward models for mapping from modality-independent representations to sensory signals, and an inference algorithm for inverting forward models—that is, an algorithm for using sensory signals to infer modality-independent representations. To evaluate this hypothesis, we instantiate it in the form of a computational model that learns object shape representations from visual and/or haptic signals. The model uses a probabilistic grammar to characterize modality-independent representations of object shape, uses a computer graphics toolkit and a human hand simulator to map from object representations to visual and haptic features, respectively, and uses a Bayesian inference algorithm to infer modality-independent object representations from visual and/or haptic signals. Simulation results show that the model infers identical object representations when an object is viewed, grasped, or both. That is, the model’s percepts are modality invariant. We also report the results of an experiment in which different subjects rated the similarity of pairs of objects in different sensory conditions, and show that the model provides a very accurate account of subjects’ ratings. Conceptually, this research significantly contributes to our understanding of modality invariance, an important type of perceptual constancy, by demonstrating how modality-independent representations can be acquired and used. Methodologically, it provides an important contribution to cognitive modeling, particularly an emerging probabilistic language-of-thought approach, by showing how symbolic and statistical approaches can be combined in order to understand aspects of human perception. PMID:26554704

Mental Representation and Mental Practice: Experimental Investigation on the Functional Links between Motor Memory and Motor Imagery

PubMed Central

Frank, Cornelia; Land, William M.; Popp, Carmen; Schack, Thomas

2014-01-01

Recent research on mental representation of complex action has revealed distinct differences in the structure of representational frameworks between experts and novices. More recently, research on the development of mental representation structure has elicited functional changes in novices' representations as a result of practice. However, research investigating if and how mental practice adds to this adaptation process is lacking. In the present study, we examined the influence of mental practice (i.e., motor imagery rehearsal) on both putting performance and the development of one's representation of the golf putt during early skill acquisition. Novice golfers (N = 52) practiced the task of golf putting under one of four different practice conditions: mental, physical, mental-physical combined, and no practice. Participants were tested prior to and after a practice phase, as well as after a three day retention interval. Mental representation structures of the putt were measured, using the structural dimensional analysis of mental representation. This method provides psychometric data on the distances and groupings of basic action concepts in long-term memory. Additionally, putting accuracy and putting consistency were measured using two-dimensional error scores of each putt. Findings revealed significant performance improvements over the course of practice together with functional adaptations in mental representation structure. Interestingly, after three days of practice, the mental representations of participants who incorporated mental practice into their practice regime displayed representation structures that were more similar to a functional structure than did participants who did not incorporate mental practice. The findings of the present study suggest that mental practice promotes the cognitive adaptation process during motor learning, leading to more elaborate representations than physical practice only. PMID:24743576

Developmental psycholinguistics teaches us that we need multi-method, not single-method, approaches to the study of linguistic representation.

PubMed

Rowland, Caroline F; Monaghan, Padraic

2017-01-01

In developmental psycholinguistics, we have, for many years, been generating and testing theories that propose both descriptions of adult representations and explanations of how those representations develop. We have learnt that restricting ourselves to any one methodology yields only incomplete data about the nature of linguistic representations. We argue that we need a multi-method approach to the study of representation.

On the mapping associated with the complex representation of functions and processes.

NASA Technical Reports Server (NTRS)

Harger, R. O.

1972-01-01

The mapping between function spaces that is implied by the representation of a real 'bandpass' function by a complex 'low-pass' function is explicitly accepted. The discussion is extended to the representation of stationary random processes where the mapping is between spaces of random processes. This approach clarifies the nature of the complex representation, especially in the case of random processes and, in addition, derives the properties of the complex representation.-

Representing the nature of science in a science textbook: Exploring author-editor-publisher interactions

NASA Astrophysics Data System (ADS)

Digiuseppe, Maurizio

Current reforms in elementary and secondary science education call for students and teachers to develop more informed views of the nature of science---a process in which learning materials like science textbooks play a significant role. This dissertation reports on a case study of the development of representations of the nature of science in one unit of a senior high school chemistry textbook by the book's author, editor, and publisher. The study examines the multiple discourses that arose as the developers reflected on their personal and shared understandings of the nature of science; squared these understandings with mandated curricula, the educational needs of chemistry students and teachers, and the exigencies of large-scale commercial textbook publishing; and developed and incorporated into the textbook representations of the nature of science they believed were the most suitable. Analyses of the data in this study indicate that a number of factors significantly influenced the development of representations of the nature of science, including representational accuracy (the degree to which suggested representations of the nature of science conformed to what the developers believed were contemporary understandings of the nature of science), representational consistency (the degree to which similar representations of the nature of science in different parts of the textbook conveyed the same meaning), representational appropriateness (the age-, grade-, and reading-level suitability of the suggested nature of science representations), representational alignment (the degree to which suggested representations of the nature of science addressed the requirements of mandated curricula), representational marketability (the degree to which textbook developers believed suggested representations of the nature of science would affect sales of the textbook in the marketplace), and a number of "Workplace Resources" factors such as the availability of time, relevant expertise, effective channels of communication, and opportunities for professional development. The developers of the unit of the textbook studied in this thesis made judicious decisions in the face of competing interests as they endeavoured to represent the nature of science in their science textbook.

32 CFR 776.29 - Imputed disqualification: General rule.

Code of Federal Regulations, 2012 CFR

2012-07-01

... their federal, state, and local bar rules governing the representation of multiple or adverse clients within the same office before such representation is initiated, as such representation may expose them to... military (or Government) service may require representation of opposing sides by covered USG attorneys...

32 CFR 776.29 - Imputed disqualification: General rule.

Code of Federal Regulations, 2014 CFR

2014-07-01

... their federal, state, and local bar rules governing the representation of multiple or adverse clients within the same office before such representation is initiated, as such representation may expose them to... military (or Government) service may require representation of opposing sides by covered USG attorneys...

32 CFR 776.29 - Imputed disqualification: General rule.

Code of Federal Regulations, 2013 CFR

2013-07-01

... their federal, state, and local bar rules governing the representation of multiple or adverse clients within the same office before such representation is initiated, as such representation may expose them to... military (or Government) service may require representation of opposing sides by covered USG attorneys...

Phonological Awareness Deficits in Developmental Dyslexia and the Phonological Representations Hypothesis.

ERIC Educational Resources Information Center

Swan, Denise; Goswami, Usha

1997-01-01

Used picture-naming task to identify accurate/inaccurate phonological representations by dyslexic and control children; compared performance on phonological measures for words with precise/imprecise representations. Found that frequency effects in phonological tasks disappeared after considering representational quality, and that availability of…

Spatial versus Tree Representations of Proximity Data.

ERIC Educational Resources Information Center

Pruzansky, Sandra; And Others

1982-01-01

Two-dimensional euclidean planes and additive trees are two of the most common representations of proximity data for multidimensional scaling. Guidelines for comparing these representations and discovering properties that could help identify which representation is more appropriate for a given data set are presented. (Author/JKS)

Successful Learning with Multiple Graphical Representations and Self-Explanation Prompts

ERIC Educational Resources Information Center

Rau, Martina A.; Aleven, Vincent; Rummel, Nikol

2015-01-01

Research shows that multiple external representations can significantly enhance students' learning. Most of this research has focused on learning with text and 1 additional graphical representation. However, real instructional materials often employ multiple "graphical" representations (MGRs) in addition to text. An important open…

Prosodic Phonological Representations Early in Visual Word Recognition

ERIC Educational Resources Information Center

Ashby, Jane; Martin, Andrea E.

2008-01-01

Two experiments examined the nature of the phonological representations used during visual word recognition. We tested whether a minimality constraint (R. Frost, 1998) limits the complexity of early representations to a simple string of phonemes. Alternatively, readers might activate elaborated representations that include prosodic syllable…

Individual differences in ensemble perception reveal multiple, independent levels of ensemble representation.

PubMed

Haberman, Jason; Brady, Timothy F; Alvarez, George A

2015-04-01

Ensemble perception, including the ability to "see the average" from a group of items, operates in numerous feature domains (size, orientation, speed, facial expression, etc.). Although the ubiquity of ensemble representations is well established, the large-scale cognitive architecture of this process remains poorly defined. We address this using an individual differences approach. In a series of experiments, observers saw groups of objects and reported either a single item from the group or the average of the entire group. High-level ensemble representations (e.g., average facial expression) showed complete independence from low-level ensemble representations (e.g., average orientation). In contrast, low-level ensemble representations (e.g., orientation and color) were correlated with each other, but not with high-level ensemble representations (e.g., facial expression and person identity). These results suggest that there is not a single domain-general ensemble mechanism, and that the relationship among various ensemble representations depends on how proximal they are in representational space. (c) 2015 APA, all rights reserved).

Attention during natural vision warps semantic representation across the human brain.

PubMed

Çukur, Tolga; Nishimoto, Shinji; Huth, Alexander G; Gallant, Jack L

2013-06-01

Little is known about how attention changes the cortical representation of sensory information in humans. On the basis of neurophysiological evidence, we hypothesized that attention causes tuning changes to expand the representation of attended stimuli at the cost of unattended stimuli. To investigate this issue, we used functional magnetic resonance imaging to measure how semantic representation changed during visual search for different object categories in natural movies. We found that many voxels across occipito-temporal and fronto-parietal cortex shifted their tuning toward the attended category. These tuning shifts expanded the representation of the attended category and of semantically related, but unattended, categories, and compressed the representation of categories that were semantically dissimilar to the target. Attentional warping of semantic representation occurred even when the attended category was not present in the movie; thus, the effect was not a target-detection artifact. These results suggest that attention dynamically alters visual representation to optimize processing of behaviorally relevant objects during natural vision.

Attention During Natural Vision Warps Semantic Representation Across the Human Brain

PubMed Central

Çukur, Tolga; Nishimoto, Shinji; Huth, Alexander G.; Gallant, Jack L.

2013-01-01

Little is known about how attention changes the cortical representation of sensory information in humans. Based on neurophysiological evidence, we hypothesized that attention causes tuning changes to expand the representation of attended stimuli at the cost of unattended stimuli. To investigate this issue we used functional MRI (fMRI) to measure how semantic representation changes when searching for different object categories in natural movies. We find that many voxels across occipito-temporal and fronto-parietal cortex shift their tuning toward the attended category. These tuning shifts expand the representation of the attended category and of semantically-related but unattended categories, and compress the representation of categories semantically-dissimilar to the target. Attentional warping of semantic representation occurs even when the attended category is not present in the movie, thus the effect is not a target-detection artifact. These results suggest that attention dynamically alters visual representation to optimize processing of behaviorally relevant objects during natural vision. PMID:23603707

Spatially variant morphological restoration and skeleton representation.

PubMed

Bouaynaya, Nidhal; Charif-Chefchaouni, Mohammed; Schonfeld, Dan

2006-11-01

The theory of spatially variant (SV) mathematical morphology is used to extend and analyze two important image processing applications: morphological image restoration and skeleton representation of binary images. For morphological image restoration, we propose the SV alternating sequential filters and SV median filters. We establish the relation of SV median filters to the basic SV morphological operators (i.e., SV erosions and SV dilations). For skeleton representation, we present a general framework for the SV morphological skeleton representation of binary images. We study the properties of the SV morphological skeleton representation and derive conditions for its invertibility. We also develop an algorithm for the implementation of the SV morphological skeleton representation of binary images. The latter algorithm is based on the optimal construction of the SV structuring element mapping designed to minimize the cardinality of the SV morphological skeleton representation. Experimental results show the dramatic improvement in the performance of the SV morphological restoration and SV morphological skeleton representation algorithms in comparison to their translation-invariant counterparts.

Low-dimensional representations of the three component loop braid group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruillard, Paul; Chang, Liang; Hong, Seung-Moon

2015-11-01

Motivated by physical and topological applications, we study representations of the group LB3 o motions of 3 unlinked oriented circles in R3. Our point of view is to regard the three strand braid group B3 as a subgroup of LB3 and study the problem of extending B3 representations. We introduce the notion of a standard extension and characterize B3 represenations admiting such an extension. In particular we show, using a classification result of Tuba and Wenzl, that every irreducible B3 representation of dimension at most 5 has a (standard) extension. We show that this result is sharp by exhibiting anmore » irreducible 6-dimensional B3 representation that has no extension (standard or otherwise). We obtain complete classifications of (1) irreducible 2-dimensional LB3 representations (2) extensions of irreducible B3 representations and (3) irreducible LB3 representations whose restriction to B3 has abelian image.« less

A unified data representation theory for network visualization, ordering and coarse-graining

PubMed Central

Kovács, István A.; Mizsei, Réka; Csermely, Péter

2015-01-01

Representation of large data sets became a key question of many scientific disciplines in the last decade. Several approaches for network visualization, data ordering and coarse-graining accomplished this goal. However, there was no underlying theoretical framework linking these problems. Here we show an elegant, information theoretic data representation approach as a unified solution of network visualization, data ordering and coarse-graining. The optimal representation is the hardest to distinguish from the original data matrix, measured by the relative entropy. The representation of network nodes as probability distributions provides an efficient visualization method and, in one dimension, an ordering of network nodes and edges. Coarse-grained representations of the input network enable both efficient data compression and hierarchical visualization to achieve high quality representations of larger data sets. Our unified data representation theory will help the analysis of extensive data sets, by revealing the large-scale structure of complex networks in a comprehensible form. PMID:26348923

Social representations of climate change in Swedish lay focus groups: local or distant, gradual or catastrophic?

PubMed

Wibeck, Victoria

2014-02-01

This paper explores social representations of climate change, investigating how climate change is discussed by Swedish laypeople interacting in focus group interviews. The analysis focuses on prototypical examples and metaphors, which were key devices for objectifying climate change representations. The paper analyzes how the interaction of focus group participants with other speakers, ideas, arguments, and broader social representations shaped their representations of climate change. Climate change was understood as a global but distant issue with severe consequences. There was a dynamic tension between representations of climate change as a gradual vs. unpredictable process. Implications for climate change communication are discussed.

Spinal cord injury affects the interplay between visual and sensorimotor representations of the body

PubMed Central

Ionta, Silvio; Villiger, Michael; Jutzeler, Catherine R; Freund, Patrick; Curt, Armin; Gassert, Roger

2016-01-01

The brain integrates multiple sensory inputs, including somatosensory and visual inputs, to produce a representation of the body. Spinal cord injury (SCI) interrupts the communication between brain and body and the effects of this deafferentation on body representation are poorly understood. We investigated whether the relative weight of somatosensory and visual frames of reference for body representation is altered in individuals with incomplete or complete SCI (affecting lower limbs’ somatosensation), with respect to controls. To study the influence of afferent somatosensory information on body representation, participants verbally judged the laterality of rotated images of feet, hands, and whole-bodies (mental rotation task) in two different postures (participants’ body parts were hidden from view). We found that (i) complete SCI disrupts the influence of postural changes on the representation of the deafferented body parts (feet, but not hands) and (ii) regardless of posture, whole-body representation progressively deteriorates proportionally to SCI completeness. These results demonstrate that the cortical representation of the body is dynamic, responsive, and adaptable to contingent conditions, in that the role of somatosensation is altered and partially compensated with a change in the relative weight of somatosensory versus visual bodily representations. PMID:26842303

An evaluation of space time cube representation of spatiotemporal patterns.

PubMed

Kristensson, Per Ola; Dahlbäck, Nils; Anundi, Daniel; Björnstad, Marius; Gillberg, Hanna; Haraldsson, Jonas; Mårtensson, Ingrid; Nordvall, Mathias; Ståhl, Josefine

2009-01-01

Space time cube representation is an information visualization technique where spatiotemporal data points are mapped into a cube. Information visualization researchers have previously argued that space time cube representation is beneficial in revealing complex spatiotemporal patterns in a data set to users. The argument is based on the fact that both time and spatial information are displayed simultaneously to users, an effect difficult to achieve in other representations. However, to our knowledge the actual usefulness of space time cube representation in conveying complex spatiotemporal patterns to users has not been empirically validated. To fill this gap, we report on a between-subjects experiment comparing novice users' error rates and response times when answering a set of questions using either space time cube or a baseline 2D representation. For some simple questions, the error rates were lower when using the baseline representation. For complex questions where the participants needed an overall understanding of the spatiotemporal structure of the data set, the space time cube representation resulted in on average twice as fast response times with no difference in error rates compared to the baseline. These results provide an empirical foundation for the hypothesis that space time cube representation benefits users analyzing complex spatiotemporal patterns.

Embedded Data Representations.

PubMed

Willett, Wesley; Jansen, Yvonne; Dragicevic, Pierre

2017-01-01

We introduce embedded data representations, the use of visual and physical representations of data that are deeply integrated with the physical spaces, objects, and entities to which the data refers. Technologies like lightweight wireless displays, mixed reality hardware, and autonomous vehicles are making it increasingly easier to display data in-context. While researchers and artists have already begun to create embedded data representations, the benefits, trade-offs, and even the language necessary to describe and compare these approaches remain unexplored. In this paper, we formalize the notion of physical data referents - the real-world entities and spaces to which data corresponds - and examine the relationship between referents and the visual and physical representations of their data. We differentiate situated representations, which display data in proximity to data referents, and embedded representations, which display data so that it spatially coincides with data referents. Drawing on examples from visualization, ubiquitous computing, and art, we explore the role of spatial indirection, scale, and interaction for embedded representations. We also examine the tradeoffs between non-situated, situated, and embedded data displays, including both visualizations and physicalizations. Based on our observations, we identify a variety of design challenges for embedded data representation, and suggest opportunities for future research and applications.

The effects of learner-generated representations versus computer-generated representations on physics problem solving

NASA Astrophysics Data System (ADS)

Price, Gwyneth A.

In this study, multiple external representations and Generative Learning Theory were used to design instruction that would facilitate physics learning. Specifically, the study looks at the learning differences that may occur when students are engaged in generating a graphical representation as compared to being presented with a computer-generated graph. It is hypothesized that by generating the graphical representation students will be able to overcome obstacles to integration and determine the relationships involved within a representation. In doing so, students will build a more complete mental model of the situation and be able to more readily use this information in transfer situations, thus improving their problem solving ability. Though the results of this study do not lend strong support for the hypothesis, the results are still informative and encouraging. Though several of the obstacles associated with learning from multiple representations such as cognitive load were cause for concern, those students with appropriate prior knowledge and familiarity with graphical representations were able to benefit from the generative activity. This finding indicates that if the issues are directly addressed within instruction, it may be that all students may be able to benefit from being actively engaged in generating representations.

Technology Focus: Multi-Representational Approaches to Equation Solving

ERIC Educational Resources Information Center

Garofalo, Joe; Trinter, Christine

2009-01-01

Most mathematical functions can be represented in numerous ways. The main representations typically addressed in school, often referred to as "the big three," are graphical, algebraic, and numerical representations, but there are others as well (e.g., diagrams, words, simulations). These different types of representations "often illuminate…

Visual Representations of DNA Replication: Middle Grades Students' Perceptions and Interpretations

ERIC Educational Resources Information Center

Patrick, Michelle D.; Carter, Glenda; Wiebe, Eric N.

2005-01-01

Visual representations play a critical role in the communication of science concepts for scientists and students alike. However, recent research suggests that novice students experience difficulty extracting relevant information from representations. This study examined students' interpretations of visual representations of DNA replication. Each…

Cognitive Dissonance as an Instructional Tool for Understanding Chemical Representations

ERIC Educational Resources Information Center

Corradi, David; Clarebout, Geraldine; Elen, Jan

2015-01-01

Previous research on multiple external representations (MER) indicates that sequencing representations (compared with presenting them as a whole) can, in some cases, increase conceptual understanding if there is interference between internal and external representations. We tested this mechanism by sequencing different combinations of scientific…

Squeezing, Striking, and Vocalizing: Is Number Representation Fundamentally Spatial?

ERIC Educational Resources Information Center

Nunez, Rafael; Doan, D.; Nikoulina, Anastasia

2011-01-01

Numbers are fundamental entities in mathematics, but their cognitive bases are unclear. Abundant research points to linear space as a natural grounding for number representation. But, is number representation fundamentally spatial? We disentangle number representation from standard number-to-line reporting methods, and compare numerical…

Role of Multiple Representations in Physics Problem Solving

ERIC Educational Resources Information Center

Maries, Alexandru

2013-01-01

This thesis explores the role of multiple representations in introductory physics students' problem solving performance through several investigations. Representations can help students focus on the conceptual aspects of physics and play a major role in effective problem solving. Diagrammatic representations can play a particularly important role…

48 CFR 2052.209-71 - Contractor organizational conflicts of interest (representation).

Code of Federal Regulations, 2010 CFR

2010-10-01

... conflicts of interest (representation). 2052.209-71 Section 2052.209-71 Federal Acquisition Regulations... of Provisions and Clauses 2052.209-71 Contractor organizational conflicts of interest (representation... Organizational Conflicts of Interest Representation (OCT 1999) I represent to the best of my knowledge and belief...

Venturing into Unknown Territory: Using Aesthetic Representations to Understand Reading Comprehension

ERIC Educational Resources Information Center

Cuero, Kimberley K.; Bonner, Jennifer; Smith, Brittaney; Schwartz, Michelle; Touchstone, Rose; Vela, Yvonne

2008-01-01

Based on Elliot Eisner's notions of multiple forms of representation and Rosenblatt's aesthetic/efferent responses to reading, a teacher educator/researcher had her undergraduate students explore their connections, using aesthetic representations, to a course entitled "Reading Comprehension". Each aesthetic representation revealed the complexities…

Representations of Nets of C*-Algebras over S 1

NASA Astrophysics Data System (ADS)

Ruzzi, Giuseppe; Vasselli, Ezio

2012-11-01

In recent times a new kind of representations has been used to describe superselection sectors of the observable net over a curved spacetime, taking into account the effects of the fundamental group of the spacetime. Using this notion of representation, we prove that any net of C*-algebras over S 1 admits faithful representations, and when the net is covariant under Diff( S 1), it admits representations covariant under any amenable subgroup of Diff( S 1).

Automatic detection of sweep-meshable volumes

DOEpatents

Tautges,; Timothy J. , White; David, R [Pittsburgh, PA

2006-05-23

A method of and software for automatically determining whether a mesh can be generated by sweeping for a representation of a geometric solid comprising: classifying surface mesh schemes for surfaces of the representation locally using surface vertex types; grouping mappable and submappable surfaces of the representation into chains; computing volume edge types for the representation; recursively traversing surfaces of the representation and grouping the surfaces into source, target, and linking surface lists; and checking traversal direction when traversing onto linking surfaces.

Motor Memory Is Encoded as a Gain-Field Combination of Intrinsic and Extrinsic Action Representations

PubMed Central

Brayanov, Jordan B.; Press, Daniel Z.; Smith, Maurice A.

2013-01-01

Actions can be planned in either an intrinsic (body-based) reference frame or an extrinsic (world-based) frame, and understanding how the internal representations associated with these frames contribute to the learning of motor actions is a key issue in motor control. We studied the internal representation of this learning in human subjects by analyzing generalization patterns across an array of different movement directions and workspaces after training a visuomotor rotation in a single movement direction in one workspace. This provided a dense sampling of the generalization function across intrinsic and extrinsic reference frames, which allowed us to dissociate intrinsic and extrinsic representations and determine the manner in which they contributed to the motor memory for a trained action. A first experiment showed that the generalization pattern reflected a memory that was intermediate between intrinsic and extrinsic representations. A second experiment showed that this intermediate representation could not arise from separate intrinsic and extrinsic learning. Instead, we find that the representation of learning is based on a gain-field combination of local representations in intrinsic and extrinsic coordinates. This gain-field representation generalizes between actions by effectively computing similarity based on the (Mahalanobis) distance across intrinsic and extrinsic coordinates and is in line with neural recordings showing mixed intrinsic-extrinsic representations in motor and parietal cortices. PMID:23100418

Visual Memories Bypass Normalization.

PubMed

Bloem, Ilona M; Watanabe, Yurika L; Kibbe, Melissa M; Ling, Sam

2018-05-01

How distinct are visual memory representations from visual perception? Although evidence suggests that briefly remembered stimuli are represented within early visual cortices, the degree to which these memory traces resemble true visual representations remains something of a mystery. Here, we tested whether both visual memory and perception succumb to a seemingly ubiquitous neural computation: normalization. Observers were asked to remember the contrast of visual stimuli, which were pitted against each other to promote normalization either in perception or in visual memory. Our results revealed robust normalization between visual representations in perception, yet no signature of normalization occurring between working memory stores-neither between representations in memory nor between memory representations and visual inputs. These results provide unique insight into the nature of visual memory representations, illustrating that visual memory representations follow a different set of computational rules, bypassing normalization, a canonical visual computation.

Visual Memories Bypass Normalization

PubMed Central

Bloem, Ilona M.; Watanabe, Yurika L.; Kibbe, Melissa M.; Ling, Sam

2018-01-01

How distinct are visual memory representations from visual perception? Although evidence suggests that briefly remembered stimuli are represented within early visual cortices, the degree to which these memory traces resemble true visual representations remains something of a mystery. Here, we tested whether both visual memory and perception succumb to a seemingly ubiquitous neural computation: normalization. Observers were asked to remember the contrast of visual stimuli, which were pitted against each other to promote normalization either in perception or in visual memory. Our results revealed robust normalization between visual representations in perception, yet no signature of normalization occurring between working memory stores—neither between representations in memory nor between memory representations and visual inputs. These results provide unique insight into the nature of visual memory representations, illustrating that visual memory representations follow a different set of computational rules, bypassing normalization, a canonical visual computation. PMID:29596038

Temporal Stability and Authenticity of Self-Representations in Adulthood

PubMed Central

Diehl, Manfred; Jacobs, Laurie M.; Hastings, Catherine T.

2008-01-01

The temporal stability of role-specific self-representations was examined in a sample of 188 young, middle-aged, and older adults. Considerable stability was observed for all self-representations. Central self-descriptors showed significantly greater temporal stability than peripheral self-descriptors. Temporal stability of self-representations was positively associated with self-concept clarity, self-esteem, and positive affect (PA). Age differences were obtained for three of the five self-representations, with older adults showing significantly lower stabilities for self with family, self with friend, and self with significant other compared to young and middle-aged adults. Assessment of the authenticity of adults’ role-specific self-representations showed that greater authenticity tended to be associated with greater temporal stability. Authenticity and the number of positive daily events were significant positive predictors of the stability of self-representations. PMID:18820732