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Sample records for bardeen-cooper-schrieffer theory

  1. Non-skew-symmetric classical r-matrices, algebraic Bethe ansatz, and Bardeen-Cooper-Schrieffer-type integrable systems

    International Nuclear Information System (INIS)

    Skrypnyk, T.

    2009-01-01

    We construct quantum integrable systems associated with non-skew-symmetric gl(2)-valued classical r-matrices. We find a new explicit multiparametric family of such the non-skew-symmetric classical r-matrices. We consider two classes of examples of the corresponding integrable systems, namely generalized Gaudin systems with and without an external magnetic field. In the case of arbitrary r-matrices diagonal in a standard gl(2)-basis, we calculate the spectrum of the corresponding quantum integrable systems using the algebraic Bethe ansatz. We apply these results to a construction of integrable fermionic models and obtain a wide class of integrable Bardeen-Cooper-Schrieffer (BCS)-type fermionic Hamiltonians containing the pairing and electrostatic interaction terms. We also consider special cases when the corresponding integrable Hamiltonians contain only pairing interaction term and are exact analogs of the 'reduced BCS Hamiltonian' of Richardson

  2. A study of self-consistent Hartree-Fock plus Bardeen-Cooper-Schrieffer calculations with finite-range interactions

    Science.gov (United States)

    Anguiano, M.; Lallena, A. M.; Co', G.; De Donno, V.

    2014-02-01

    In this work we test the validity of a Hartree-Fock plus Bardeen-Cooper-Schrieffer model in which a finite-range interaction is used in the two steps of the calculation by comparing the results obtained to those found in fully self-consistent Hartree-Fock-Bogoliubov calculations using the same interaction. Specifically, we consider the Gogny-type D1S and D1M forces. We study a wide range of spherical nuclei, far from the stability line, in various regions of the nuclear chart, from oxygen to tin isotopes. We calculate various quantities related to the ground state properties of these nuclei, such as binding energies, radii, charge and density distributions, and elastic electron scattering cross sections. The pairing effects are studied by direct comparison with the Hartree-Fock results. Despite its relative simplicity, in most cases, our model provides results very close to those of the Hartree-Fock-Bogoliubov calculations, and it reproduces the empirical evidence of pairing effects rather well in the nuclei investigated.

  3. Observation of preformed electron-hole Cooper pairs in highly excited ZnO

    NARCIS (Netherlands)

    Versteegh, M.A.M.; van Lange, A.J.; Stoof, H.T.C.; Dijkhuis, J.I.

    2012-01-01

    Electrons and holes in a semiconductor form hydrogen-atom-like bound states, called excitons. At high electron-hole densities the attractive Coulomb force becomes screened and excitons can no longer exist. Bardeen-Cooper-Schrieffer theory predicts that at such high densities co-operative many-body

  4. Bardeen-Cooper-Schrieffer universal constants generalized

    International Nuclear Information System (INIS)

    Hazaimeh, A.H.

    1992-01-01

    Weak- and moderate-coupling BCS superconductivity theory is shown to admit a more general T c formula, wherein T c approaches zero somewhat faster than with the familiar BCS T c -formula. This theory leads to a departure from the universal behavior of the gap-to-T c ratio and is consistent with some recent empirical values for exotic superconductors. This ratio is smaller than the universal BCS value of 3.53 in a way which is consistent with weak electron-boson coupling. Similarly, other universal constants related to specific heat and critical magnetic field are modified. In this dissertation, The author investigates the latter constants for weak-coupling and moderate-coupling and carry out detailed comparisons with experimental data for the cuprates and with the corresponding predictions of strong-coupling theory. This effort is to elucidate the nature of these superconductors with regards to coupling strength within an electron-boson mechanism

  5. Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

    OpenAIRE

    Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.

    2014-01-01

    Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguo...

  6. Derivation of Ginzburg-Landau theory for a one-dimensional system with contact interaction

    DEFF Research Database (Denmark)

    Frank, Rupert; Hanizl, Christian; Seiringer, Robert

    2013-01-01

    In a recent paper we give the first rigorous derivation of the celebrated Ginzburg-Landau (GL) theory, starting from the microscopic Bardeen-Cooper-Schrieffer (BCS) model. Here we present our results in the simplified case of a one-dimensional system of particles interacting via a delta-potential....

  7. Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

    Energy Technology Data Exchange (ETDEWEB)

    Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L. [Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland)

    2015-07-01

    Based on the Bardeen Cooper Schrieffer (BCS) theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the produced photon pairs can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.

  8. Detecting nonlocal Cooper pair entanglement by optical Bell inequality violation

    Science.gov (United States)

    Nigg, Simon E.; Tiwari, Rakesh P.; Walter, Stefan; Schmidt, Thomas L.

    2015-03-01

    Based on the Bardeen-Cooper-Schrieffer theory of superconductivity, the coherent splitting of Cooper pairs from a superconductor to two spatially separated quantum dots has been predicted to generate nonlocal pairs of entangled electrons. In order to test this hypothesis, we propose a scheme to transfer the spin state of a split Cooper pair onto the polarization state of a pair of optical photons. We show that the photon pairs produced can be used to violate a Bell inequality, unambiguously demonstrating the entanglement of the split Cooper pairs.

  9. John Bardeen and the theory of superconductivity

    International Nuclear Information System (INIS)

    Schrieffer, J.R.

    1992-01-01

    Bardeen's knowledge of the experimental data had bounded the theory of superconductivity quite tightly before B, C and S developed their theory. When one speaks with John Bardeen's friends about him, one frequently hears words such as brilliant, quiet, persistent, generous, visionary, athletic, kind, thoughtful and remarkable. It is the author's good fortune to have the chance to recount some incidents from his life that are connected with the theory of superconductivity. This article draws on the author's personal memories; his many other friends and colleagues will set down their own recollections elsewhere. The evolution of the microscopic theory of superconductivity closely parallels the scientific life of Joh Bardeen. Starting with his PhD dissertation, done under the guidance of Eugene Wigner, he spent much of his life developing an understanding of electron interaction effects and transport properties of metals, semiconductors and superconductors. His fascination with the remarkable phenomenon of superconductivity goes back to his graduate student days at Princeton. Although interrupted during the war years and in the late 1940's at Bell Labs, he returned to this perplexing topic when he moved to the University of Illinois in 1951. 20 refs., 7 figs

  10. Supercurrent and the Adler-Bardeen theorem in coupled supersymmetric Yang-Mills theories

    International Nuclear Information System (INIS)

    Ensign, P.; Mahanthappa, K.T.

    1987-01-01

    We construct the supercurrent and a supersymmetric current which satisfies the Adler-Bardeen theorem in supersymmetric Yang-Mills theory coupled to non-self-interacting chiral matter. Using the formulation recently developed by Grisaru, Milewski, and Zanon, supersymmetry and gauge invariance are maintained with supersymmetric background-field theory and regularization by dimensional reduction. We verify the finiteness of the supercurrent to one loop, and the Adler-Bardeen theorem to two loops by explicit calculations in the minimal-subtraction scheme. We then demonstrate the subtraction-scheme independence of the one-loop Adler-Bardeen anomaly and prove the existence of a subtraction scheme in which the Adler-Bardeen theorem is satisfied to all orders in perturbation theory

  11. Interband superconductivity: Contrasts between Bardeen-Cooper-Schrieffer and Eliashberg theories

    NARCIS (Netherlands)

    Dolgov, Oleg V.; Mazin, Igor I.; Parker, David; Golubov, Alexandre Avraamovitch

    2009-01-01

    recently discovered iron pnictide superconductors apparently present an unusual case of interband-channel pairing superconductivity. Here we show that in the limit where the pairing occurs within the interband channel, several surprising effects occur quite naturally and generally: different density

  12. Supercurrent and the Adler-Bardeen theorem in coupled supersymmetric Yang-Mills theories

    International Nuclear Information System (INIS)

    Ensign, P.W.

    1987-01-01

    By the Adler-Bardeen theorem, only one-loop Feynman diagrams contribute to the anomalous divergences of quantum axial currents. The anomalous nature of scale transformations is manifested by an anomalous trace of the energy-momentum tensor, T/sup μ//sub μ/. Renormalization group arguments show that the quantum T/sup μ//sub μ/ must be proportional to the β-function. Since the β-function receives contributions at all loop levels, the Adler-Bardeen theorem appears to conflict with supersymmetry. Recently Grisaru, Milewski and Zanon constructed a supersymmetric axial current for pure supersymmetric Yang-Mills theory which satisfies the Adler-Bardeen theorem to two-loops. They used supersymmetric background field theory and regularization by dimensional reduction to maintain manifest supersymmetry and gauge invariance. In this thesis, their construction is extended to supersymmetric Yang-Mills theory coupled to chiral matter fields. The Adler-Bardeen theorem is then proven to all orders in perturbation theory for both the pure and coupled theories. The extension to coupled supersymmetric Yang-Mills supports the general validity of these techniques, and adds considerable insight into the structure of the anomalies. The all orders proof demonstrates that there is no conflict between supersymmetry and the Adler-Bardeen theorem

  13. Microscopic Derivation of the Ginzburg-Landau Model

    DEFF Research Database (Denmark)

    Frank, Rupert; Hainzl, Christian; Seiringer, Robert

    2014-01-01

    We present a summary of our recent rigorous derivation of the celebrated Ginzburg-Landau (GL) theory, starting from the microscopic Bardeen-Cooper-Schrieffer (BCS) model. Close to the critical temperature, GL arises as an effective theory on the macroscopic scale. The relevant scaling limit...

  14. Excited cooper pairs

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Arrietea, M. G.; Solis, M. A.; De Llano, M. [Universidad Nacional Autonoma de Mexico, Mexico, D.F (Mexico)

    2001-02-01

    Excited cooper pairs formed in a many-fermion system are those with nonzero total center-of mass momentum (CMM). They are normally neglected in the standard Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity for being too few compared with zero CMM pairs. However, a Bose-Einstein condensation picture requires both zero and nonzero CMM pairs. Assuming a BCS model interaction between fermions we determine the populations for all CMM values of Cooper pairs by actually calculating the number of nonzero-CMM pairs relative to that of zero-CMM ones in both 2D and 3D. Although this ratio decreases rapidly with CMM, the number of Cooper pairs for any specific CMM less than the maximum (or breakup of the pair) momentum turns out to be typically larger than about 95% of those with zero-CMM at zero temperature T. Even at T {approx}100 K this fraction en 2D is still as large as about 70% for typical quasi-2D cuprate superconductor parameters. [Spanish] Los pares de cooper excitados formados en un sistema de muchos electrones, son aquellos con momentos de centro de masa (CMM) diferente de cero. Normalmente estos no son tomados en cuenta en la teoria estandar de la superconductividad de Bardeen-Cooper-Schrieffer (BCS) al suponer que su numero es muy pequeno comparados con los pares de centro de masa igual a cero. Sin embargo, un esquema de condensacion Bose-Einstein requiere de ambos pares, con CMM cero y diferente de cero. Asumiendo una interaccion modelo BCS entre los fermiones, determinamos la poblacion de pares cooper con cada uno de todos los posibles valores del CMM calculando el numero de pares con momentos de centro de masa diferente de cero relativo a los pares de CMM igual a cero, en 2D y 3D. Aunque esta razon decrece rapidamente con el CMM, el numero de pares de cooper para cualquier CMM especifico menor que el momento maximo (o rompimiento de par) es tipicamente mas grande que el 95% de aquellos con CMM cero. Aun a T {approx}100 K esta fraccion en 2D es

  15. Sixty years of broken symmetries in quantum physics (from the Bogoliubov theory of superfluidity to the Standard Model)

    International Nuclear Information System (INIS)

    Shirkov, Dmitrii V

    2009-01-01

    This is a retrospective historical review of the ideas that led to the concept of the spontaneous symmetry breaking (SSB), the issue that has been implemented in quantum field theory in the form of the Higgs mechanism. The key stages covered include: the Bogoliubov microscopic theory of superfluidity (1946); the Bardeen-Cooper-Schrieffer-Bogoliubov microscopic theory of superconductivity (1957); superconductivity as superfluidity of Cooper pairs (Bogoliubov, 1958); the extension of the SSB concept to simple quantum field models (early 1960s); triumph of the Higgs model in electroweak theory (early 1980s). The role and status of the Higgs mechanism in the current Standard Model are discussed. (oral issue of the journal 'uspekhi fizicheskikh nauk')

  16. On Pokrovskii's anisotropic gap equations in superconductivity theory

    Science.gov (United States)

    Yang, Yisong

    2003-11-01

    An existence and uniqueness theorem for Pokrovskii's zero-temperature anisotropic gap equation is proved. Furthermore, it is shown that Pokrovskii's finite-temperature equation is inconsistent with the Bardeen-Cooper-Schrieffer (BCS) theory. A reformulation of the anisotropic gap equation is presented along the line of Pokrovskii and it is shown that the new equation is consistent with the BCS theory for the whole temperature range. As an application, the Markowitz-Kadanoff model for anisotropic superconductivity is considered and a rigorous proof of the half-integer-exponent isotope effect is obtained. Furthermore, a sharp estimate of the gap solution near the transition temperature is established.

  17. Resonance superfluidity in a quantum degenerate Fermi gas

    NARCIS (Netherlands)

    Kokkelmans, S.J.J.M.F.; Holland, M.; Walser, R.; Chiofalo, M.L.; Chu, S.; Vuletic, V.; Kerman, A.J.; Chin, C.

    2002-01-01

    We consider the superfluid phase transition that arises when a Feshbach resonance pairing occurs in a dilute Fermi gas. This is related to the phenomenon of superconductivity described by the seminal Bardeen-Cooper-Schrieffer (BCS) theory. In superconductivity, the phase transition is caused by a

  18. INTERLAYER OPTICAL CONDUCTIVITY OF A SUPERCONDUCTING BILAYER

    NARCIS (Netherlands)

    GARTSTEIN, YN; RICE, MJ; VANDERMAREL, D

    1994-01-01

    We employ the Bardeen-Cooper-Schrieffer theory to calculate the frequency-dependent interlayer conductivity of a superconducting bilayer, the two layers of which are coupled by weak single-particle tunneling. The effect of the superconducting transition on the normal-state absorption band is to

  19. ON THE BARDEEN-COOPER-SCHRIEFFER(BCS) HAMILTONIAN

    African Journals Online (AJOL)

    USER

    2012-10-29

    Oct 29, 2012 ... Magnetic Resonance(NMR) and Angle Resolved. Photoemission ... describe the state of the non interacting individual particles of the Fermi gas and can no more be used when the .... It serves as a testing ground for statistical.

  20. Theory of superconductivity with non-Hermitian and parity-time reversal symmetric Cooper pairing symmetry

    Science.gov (United States)

    Ghatak, Ananya; Das, Tanmoy

    2018-01-01

    Recently developed parity (P ) and time-reversal (T ) symmetric non-Hermitian systems govern a rich variety of new and characteristically distinct physical properties, which may or may not have a direct analog in their Hermitian counterparts. We study here a non-Hermitian, PT -symmetric superconducting Hamiltonian that possesses a real quasiparticle spectrum in the PT -unbroken region of the Brillouin zone. Within a single-band mean-field theory, we find that real quasiparticle energies are possible when the superconducting order parameter itself is either Hermitian or anti-Hermitian. Within the corresponding Bardeen-Cooper-Schrieffer (BCS) theory, we find that several properties are characteristically distinct and novel in the non-Hermitian pairing case than its Hermitian counterpart. One of our significant findings is that while a Hermitian superconductor gives a second-order phase transition, the non-Hermitian one produces a robust first-order phase transition. The corresponding thermodynamic properties and the Meissner effect are also modified accordingly. Finally, we discuss how such a PT -symmetric pairing can emerge from an antisymmetric potential, such as the Dzyloshinskii-Moriya interaction, but with an external bath, or complex potential, among others.

  1. Comment on the Adler-Bardeen theorem in non-Abelian gauge theories

    International Nuclear Information System (INIS)

    Fujikawa, Kazuo.

    1981-09-01

    It is pointed out that the constructive proof of the Adler-Bardeen theorem for the chiral and scale (counting identity) anomalies in non-Abelian gauge theories proceeds just as in the spinor electrodynamics, although several interesting features characteristic of non-Abelian theories appear. (author)

  2. Supersymmetric Adler-Bardeen anomaly in N=1 super-Yang-Mills theories

    International Nuclear Information System (INIS)

    Baulieu, Laurent; Martin, Alexis

    2008-01-01

    We provide a study of the supersymmetric Adler-Bardeen anomaly in the N=1, d=4,6,10 super-Yang-Mills theories. We work in the component formalism that includes shadow fields, for which Slavnov-Taylor identities can be independently set for both gauge invariance and supersymmetry. We find a method with improved descent equations for getting the solutions of the consistency conditions of both Slavnov-Taylor identities and finding the local field polynomials for the standard Adler-Bardeen anomaly and its supersymmetric counterpart. We give the explicit solution for the ten-dimensional case

  3. Nonperturbative Adler-Bardeen theorem

    International Nuclear Information System (INIS)

    Mastropietro, Vieri

    2007-01-01

    The Adler-Bardeen theorem has been proven only as a statement valid at all orders in perturbation theory, without any control on the convergence of the series. In this paper we prove a nonperturbative version of the Adler-Bardeen theorem in d=2 by using recently developed technical tools in the theory of Grassmann integration. The proof is based on the assumption that the boson propagator decays fast enough for large momenta. If the boson propagator does not decay, as for Thirring contact interactions, the anomaly in the WI (Ward Identities) is renormalized by higher order contributions

  4. Supersymmetric extension of the Adler-Bardeen theorem

    International Nuclear Information System (INIS)

    Novikov, V.A.; Zakharov, V.I.; Shifman, M.A.; Vainshtein, A.I.

    1985-01-01

    A supersymmetric generalization of the Adler-Bardeen theorem in SUSY gauge theories is given. We show that within the Adler-Bardeen procedure, both the conformal and axial anomalies are exhausted by one loop. (orig.)

  5. The new superconductors. Les nouveaux supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Gervais, F

    1991-01-01

    The first half of the book is a scanning of superconductivity from 1911 to our days, with Bardeen-Cooper-Schrieffer theory in 1957, with the concept of phonons and the importance of the Brillouin zone, with the discovery of high-tc superconductors oxides by Bednortz and Mueller in 1986. The second part is dealing with physical investigation means for trying to explain this high-tc superconductivity.

  6. Normal and superconducting metals at microwave frequencies-classic experiments

    International Nuclear Information System (INIS)

    Dheer, P.N.

    1999-01-01

    A brief review of experimental and theoretical work on the behaviour of normal and superconducting materials at microwave frequencies before the publication of Bardeen, Cooper and Schrieffer's theory of superconductivity is given. The work discussed is mostly that of Pippard and his coworkers. It is shown that these investigations lead not only to a better understanding of the electrodynamics of normal and superconducting state but also of the nature of the superconducting state itself. (author)

  7. Evidence for hyperconductivity and thermal superconductivity

    OpenAIRE

    Vdovenkov, V. A.

    2008-01-01

    Physical explanation of hyperconductivity and thermal superconductivity existence is done in given article on the basis of inherent atomic nuclei oscillations in atoms of materials which are connected with electrons and phonons and in accordance with the well known Bardeen-Cooper-Schrieffer superconductivity theory. It is shown that hyperconductivity is the self-supporting, independent physical phenomenon which is caused by oscillations of atomic nuclei in atoms of materials and the minimal t...

  8. Ab initio theory of superconductivity in a magnetic field. II. Numerical solution

    Science.gov (United States)

    Linscheid, A.; Sanna, A.; Gross, E. K. U.

    2015-07-01

    We numerically investigate the spin density functional theory for superconductors (SpinSCDFT) and the approximated exchange-correlation functional, derived and presented in the preceding Paper I [A. Linscheid et al., Phys. Rev. B 92, 024505 (2015), 10.1103/PhysRevB.92.024505]. As a test system, we employ a free-electron gas featuring an exchange splitting, a phononic pairing field, and a Coulomb repulsion. SpinSCDFT results are compared with Sarma, the Bardeen-Cooper-Schrieffer theory, and with an Eliashberg type of approach. We find that the spectrum of the superconducting Kohn-Sham SpinSCDFT system is not in agreement with the true quasiparticle structure. Therefore, starting from the Dyson equation, we derive a scheme that allows to compute the many-body excitations of the superconductor and represents the extension to superconductivity of the G0W0 method in band-structure theory. This superconducting G0W0 method vastly improves the predicted spectra.

  9. The war of the cold: an history of the superconductivity; La guerre du froid: une histoire de la supraconductivite

    Energy Technology Data Exchange (ETDEWEB)

    Matricon, J; Waysand, G [Paris-7 Univ., 75 (France)

    1994-12-31

    The evolution of superconductivity is described from a scientific, and social points of view. The evolution of researches and realizations towards the absolute zero temperature leading to the discovery of superconductivity by Gilles Holst in 1991, is followed by the theoretical modelization of the superconductivity phenomena leading to the Ginzburg and Landau theory in 1950 and to the Bardeen, Cooper and Schrieffer theory in 1957. Then researches on materials that lead to high-tc superconductors are presented with some applications. (A.B.). refs., figs,. tabs.

  10. The war of the cold: an history of the superconductivity

    International Nuclear Information System (INIS)

    Matricon, J.; Waysand, G.

    1994-01-01

    The evolution of superconductivity is described from a scientific, and social points of view. The evolution of researches and realizations towards the absolute zero temperature leading to the discovery of superconductivity by Gilles Holst in 1991, is followed by the theoretical modelization of the superconductivity phenomena leading to the Ginzburg and Landau theory in 1950 and to the Bardeen, Cooper and Schrieffer theory in 1957. Then researches on materials that lead to high-tc superconductors are presented with some applications. (A.B.). refs., figs,. tabs

  11. BCS 50 years

    CERN Document Server

    Feldman, Dimitri

    2011-01-01

    The BCS theory of superconductivity developed in 1957 by Bardeen, Cooper and Schrieffer has been remarkably successful in explaining the properties of superconductors. In addition, concepts from BCS have been incorporated into diverse fields of physics, from nuclear physics and dense quark matter to the current standard model. Practical applications include SQUIDs, magnetic resonance imaging, superconducting electronics and the transmission of electricity. This invaluable book is a compilation of both a historical account and a discussion of the current state of theory and experiment. With con

  12. Electron and Cooper-pair transport across a single magnetic molecule explored with a scanning tunneling microscope

    Science.gov (United States)

    Brand, J.; Gozdzik, S.; Néel, N.; Lado, J. L.; Fernández-Rossier, J.; Kröger, J.

    2018-05-01

    A scanning tunneling microscope is used to explore the evolution of electron and Cooper-pair transport across single Mn-phthalocyanine molecules adsorbed on Pb(111) from tunneling to contact ranges. Normal-metal as well as superconducting tips give rise to a gradual transition of the Bardeen-Cooper-Schrieffer energy gap in the tunneling range into a zero-energy resonance close to and at contact. Supporting transport calculations show that in the normal-metal-superconductor junctions this resonance reflects the merging of in-gap Yu-Shiba-Rusinov states as well as the onset of Andreev reflection. For the superconductor-superconductor contacts, the zero-energy resonance is rationalized in terms of a finite Josephson current that is carried by phase-dependent Andreev and Yu-Shiba-Rusinov levels.

  13. The supersymmetric Adler-Bardeen theorem and regularization by dimensional reduction

    International Nuclear Information System (INIS)

    Ensign, P.; Mahanthappa, K.T.

    1987-01-01

    We examine the subtraction scheme dependence of the anomaly of the supersymmetric, gauge singlet axial current in pure and coupled supersymmetric Yang-Mills theories. Preserving supersymmetry and gauge invariance explicitly by using supersymmetric background field theory and dimensional reduction, we show that only the one-loop value of the axial anomaly is subtraction scheme independent, and that one can always define a subtraction scheme in which the Adler-Bardeen theorem is satisfied to all orders in perturbation theory. In general this subtraction scheme may be non-minimal, but in both the pure and the coupled theories, the Adler-Bardeen theorem is satisfied to two loops in minimal subtraction. (orig.)

  14. Multi-band description of the specific heat and thermodynamic critical field in MgB2 superconductor

    Science.gov (United States)

    Szcześniak, R.; Jarosik, M. W.; Tarasewicz, P.; Durajski, A. P.

    2018-05-01

    The thermodynamic properties of MgB2 superconductor can be explained using the multi-band models. In the present paper we have examined the experimental data available in literature and we have found out that it is possible to reproduce the measured values of the superconducting energy gaps, the thermodynamic critical magnetic field and specific heat jump within the framework of two-band Eliashberg formalism and appropriate defined free energy difference between superconducting and normal state. Moreover, we found that the obtained results differ significantly from the predictions of the conventional Bardeen-Cooper-Schrieffer theory.

  15. Bardeen regular black hole with an electric source

    Science.gov (United States)

    Rodrigues, Manuel E.; Silva, Marcos V. de S.

    2018-06-01

    If some energy conditions on the stress-energy tensor are violated, is possible construct regular black holes in General Relativity and in alternative theories of gravity. This type of solution has horizons but does not present singularities. The first regular black hole was presented by Bardeen and can be obtained from Einstein equations in the presence of an electromagnetic field. E. Ayon-Beato and A. Garcia reinterpreted the Bardeen metric as a magnetic solution of General Relativity coupled to a nonlinear electrodynamics. In this work, we show that the Bardeen model may also be interpreted as a solution of Einstein equations in the presence of an electric source, whose electric field does not behave as a Coulomb field. We analyzed the asymptotic forms of the Lagrangian for the electric case and also analyzed the energy conditions.

  16. The external field dependence of the BCS critical temperature

    DEFF Research Database (Denmark)

    Frank, Rupert L.; Hainzl, Christian; Seiringer, Robert

    2016-01-01

    We consider the Bardeen-Cooper-Schrieffer free energy functional for particles interacting via a two-body potential on a microscopic scale and in the presence of weak external fields varying on a macroscopic scale. We study the influence of the external fields on the critical temperature. We show...

  17. Fluctuations of Imbalanced Fermionic Superfluids in Two Dimensions Induce Continuous Quantum Phase Transitions and Non-Fermi-Liquid Behavior

    Directory of Open Access Journals (Sweden)

    Philipp Strack

    2014-04-01

    Full Text Available We study the nature of superfluid pairing in imbalanced Fermi mixtures in two spatial dimensions. We present evidence that the combined effect of Fermi surface mismatch and order parameter fluctuations of the superfluid condensate can lead to continuous quantum phase transitions from a normal Fermi mixture to an intermediate Sarma-Liu-Wilczek superfluid with two gapless Fermi surfaces—even when mean-field theory (incorrectly predicts a first-order transition to a phase-separated “Bardeen-Cooper-Schrieffer plus excess fermions” ground state. We propose a mechanism for non-Fermi-liquid behavior from repeated scattering processes between the two Fermi surfaces and fluctuating Cooper pairs. Prospects for experimental observation with ultracold atoms are discussed.

  18. Evidence for pair correlation effects in heavy ion reactions

    CERN Document Server

    Auditore, L; D'Amico, V; De Pasquale, D; Trifiró, A; Trimarchi, M; Italiano, A

    2003-01-01

    The study of the sup 1 sup 2 C( sup 1 sup 4 N, sup 1 sup 4 N) sup 1 sup 2 C reaction was performed at 28 and 35 MeV beam energies. The results were analyzed in the frame of the EFRDWBA (Exact-Finite-Range Distorted Wave Born Approximation) assuming the simultaneous and sequential transfer of a np pair. The angular distributions, fairly reproduced in the first case, confirm the validity of the generalized BCS (Bardeen-Cooper-Schrieffer) theory to explain this behaviour. Moreover, this process could be regarded as a possible Nuclear Josephson Effect. (author)

  19. Positron-annihilation studies of the superconductivity transition in YBa2Cu3O/sub 7-//sub x/

    International Nuclear Information System (INIS)

    Smedskjaer, L.C.; Veal, B.W.; Legnini, D.G.; Paulikas, A.P.; Nowicki, L.J.

    1988-01-01

    Positron-annihilation studies, by Doppler broadening, of the superconducting transition in YBa 2 Cu 3 O/sub 7-//sub x/(x≅0.1) have been made. Below T/sub c/ a large positive temperature dependence of the lineshape parameter is observed, while at (or near) T/sub c/ an almost discontinuous increase in the lineshape parameter takes place. The behavior below T/sub c/ may be consistent with a Bardeen-Cooper-Schrieffer-like theory if an energy band with a small dispersion crosses the Fermi level. The discontinuity is not clearly understood, but may be due to a major change in the electronic structure taking place with the onset of superconductivity

  20. Interplay of Phonon and Exciton-Mediated Superconductivity in Hybrid Semiconductor-Superconductor Structures

    Science.gov (United States)

    Skopelitis, Petros; Cherotchenko, Evgenia D.; Kavokin, Alexey V.; Posazhennikova, Anna

    2018-03-01

    We predict a strong enhancement of the critical temperature in a conventional Bardeen-Cooper-Schrieffer (BCS) superconductor in the presence of a bosonic condensate of exciton polaritons. The effect depends strongly on the ratio of the cutoff frequencies for phonon and exciton-polariton mediated BCS superconductivity, respectively. We also discuss a possible design of hybrid semiconductor-superconductor structures suitable for the experimental observation of such an effect.

  1. Superfluidity of a dipolar Fermi gas in 2D optical lattices bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Camacho-Guardian, A.; Paredes, R. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico (Mexico)

    2016-12-15

    Ultracold Fermi molecules lying in 2D square optical lattices bilayers with its dipole moment perpendicularly aligned to the layers, having interlayer finite range s-wave interactions, are shown to form superfluid phases, both, in the Bardeen, Cooper and Schrieffer (BCS) regime of Cooper pairs, and in the condensate regime of bound dimeric molecules. We demonstrate this result using a functional integral scheme within the Ginzburg-Landau theory. For the deep Berezinskii-Kosterlitz-Thouless (BKT) phase transition, we predict critical temperatures around 5 nK and 20 nK for {sup 23}Na{sup 40}K and OH molecules, which are within reach of current experiments [J. W. Park, S. Will and M. Zwierlein, Phys. Rev. Lett. 114, 205302 (2015)]. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Regularization with higher covariant derivatives, anomalies and the Adler-Bardeen theorem

    International Nuclear Information System (INIS)

    Day, M.

    1983-01-01

    Complications arising in the renormalization of a theory regulated by the method of higher covariant derivatives supplemented with a modified Pauli-Villars regularization are discussed. The proof of the Adler-Bardeen theorem using the method of higher covariant derivatives has to be modified. (orig.)

  3. Superconductivity in borides and carbides

    International Nuclear Information System (INIS)

    Muranaka, Takahiro

    2007-01-01

    It was thought that intermetallic superconductors do not exhibit superconductivity at temperatures over 30 K because of the Bardeen-Cooper-Schrieffer (BCS) limit; therefore, researchers have been interested in high-T c cuprates. Our group discovered high-T c superconductivity in MgB 2 at 39 K in 2001. This discovery has initiated a substantial interest in the potential of high-T c superconductivity in intermetallic compounds that include 'light' elements (borides, carbides, etc.). (author)

  4. Energy gap and upper critical field of the new magnetic superconductor Mo3Sb7 found by the Andreev reflection method

    International Nuclear Information System (INIS)

    Dmitriev, V M; Rybaltchenko, L F; Ishchenko, L A; Khristenko, E V; Bukowski, Z; Troc, R

    2006-01-01

    We present the data of the point contact (PC) Andreev-reflection measurements on the new paramagnetic superconductor Mo 3 Sb 7 , which were used for finding the energy gap Δ and upper critical field H c2 for this compound. The maximum gap value, reduced to the zero temperature via the Bardeen-Cooper-Schrieffer (BCS) theory, turned out to be Δ (0) ≅ 0.32 meV, which is slightly smaller than that expected from the BCS theory, Δ BCS (0) ≅ 0.35 meV. The temperature dependence of the gap obeys the BCS theory approximately. The H c2 (0) value of about 16.5 kOe was obtained from fitting the experimental data to the conventional H(T) dependence, which is quadratic in temperature. This value is in close agreement with the result from magnetization measurements of 17.2 kOe

  5. Quantitative comparison between theoretical predictions and experimental results for the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Perali, A.; Pieri, P.; Strinati, G.C.

    2004-01-01

    Theoretical predictions for the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover of trapped Fermi atoms are compared with recent experimental results for the density profiles of L 6 i. The calculations rest on a single theoretical approach that includes pairing fluctuations beyond mean-field. Excellent agreement with experimental results is obtained. Theoretical predictions for the zero-temperature chemical potential and gap at the unitarity limit are also found to compare extremely well with Quantum Monte Carlo simulations and with recent experimental results

  6. Algebraic methods for a direct calculus of observables in the theory of nuclear band structure

    International Nuclear Information System (INIS)

    Klein, A.

    1983-01-01

    The basis for much of the present understanding of nuclear structure derives from the study of mean field approximations (such as Hartree-Fock or Bardeen-Cooper-Schrieffer) and of small deviations from the mean field (random phase approximation and the cranking model). This review is devoted to the study of a theoretical framework for these and other approximations. The approach is the application of Heisenberg matrix mechanics to the nuclear many-body problem. It utilizes a calculus for matrix elements of suitably chosen simple operators between exact eigenstates of the Hamiltonian. In the first class of investigations, in which single fermion operators were chosen, one ends with a theory providing a justification for and generalization of various core-particle coupling models and a basis for nuclear field theory. In a further group of studies of matrix elements of multipole and/or pair operators, the collective behavior of even nuclei can be examined, divorced from their coupling to neighboring odd nuclei. Various investigations carried out over two decades are described. A common theoretical thread is that the calculations are done uniformly in fermion shell model space in a representation in which the Hamiltonian is diagonal. New developments which may alter these considerations profoundly by enlarging the framework in which they may be carried out are envisaged. (author)

  7. Fluctuation instability of the Dirac Sea in quark models of strong interactions

    Science.gov (United States)

    Zinovjev, G. M.; Molodtsov, S. V.

    2016-03-01

    A number of exactly integrable (quark) models of quantum field theory that feature an infinite correlation length are considered. An instability of the standard vacuum quark ensemble, a Dirac sea (in spacetimes of dimension higher than three), is highlighted. It is due to a strong ground-state degeneracy, which, in turn, stems from a special character of the energy distribution. In the case where the momentumcutoff parameter tends to infinity, this distribution becomes infinitely narrow and leads to large (unlimited) fluctuations. A comparison of the results for various vacuum ensembles, including a Dirac sea, a neutral ensemble, a color superconductor, and a Bardeen-Cooper-Schrieffer (BCS) state, was performed. In the presence of color quark interaction, a BCS state is unambiguously chosen as the ground state of the quark ensemble.

  8. Microscopic description of average level spacing in even-even nuclei

    International Nuclear Information System (INIS)

    Huong, Le Thi Quynh; Hung, Nguyen Quang; Phuc, Le Tan

    2017-01-01

    A microscopic theoretical approach to the average level spacing at the neutron binding energy in even-even nuclei is proposed. The approach is derived based on the Bardeen-Cooper-Schrieffer (BCS) theory at finite temperature and projection M of the total angular momentum J , which is often used to describe the superfluid properties of hot rotating nuclei. The exact relation of the J -dependent total level density to the M -dependent state densities, based on which the average level spacing is calculated, was employed. The numerical calculations carried out for several even-even nuclei have shown that in order to reproduce the experimental average level spacing, the M -dependent pairing gaps as well as the exact relation of the J -dependent total level density formula should be simultaneously used. (paper)

  9. Proximity effect and Andreev reflection in single-C{sub 60} junctions

    Energy Technology Data Exchange (ETDEWEB)

    Brand, Jonathan; Neel, Nicolas; Kroeger, Joerg [Institut fuer Physik, Technische Universitaet Ilmenau, D-98693 Ilmenau (Germany)

    2016-07-01

    Single C{sub 60} molecules deposited on an ultrathin oxide film on Nb(110) were investigated using a low-temperature scanning tunnelling microscope. Spectroscopy of the differential conductance (dI/dV) in the tunnelling range indicates proximity-induced superconductivity in junctions comprising the oxide layer as well as single C{sub 60} molecules. Andreev reflection is enhanced upon controlled fabrication of tip-surface contacts. With decreasing electrode separation the Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak in dI/dV spectra reflecting the spectroscopic signature of Andreev reflection. The current-voltage characteristics of the tunnelling and contact junctions are well described by the Blonder-Tinkham-Klapwijk theory. Our spectroscopic data evidence the influence of the electrodes' atomic-scale structure on electron transport across normal metal-superconductor interfaces.

  10. Thermodynamical stability of the Bardeen black hole

    Energy Technology Data Exchange (ETDEWEB)

    Bretón, Nora [Dpto. de Física, Centro de Investigación y de Estudios Avanzados del I. P. N., Apdo. 14-740, D.F. (Mexico); Perez Bergliaffa, Santiago E. [Dpto. de Física, U. Estado do Rio de Janeiro (Brazil)

    2014-01-14

    We analyze the stability of the regular magnetic Bardeen black hole both thermodynamically and dynamically. For the thermodynamical analysis we consider a microcanonical ensemble and apply the turning point method. This method allows to decide a change in stability (or instability) of a system, requiring only the assumption of smoothness of the area functional. The dynamical stability is asserted using criteria based on the signs of the Lagrangian and its derivatives. It turns out from our analysis that the Bardeen black hole is both thermodynamically and dynamically stable.

  11. BEC-BCS-laser crossover in Coulomb-correlated electron-hole-photon systems

    International Nuclear Information System (INIS)

    Yamaguchi, M; Kamide, K; Ogawa, T; Yamamoto, Y

    2012-01-01

    Many-body features caused by Coulomb correlations are of great importance for understanding phenomena pertaining to polariton systems in semiconductor microcavities, i.e. electron-hole-photon systems. Remarkable many-body effects are shown to exist in both thermal-equilibrium phases and non-equilibrium lasing states. We then show a unified framework for connecting the thermal-equilibrium and the non-equilibrium steady states based on a non-equilibrium Green's function approach. Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS)-laser crossovers are investigated by using this approach. (paper)

  12. Pseudo-Coulomb potential in singlet superconductivity

    International Nuclear Information System (INIS)

    Daemen, L.L.; Overhauser, A.W.

    1988-01-01

    Reduction of the screened Coulomb potential parameter μ to μ/sup */ = μ/[1+μ ln(E/sub F//(h/2π)ω/sub D/)] is related to the pair correlation function at r = 0. This correlation function is calculated for both the simple Cooper-pair problem and standard Bardeen-Cooper-Schrieffer (BCS) theory by use of a two-square-well model (with λ and μ describing the attraction and repulsion). Results are compared with values obtained for a one-square-well model (having the suitable net attraction, e.g., λ-μ/sup */ in the BCS case). For the BCS case, the ''true'' pair correlation at r = 0 is reduced by a factor (μ/sup *//μ) 2 relative to the fictitious (one-square-well) value (even though Δ is the same for both models). The reduction factor is typically ≅(1/25. It follows that any short-range attractive contribution to superconducting pairing will suffer a reduction similar to that for the Coulomb repulsion

  13. Signature of magnetic-dependent gapless odd frequency states at superconductor / ferromagnet interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Jason [Department of Materials Science, 27 Charles Babbage Road, Cambridge, CB30FS (United Kingdom)

    2015-07-01

    The theory of superconductivity developed by Bardeen, Cooper, and Schrieffer (BCS) explains the stabilisation of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap below which the density of states (DoS) is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. In this talk I will present scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb sub-gap superconducting DoS on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results verify odd frequency spin-triplet superconductivity at superconductor / inhomogeneous magnet interfaces.

  14. S-pairing in neutron matter: I. Correlated basis function theory

    International Nuclear Information System (INIS)

    Fabrocini, Adelchi; Fantoni, Stefano; Illarionov, Alexey Yu.; Schmidt, Kevin E.

    2008-01-01

    S-wave pairing in neutron matter is studied within an extension of correlated basis function (CBF) theory to include the strong, short range spatial correlations due to realistic nuclear forces and the pairing correlations of the Bardeen, Cooper and Schrieffer (BCS) approach. The correlation operator contains central as well as tensor components. The correlated BCS scheme of [S. Fantoni, Nucl. Phys. A 363 (1981) 381], developed for simple scalar correlations, is generalized to this more realistic case. The energy of the correlated pair condensed phase of neutron matter is evaluated at the two-body order of the cluster expansion, but considering the one-body density and the corresponding energy vertex corrections at the first order of the Power Series expansion. Based on these approximations, we have derived a system of Euler equations for the correlation factors and for the BCS amplitudes, resulting in correlated nonlinear gap equations, formally close to the standard BCS ones. These equations have been solved for the momentum independent part of several realistic potentials (Reid, Argonne v 14 and Argonne v 8 ' ) to stress the role of the tensor correlations and of the many-body effects. Simple Jastrow correlations and/or the lack of the density corrections enhance the gap with respect to uncorrelated BCS, whereas it is reduced according to the strength of the tensor interaction and following the inclusion of many-body contributions

  15. Superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O3

    International Nuclear Information System (INIS)

    Schlesinger, Z.; Collins, R.T.; Scott, B.A.; Calise, J.A.

    1988-01-01

    We report the first infrared measurement of the superconducting energy gap of BaPb/sub 1-//sub x/Bi/sub x/O 3 . In our polycrystalline samples with T/sub c/≅9.5 K (x≅0.2) we obtain 2Δ≅3.2kT/sub c/, roughly in agreement with the weak-coupling Bardeen-Cooper-Schrieffer prediction, 2Δ = 3.5kT/sub c/, and with tunneling measurements of the gap. We do not observe any structure above the gap energy associated with strong coupling

  16. The BCS-BEC Crossover

    Science.gov (United States)

    Parish, Meera M.

    2015-09-01

    This chapter presents the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of weakly correlated pairs of fermions to the Bose-Einstein condensation (BEC) of diatomic molecules in the atomic Fermi gas. Our aim is to provide a pedagogical review of the BCS-BEC crossover, with an emphasis on the basic concepts, particularly those that are not generally known or are difficult to find in the literature. We shall not attempt to give an exhaustive survey of current research in the limited space here; where possible, we will direct the reader to more extensive reviews.

  17. Phase diagrams for an ideal gas mixture of fermionic atoms and bosonic molecules

    DEFF Research Database (Denmark)

    Williams, J. E.; Nygaard, Nicolai; Clark, C. W.

    2004-01-01

    We calculate the phase diagrams for a harmonically trapped ideal gas mixture of fermionic atoms and bosonic molecules in chemical and thermal equilibrium, where the internal energy of the molecules can be adjusted relative to that of the atoms by use of a tunable Feshbach resonance. We plot...... diagrams obtained in recent experiments on the Bose-Einstein condensation to Bardeen-Cooper-Schrieffer crossover, in which the condensate fraction is plotted as a function of the initial temperature of the Fermi gas measured before a sweep of the magnetic field through the resonance region....

  18. Importance of the single-particle continuum in BCS pairing with a pseudostate basis

    Directory of Open Access Journals (Sweden)

    Lay J. A.

    2016-01-01

    Full Text Available In a recent work [arXiv:1510.03185] the use of the Transformed Harmonic Oscillator (THO basis for the discretization of the singleparticle continuum into a Generalized Bardeen-Cooper-Schrieffer (BCS formalism was proposed for the description of weakly bound nuclei. We make use of the flexibility of this formalism to study the evolution of the pairing when the nucleus becomes more and more weakly bound. Specifically we focus on the evolution of the occupation of the different partial waves in 22O when the Fermi level approaches zero.

  19. Pairing in exotic neutron-rich nuclei near the drip line and in the crust of neutron stars

    Science.gov (United States)

    Pastore, A.; Margueron, J.; Schuck, P.; Viñas, X.

    2013-09-01

    Exotic and drip-line nuclei as well as nuclei immersed in a low-density gas of neutrons in the inner crust of neutron stars are systematically investigated with respect to their neutron pairing properties. This is done using Skyrme density-functional and different pairing forces such as a density-dependent contact interaction and a separable form of a finite-range Gogny interaction. Hartree-Fock-Bogoliubov (HFB) and Bardeen-Cooper-Schrieffer (BCS) theories are compared. It is found that neutron pairing is reduced towards the drip line while overcast by strong shell effects. Furthermore, resonances in the continuum can have an important effect counterbalancing the tendency of reduction and leading to a persistence of pairing at the drip line. It is also shown that in these systems the difference between HFB and BCS approaches can be quantitatively large.

  20. Bardeen-anomaly and Wess-Zumino term in the supersymmetric standard model

    CERN Document Server

    Ferrara, Sergio; Porrati, Massimo; Stora, Raymond Félix

    1994-01-01

    We construct the Bardeen anomaly and its related Wess-Zumino term in the supersymmetric standard model. In particular we show that it can be written in terms of a composite linear superfield related to supersymmetrized Chern-Simons forms, in very much the same way as the Green-Schwarz term in four-dimensional string theory. Some physical applications, such as the contribution to the g-2 of gauginos when a heavy top is integrated out, are briefly discussed.

  1. Theory of the Anderson impurity model: The Schrieffer endash Wolff transformation reexamined

    International Nuclear Information System (INIS)

    Kehrein, S.K.; Mielke, A.

    1996-01-01

    We test the method of infinitesimal unitary transformations recently introduced by Wegner on the Anderson single impurity model. It is demonstrated that infinitesimal unitary transformations in contrast to the Schrieffer endash Wolff transformation allow the construction of an effective Kondo Hamiltonian consistent with the established results in this well understood model. The main reason for this is the intrinsic energy scale separation of Wegner close-quote s approach with respect to arbitrary energy differences coupled by matrix elements. This allows the construction of an effective Hamiltonian without facing a vanishing energy denominator problem. Similar energy denominator problems are troublesome in many models. Infinitesimal unitary transformations have the potential to provide a general framework for the systematic derivation of effective Hamiltonians without such problems. Copyright copyright 1996 Academic Press, Inc

  2. Dependence of the microwave surface resistance of superconducting niobium on the magnitude of the rf field

    Energy Technology Data Exchange (ETDEWEB)

    Romanenko, A.; Grassellino, A. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

    2013-06-24

    Utilizing difference in temperature dependencies we decoupled Bardeen-Cooper-Schrieffer (BCS) and residual components of the microwave surface resistance of superconducting niobium at all rf fields up to B{sub rf}{approx}115 mT. We reveal that the residual resistance decreases with field at B{sub rf} Less-Than-Or-Equivalent-To 40 mT and strongly increases in chemically treated niobium at B{sub rf}>80 mT. We find that BCS surface resistance is weakly dependent on field in the clean limit, whereas a strong and peculiar field dependence emerges after 120 Degree-Sign C vacuum baking.

  3. Electron tunneling and the energy gap in Bi2Sr2CaCu2Ox

    Science.gov (United States)

    Lee, Mark; Mitzi, D. B.; Kapitulnik, A.; Beasley, M. R.

    1989-01-01

    Results of electron tunneling on single crystals of the Bi2Sr2CaCu2Ox superconductor are reported. The junctions show a gap structure with Δ~=25 meV, whose temperature dependence exhibits a qualitatively Bardeen-Cooper-Schrieffer-like behavior with a gap-closing Tc~=81-85 K. Comparisons of these tunneling spectra to those obtained on YBa2Cu3O7-x are made. Evidence that 2Δ/kTc~7 for both Ba2Sr2CaCu2Ox and YBa2Cu3O7-x is also discussed.

  4. Goldstone mode and pair-breaking excitations in atomic Fermi superfluids

    Science.gov (United States)

    Hoinka, Sascha; Dyke, Paul; Lingham, Marcus G.; Kinnunen, Jami J.; Bruun, Georg M.; Vale, Chris J.

    2017-10-01

    Spontaneous symmetry breaking is a central paradigm of elementary particle physics, magnetism, superfluidity and superconductivity. According to Goldstone's theorem, phase transitions that break continuous symmetries lead to the existence of gapless excitations in the long-wavelength limit. These Goldstone modes can become the dominant low-energy excitation, showing that symmetry breaking has a profound impact on the physical properties of matter. Here, we present a comprehensive study of the elementary excitations in a homogeneous strongly interacting Fermi gas through the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC) of molecules using two-photon Bragg spectroscopy. The spectra exhibit a discrete Goldstone mode, associated with the broken-symmetry superfluid phase, as well as pair-breaking single-particle excitations. Our techniques yield a direct determination of the superfluid pairing gap and speed of sound in close agreement with strong-coupling theories.

  5. Experimental evidence for s-wave pairing symmetry in superconducting Cu(x)Bi2Se3 single crystals using a scanning tunneling microscope.

    Science.gov (United States)

    Levy, Niv; Zhang, Tong; Ha, Jeonghoon; Sharifi, Fred; Talin, A Alec; Kuk, Young; Stroscio, Joseph A

    2013-03-15

    Topological superconductors represent a newly predicted phase of matter that is topologically distinct from conventional superconducting condensates of Cooper pairs. As a manifestation of their topological character, topological superconductors support solid-state realizations of Majorana fermions at their boundaries. The recently discovered superconductor Cu(x)Bi(2)Se(3) has been theoretically proposed as an odd-parity superconductor in the time-reversal-invariant topological superconductor class, and point-contact spectroscopy measurements have reported the observation of zero-bias conductance peaks corresponding to Majorana states in this material. Here we report scanning tunneling microscopy measurements of the superconducting energy gap in Cu(x)Bi(2)Se(3) as a function of spatial position and applied magnetic field. The tunneling spectrum shows that the density of states at the Fermi level is fully gapped without any in-gap states. The spectrum is well described by the Bardeen-Cooper-Schrieffer theory with a momentum independent order parameter, which suggests that Cu(x)Bi(2)Se(3) is a classical s-wave superconductor contrary to previous expectations and measurements.

  6. Supercurrents, anomalies, and the Adler-Bardeen theorem

    International Nuclear Information System (INIS)

    Grisaru, M.T.; Milewski, B.; Zanon, D.

    1985-01-01

    If SSYM is regularized by dimensional reduction in superspace it is possible to explicitly construct two distinct composite operators that describe the supercurrent and the Adler-Bardeen current respectively. We exhibit these operators and study their properties. (orig.)

  7. The essential role of vibronic interactions in electron pairing in the micro- and macroscopic sized materials

    International Nuclear Information System (INIS)

    Kato, Takashi

    2010-01-01

    Graphical abstract: The electron-phonon interactions destroy the electron pairs formed by Coulomb interactions, and at the same time, form the energy gap by which the electron pairs become stable. - Abstract: In order to discuss how the nondissipative delocalized diamagnetic currents in the microscopic sized materials are closely related to the conventional superconductivity in the macroscopic sized materials, the unified theory, by which various sized superconductivity can be explained, is suggested. It has been believed for a long time that the electron-phonon interactions play an essential role in the attractive electron-electron interactions, as described in the Bardeen-Cooper-Schrieffer (BCS) theory in the conventional superconductivity. However, it is suggested in this paper that the electron-phonon interactions do not play an essential role in the attractive electron-electron interactions but play an essential role in the forming of energy gap by which the electron pairs formed by the attractive Coulomb interactions in the conventional superconducting states become more stable than those in the normal metallic states at low temperatures.

  8. Superconductivity in transition metals.

    Science.gov (United States)

    Slocombe, Daniel R; Kuznetsov, Vladimir L; Grochala, Wojciech; Williams, Robert J P; Edwards, Peter P

    2015-03-13

    A qualitative account of the occurrence and magnitude of superconductivity in the transition metals is presented, with a primary emphasis on elements of the first row. Correlations of the important parameters of the Bardeen-Cooper-Schrieffer theory of superconductivity are highlighted with respect to the number of d-shell electrons per atom of the transition elements. The relation between the systematics of superconductivity in the transition metals and the periodic table high-lights the importance of short-range or chemical bonding on the remarkable natural phenomenon of superconductivity in the chemical elements. A relationship between superconductivity and lattice instability appears naturally as a balance and competition between localized covalent bonding and so-called broken covalency, which favours d-electron delocalization and superconductivity. In this manner, the systematics of superconductivity and various other physical properties of the transition elements are related and unified. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  9. Excitonic condensation for the surface states of topological insulator bilayers

    International Nuclear Information System (INIS)

    Wang Zhigang; Fu Zhenguo; Zhang Ping; Hao Ningning

    2012-01-01

    We propose a generic topological insulator bilayer (TIB) system to study the excitonic condensation with self-consistent mean-field (SCMF) theory. We show that the TIB system presents the crossover behavior from the Bardeen-Cooper-Schrieffer (BCS) limit to the Bose-Einstein condensation (BEC) limit. Moreover, in comparison with traditional semiconductor systems, we find that for the present system the superfluid property in the BEC phase is more sensitive to electron-hole density imbalance and the BCS phase is more robust. Applying this TIB model to the Bi 2 Se 3 -family material, we find that the BEC phase is most likely to be observed in experiment. We also calculate the critical temperature for the Bi 2 Se 3 -family TIB system, which is ∼100 K. More interestingly, one can expect this relative high-temperature excitonic condensation, since our calculated SCMF critical temperature is approximately equal to the Kosterlitz-Thouless transition temperature. (paper)

  10. Electron tunneling and the energy gap in Bi2Sr2CaCu2O/sub x/

    International Nuclear Information System (INIS)

    Lee, M.; Mitzi, D.B.; Kapitulnik, A.; Beasley, M.R.

    1989-01-01

    Results of electron tunneling on single crystals of the Bi 2 Sr 2 CaCu 2 O/sub x/ superconductor are reported. The junctions show a gap structure with Δ≅25 meV, whose temperature dependence exhibits a qualitatively Bardeen-Cooper-Schrieffer-like behavior with a gap-closing T/sub c/≅81--85 K. Comparisons of these tunneling spectra to those obtained on YBa 2 Cu 3 O/sub 7-//sub x/ are made. Evidence that 2Δ/kT/sub c/∼7 for both Ba 2 Sr 2 CaCu 2 O/sub x/ and YBa 2 Cu 3 O/sub 7-//sub x/ is also discussed

  11. What is strange about high-temperature superconductivity in cuprates?

    Science.gov (United States)

    Božović, I.; He, X.; Wu, J.; Bollinger, A. T.

    2017-10-01

    Cuprate superconductors exhibit many features, but the ultimate question is why the critical temperature (Tc) is so high. The fundamental dichotomy is between the weak-pairing, Bardeen-Cooper-Schrieffer (BCS) scenario, and Bose-Einstein condensation (BEC) of strongly-bound pairs. While for underdoped cuprates it is hotly debated which of these pictures is appropriate, it is commonly believed that on the overdoped side strongly-correlated fermion physics evolves smoothly into the conventional BCS behavior. Here, we test this dogma by studying the dependence of key superconducting parameters on doping, temperature, and external fields, in thousands of cuprate samples. The findings do not conform to BCS predictions anywhere in the phase diagram.

  12. Analytic solution of the BCS gap equation with a logarithmic singularity in the density of states

    International Nuclear Information System (INIS)

    Bhardwaj, A.; Muthu, S.K.

    1999-01-01

    The Bardeen-Cooper-Schrieffer (BCS) gap equation is solved analytically for a density of states function with a logarithmic singularity. It is an extension of our earlier work where we had assumed a constant density of states. We continue to work in the weak-coupling limit and consider both phononic and non-phononic pairings. Expressions are obtained for T c , Δ 0 (the gap at T=0), and the jump in the electronic specific heat at T=T c . We also calculate the isotope exponent and show that it is possible to reproduce the broad features of the experimental results in this framework. (orig.)

  13. Cooper pairs versus Bose condensed molecules: The ground-state current in superfluid 3He-A

    International Nuclear Information System (INIS)

    Mermin, N.D.; Muzikar, P.

    1980-01-01

    We present a new calculation of the current g flowing in a ground state of the Bardeen-Cooper-Schrieffer (BCS) form for a weakly inhomogeneous superfluid with the symmetry of 3 He-A. When the structure of the order parameter not determined by symmetry is appropriate to 3 He-A and when the mass density rho of the helium is essentially uniform, our current reduces to that calculated by Cross. If the mass density is allowed to vary, we find a generalization of the Cross current which shows that when v/sub s/=0 and the anisotropy axis l is uniform, then the current is simply (h/4M) del-arrow-rightrho x l. We show that this property of the BCS ground state, which taken with the Cross definition leads to an ''intrinsic angular momentum density'' of rhoh/2M at zero temperature, also follows directly from the Gor'kov equations. If the range of the order parameter is taken to be small compared with the interatomic separation, then the ground state does not describe 3 He-A, but a Bose-Einstein condensate of tightly bound diatomic molecules. In this limit our current reduces to the form calculated by Ishikawa et al. We indicate why their analysis is only valid in this limit, and offer some rather more general remarks on the differences between Cooper pairing and the Bose-Einstein condensation of diatomic molecules

  14. Comparison between a diagrammatic theory for the BCS-BEC crossover and quantum Monte Carlo results

    International Nuclear Information System (INIS)

    Pieri, P.; Pisani, L.; Strinati, G.C.

    2005-01-01

    Predictions for the chemical potential and the excitation gap recently obtained by our diagrammatic theory for the Bardeen-Cooper-Schreiffer-Bose-Einstein Condensation crossover in the superfluid phase are compared with quantum Monte Carlo results at zero temperature now available in the literature. A remarkable agreement is found between the results obtained by the two approaches

  15. Quantum molecular dynamics study of the Su-Schrieffer-Heeger model

    NARCIS (Netherlands)

    Michielsen, Kristel; Raedt, Hans De

    A quantum molecular dynamics technique is presented to compute the static and dynamic properties of a system of fermions coupled to classical degrees of freedom. The method is employed to investigate the properties of the Su-Schrieffer-Heeger model, an electron-phonon model which is often used to

  16. Gravitational lensing and ghost images in the regular Bardeen no-horizon spacetimes

    International Nuclear Information System (INIS)

    Schee, Jan; Stuchlík, Zdeněk

    2015-01-01

    We study deflection of light rays and gravitational lensing in the regular Bardeen no-horizon spacetimes. Flatness of these spacetimes in the central region implies existence of interesting optical effects related to photons crossing the gravitational field of the no-horizon spacetimes with low impact parameters. These effects occur due to existence of a critical impact parameter giving maximal deflection of light rays in the Bardeen no-horizon spacetimes. We give the critical impact parameter in dependence on the specific charge of the spacetimes, and discuss 'ghost' direct and indirect images of Keplerian discs, generated by photons with low impact parameters. The ghost direct images can occur only for large inclination angles of distant observers, while ghost indirect images can occur also for small inclination angles. We determine the range of the frequency shift of photons generating the ghost images and determine distribution of the frequency shift across these images. We compare them to those of the standard direct images of the Keplerian discs. The difference of the ranges of the frequency shift on the ghost and direct images could serve as a quantitative measure of the Bardeen no-horizon spacetimes. The regions of the Keplerian discs giving the ghost images are determined in dependence on the specific charge of the no-horizon spacetimes. For comparison we construct direct and indirect (ordinary and ghost) images of Keplerian discs around Reissner-Nördström naked singularities demonstrating a clear qualitative difference to the ghost direct images in the regular Bardeen no-horizon spacetimes. The optical effects related to the low impact parameter photons thus give clear signature of the regular Bardeen no-horizon spacetimes, as no similar phenomena could occur in the black hole or naked singularity spacetimes. Similar direct ghost images have to occur in any regular no-horizon spacetimes having nearly flat central region

  17. Hilbert Space Inner Products for PJ-symmetric Su-Schrieffer-Heeger Models

    Czech Academy of Sciences Publication Activity Database

    Růžička, František

    2015-01-01

    Roč. 54, č. 11 (2015), s. 4154-4163 ISSN 0020-7748 Institutional support: RVO:61389005 Keywords : Su-Schrieffer-Heeger model * physical inner products * complete set of pseudometrics * exceptional points Subject RIV: BE - Theoretical Physics Impact factor: 1.041, year: 2015

  18. Non-cooperative game theory

    CERN Document Server

    Fujiwara-Greve, Takako

    2015-01-01

    This is a textbook for university juniors, seniors, and graduate students majoring in economics, applied mathematics, and related fields. Each chapter is structured so that a core concept of that chapter is presented with motivations, useful applications are given, and related advanced topics are discussed for future study. Many helpful exercises at various levels are provided at the end of each chapter. Therefore, this book is most suitable for readers who intend to study non-cooperative game theory rigorously for both theoretical studies and applications. Game theory consists of non-cooperative games and cooperative games. This book covers only non-cooperative games, which are major tools used in current economics and related areas. Non-cooperative game theory aims to provide a mathematical prediction of strategic choices by decision makers (players) in situations of conflicting interest. Through the logical analyses of strategic choices, we obtain a better understanding of social (economic, business) probl...

  19. Confinement effects on electron and phonon degrees of freedom in nanofilm superconductors: A Green function approach

    Science.gov (United States)

    Saniz, R.; Partoens, B.; Peeters, F. M.

    2013-02-01

    The Green function approach to the Bardeen-Cooper-Schrieffer theory of superconductivity is used to study nanofilms. We go beyond previous models and include effects of confinement on the strength of the electron-phonon coupling as well as on the electronic spectrum and on the phonon modes. Within our approach, we find that in ultrathin films, confinement effects on the electronic screening become very important. Indeed, contrary to what has been advanced in recent years, the sudden increases of the density of states when new bands start to be occupied as the film thickness increases, tend to suppress the critical temperature rather than to enhance it. On the other hand, the increase of the number of phonon modes with increasing number of monolayers in the film leads to an increase in the critical temperature. As a consequence, the superconducting critical parameters in such nanofilms are determined by these two competing effects. Furthermore, in sufficiently thin films, the condensate consists of well-defined subcondensates associated with the occupied bands, each with a distinct coherence length. The subcondensates can interfere constructively or destructively giving rise to an interference pattern in the Cooper pair probability density.

  20. Exotic superconducting states in the extended attractive Hubbard model.

    Science.gov (United States)

    Nayak, Swagatam; Kumar, Sanjeev

    2018-04-04

    We show that the extended attractive Hubbard model on a square lattice allows for a variety of superconducting phases, including exotic mixed-symmetry phases with [Formula: see text] and [Formula: see text] symmetries, and a novel [Formula: see text] state. The calculations are performed within the Hartree-Fock Bardeen-Cooper-Schrieffer framework. The ground states of the mean-field Hamiltonian are obtained via a minimization scheme that relaxes the symmetry constraints on the superconducting solutions, hence allowing for a mixing of s-, p- and d-wave order parameters. The results are obtained within the assumption of uniform-density states. Our results show that extended attractive Hubbard model can serve as an effective model for investigating properties of exotic superconductors.

  1. Dynamical vanishing of the order parameter in a confined Bardeen-Cooper-Schrieffer Fermi gas after an interaction quench

    Science.gov (United States)

    Hannibal, S.; Kettmann, P.; Croitoru, M. D.; Axt, V. M.; Kuhn, T.

    2018-01-01

    We present a numerical study of the Higgs mode in an ultracold confined Fermi gas after an interaction quench and find a dynamical vanishing of the superfluid order parameter. Our calculations are done within a microscopic density-matrix approach in the Bogoliubov-de Gennes framework which takes the three-dimensional cigar-shaped confinement explicitly into account. In this framework, we study the amplitude mode of the order parameter after interaction quenches starting on the BCS side of the BEC-BCS crossover close to the transition and ending in the BCS regime. We demonstrate the emergence of a dynamically vanishing superfluid order parameter in the spatiotemporal dynamics in a three-dimensional trap. Further, we show that the signal averaged over the whole trap mirrors the spatiotemporal behavior and allows us to systematically study the effects of the system size and aspect ratio on the observed dynamics. Our analysis enables us to connect the confinement-induced modifications of the dynamics to the pairing properties of the system. Finally, we demonstrate that the signature of the Higgs mode is contained in the dynamical signal of the condensate fraction, which, therefore, might provide a new experimental access to the nonadiabatic regime of the Higgs mode.

  2. Characterization of the superconducting state in hafnium hydride under high pressure

    Science.gov (United States)

    Duda, A. M.; Szewczyk, K. A.; Jarosik, M. W.; Szcześniak, K. M.; Sowińska, M. A.; Szcześniak, D.

    2018-05-01

    The hydrogen-rich compounds at high pressure may exhibit notably high superconducting transition temperatures. In the paper, we have calculated the basic thermodynamic parameters of the superconducting state in two selected phases of HfH2 hydride under high-pressure respectively at 180 GPa for Cmma and 260 GPa for P21 / m . Calculations has been conducted in the framework of the Eliashberg formalism. In particular, we have determined the values of the critical temperature (TC) to be equal to 8 K and 13 K for the Cmma and P21 / m phases, respectively. Moreover, we have estimated other thermodynamic properties such as the order parameter (Δ (T)) , the thermodynamic critical field (HC (T)) , and the specific heat for the normal (CN) and superconducting (CS) state. Finally, we have shown that the characteristic ratios: RΔ = 2 Δ (0) /kBTC and RC = ΔC (TC) /CN (TC) , which are related to the above thermodynamic functions, slightly differ from the predictions of the Bardeen-Cooper-Schrieffer theory due to the strong-coupling and retardation effects.

  3. The strength of electron electron correlation in Cs3C60

    Science.gov (United States)

    Baldassarre, L.; Perucchi, A.; Mitrano, M.; Nicoletti, D.; Marini, C.; Pontiroli, D.; Mazzani, M.; Aramini, M.; Riccó, M.; Giovannetti, G.; Capone, M.; Lupi, S.

    2015-10-01

    Cs3C60 is an antiferromagnetic insulator that under pressure (P) becomes metallic and superconducting below Tc = 38 K. The superconducting dome present in the T - P phase diagram close to a magnetic state reminds what found in superconducting cuprates and pnictides, strongly suggesting that superconductivity is not of the conventional Bardeen-Cooper-Schrieffer (BCS) type We investigate the insulator to metal transition induced by pressure in Cs3C60 by means of infrared spectroscopy supplemented by Dynamical Mean-Field Theory calculations. The insulating compound is driven towards a metallic-like behaviour, while strong correlations survive in the investigated pressure range. The metallization process is accompanied by an enhancement of the Jahn-Teller effect. This shows that electronic correlations are crucial in determining the insulating behaviour at ambient pressure and the bad metallic nature for increasing pressure. On the other hand, the relevance of the Jahn-Teller coupling in the metallic state confirms that phonon coupling survives in the presence of strong correlations.

  4. Conventional superconductivity at 203 K at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Drozdov, Alexander; Eremets, Mikhail; Troyan, Ivan [Max-Planck-Institut fuer Chemie, Hahn-Meitner-Weg 1, 55128 Mainz (Germany); Ksenofontov, Vadim; Shylin, Sergii [Institut fuer Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universitet Mainz, Staudingerweg 9, 55099 Mainz (Germany)

    2016-07-01

    A search for high, room temperature conventional superconductivity is promising as the Bardeen-Cooper-Schrieffer (BCS) theory in the Eliashberg formulation puts no apparent limits on T{sub c}. Materials with light elements are especially favorable as they provide high frequencies in the phonon spectrum. However only a moderately high T{sub c} = 39 K has been found in this search in MgB{sub 2}. We systematically studied metallic hydrogen and covalent hydrogen dominant compounds and found the record T{sub c} of 203 K at pressure 140 GPa in sulfur hydride. We proved occurrence of superconductivity by the sharp drop of the resistivity to zero; the decrease of T{sub c} with magnetic field; the pronounce isotope shift of T{sub c} in D{sub 2}S which evidences of a major role of phonons in the superconductivity; and the magnetic susceptibility measurements. The X-ray diffraction data confirmed that the superconductive phase has the predicted bcc structure. This phase can be considered as an atomic hydrogen superconductor stabilized by sulfur.

  5. Superconductivity at 43K in SmFeAsO1-xFx

    Science.gov (United States)

    Chen, X. H.; Wu, T.; Wu, G.; Liu, R. H.; Chen, H.; Fang, D. F.

    2008-06-01

    Since the discovery of high-transition-temperature (high-Tc) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A Tc higher than 40K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is Tc = 39K in MgB2 (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26K in the iron-based LaO1-xFxFeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO1-xFx, which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43K. This provides a new material base for studying the origin of high-temperature superconductivity.

  6. Metal-insulator transition and Frohlich conductivity in the Su-Schrieffer-Heeger model

    NARCIS (Netherlands)

    Michielsen, K.F L; de Raedt, H.A.

    1996-01-01

    A quantum molecular dynamics technique is used to study the single-particle density of states, Drude weight, optical conductivity and flux quantization in the Su-Schrieffer-Heeger (SSH) model. Our simulation data show that the SSH model has a metal-insulator transition away from half-filling. In the

  7. A User Cooperation Stimulating Strategy Based on Cooperative Game Theory in Cooperative Relay Networks

    Directory of Open Access Journals (Sweden)

    Ping Zhang

    2009-01-01

    Full Text Available This paper proposes a user cooperation stimulating strategy among rational users. The strategy is based on cooperative game theory and enacted in the context of cooperative relay networks. Using the pricing-based mechanism, the system is modeled initially with two nodes and a Base Station (BS. Within this framework, each node is treated as a rational decision maker. To this end, each node can decide whether to cooperate and how to cooperate. Cooperative game theory assists in providing an optimal system utility and provides fairness among users. Under different cooperative forwarding modes, certain questions are carefully investigated, including “what is each node's best reaction to maximize its utility?” and “what is the optimal reimbursement to encourage cooperation?” Simulation results show that the nodes benefit from the proposed cooperation stimulating strategy in terms of utility and thus justify the fairness between each user.

  8. A User Cooperation Stimulating Strategy Based on Cooperative Game Theory in Cooperative Relay Networks

    Directory of Open Access Journals (Sweden)

    Jiang Fan

    2009-01-01

    Full Text Available This paper proposes a user cooperation stimulating strategy among rational users. The strategy is based on cooperative game theory and enacted in the context of cooperative relay networks. Using the pricing-based mechanism, the system is modeled initially with two nodes and a Base Station (BS. Within this framework, each node is treated as a rational decision maker. To this end, each node can decide whether to cooperate and how to cooperate. Cooperative game theory assists in providing an optimal system utility and provides fairness among users. Under different cooperative forwarding modes, certain questions are carefully investigated, including "what is each node's best reaction to maximize its utility?" and "what is the optimal reimbursement to encourage cooperation?" Simulation results show that the nodes benefit from the proposed cooperation stimulating strategy in terms of utility and thus justify the fairness between each user.

  9. Superconducting states in strongly correlated systems with nonstandard quasiparticles and real space pairing: an unconventional Fermi-liquid limit

    Directory of Open Access Journals (Sweden)

    J. Spałek

    2010-01-01

    Full Text Available We use the concept of generalized (almost localized Fermi Liquid composed of nonstandard quasiparticles with spin-dependence effective masses and the effective field induced by electron correlations. This Fermi liquid is obtained within the so-called statistically-consistent Gutzwiller approximation (SGA proposed recently [cf. J. Jędrak et al., arXiv: 1008.0021] and describes electronic states of the correlated quantum liquid. Particular emphasis is put on real space pairing driven by the electronic correlations, the Fulde-Ferrell state of the heavy-fermion liquid, and the d-wave superconducting state of high temperature curate superconductors in the overdoped limit. The appropriate phase diagrams are discussed showing in particular the limits of stability of the Bardeen-Cooper-Schrieffer (BCS type of state.

  10. Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2002-01-01

    Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......150 K. We suggest that the marginal ingredient of the high-temperature superconducting phase is provided by fracton coupled holes that condensate in the conducting copper-oxygen planes owing to the intrinsic field-effect-transistor configuration of the cuprate compounds. For the gate...

  11. Non-cooperative game theory in biology and cooperative reasoning in humans.

    Science.gov (United States)

    Kabalak, Alihan; Smirnova, Elena; Jost, Jürgen

    2015-06-01

    The readiness for spontaneous cooperation together with the assumptions that others share this cooperativity has been identified as a fundamental feature that distinguishes humans from other animals, including the great apes. At the same time, cooperativity presents an evolutionary puzzle because non-cooperators do better in a group of cooperators. We develop here an analysis of the process leading to cooperation in terms of rationality concepts, game theory and epistemic logic. We are, however, not attempting to reconstruct the actual evolutionary process. We rather want to provide the logical structure underlying cooperation in order to understand why cooperation is possible and what kind of reasoning and beliefs would lead to cooperative decision-making. Game theory depends on an underlying common belief in non-cooperative rationality of the players, and cooperativity similarly can utilize a common belief in cooperative rationality as its basis. We suggest a weaker concept of rational decision-making in games that encompasses both types of decision-making. We build this up in stages, starting from simple optimization, then using anticipation of the reaction of others, to finally arrive at reflexive and cooperative reasoning. While each stage is more difficult than the preceding, importantly, we also identify a reduction of complexity achieved by the consistent application of higher stage reasoning.

  12. Possible superconductivity in the Bismuth IV solid phase under pressure.

    Science.gov (United States)

    Valladares, Ariel A; Rodríguez, Isaías; Hinojosa-Romero, David; Valladares, Alexander; Valladares, Renela M

    2018-04-13

    The first successful theory of superconductivity was the one proposed by Bardeen, Cooper and Schrieffer in 1957. This breakthrough fostered a remarkable growth of the field that propitiated progress and questionings, generating alternative theories to explain specific phenomena. For example, it has been argued that Bismuth, being a semimetal with a low number of carriers, does not comply with the basic hypotheses underlying BCS and therefore a different approach should be considered. Nevertheless, in 2016 based on BCS we put forth a prediction that Bi at ambient pressure becomes a superconductor at 1.3 mK. A year later an experimental group corroborated that in fact Bi is a superconductor with a transition temperature of 0.53 mK, a result that eluded previous work. So, since Bi is superconductive in almost all the different structures and phases, the question is why Bi-IV has been elusive and has not been found yet to superconduct? Here we present a study of the electronic and vibrational properties of Bi-IV and infer its possible superconductivity using a BCS approach. We predict that if the Bi-IV phase structure were cooled down to liquid helium temperatures it would also superconduct at a T c of 4.25 K.

  13. Intrinsic Paramagnetic Meissner Effect Due to s-Wave Odd-Frequency Superconductivity

    Directory of Open Access Journals (Sweden)

    A. Di Bernardo

    2015-11-01

    Full Text Available In 1933, Meissner and Ochsenfeld reported the expulsion of magnetic flux—the diamagnetic Meissner effect—from the interior of superconducting lead. This discovery was crucial in formulating the Bardeen-Cooper-Schrieffer (BCS theory of superconductivity. In exotic superconducting systems BCS theory does not strictly apply. A classical example is a superconductor-magnet hybrid system where magnetic ordering breaks time-reversal symmetry of the superconducting condensate and results in the stabilization of an odd-frequency superconducting state. It has been predicted that under appropriate conditions, odd-frequency superconductivity should manifest in the Meissner state as fluctuations in the sign of the magnetic susceptibility, meaning that the superconductivity can either repel (diamagnetic or attract (paramagnetic external magnetic flux. Here, we report local probe measurements of faint magnetic fields in a Au/Ho/Nb trilayer system using low-energy muons, where antiferromagnetic Ho (4.5 nm breaks time-reversal symmetry of the proximity-induced pair correlations in Au. From depth-resolved measurements below the superconducting transition of Nb, we observe a local enhancement of the magnetic field in Au that exceeds the externally applied field, thus proving the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.

  14. Phases and density of states in a generalized Su-Schrieffer-Heeger model

    International Nuclear Information System (INIS)

    Voo, K.-K.; Mou, C.-Y.

    2004-01-01

    Self-consistent solutions of a generalized Su-Schrieffer-Heeger model on the two-dimensional square lattice are investigated. Away from half-filling, spatially inhomogeneous phases are found. These phases may have topological structures on the flux order, large-unit-cell bond order, localized bipolarons, or they are simply short-range ordered and glassy. They have an universal feature of possessing a gapped Fermi level

  15. Etude, par principes premiers, des effets de la correlation entre electrons sur les proprietes electroniques et magnetiques de polymeres pontes et de supraconducteurs a haute temperature critique

    Science.gov (United States)

    Pesant, Simon

    Description of complex systems by Density functional theory is treated in this thesis. First, the Density functional theory and a few functionals used to simulate cristals are presented. Specifically, the LDA and GGA functionnals are described and their limits are exposed. Furthermore, the Hubbard model as well as the LDA+U functionnal are addressed in this chapter. These methods enable the study of highly correlated materials. Then, results obtained on polymers are summarized in two articles. The first one treats the band gap variation of ladder-type polymers compared to non ladder type ones. The second article considers small band gap polymers. In this case, it will be shown that an hybrid functional, which contains exact exchange, is required to describe the electronic properties of the polymers under study. Finally, the last chapter address the study of cuprates superconductors. The LDA+U can account for the localization of electrons in copper orbitals. Consequently, a study of the impact of this functionnal on electronic properties of cuprates is conducted. The chapter is ended by an article treating magnetic orders in doped La 2CuO4. Supplementary materials of the second article and a description of the theory of superconductivity of Bardeen, Cooper and Schrieffer are put in annex. Keywords : Electronic correlation, DFT, LDA+U, cuprates, polymers, magnetic orders

  16. Circular geodesic of Bardeen and Ayon-Beato-Garcia regular black-hole and no-horizon spacetimes

    Science.gov (United States)

    Stuchlík, Zdeněk; Schee, Jan

    2015-12-01

    In this paper, we study circular geodesic motion of test particles and photons in the Bardeen and Ayon-Beato-Garcia (ABG) geometry describing spherically symmetric regular black-hole or no-horizon spacetimes. While the Bardeen geometry is not exact solution of Einstein's equations, the ABG spacetime is related to self-gravitating charged sources governed by Einstein's gravity and nonlinear electrodynamics. They both are characterized by the mass parameter m and the charge parameter g. We demonstrate that in similarity to the Reissner-Nordstrom (RN) naked singularity spacetimes an antigravity static sphere should exist in all the no-horizon Bardeen and ABG solutions that can be surrounded by a Keplerian accretion disc. However, contrary to the RN naked singularity spacetimes, the ABG no-horizon spacetimes with parameter g/m > 2 can contain also an additional inner Keplerian disc hidden under the static antigravity sphere. Properties of the geodesic structure are reflected by simple observationally relevant optical phenomena. We give silhouette of the regular black-hole and no-horizon spacetimes, and profiled spectral lines generated by Keplerian rings radiating at a fixed frequency and located in strong gravity region at or nearby the marginally stable circular geodesics. We demonstrate that the profiled spectral lines related to the regular black-holes are qualitatively similar to those of the Schwarzschild black-holes, giving only small quantitative differences. On the other hand, the regular no-horizon spacetimes give clear qualitative signatures of their presence while compared to the Schwarschild spacetimes. Moreover, it is possible to distinguish the Bardeen and ABG no-horizon spacetimes, if the inclination angle to the observer is known.

  17. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus

    International Nuclear Information System (INIS)

    Teichmann, M.

    2007-09-01

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between 6 Li and 7 Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  18. Stability of Sarma phases in density imbalanced electron-hole bilayer systems

    International Nuclear Information System (INIS)

    Subasi, A. L.; Tanatar, B.; Pieri, P.; Senatore, G.

    2010-01-01

    We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

  19. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

    Energy Technology Data Exchange (ETDEWEB)

    Teichmann, M

    2007-09-15

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  20. Ultracold lithium-6 atoms in the BEC-BCS crossover: experiments and the construction of a new apparatus; Atomes de lithium-6 ultra froids dans la transition BEC-BCS: experiences et construction d'un montage experimental

    Energy Technology Data Exchange (ETDEWEB)

    Teichmann, M

    2007-09-15

    We use a fermionic gas of Lithium-6 as a model system to study superfluidity. The limiting cases of superfluidity are Bose-Einstein condensation (BEC) and superconductivity, described by the theory by Bardeen, Cooper and Schrieffer (BCS). In Lithium-6 gases, we can explore the whole range between the two cases, known as the BEC-BCS crossover, using a Feshbach resonance. We study the change of the momentum distribution of the gas in this cross-over and compare to theoretical models. We also investigate the hydrodynamic expansion, characteristic for a superfluid gas. We observe a sudden change of the ellipticity of the gas close to the transition to the superfluid phase. Moreover, we localized heteronuclear Feshbach resonances between {sup 6}Li and {sup 7}Li. We are currently constructing a second generation of the experimental setup. An new laser system, based on high power laser diodes, was developed. Changes in the vacuum chamber, including a complete reconstruction of the Zeeman slower, have increased the atomic flux, allowing us to increase the repetition rate of our experiment. Modifications of the geometry of the magnetic traps lead to a higher number of trapped atoms. (author)

  1. Temperature dependence of differential conductance in Co-based Heusler alloy Co2TiSn and superconductor Pb junctions

    Science.gov (United States)

    Ooka, Ryutaro; Shigeta, Iduru; Umetsu, Rie Y.; Nomura, Akiko; Yubuta, Kunio; Yamauchi, Touru; Kanomata, Takeshi; Hiroi, Masahiko

    2018-05-01

    We investigated temperature dependence of differential conductance G (V) in planar junctions consisting of Co-based Heusler alloy Co2TiSn and superconductor Pb. Ferromagnetic Co2TiSn was predicted to be half-metal by first-principles band calculations. The spin polarization P of Co2TiSn was deduced to be 60.0% at 1.4 K by the Andreev reflection spectroscopy. The G (V) spectral shape was smeared gradually with increasing temperature and its structure was disappeared above the superconducting transition temperature Tc. Theoretical model analysis revealed that the superconducting energy gap Δ was 1.06 meV at 1.4 K and the Tc was 6.8 K , indicating that both values were suppressed from bulk values. However, the temperature dependent Δ (T) behavior was in good agreement with that of the Bardeen-Cooper-Schrieffer (BCS) theory. The experimental results exhibit that the superconductivity of Pb attached to half-metallic Co2TiSn was kept the conventional BCS mechanism characterized strong-coupling superconductors while its superconductivity was slightly suppressed by the superconducting proximity effect at the Co2TiSn/Pb interface.

  2. SU(3)味极限附近色味连锁型超导体中的束缚双夸克态%Bound Diquark States in Color-Flavor-Locked Type Superconductor near the SU(3) Flavor Limit

    Institute of Scientific and Technical Information of China (English)

    任春福; 张一; 张小兵

    2011-01-01

    Starting from the ideal color-flavor locked phase, an approximate description for three-flavor quark superconductor is proposed near the SU (3) flavor limit. Under the physical influence from explicitly chiral-symmetry-breaking, we investigate the behaviors for two species of diquark states and the formations of bound diquark states at the mean-field level. In strongly coupling density regime, a theoretical possibility is pointed out at the first time,that Bose-Einstein condensation of light-flavor diquark states occur in the environment where all three-flavor and three-color quarks participate the Bardeen-Cooper-Schrieffer pairing.%从理想的色味连锁相出发,在SU(3)味极限附近,给出了一个3味夸克超导体的近似描述.在手征对称性明显破缺的物理影响下,运用Nambu-Jona-Lasinio(NJL)模型在平均场层次上研究了两种双夸克态和束缚双夸克态的形成.当夸克之间的相互作用非常强时,首次指出了在3色和3味夸克参与Bardeen-Cooper-Schrieffer配对的环境下,轻味双夸克态发生玻色-爱因斯坦凝聚的可能性.

  3. Normal modes of Bardeen discs

    International Nuclear Information System (INIS)

    Verdaguer, E.

    1983-01-01

    The short wavelength normal modes of self-gravitating rotating polytropic discs in the Bardeen approximation are studied. The discs' oscillations can be seen in terms of two types of modes: the p-modes whose driving forces are pressure forces and the r-modes driven by Coriolis forces. As a consequence of differential rotation coupling between the two takes place and some mixed modes appear, their properties can be studied under the assumption of weak coupling and it is seen that they avoid the crossing of the p- and r-modes. The short wavelength analysis provides a basis for the classification of the modes, which can be made by using the properties of their phase diagrams. The classification is applied to the large wavelength modes of differentially rotating discs with strong coupling and to a uniformly rotating sequence with no coupling, which have been calculated in previous papers. Many of the physical properties and qualitative features of these modes are revealed by the analysis. (author)

  4. Jigsaw Cooperative Learning: Acid-Base Theories

    Science.gov (United States)

    Tarhan, Leman; Sesen, Burcin Acar

    2012-01-01

    This study focused on investigating the effectiveness of jigsaw cooperative learning instruction on first-year undergraduates' understanding of acid-base theories. Undergraduates' opinions about jigsaw cooperative learning instruction were also investigated. The participants of this study were 38 first-year undergraduates in chemistry education…

  5. Models in cooperative game theory

    CERN Document Server

    Branzei, Rodica; Tijs, Stef

    2008-01-01

    This book investigates models in cooperative game theory in which the players have the possibility to cooperate partially. In a crisp game the agents are either fully involved or not involved at all in cooperation with some other agents, while in a fuzzy game players are allowed to cooperate with infinite many different participation levels, varying from non-cooperation to full cooperation. A multi-choice game describes the intermediate case in which each player may have a fixed number of activity levels. Different set and one-point solution concepts for these games are presented. The properties of these solution concepts and their interrelations on several classes of crisp, fuzzy, and multi-choice games are studied. Applications of the investigated models to many economic situations are indicated as well. The second edition is highly enlarged and contains new results and additional sections in the different chapters as well as one new chapter.

  6. Computational Aspects of Cooperative Game Theory

    CERN Document Server

    Chalkiadakis, Georgios; Wooldridge, Michael

    2011-01-01

    Cooperative game theory is a branch of (micro-)economics that studies the behavior of self-interested agents in strategic settings where binding agreements among agents are possible. Our aim in this book is to present a survey of work on the computational aspects of cooperative game theory. We begin by formally defining transferable utility games in characteristic function form, and introducing key solution concepts such as the core and the Shapley value. We then discuss two major issues that arise when considering such games from a computational perspective: identifying compact representation

  7. Comment on the Adler-Bardeen theorem and related problems

    International Nuclear Information System (INIS)

    Fujikawa, Kazuo

    1987-06-01

    Some aspects of the constructive proof of the Adler-Bardeen theorem in the sense of exact bare identities are discussed by using the higher derivative regularization. It is argued that the formal path integral derivation of chiral and scale (counting identity) anomalies is compatible with the construction of those regularized Green's functions. We also comment on the T*-product in the Lagrangian formalism and discuss how the complications associated with the (anomalous) symmetry charges in the operator approach are avoided in a suitably defined path integral formalism. (author)

  8. Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

    Science.gov (United States)

    Lee, Patrick A.

    2014-07-01

    The enigmatic pseudogap phase in underdoped cuprate high-Tc superconductors has long been recognized as a central puzzle of the Tc problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing.

  9. High-temperature study of superconducting hydrogen and deuterium sulfide

    Energy Technology Data Exchange (ETDEWEB)

    Durajski, A.P. [Institute of Physics, Czestochowa University of Technology, Ave. Armii Krajowej 19, 42-200 Czestochowa (Poland); Szczesniak, R. [Institute of Physics, Czestochowa University of Technology, Ave. Armii Krajowej 19, 42-200 Czestochowa (Poland); Institute of Physics, Jan Dlugosz University, Ave. Armii Krajowej 13/15, 42-200 Czestochowa (Poland); Pietronero, L. [Sapienza, Universita di Roma, Dip. Fisica, P. le A. Moro 2, 00185 Roma (Italy); Institute of Complex Systems, CNR, Via dei Taurini 19 Roma (Italy); London Institute for Mathematical Sciences, South Street 22, Mayfair London (United Kingdom)

    2016-05-15

    Hydrogen-rich compounds are extensively explored as candidates for a high-temperature superconductors. Currently, the measured critical temperature of 203 K in hydrogen sulfide (H{sub 3}S) is among the highest over all-known superconductors. In present paper, using the strong-coupling Eliashberg theory of superconductivity, we compared in detail the thermodynamic properties of two samples containing different hydrogen isotopes H{sub 3}S and D{sub 3}S at 150 GPa. Our research indicates that it is possible to reproduce the measured values of critical temperature 203 K and 147 K for H{sub 3}S and D{sub 3}S by using a Coulomb pseudopotential of 0.123 and 0.131, respectively. However, we also discuss a scenario in which the isotope effect is independent of pressure and the Coulomb pseudopotential for D{sub 3}S is smaller than for H{sub 3}S. For both scenarios, the energy gap, specific heat, thermodynamic critical field and related dimensionless ratios are calculated and compared with other conventional superconductors. We shown that the existence of the strong-coupling and retardation effects in the systems analysed result in significant differences between values obtained within the framework of the Eliashberg formalism and the prediction of the Bardeen-Cooper-Schrieffer theory. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Horizon structure of rotating Bardeen black hole and particle acceleration

    International Nuclear Information System (INIS)

    Ghosh, Sushant G.; Amir, Muhammed

    2015-01-01

    We investigate the horizon structure and ergosphere in a rotating Bardeen regular black hole, which has an additional parameter (g) due to the magnetic charge, apart from the mass (M) and the rotation parameter (a). Interestingly, for each value of the parameter g, there exists a critical rotation parameter (a = a E ), which corresponds to an extremal black hole with degenerate horizons, while for a < a E it describes a non-extremal black hole with two horizons, and no black hole for a > a E . We find that the extremal value a E is also influenced by the parameter g, and so is the ergosphere. While the value of a E remarkably decreases when compared with the Kerr black hole, the ergosphere becomes thicker with the increase in g.We also study the collision of two equal mass particles near the horizon of this black hole, and explicitly show the effect of the parameter g. The center-of-mass energy (E CM ) not only depend on the rotation parameter a, but also on the parameter g. It is demonstrated that the E CM could be arbitrarily high in the extremal cases when one of the colliding particles has a critical angular momentum, thereby suggesting that the rotating Bardeen regular black hole can act as a particle accelerator. (orig.)

  11. Inter-ribbon tunneling in graphene: An atomistic Bardeen approach

    Energy Technology Data Exchange (ETDEWEB)

    Van de Put, Maarten L., E-mail: maarten.vandeput@uantwerpen.be; Magnus, Wim [Department of Physics, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); imec, B-3001 Heverlee (Belgium); Vandenberghe, William G.; Fischetti, Massimo V. [Department of Material Science, University of Texas at Dallas, Texas 75080 (United States); Sorée, Bart [Department of Physics, Universiteit Antwerpen, B-2020 Antwerpen (Belgium); imec, B-3001 Heverlee (Belgium); Department of Electrical Engineering, KU Leuven, B-3001 Leuven (Belgium)

    2016-06-07

    A weakly coupled system of two crossed graphene nanoribbons exhibits direct tunneling due to the overlap of the wavefunctions of both ribbons. We apply the Bardeen transfer Hamiltonian formalism, using atomistic band structure calculations to account for the effect of the atomic structure on the tunneling process. The strong quantum-size confinement of the nanoribbons is mirrored by the one-dimensional character of the electronic structure, resulting in properties that differ significantly from the case of inter-layer tunneling, where tunneling occurs between bulk two-dimensional graphene sheets. The current-voltage characteristics of the inter-ribbon tunneling structures exhibit resonance, as well as stepwise increases in current. Both features are caused by the energetic alignment of one-dimensional peaks in the density-of-states of the ribbons. Resonant tunneling occurs if the sign of the curvature of the coupled energy bands is equal, whereas a step-like increase in the current occurs if the signs are opposite. Changing the doping modulates the onset-voltage of the effects as well as their magnitude. Doping through electrostatic gating makes these structures promising for application towards steep slope switching devices. Using the atomistic empirical pseudopotentials based Bardeen transfer Hamiltonian method, inter-ribbon tunneling can be studied for the whole range of two-dimensional materials, such as transition metal dichalcogenides. The effects of resonance and of step-like increases in the current we observe in graphene ribbons are also expected in ribbons made from these alternative two-dimensional materials, because these effects are manifestations of the one-dimensional character of the density-of-states.

  12. From ultracold Fermi Gases to Neutron Stars

    Science.gov (United States)

    Salomon, Christophe

    2012-02-01

    Ultracold dilute atomic gases can be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. We have developed a general method to probe with high precision the thermodynamics of locally homogeneous ultracold Bose and Fermi gases [1,2,3]. This method allows stringent tests of recent many-body theories. For attractive spin 1/2 fermions with tunable interaction (^6Li), we will show that the gas thermodynamic properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. First, we focus on the finite-temperature Equation of State (EoS) of the unpolarized unitary gas. Surprisingly, the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory [3] and we localize the superfluid phase transition. A detailed comparison with theories including recent Monte-Carlo calculations will be presented. Moving away from the unitary gas, the Lee-Huang-Yang and Lee-Yang beyond-mean-field corrections for low density bosonic and fermionic superfluids are quantitatively measured for the first time. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. [4pt] [1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010) [0pt] [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010) [0pt] [3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett. 106, 215303 (2011)

  13. Attribution models and the Cooperative Game Theory

    OpenAIRE

    Cano Berlanga, Sebastian; Vilella, Cori

    2017-01-01

    The current paper studies the attribution model used by Google Analytics. Precisely, we use the Cooperative Game Theory to propose a fair distribution of the revenues among the considered channels, in order to facilitate the cooperation and to guarantee stability. We define a transferable utility convex cooperative game from the observed frequencies and we use the Shapley value to allocate the revenues among the di erent channels. Furthermore, we evaluate the impact of an advertising...

  14. Cooling of hypernuclear compact stars

    Science.gov (United States)

    Raduta, Adriana R.; Sedrakian, Armen; Weber, Fridolin

    2018-04-01

    We study the thermal evolution of hypernuclear compact stars constructed from covariant density functional theory of hypernuclear matter and parametrizations which produce sequences of stars containing two-solar-mass objects. For the input in the simulations, we solve the Bardeen-Cooper-Schrieffer gap equations in the hyperonic sector and obtain the gaps in the spectra of Λ, Ξ0, and Ξ- hyperons. For the models with masses M/M⊙ ≥ 1.5 the neutrino cooling is dominated by hyperonic direct Urca processes in general. In the low-mass stars the (Λp) plus leptons channel is the dominant direct Urca process, whereas for more massive stars the purely hyperonic channels (Σ-Λ) and (Ξ-Λ) are dominant. Hyperonic pairing strongly suppresses the processes on Ξ-s and to a lesser degree on Λs. We find that intermediate-mass 1.5 ≤ M/M⊙ ≤ 1.8 models have surface temperatures which lie within the range inferred from thermally emitting neutron stars, if the hyperonic pairing is taken into account. Most massive models with M/M⊙ ≃ 2 may cool very fast via the direct Urca process through the (Λp) channel because they develop inner cores where the S-wave pairing of Λs and proton is absent.

  15. Thermodynamics of pairing phase transition in nuclei

    International Nuclear Information System (INIS)

    Karim, Afaque; Ahmad, Shakeb

    2014-01-01

    The pairing gaps, pairing energy, heat capacity and entropy are calculated within BCS (Bardeen- Cooper-Schrieffer) based quasi particle approach, including thermal fluctuations on pairing field within pairing model for all nuclei (light, medium, heavy and super heavy nuclei). Quasi particles approach in BCS theory was introduced and reformulated to study various properties. For thermodynamic behavior of nuclei at finite temperatures, the anomalous averages of creation and annihilation operators are introduced. It is solved self consistently at finite temperatures to obtain BCS Hamiltonian. After doing unitary transformation, we obtained the Hamiltonian in the diagonal form. Thus, one gets temperature dependence gap parameter and pairing energy for nuclei. Moreover, the energy at finite temperatures is the sum of the condensation energy and the thermal energy of fermionic quasi particles. With the help of BCS Hamiltonian, specific heat, entropy and free energy are calculated for different nuclei. In this paper the gap parameter occupation number and pairing energy as a function of temperature which is important for all the light, medium, heavy and super heavy nuclei is calculated. Moreover, the various thermo dynamical quantities like specific heat, entropy and free energy is also obtained for different nuclei. Thus, the thermodynamics of pairing phase transition in nuclei is studied

  16. Detecting the BCS pairing amplitude via a sudden lattice ramp in a honeycomb lattice

    Science.gov (United States)

    Tiesinga, Eite; Nuske, Marlon; Mathey, Ludwig

    2016-05-01

    We determine the exact time evolution of an initial Bardeen-Cooper-Schrieffer (BCS) state of ultra-cold atoms in a hexagonal optical lattice. The dynamical evolution is triggered by ramping the lattice potential up, such that the interaction strength Uf is much larger than the hopping amplitude Jf. The quench initiates collective oscillations with frequency | Uf | /(2 π) in the momentum occupation numbers and imprints an oscillating phase with the same frequency on the order parameter Δ. The latter is not reproduced by treating the time evolution in mean-field theory. The momentum density-density or noise correlation functions oscillate at frequency | Uf | /(2 π) as well as its second harmonic. For a very deep lattice, with negligible tunneling energy, the oscillations of momentum occupation numbers are undamped. Non-zero tunneling after the quench leads to dephasing of the different momentum modes and a subsequent damping of the oscillations. This occurs even for a finite-temperature initial BCS state, but not for a non-interacting Fermi gas. We therefore propose to use this dephasing to detect a BCS state. Finally, we predict that the noise correlation functions in a honeycomb lattice will develop strong anti-correlations near the Dirac point. We acknowledge funding from the National Science Foundation.

  17. The cooperative game theory of networks and hierarchies

    CERN Document Server

    Gilles, Robert P

    2010-01-01

    This book details standard concepts in cooperative game theory with applications to the analysis of social networks and hierarchical authority organizations. It covers the multi-linear extension, the Core, the Shapley value, and the cooperative potential.

  18. Cooperative Learning: Improving University Instruction by Basing Practice on Validated Theory

    Science.gov (United States)

    Johnson, David W.; Johnson, Roger T.; Smith, Karl A.

    2014-01-01

    Cooperative learning is an example of how theory validated by research may be applied to instructional practice. The major theoretical base for cooperative learning is social interdependence theory. It provides clear definitions of cooperative, competitive, and individualistic learning. Hundreds of research studies have validated its basic…

  19. Game theory in communication networks cooperative resolution of interactive networking scenarios

    CERN Document Server

    Antoniou, Josephina

    2012-01-01

    A mathematical tool for scientists and researchers who work with computer and communication networks, Game Theory in Communication Networks: Cooperative Resolution of Interactive Networking Scenarios addresses the question of how to promote cooperative behavior in interactive situations between heterogeneous entities in communication networking scenarios. It explores network design and management from a theoretical perspective, using game theory and graph theory to analyze strategic situations and demonstrate profitable behaviors of the cooperative entities. The book promotes the use of Game T

  20. COalitions in COOperation Networks (COCOON): Social Network Analysis and Game Theory to Enhance Cooperation Networks

    NARCIS (Netherlands)

    Sie, Rory

    2012-01-01

    Sie, R. L. L. (2012). COalitions in COOperation Networks (COCOON): Social Network Analysis and Game Theory to Enhance Cooperation Networks (Unpublished doctoral dissertation). September, 28, 2012, Open Universiteit in the Netherlands (CELSTEC), Heerlen, The Netherlands.

  1. nuclei

    Directory of Open Access Journals (Sweden)

    Minkov N.

    2016-01-01

    Full Text Available We study the effects of quadrupole-octupole deformations on the energy and magnetic properties of high-K isomeric states in even-even heavy and superheavy nuclei. The neutron two-quasiparticle (2qp isomeric energies and magnetic dipole moments are calculated within a deformed shell model with the Bardeen-Cooper- Schrieffer (BCS pairing interaction over a wide range of quadrupole and octupole deformations. We found that in most cases the magnetic moments exhibit a pronounced sensitivity to the octupole deformation, while the 2qp energies indicate regions of nuclei in which the presence of high-K isomeric states may be associated with the presence of octupole softness or even with octupole deformation. In the present work we also examine the influence of the BCS pairing strength on the energy of the blocked isomer configuration. We show that the formation of 2qp energy minima in the space of quadrupole-octupole and eventually higher multipolarity deformations is a subtle effect depending on nuclear pairing correlations.

  2. High-pressure studies on a new superconducting clathrate: Ba sub 6 Ge sub 2 sub 5

    CERN Document Server

    Yuan, H Q; Carrillo-Cabrera, W; Paschen, S; Sparn, G; Baenitz, M; Grin, Y; Steglich, F

    2002-01-01

    The effect of pressure on the low-temperature states of the newly discovered clathrate Ba sub 6 Ge sub 2 sub 5 is investigated by means of measurements of the electrical resistivity. At ambient pressure, Ba sub 6 Ge sub 2 sub 5 undergoes a two-step structural phase transition between 230 and 180 K from metallic behaviour to a high-resistivity state characterized by a mean free path of about 3 A. Interestingly, a Bardeen-Cooper-Schrieffer-like (BCS-like) superconducting transition occurs at T sub C approx 0.24 K from the resulting 'bad metal'. With increasing pressure, the structural phase transition is depressed but T sub C increases drastically. T sub C reaches a maximum value of 3.85 K at the critical pressure p sub C approx 2.8 GPa, where the structural distortion is completely suppressed and the system exhibits metallic behaviour. Higher pressures lead to a slight decrease of T sub C.

  3. Cooperative learning of neutron diffusion and transport theories

    International Nuclear Information System (INIS)

    Robinson, Michael A.

    1999-01-01

    A cooperative group instructional strategy is being used to teach a unit on neutron transport and diffusion theory in a first-year-graduate level, Reactor Theory course that was formerly presented in the traditional lecture/discussion style. Students are divided into groups of two or three for the duration of the unit. Class meetings are divided into traditional lecture/discussion segments punctuated by cooperative group exercises. The group exercises were designed to require the students to elaborate, summarize, or practice the material presented in the lecture/discussion segments. Both positive interdependence and individual accountability are fostered by adjusting individual grades on the unit exam by a factor dependent upon group achievement. Group collaboration was also encouraged on homework assignments by assigning each group a single grade on each assignment. The results of the unit exam have been above average in the two classes in which the cooperative group method was employed. In particular, the problem solving ability of the students has shown particular improvement. Further,the students felt that the cooperative group format was both more educationally effective and more enjoyable than the lecture/discussion format

  4. Non-cooperative planning theory

    CERN Document Server

    Bogetoft, Peter

    1994-01-01

    Planning in a general sense is concerned with the design of communication and decision making mechanisms in organizations where information and choice are decentralized. Non-cooperative planning theory as it is developed in this book treats the incentive aspects hereof. It stresses how strategic behavior and opportunism may impede planning, and how this can be coped with via the organization of communication and decision making, the design of information and control systems, and the development of incentive schemes. In particular, the book contains a thorough investigation of incentive provision in information production.

  5. A Perspective on Helmberger and Hoos' Theory of Cooperatives

    OpenAIRE

    Sexton, Richard J.

    1995-01-01

    Helmberger and Hoos' (HH) 1962 paper is a landmark in the economic theory of agricultural cooperatives, Along with the related work by Helmberger (1964), it represented the definitive treatment of marketing cooperative behavior and standard reading for graduate students in agricultural marketing for more than two decades, To understand fully HH's paper, appreciate its many strengths, and also recognize its weaknesses: one must interpret it both in the context of the work on cooperatives that ...

  6. Adler-Bardeen Theorem for the Axial Anomaly and the First Moment of the Polarized Virtual Photon Structure Function

    International Nuclear Information System (INIS)

    Ueda, Takahiro; Sasaki, Ken; Uematsu, Tsuneo

    2007-01-01

    The Adler-Bardeen theorem for the axial anomaly is extensively used to calculate the next-to-next-to-leading order (αα s 2 ) corrections to the first moment of the polarized virtual photon structure function g 1 γ (x,P 2 ,Q 2 )

  7. Andreev reflections and the quantum physics of black holes

    Science.gov (United States)

    Manikandan, Sreenath K.; Jordan, Andrew N.

    2017-12-01

    We establish an analogy between superconductor-metal interfaces and the quantum physics of a black hole, using the proximity effect. We show that the metal-superconductor interface can be thought of as an event horizon and Andreev reflection from the interface is analogous to the Hawking radiation in black holes. We describe quantum information transfer in Andreev reflection with a final state projection model similar to the Horowitz-Maldacena model for black hole evaporation. We also propose the Andreev reflection analogue of Hayden and Preskill's description of a black hole final state, where the black hole is described as an information mirror. The analogy between crossed Andreev reflections and Einstein-Rosen bridges is discussed: our proposal gives a precise mechanism for the apparent loss of quantum information in a black hole by the process of nonlocal Andreev reflection, transferring the quantum information through a wormhole and into another universe. Given these established connections, we conjecture that the final quantum state of a black hole is exactly the same as the ground state wave function of the superconductor/superfluid in the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity; in particular, the infalling matter and the infalling Hawking quanta, described in the Horowitz-Maldacena model, forms a Cooper pairlike singlet state inside the black hole. A black hole evaporating and shrinking in size can be thought of as the analogue of Andreev reflection by a hole where the superconductor loses a Cooper pair. Our model does not suffer from the black hole information problem since Andreev reflection is unitary. We also relate the thermodynamic properties of a black hole to that of a superconductor, and propose an experiment which can demonstrate the negative specific heat feature of black holes in a growing/evaporating condensate.

  8. History of the theory of superconductivity

    International Nuclear Information System (INIS)

    Frohlich, H.

    1983-01-01

    This chapter points out that in the years from Onnes' discovery that the electric resistivity of mercury completely disappeared at about 4K in 1911 up to 1950, many attempts to develop a theory of superconductivity failed, and the subject became an outstanding problem in physics. Discusses the introduction of field theory into solid state physics, which proved to be the decisive step toward a theory. Describes how Schrieffer's suggestion of a wave function for the multielectron problem in terms of electron pairs led to the theory of superconductivity, or the so called B.C.S. theory

  9. Description of excitations in odd nonmagic nuclei by the Green's function method

    International Nuclear Information System (INIS)

    Avdeenkov, A.V.; Kamerdzhiev, S.P.

    1999-01-01

    General equations for single-particle Green's functions in nonmagic nuclei have been derived. A pairing mechanism similar to the Bardeen-Cooper-Schrieffer mechanism is singled out explicitly in these equations. A refining procedure for phenomenological single-particle energies and for the gap has been developed to avoid doubly taking into account mixing with phonons for the situation in which the input data for the problem in question are formulated in terms of these phenomenological quantities. The resulting general equations are written within the second-order approximation in the phonon-creation amplitude. This corresponds to taking into account quasiparticle(multiply-in-circle sign)phonon configuration and is shown to be a fairly good approximation for semimagic nuclei. A secular equation for calculating excitations in odd nuclei that takes fully into account ground-state correlations and which is invariant under the reversal of the sign of the energy variable has been derived in this approximation. Distributions of single-particle strengths have been computed for 119 Sn and 121 Sn. Reasonably good agreement with available experimental data has been obtained

  10. The importance of the electron mean free path for superconducting radio-frequency cavities

    Science.gov (United States)

    Maniscalco, J. T.; Gonnella, D.; Liepe, M.

    2017-01-01

    Impurity-doping of niobium is an exciting new technology in the field of superconducting radio-frequency accelerators, producing cavities with record-high quality factor Q0 and Bardeen-Cooper-Schrieffer surface resistance that decreases with increasing radio-frequency field. Recent theoretical work has offered a promising explanation for this so-called "anti-Q-slope," but the link between the decreasing surface resistance and the shortened electron mean free path of doped cavities has remained elusive. In this work, we investigate this link, finding that the magnitude of this decrease varies directly with the mean free path: shorter mean free paths correspond to stronger anti-Q-slopes. We draw a theoretical connection between the mean free path and the overheating of the quasiparticles, which leads to the reduction of the anti-Q-slope towards the normal Q-slope of long-mean-free-path cavities. We also investigate the sensitivity of the residual resistance to trapped magnetic flux, a property that is greatly enhanced for doped cavities, and calculate an optimal doping regime for a given amount of trapped flux.

  11. Spectral properties of excitons in the bilayer graphene

    Science.gov (United States)

    Apinyan, V.; Kopeć, T. K.

    2018-01-01

    In this paper, we consider the spectral properties of the bilayer graphene with the local excitonic pairing interaction between the electrons and holes. We consider the generalized Hubbard model, which includes both intralayer and interlayer Coulomb interaction parameters. The solution of the excitonic gap parameter is used to calculate the electronic band structure, single-particle spectral functions, the hybridization gap, and the excitonic coherence length in the bilayer graphene. We show that the local interlayer Coulomb interaction is responsible for the semimetal-semiconductor transition in the double layer system, and we calculate the hybridization gap in the band structure above the critical interaction value. The formation of the excitonic band gap is reported as the threshold process and the momentum distribution functions have been calculated numerically. We show that in the weak coupling limit the system is governed by the Bardeen-Cooper-Schrieffer (BCS)-like pairing state. Contrary, in the strong coupling limit the excitonic condensate states appear in the semiconducting phase, by forming the Dirac's pockets in the reciprocal space.

  12. On the problem of axial anomaly in supersymmetric gauge theories

    International Nuclear Information System (INIS)

    Kazakov, D.I.

    1984-01-01

    The explicit relation is found between the axial current obeying the Adler-Bardeen theorem and the supersymmetric one belonging to a supermultiplet. It is shown that the axial and superconformal anomalies are consistent in all orders of perturbation theory

  13. Wentzel-Bardeen singularity in coupled Luttinger liquids: Transport properties

    International Nuclear Information System (INIS)

    Martin, T.

    1994-01-01

    The recent progress on 1 D interacting electrons systems and their applications to study the transport properties of quasi one dimensional wires is reviewed. We focus on strongly correlated elections coupled to low energy acoustic phonons in one dimension. The exponents of various response functions are calculated, and their striking sensitivity to the Wentzel-Bardeen singularity is discussed. For the Hubbard model coupled to phonons the equivalent of a phase diagram is established. By increasing the filling factor towards half filling the WB singularity is approached. This in turn suppresses antiferromagnetic fluctuations and drives the system towards the superconducting regime, via a new intermediate (metallic) phase. The implications of this phenomenon on the transport properties of an ideal wire as well as the properties of a wire with weak or strong scattering are analyzed in a perturbative renormalization group calculation. This allows to recover the three regimes predicted from the divergence criteria of the response functions

  14. Models in cooperative game theory crisp, fuzzy, and multi-choice games

    CERN Document Server

    Branzei, Rodica; Tijs, Stef

    2005-01-01

    This book investigates models in cooperative game theory in which the players have the possibility to cooperate partially. In a crisp game the agents are either fully involved or not involved at all in coperation with some other agents, while in a fuzzy game players are allowed to cooperate with infinite many different participation levels, varying from non-cooperation to full cooperation. A multi-choice game describes the intermediate case in which each player may have a fixed number of activity levels. Different set and one-point solution concepts for these games are presented. The propertie

  15. Nonlinear analysis of the cooperation of strategic alliances through stochastic catastrophe theory

    Science.gov (United States)

    Xu, Yan; Hu, Bin; Wu, Jiang; Zhang, Jianhua

    2014-04-01

    The excitation intervention of strategic alliance may change with the changes in the parameters of circumstance (e.g., external alliance tasks). As a result, the stable cooperation between members may suffer a complete unplanned betrayal at last. However, current perspectives on strategic alliances cannot adequately explain this transition mechanism. This study is a first attempt to analyze this nonlinear phenomenon through stochastic catastrophe theory (SCT). A stochastic dynamics model is constructed based on the cooperation of strategic alliance from the perspective of evolutionary game theory. SCT explains the discontinuous changes caused by the changes in environmental parameters. Theoretically, we identify conditions where catastrophe can occur in the cooperation of alliance members.

  16. Non-cooperative stochastic differential game theory of generalized Markov jump linear systems

    CERN Document Server

    Zhang, Cheng-ke; Zhou, Hai-ying; Bin, Ning

    2017-01-01

    This book systematically studies the stochastic non-cooperative differential game theory of generalized linear Markov jump systems and its application in the field of finance and insurance. The book is an in-depth research book of the continuous time and discrete time linear quadratic stochastic differential game, in order to establish a relatively complete framework of dynamic non-cooperative differential game theory. It uses the method of dynamic programming principle and Riccati equation, and derives it into all kinds of existence conditions and calculating method of the equilibrium strategies of dynamic non-cooperative differential game. Based on the game theory method, this book studies the corresponding robust control problem, especially the existence condition and design method of the optimal robust control strategy. The book discusses the theoretical results and its applications in the risk control, option pricing, and the optimal investment problem in the field of finance and insurance, enriching the...

  17. Economic game theory for mutualism and cooperation.

    Science.gov (United States)

    Archetti, Marco; Scheuring, István; Hoffman, Moshe; Frederickson, Megan E; Pierce, Naomi E; Yu, Douglas W

    2011-12-01

    We review recent work at the interface of economic game theory and evolutionary biology that provides new insights into the evolution of partner choice, host sanctions, partner fidelity feedback and public goods. (1) The theory of games with asymmetrical information shows that the right incentives allow hosts to screen-out parasites and screen-in mutualists, explaining successful partner choice in the absence of signalling. Applications range from ant-plants to microbiomes. (2) Contract theory distinguishes two longstanding but weakly differentiated explanations of host response to defectors: host sanctions and partner fidelity feedback. Host traits that selectively punish misbehaving symbionts are parsimoniously interpreted as pre-adaptations. Yucca-moth and legume-rhizobia mutualisms are argued to be examples of partner fidelity feedback. (3) The theory of public goods shows that cooperation in multi-player interactions can evolve in the absence of assortment, in one-shot social dilemmas among non-kin. Applications include alarm calls in vertebrates and exoenzymes in microbes. 2011 Blackwell Publishing Ltd/CNRS.

  18. Explaining Helping Behavior in a Cooperative Learning Classroom Setting Using Attribution Theory

    Science.gov (United States)

    Ahles, Paula M.; Contento, Jann M.

    2006-01-01

    This recently completed study examined whether attribution theory can explain helping behavior in an interdependent classroom environment that utilized a cooperative-learning model. The study focused on student participants enrolled in 6 community college communication classes taught by the same instructor. Three levels of cooperative-learning…

  19. Gray solitons in a strongly interacting superfluid Fermi gas

    International Nuclear Information System (INIS)

    Spuntarelli, Andrea; Pieri, Pierbiagio; Strinati, Giancarlo C; Carr, Lincoln D

    2011-01-01

    The Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover problem is solved for stationary gray solitons via the Boguliubov-de Gennes equations at zero temperature. These crossover solitons exhibit a localized notch in the gap and a characteristic phase difference across the notch for all interaction strengths, from BEC to BCS regimes. However, they do not follow the well-known Josephson-like sinusoidal relationship between velocity and phase difference except in the far BEC limit: at unitarity, the velocity has a nearly linear dependence on phase difference over an extended range. For a fixed phase difference, the soliton is of nearly constant depth from the BEC limit to unitarity and then grows progressively shallower into the BCS limit, and on the BCS side, Friedel oscillations are apparent in both gap amplitude and phase. The crossover soliton appears fundamentally in the gap; we show, however, that the density closely follows the gap, and the soliton is therefore observable. We develop an approximate power-law relationship to express this fact: the density of gray crossover solitons varies as the square of the gap amplitude in the BEC limit and as a power of about 1.5 at unitarity.

  20. Faraday instability and Faraday patterns in a superfluid Fermi gas

    International Nuclear Information System (INIS)

    Tang Rongan; Xue Jukui; Li Haocai

    2011-01-01

    With the consideration of the coupling between the transverse width and the longitudinal density, the parametric excitations related to Faraday waves in a cigar-shaped superfluid Fermi gas are studied. A Mathieu equation is obtained, and it is demonstrated firstly that the excited actual 3D Faraday pattern is the combination of the longitudinal Faraday density wave and the corresponding transverse width fluctuation in the longitudinal direction. The Faraday instability growth index and the kinematic equations of the Faraday density wave and the width fluctuation along the Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS) crossover are also given for the first time. It is found that the 3D Faraday pattern presents quite different behaviours (such as the excitations and the motions) when the system crosses from the BEC side to the BCS side. The coupling not only plays an important role in the parametric excitation, but also determines the dominant wavelength of the spatial structure. Along the crossover, the coupling effects are more significant in the BCS side. The final numerical investigation verifies these results and gives a detailed study of the parametric excitations (i.e. Faraday instability) and the 3D pattern formation.

  1. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions.

    Science.gov (United States)

    Muhammed, Dalhatu; Anisi, Mohammad Hossein; Zareei, Mahdi; Vargas-Rosales, Cesar; Khan, Anwar

    2018-02-01

    Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node's cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  2. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

    Directory of Open Access Journals (Sweden)

    Dalhatu Muhammed

    2018-02-01

    Full Text Available Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal, long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  3. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

    Science.gov (United States)

    Muhammed, Dalhatu; Anisi, Mohammad Hossein; Vargas-Rosales, Cesar; Khan, Anwar

    2018-01-01

    Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted. PMID:29389874

  4. Continuum gauge theories

    International Nuclear Information System (INIS)

    Stora, R.

    1976-09-01

    The mathematics of gauge fields and some related concepts are discussed: some corrections on the principal fiber bundles emphasize the idea that the present formulation of continuum theories is incomplete. The main ingredients used through the construction of the renormalized perturbation series are then described: the Faddeev Popov argument, and the Faddeev Popov Lagrangian; the Slavnov symmetry and the nature of the Faddeev Popov ghost fields; the Slavnov identity, with an obstruction: the Adler Bardeen anomaly, and its generalization to the local cohomology of the gauge Lie algebra. Some smooth classical configurations of gauge fields which ought to play a prominent role in the evaluation of the functional integral describing the theory are also reviewed

  5. [International development cooperation from the D. Orem self-care theory].

    Science.gov (United States)

    Velo Higueras, María; Fajardo Galván, Darío; Cruces González, Marta; Sánchez Merino, Begoña; Santos Muñiz, Ana

    2013-05-01

    This article aim is to analyze the performance of Spanish cooperation from the perspective of Orem self-care theory, from the next hypothesis: the Spanish international cooperation programs works as total compensation systems. cross sectional and descriptive study in which qualitative analysis was performed 3 African countries: Mozambique, Angola and Namibia. The variables were management, focused area and resources used. All countries have a shared management of the cooperation. Mozambique has developed training activities (72%), management support (38%) and direct health care (27%), focused on the area of the fight against infection and tropical diseases. In Angola, the activities are based in training (37%), management support (37%) and health care (75%) in the area of basic health services (25%), fighting against tropical diseases (50%) and improving maternal and child health (25%). Namibia focuses on the health care area (100%) through direct assistance activities and management support. Health cooperation programs developed by the Spanish state have probed to work as partial compensation system.

  6. Nonlinearity in superconductivity and Josephson junctions

    International Nuclear Information System (INIS)

    Lazarides, N.

    1995-01-01

    Within the framework of the Bardeen, Cooper and Schrieffers (BCS) theory, the influence of anisotropy on superconducting states are investigated. Crystal anisotropy exists in un-conventional low temperature superconductors as e.g. U 1-x Th x Be 13 and in high temperature superconductors. Starting from a phenomenological pairing interaction of the electrons or holes, the BCS approach is used to derive a set of coupled nonlinear algebraic equations for the momentum dependent gap parameter. The emphasis is put on bifurcation phenomena between s-, d-wave and mixed s- and d-wave symmetry and the influence on measurable quantities as the electron specific heat, spin susceptibility and Josephson tunnelling. Pitch-fork and perturbed pitch-fork bifurcations have been found separating s- and d-wave superconducting states from mixed s- and d-wave states. The additional superconducting states give rise to jumps in the electron specific heat below the transition temperature. These jumps are rounded in the case of perturbed pitch-fork bifurcations. An experiment to measure the sign of the interlayer interaction using dc SQUIDS is suggested. The Ambegaokar-Baratoff formalism has been used for calculating the quasiparticle current and the two phase coherent tunnelling currents in a Josephson junction made of anisotropic superconductors. It is shown that anisotropy can lead to a reduction in the product of the normal resistance and the critical current. For low voltages across the junction the usual resistively shunted Josephson model can be used. Finally, bunching in long circular Josephson junctions and suppression of chaos in point junctions have been investigated. (au) 113 refs

  7. Angular momentum, g-value, and magnetic flux of gyration states

    International Nuclear Information System (INIS)

    Arunasalam, V.

    1991-10-01

    Two of the world's leading (Nobel laureate) physicists disagree on the definition of the orbital angular momentum L of the Landau gyration states of a spinless charged particle in a uniform external magnetic field B = B i Z . According to Richard P. Feynman (and also Frank Wilczek) L = (rxμv) = rx(p - qA/c), while Felix Bloch (and also Kerson Huang) defines it as L = rxp. We show here that Bloch's definition is the correct one since it satisfies the necessary and sufficient condition LxL = iℎ L, while Feynman's definition does not. However, as a consequence of the quantized Aharonov-Bohm magnetic flux, this canonical orbital angular momentum (surprisingly enough) takes half-odd-integral values with a zero-point gyration states of L Z = ℎ/2. Further, since the diamagnetic and the paramagnetic contributions to the magnetic moment are interdependent, the g-value of these gyration states is two and not one, again a surprising result for a spinless case. The differences between the gauge invariance in classical and quantum mechanics, Onsager's suggestion that the flux quantization might be an intrinsic property of the electromagnetic field-charged particle interaction, the possibility that the experimentally measured fundamental unit of the flux quantum need not necessarily imply the existence of ''electron pairing'' of the Bardeen-Cooper-Schrieffer superconductivity theory, and the relationship to the Dirac's angular momentum quantization condition for the magnetic monopole-charged particle composites (i.e. Schwinger's dyons), are also briefly examined from a pedestrian viewpoint

  8. A Cross-Layer Cooperation Mechanism of Wireless Networks Based on Game Theory

    OpenAIRE

    Chunsheng, Cui; Yongjian, Yang; Liping, Huang

    2014-01-01

    To meet the wireless network congestion control problem, we give a definition of congestion degree classification and propose a mechanism of directed cooperative path net, guided by the wireless network’s cross-layer design methods and node cooperation principles. Considering the virtual collision and “starved” phenomenon in congested networks, the QRD mechanism and channel competition mechanism QPCG are proposed, with introducing the game theory into the cross-layer design. Simulation result...

  9. Bacteria and game theory: the rise and fall of cooperation in spatially heterogeneous environments.

    Science.gov (United States)

    Lambert, Guillaume; Vyawahare, Saurabh; Austin, Robert H

    2014-08-06

    One of the predictions of game theory is that cooperative behaviours are vulnerable to exploitation by selfish individuals, but this result seemingly contradicts the survival of cooperation observed in nature. In this review, we will introduce game theoretical concepts that lead to this conclusion and show how the spatial competition dynamics between microorganisms can be used to model the survival and maintenance of cooperation. In particular, we focus on how Escherichia coli bacteria with a growth advantage in stationary phase (GASP) phenotype maintain a proliferative phenotype when faced with overcrowding to gain a fitness advantage over wild-type populations. We review recent experimental approaches studying the growth dynamics of competing GASP and wild-type strains of E. coli inside interconnected microfabricated habitats and use a game theoretical approach to analyse the observed inter-species interactions. We describe how the use of evolutionary game theory and the ideal free distribution accurately models the spatial distribution of cooperative and selfish individuals in spatially heterogeneous environments. Using bacteria as a model system of cooperative and selfish behaviours may lead to a better understanding of the competition dynamics of other organisms-including tumour-host interactions during cancer development and metastasis.

  10. A Lifespan Perspective on Cooperative Education Learning: A Grounded Theory

    Science.gov (United States)

    Linn, Patricia

    2015-01-01

    This qualitative study sits at the intersection of two trends in vocational education. The first trend is a narrative approach to understanding cooperative education learning; the second is a movement away from career development theories toward the view that individuals use work experiences to help construct their lives. Both trends view learning…

  11. Teaching Theory in Occupational Therapy Using a Cooperative Learning: A Mixed-Methods Study.

    Science.gov (United States)

    Howe, Tsu-Hsin; Sheu, Ching-Fan; Hinojosa, Jim

    2018-01-01

    Cooperative learning provides an important vehicle for active learning, as knowledge is socially constructed through interaction with others. This study investigated the effect of cooperative learning on occupational therapy (OT) theory knowledge attainment in professional-level OT students in a classroom environment. Using a pre- and post-test group design, 24 first-year, entry-level OT students participated while taking a theory course in their second semester of the program. Cooperative learning methods were implemented via in-class group assignments. The students were asked to complete two questionnaires regarding their attitudes toward group environments and their perception toward group learning before and after the semester. MANCOVA was used to examine changes in attitudes and perceived learning among groups. Students' summary sheets for each in-class assignment and course evaluations were collected for content analysis. Results indicated significant changes in students' attitude toward working in small groups regardless of their prior group experience.

  12. A game theory approach for competition and cooperation among project’s subcontractors with interaction activities

    Directory of Open Access Journals (Sweden)

    Ashkan Hafezalkotob

    2017-04-01

    Full Text Available Some projects are often performed by many subcontractors that cooperate with each other and some of them are conducted by outsourcing them to several firms; so subcontractors carry out activities in competition. Appropriate trade-off between time and cost and achieving more benefit and cost saving are objectives of both models. In this paper, it is investigated that how different subcontractors of a project can cooperate to achieve more advantages if possible and how sub-contractors can compete to make the results better and find the optimum cost to minimize the time for each of them. The competition here does not mean eliminating a competitor, but the aim is to challenge the contractors in order to choose the best decision. The purpose of this study is to address the challenges in time and cost management and to find more profit allocation among subcontractors and fair competition for fair allocation as well. A model based on cooperative game theory in time/cost trade-off problem of projects is suggested and then a competition model among subcontractors based on non-cooperative game theory is proposed. A case study is rep-resented to comprehensively illustrate the problem, the cooperative techniques of cooperative game theory, and the payoff matrix of non-cooperative model among subcontractors. Results of the proposed model reveal that subcontractors can obtain higher profit from cooperation if pos-sible. When they outsource the project and compete with each other, they must consider the in-teraction activities and choose the best strategies for cost saving and gain more reward from the client. Moreover, it is found that some techniques such as Shapley value, Core, Max-Min Core, or Equal Profit Method (EPM are able to fairly assign extra profit of cooperation, and using the payoff matrix, Nash equilibrium, and Nash bargaining helps to find the optimum point to mini-mize time and cost for interaction activities state.

  13. Theory of ground state factorization in quantum cooperative systems.

    Science.gov (United States)

    Giampaolo, Salvatore M; Adesso, Gerardo; Illuminati, Fabrizio

    2008-05-16

    We introduce a general analytic approach to the study of factorization points and factorized ground states in quantum cooperative systems. The method allows us to determine rigorously the existence, location, and exact form of separable ground states in a large variety of, generally nonexactly solvable, spin models belonging to different universality classes. The theory applies to translationally invariant systems, irrespective of spatial dimensionality, and for spin-spin interactions of arbitrary range.

  14. Asymptotic Analysis of Large Cooperative Relay Networks Using Random Matrix Theory

    Directory of Open Access Journals (Sweden)

    H. Poor

    2008-04-01

    Full Text Available Cooperative transmission is an emerging communication technology that takes advantage of the broadcast nature of wireless channels. In cooperative transmission, the use of relays can create a virtual antenna array so that multiple-input/multiple-output (MIMO techniques can be employed. Most existing work in this area has focused on the situation in which there are a small number of sources and relays and a destination. In this paper, cooperative relay networks with large numbers of nodes are analyzed, and in particular the asymptotic performance improvement of cooperative transmission over direction transmission and relay transmission is analyzed using random matrix theory. The key idea is to investigate the eigenvalue distributions related to channel capacity and to analyze the moments of this distribution in large wireless networks. A performance upper bound is derived, the performance in the low signal-to-noise-ratio regime is analyzed, and two approximations are obtained for high and low relay-to-destination link qualities, respectively. Finally, simulations are provided to validate the accuracy of the analytical results. The analysis in this paper provides important tools for the understanding and the design of large cooperative wireless networks.

  15. Cooperative Trust Games

    Science.gov (United States)

    2013-01-01

    the more widely recognized competitive (non-cooperative) game theory. Cooperative game theory focuses on what groups of self-interested agents can...provides immediate justification for using non-cooperative game theory as the basis for modeling the purely competitive agents. 2.4. Superadditive...the competitive and altruistic contributions of the subset team. Definition: Given a payoff function ( ) in a subset team game , the total marginal

  16. Cooling compact stars and phase transitions in dense QCD

    Energy Technology Data Exchange (ETDEWEB)

    Sedrakian, Armen [J.W. Goethe University, Institute for Theoretical Physics, Frankfurt am Main (Germany)

    2016-03-15

    We report new simulations of cooling of compact stars containing quark cores and updated fits to the Cas A fast cooling data. Our model is built on the assumption that the transient behaviour of the star in Cas A is due to a phase transition within the dense QCD matter in the core of the star. Specifically, the fast cooling is attributed to an enhancement in the neutrino emission triggered by a transition from a fully gapped, two-flavor, red-green color-superconducting quark condensate to a superconducting crystalline or an alternative gapless, color-superconducting phase. The blue-colored condensate is modeled as a Bardeen-Cooper-Schrieffer (BCS)-type color superconductor with spin-one pairing order parameter. We study the sensitivity of the fits to the phase transition temperature, the pairing gap of blue quarks and the timescale characterizing the phase transition (the latter modelled in terms of a width parameter). Relative variations in these parameter around their best-fit values larger than 10{sup -3} spoil the fit to the data. We confirm the previous finding that the cooling curves show significant variations as a function of compact star mass, which allows one to account for dispersion in the data on the surface temperatures of thermally emitting neutron stars. (orig.)

  17. Absence of coherent peaks in a Z2 fractionalized BCS superconducting state

    Science.gov (United States)

    Zhong, Yin; Lu, Han-Tao; Luo, Hong-Gang

    2015-01-01

    We explore a Z2 fractionalized Bardeen-Cooper-Schrieffer (BCS) superconducting state, which is a minimal extension of usual BCS framework. It is found that this state has similar thermal and transport properties, but its single-particle feature strongly deviates from the coherent quasiparticle behavior of the classic/conventional BCS superconducting state. The fingerprint of such Z2 BCS state is the absence of the BCS coherent peaks and instead a kink in the local density of state occurs, which in principle could be probed by scanning tunneling microscopy or point-contact spectroscopy experiments. The corresponding exactly soluble models that realize the desirable Z2 fractionalized BCS state are presented. In addition, we also study the extended t-U-J model by using Z2 slave-spin representation and find that the Z2 BCS state may exist when the paring structure is fully gapped or has nodes. The prototypical wave-function of such a Z2 BCS state is also proposed, which could be taken as trial wave-function in current numerical techniques. Furthermore, the pairing mechanism of Z2 BCS state is argued from both weak and strong coupling perspective. The present work may be helpful to further study the unconventional superconductivity and its relation to non-Fermi liquids.

  18. South-South cooperation in health: bringing in theory, politics, history, and social justice.

    Science.gov (United States)

    Birn, Anne-Emanuelle; Muntaner, Carles; Afzal, Zabia

    2017-10-02

    Since the mid-2000s, the practice of South-South cooperation in health (SSC) has attracted growing attention among policymakers, health and foreign affairs ministries, global health agencies, and scholars from a range of fields. But the South-South label elucidates little about the actual content of the cooperation and conflates the "where" with the "who, what, how, and why". While there have been some attempts to theorize global health diplomacy and South-South cooperation generally, these efforts do not sufficiently distinguish among the different kinds of practices and political values that fall under the South-South rubric, ranging from economic and geopolitical interests to social justice forms of solidarity. In the spirit of deepening theoretical, historical, and social justice analyses of SSC, this article: (1) critically revisits international relations theories that seek to explain SSC, exploring Marxian and other heterodox theories ignored in the mainstream literature; (2) traces the historical provenance of a variety of forms of SSC; and (3) introduces the concept of social justice-oriented South-South.

  19. Study on Cooperative Mechanism of Prefabricated Producers Based on Evolutionary Game Theory

    Directory of Open Access Journals (Sweden)

    Tongyao Feng

    2017-01-01

    Full Text Available Good cooperation mechanism is an important guarantee for the advancement of industrialization construction. To strengthen the partnership between producers, we analyze the behavior evolution trend of both parties using an evolutionary game theory. Based on the original model, the mechanism of coordination and cooperation between prefabricated producers is explained under the condition of punishment and incentive. The results indicate that stable evolutionary strategies exist under both cooperation and noncooperation, and the evolutionary results are influenced by the initial proportion of both decision-making processes. The government can support the production enterprises to establish a solid partnership through effective punishment and incentive mechanisms to reduce the initial cost in the supply chain of prefabricated construction, resulting in a win-win situation.

  20. The Inner Eye Theory of Laughter: Mindreader Signals Cooperator Value

    Directory of Open Access Journals (Sweden)

    Wonil Edward Jung

    2003-01-01

    Full Text Available In this hypothesis paper, I propose a three-component set of jointly necessary and sufficient trigger criteria for all cases of involuntary laughter. The theory incorporates concepts from the theory of mind in cognitive science. I then examine the information content of the laughter signal from a game theoretic perspective. I conclude that laughter is a signal of cooperator value as it provides information on the laugher's empathy with the attributed mental states and her sympathy levels for all affected by the laugh-inducing situation. Laughter also indicates what types of mental representations children, autistic people, nonhuman primates and adults possess and can falsify.

  1. Superconductivity in hydrogen-rich materials at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Drozdov, Alexander

    2016-07-01

    A room temperature superconductor is probably one of the most desired systems in solid state physics. The highest critical temperature (T{sub c}) that has been achieved so far is in the copper oxide system: 133 kelvin (K) at ambient pressure ([82]Schilling et al. 1993) and 160 K under pressure ([42]Gao et al. 1994). The nature of superconductivity in the cuprates and in the recently discovered iron-based superconductor family (T{sub c}=57 K) is still not fully understood. In contrast, there is a class of superconductors which is well-described by the Bardeen, Cooper, Schrieffer (BCS) theory - conventional superconductors. Great efforts were spent in searching for high-temperature (T{sub c} > 77 K) conventional superconductor but only T{sub c} = 39 K has been reached in MgB2 ([68]Nagamatsu et al. 2001). BCS theory puts no bounds for T{sub c} as follows from Eliashberg's formulation of BCS theory. T{sub c} can be high, if there is a favorable combination of high-frequency phonons, strong electron-phonon coupling, and a high density of states. It does not predict however in which materials all three parameters are large. At least it gives a clear indication that materials with light elements are favorable as light elements provide high frequencies in the phonon spectrum. The lightest element is hydrogen, and Ashcroft made a first prediction that metallic hydrogen will be a high-temperature superconductor ([6]Ashcroft 1968). As pressure of hydrogen metallization was too high (about 400-500 GPa) for experimental techniques then he proposed that compounds dominated by hydrogen (hydrides) also might be good high temperature superconductors ([6]Ashcroft 1968; [7]Ashcroft 2004). A lot of the followed calculations supported this idea. T{sub c} in the range of 50-235 kelvin was predicted for many hydrides. Unfortunately, only a moderate T{sub c} of 17 kelvin has been observed experimentally ([27]Eremets et al. 2008) so far. A goal of the present work is to find a

  2. Cooperation or Competition: Does Game Theory Have Relevance for Public Health?

    Science.gov (United States)

    Westhoff, Wayne W.; Cohen, Cynthia F.; Cooper, Elizabeth Elliott; Corvin, Jaime; McDermott, Robert J.

    2012-01-01

    In this paper, we use game theory to understand decisions to cooperate or to compete in the delivery of public health services. Health care is a quasi-public good that is often associated with altruistic behavior, yet it operates in an increasingly competitive environment. With mounting health care regulation and changes in privatization,…

  3. GCPSO in cooperation with graph theory to distribution network reconfiguration for energy saving

    International Nuclear Information System (INIS)

    Assadian, Mehdi; Farsangi, Malihe M.; Nezamabadi-pour, Hossein

    2010-01-01

    Network reconfiguration for loss reduction in distribution system is an important way to save energy. This paper investigates the ability of guaranteed convergence particle swarm optimization (GCPSO) and particle swarm optimization (PSO) in cooperation with graph theory for network reconfiguration to reduce the power loss and enhancement of voltage profile of distribution systems. Numerical results of three distribution systems are presented which illustrate the feasibility of the proposed method by GCPSO and PSO using the graph theory. To validate the obtained results, genetic algorithm (GA) using graph theory is also applied and is compared with the proposed GCPSO and PSO using graph theory.

  4. Cooperative games and network structures

    NARCIS (Netherlands)

    Musegaas, Marieke

    2017-01-01

    This thesis covers various research topics involving cooperative game theory, a mathematical tool to analyze the cooperative behavior within a group of players. The focus is mainly on interrelations between operations research and cooperative game theory by analyzing specific types of cooperative

  5. Testing the renormalisation group theory of cooperative transitions at the lambda point of helium

    Science.gov (United States)

    Lipa, J. A.; Li, Q.; Chui, T. C. P.; Marek, D.

    1988-01-01

    The status of high resolution tests of the renormalization group theory of cooperative phase transitions performed near the lambda point of helium is described. The prospects for performing improved tests in space are discussed.

  6. Schwarzschild tests of the Wahlquist-Estabrook-Buchman-Bardeen tetrad formulation for numerical relativity

    International Nuclear Information System (INIS)

    Buchman, L.T.; Bardeen, J.M.

    2005-01-01

    A first order symmetric hyperbolic tetrad formulation of the Einstein equations developed by Estabrook and Wahlquist and put into a form suitable for numerical relativity by Buchman and Bardeen (the WEBB formulation) is adapted to explicit spherical symmetry and tested for accuracy and stability in the evolution of spherically symmetric black holes (the Schwarzschild geometry). The lapse and shift, which specify the evolution of the coordinates relative to the tetrad congruence, are reset at frequent time intervals to keep the constant-time hypersurfaces nearly orthogonal to the tetrad congruence and the spatial coordinate satisfying a kind of minimal rate of strain condition. By arranging through initial conditions that the constant-time hypersurfaces are asymptotically hyperbolic, we simplify the boundary value problem and improve stability of the evolution. Results are obtained for both tetrad gauges ('Nester' and 'Lorentz') of the WEBB formalism using finite difference numerical methods. We are able to obtain stable unconstrained evolution with the Nester gauge for certain initial conditions, but not with the Lorentz gauge

  7. Cooperation, psychological game theory, and limitations of rationality in social interaction.

    Science.gov (United States)

    Colman, Andrew M

    2003-04-01

    Rational choice theory enjoys unprecedented popularity and influence in the behavioral and social sciences, but it generates intractable problems when applied to socially interactive decisions. In individual decisions, instrumental rationality is defined in terms of expected utility maximization. This becomes problematic in interactive decisions, when individuals have only partial control over the outcomes, because expected utility maximization is undefined in the absence of assumptions about how the other participants will behave. Game theory therefore incorporates not only rationality but also common knowledge assumptions, enabling players to anticipate their co-players' strategies. Under these assumptions, disparate anomalies emerge. Instrumental rationality, conventionally interpreted, fails to explain intuitively obvious features of human interaction, yields predictions starkly at variance with experimental findings, and breaks down completely in certain cases. In particular, focal point selection in pure coordination games is inexplicable, though it is easily achieved in practice; the intuitively compelling payoff-dominance principle lacks rational justification; rationality in social dilemmas is self-defeating; a key solution concept for cooperative coalition games is frequently inapplicable; and rational choice in certain sequential games generates contradictions. In experiments, human players behave more cooperatively and receive higher payoffs than strict rationality would permit. Orthodox conceptions of rationality are evidently internally deficient and inadequate for explaining human interaction. Psychological game theory, based on nonstandard assumptions, is required to solve these problems, and some suggestions along these lines have already been put forward.

  8. A cooperative game theory approach to transmission planning in power systems

    Science.gov (United States)

    Contreras, Javier

    The rapid restructuring of the electric power industry from a vertically integrated entity into a decentralized industry has given rise to complex problems. In particular, the transmission component of the electric power system requires new methodologies to fully capture this emerging competitive industry. Game theory models are used to model strategic interactions in a competitive environment. This thesis presents a new decentralized framework to study the transmission network expansion problem using cooperative game theory. First, the players and the rules of the game are defined. Second, a coalition formation scheme is developed. Finally, the optimized cost of expansion is allocated based on the history of the coalition formation.

  9. Cooperation, Fast and Slow: Meta-Analytic Evidence for a Theory of Social Heuristics and Self-Interested Deliberation.

    Science.gov (United States)

    Rand, David G

    2016-09-01

    Does cooperating require the inhibition of selfish urges? Or does "rational" self-interest constrain cooperative impulses? I investigated the role of intuition and deliberation in cooperation by meta-analyzing 67 studies in which cognitive-processing manipulations were applied to economic cooperation games (total N = 17,647; no indication of publication bias using Egger's test, Begg's test, or p-curve). My meta-analysis was guided by the social heuristics hypothesis, which proposes that intuition favors behavior that typically maximizes payoffs, whereas deliberation favors behavior that maximizes one's payoff in the current situation. Therefore, this theory predicts that deliberation will undermine pure cooperation (i.e., cooperation in settings where there are few future consequences for one's actions, such that cooperating is not in one's self-interest) but not strategic cooperation (i.e., cooperation in settings where cooperating can maximize one's payoff). As predicted, the meta-analysis revealed 17.3% more pure cooperation when intuition was promoted over deliberation, but no significant difference in strategic cooperation between more intuitive and more deliberative conditions. © The Author(s) 2016.

  10. Cooperation between territorial communities: theory and practice

    Directory of Open Access Journals (Sweden)

    П. М. Любченко

    2015-05-01

    Full Text Available Problem Setting. The paper analyzes the problems in the system of legal regulation of cooperation between communities, highlights the advantages and disadvantages of such cooperation in Ukrainian local government. Analysis of the recent researches and publications. The legal basis for cooperation in the field of local government are provisions of the Constitution and laws of Ukraine, by-laws. The organizational principles of communities cooperation, principles, forms and mechanisms of such cooperation and its promotion, financing and monitoring prescribed by the Law of Ukraine «On cooperation of local communities» 17 June 2014, which provides five possible forms of cooperation. Paper main body. The first form - delegation to one party of cooperation by another parties of cooperation execution of one or few tasks with transferring of appropriate resources - one of the most difficult to implement, therefore in Ukraine it is not yet implemented. The second form – realization of joint projects, involving coordination of activities between parties of cooperation and accumulating them for a certain period resources to joint implementation of appropriate measures - one of the most common. This  form is popular because of its simplicity and versatility. Parties are determining the purpose of the project, terms and conditions of its implementation, a list of activities and conditions for their implementation, financial liabilities, other forms of local governments participation in implementation of the project and mechanism of coordination. The third and fourth forms aimed on the creation and maintenance of communal enterprises, institutions and organizations - joint infrastructure projects by parties of cooperation. This form of cooperation with the prospect of widespread use because it is aimed at ensuring effective use of resources of local communities based on common application available in one of the subjects of cooperation of municipal

  11. Games microbes play: The game theory behind cooperative sucrose metabolism in yeast

    Science.gov (United States)

    Gore, Jeff

    2010-03-01

    The origin of cooperation is a central challenge to our understanding of evolution. Microbial interactions can be manipulated in ways that animal interactions cannot, thus leading to growing interest in microbial models of cooperation and competition. In order for the budding yeast S. cerevisiae to grow on sucrose, the disaccharide must first be hydrolyzed by the enzyme invertase. This hydrolysis reaction is performed outside of the cytoplasm in the periplasmic space between the plasma membrane and the cell wall. Here we demonstrate that the vast majority (˜99%) of the monosaccharides created by sucrose hydrolysis diffuse away before they can be imported into the cell, thus making invertase production and secretion a cooperative behavior [1]. A mutant cheater strain that does not produce invertase is able to take advantage of and invade a population of wildtype cooperator cells. However, over a wide range of conditions, the wildtype cooperator can also invade a population of cheater cells. Therefore, we observe coexistence between the two strains in well-mixed culture at steady state resulting from the fact that rare strategies outperform common strategies---the defining features of what game theorists call the snowdrift game. A simple model of the cooperative interaction incorporating nonlinear benefits explains the origin of this coexistence. Glucose repression of invertase expression in wildtype cells produces a strategy which is optimal for the snowdrift game---wildtype cells cooperate only when competing against cheater cells. In disagreement with recent theory [2], we find that spatial structure always aids the evolution of cooperation in our experimental snowdrift game. [4pt] [1] Gore, J., Youk, H. & van Oudenaarden, A., Nature 459, 253 -- 256 (2009) [0pt] [2] Hauert, C. & Doebeli, M., Nature 428, 643 -- 646 (2004)

  12. Evolutionary game theory meets social science: is there a unifying rule for human cooperation?

    Science.gov (United States)

    Rosas, Alejandro

    2010-05-21

    Evolutionary game theory has shown that human cooperation thrives in different types of social interactions with a PD structure. Models treat the cooperative strategies within the different frameworks as discrete entities and sometimes even as contenders. Whereas strong reciprocity was acclaimed as superior to classic reciprocity for its ability to defeat defectors in public goods games, recent experiments and simulations show that costly punishment fails to promote cooperation in the IR and DR games, where classic reciprocity succeeds. My aim is to show that cooperative strategies across frameworks are capable of a unified treatment, for they are governed by a common underlying rule or norm. An analysis of the reputation and action rules that govern some representative cooperative strategies both in models and in economic experiments confirms that the different frameworks share a conditional action rule and several reputation rules. The common conditional rule contains an option between costly punishment and withholding benefits that provides alternative enforcement methods against defectors. Depending on the framework, individuals can switch to the appropriate strategy and method of enforcement. The stability of human cooperation looks more promising if one mechanism controls successful strategies across frameworks. Published by Elsevier Ltd.

  13. Theory and simulation of charge transfer through DNA - nanotube contacts

    International Nuclear Information System (INIS)

    Rink, Gunda; Kong Yong; Koslowski, Thorsten

    2006-01-01

    We address the problem of charge transfer between a single-stranded adenine oligomer and semiconducting boron nitride nanotubes from a theoretical and numerical perspective. The model structures have been motivated by computer simulations; sample geometries are used as the input of an electronic structure theory that is based upon an extended Su-Schrieffer-Heeger Hamiltonian. By analyzing the emerging potential energy surfaces, we obtain hole transfer rates via Marcus' theory of charge transfer. In the presence of nanotubes, these rates exceed those of isolated DNA single strands by a factor of up to 10 4 . This enhancement can be rationalized and quantified as a combination of a template effect and the participation of the tube within a superexchange mechanism

  14. Two decades on[Research into high-temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Durrani, M. [Physics World (United Kingdom)

    2006-04-15

    Research into high-temperature superconductors should focus on experiment, not theory. While the world looked on in horror at the events unfolding at the Chernobyl nuclear-power plant in the Soviet Union 20 years ago this month, another significant - but far less reported - development in the world of physics had just taken place. On 17 April 1986 a short paper by Georg Bednorz and Alexander Mueller arrived at the offices of Zeitschrift fuer Physik in Heidelberg, Germany. The two physicists, based at IBM's Zurich Research Laboratory in Switzerland, announced they had made a material from barium, lanthanum, copper and oxygen that could conduct electricity without resistance when cooled below a transition temperature, T{sub c}, of about 30 K. It was the world's first 'high-temperature' superconductor. Driven by the dream of materials that can superconduct at room temperature, experimentalists scurried back to their labs. Within a year, a T{sub c} of 90 K in another material had been reported and by October 1987 Bednorz and Mueller had been crowned with a Nobel prize. While papers on high-temperature superconductivity have continued to stream out since those heady days, progress has been slower than expected. Applications like levitating trains and resistance-free power cables are only now starting to come to market. Scientists have been unable to make superconducting wires that work much above 130 K, while a reliable theory of high-temperature superconductivity remains elusive. Even if we had such a theory, it is not clear that it would predict which materials might superconduct at room temperature. After all, the Bardeen-Cooper-Schrieffer theory, which explains the behaviour of low-temperature superconductors with admirable success, said nothing about the superconducting properties of Bednorz and Mueller's copper-oxide ceramics. What successes there have been over the last 20 years - such as the recent discoveries that iron, single crystals

  15. Thermal evolution of massive compact objects with dense quark cores

    International Nuclear Information System (INIS)

    Hess, Daniel; Sedrakian, Armen

    2011-01-01

    We examine the thermal evolution of a sequence of compact objects containing low-mass hadronic and high-mass quark-hadronic stars constructed from a microscopically motivated equation of state. The dependence of the cooling tracks in the temperature versus age plane is studied on the variations of the gaplessness parameter (the ratio of the pairing gap for red-green quarks to the electron chemical potential) and the magnitude of blue quark gap. The pairing in the red-green channel is modeled assuming an inhomogeneous superconducting phase to avoid tachionic instabilities and anomalies in the specific heat; the blue colored condensate is modeled as a Bardeen-Cooper-Schrieffer (BCS)-type color superconductor. We find that massive stars containing quark matter cool faster in the neutrino-cooling era if one of the colors (blue) is unpaired and/or the remaining colors (red-green) are paired in a inhomogeneous gapless superconducting state. The cooling curves show significant variations along the sequence, as the mass (or the central density) of the models is varied. This feature provides a handle for fine-tuning the models to fit the data on the surface temperatures of same-age neutron stars. In the late-time photon cooling era we observe inversion in the temperature arrangement of models, i.e., stars experiencing fast neutrino cooling are asymptotically hotter than their slowly cooling counterparts.

  16. Localized superconductors

    International Nuclear Information System (INIS)

    Ma, M.; Lee, P.A.

    1985-01-01

    We study the effects of Anderson localization on superconductivity by using a Bardeen-Cooper-Schrieffer (BCS)-type trial wave function which pairs electrons in exact time-reversed eigenstates of the single-particle Hamiltonian. Within this approximation, and neglecting localization effects on the effective Coulomb repulsion and the electron-phonon coupling, we find that superconductivity persists below the mobility edge. In fact, Anderson's theorem is valid in the localized phase as long as rhoΔ 0 L/sup d/ > 1 (rho is the density of states averaged over +- Δ 0 of the Fermi energy, Δ 0 the BCS gap parameter, and L the localization length). Hence the gap order parameter Δ(r) remains uniform in space at the BCS value Δ 0 . The superfluid density and response to electromagnetic perturbations, however, show marked differences from the ''dirty superconductor'' regime. For rhoΔ 0 L/sup d/ < 1, Δ(r) fluctuates spatially and eventually drops to zero. In the limit when states are site localized, the system crosses over into the ''Anderson negative-U glass.'' Considerations beyond the trial wave-function approximation will speed up the destruction of superconductivity. The superconductor formed from localized states has the property that its quasiparticle excitations are also localized. Such excitations can be probed by observing the normal current in a tunneling junction

  17. Anisotropy of the penetration depth in La2-xSrxCuO4 in underdoped and overdoped regions

    Science.gov (United States)

    Zaleski, A. J.; Klamut, J.

    1999-12-01

    We present the results of measurements of the penetration depth anisotropy in pulverized, ceramic La2-xSrxCuO4. The measurements were carried out for x = 0.08, 0.1, 0.125, 0.15 and 0.2. The powdered samples, immersed in wax, were magnetically oriented in a static magnetic field of 10 T. The penetration depth in the a-b plane, icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/>ab, and perpendicular to it, icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/>icons/Journals/Common/perp" ALT="perp" ALIGN="MIDDLE"/>, were derived from alternating-current susceptibility measurements. For underdoped samples they both vary linearly with temperature (for the low-temperature region), while for the samples from the overdoped region the measured points can be fitted by an exponential function. These results support Uemura's picture (Uemura Y J 1997 Physica C 282-287 194) of crossover from Bose-Einstein condensation to a Bardeen-Cooper-Schrieffer mechanism of superconductivity. The penetration depth values extrapolated to T = 0 may be described by a quadratic function of the strontium concentration (for both icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/>ab and icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/>icons/Journals/Common/perp" ALT="perp" ALIGN="MIDDLE"/>). The anisotropy of the penetration depth as a function of the substitution shows a similar dependence to the critical temperature Tc(x).

  18. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

    In this review we consider three classes of superconductors, namely cuprate superconductors, MgB(2) and the new Fe based superconductors. All of these three systems are layered materials and multiband compounds. Their pairing mechanisms are under discussion with the exception of MgB(2), which is widely accepted to be a 'conventional' electron-phonon interaction mediated superconductor, but extending the Bardeen-Cooper-Schrieffer (BCS) theory to account for multiband effects. Cuprates and Fe based superconductors have higher superconducting transition temperatures and more complex structures. Superconductivity is doping dependent in these material classes unlike in MgB(2) which, as a pure compound, has the highest values of T(c) and a rapid suppression of superconductivity with doping takes place. In all three material classes isotope effects have been observed, including exotic ones in the cuprates, and controversial ones in the Fe based materials. Before the area of high-temperature superconductivity, isotope effects on T(c) were the signature for phonon mediated superconductivity-even when deviations from the BCS value to smaller values were observed. Since the discovery of high T(c) materials this is no longer evident since competing mechanisms might exist and other mediating pairing interactions are discussed which are of purely electronic origin. In this work we will compare the three different material classes and especially discuss the experimentally observed isotope effects of all three systems and present a rather general analysis of them. Furthermore, we will concentrate on multiband signatures which are not generally accepted in cuprates even though they are manifest in various experiments, the evidence for those in MgB(2), and indications for them in the Fe based compounds. Mostly we will consider experimental data, but when possible also discuss theoretical models which are suited to explain the data.

  19. An investigation of proton pair correlations relevant to the neutrinoless double beta decay of 76Ge

    Science.gov (United States)

    Ticehurst, David R.

    The observation of neutrinoless double beta decay (0nubetabeta ) would demonstrate that the neutrino is a Majorana particle and allow determination of its mass by comparing the measured decay rate to the calculated rate. The main uncertainty in the calculation of the 0 nubetabeta rate is due to uncertainties in the nuclear structure models used in the computation of the nuclear matrix elements for the decay process. This project tested the validity of using wavefunctions for the nuclear states involved in the 0nubetabeta process that are based on a first-order application of the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity. In the BCS approximation, most of the strength for two-nucleon transfer reactions should be for transitions to the 0 + ground state of the final nucleus (i.e., little strength should go to the 0+ excited states). This experiment measured the strength to the first 0+ excited state for the 74Ge( 3He,n)76Se and 76Ge( 3He,n)78Se reactions relative to the strength for transition to the 0+ ground state in selenium. For both nuclei, and at 3He beam energies of 15 and 21 MeV, the observed relative strength for transfer to the first 0+ excited state was less than 13%. This result supports the validity of using the BCS approximation to describe the ground state of both 76Se and 78Se and is consistent with the results of recent ( 3He,n) cross section measurements on 74Ge and 76Ge. In addition, the magnitude and shape of the measured angular distributions suggest that contribution of the sequential two-nucleon transfer process, which is an indicator of long-range nucleon-nucleon correlations, is over-predicted by the DWBA code FRESCO.

  20. European cooperation in the field of security and defence. International Relation theories perspective

    Directory of Open Access Journals (Sweden)

    Jacek Czaputowicz

    2014-06-01

    Full Text Available The paper discusses various theoretical explanations of the European cooperation in the field of security and defence. According to realist explanations this cooperation was a response to external evolutions in the international system, i.e. changes in polarity and distribution of power. Liberals say that it was rather due to internal factors. Constructivists argue that it was a result of elites’ socialisation, while according to Pierre Bourdieu’s field theory, it was caused by civil servants and military staff at the policy implementation level. The paper argues that external factors underlined by realists were decisive, i.e. America’s decreasing involvement in European security.

  1. The study of some physical properties of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atif Mahmoud

    2008-07-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F({omega}) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on

  2. The study of some physical properties of high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Atif Mahmoud

    2008-07-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F({omega}) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on the

  3. The study of some physical properties of high temperature superconductors

    International Nuclear Information System (INIS)

    Ismail, Atif Mahmoud

    2008-01-01

    The phenomenon of superconductivity, the discovery of high temperature superconductivity in the Cuprates and the properties of these materials is described in the introductory chapter. It also includes a discussion of the pseudogap, which has remained a mystery as has the high transition temperature. Possible applications of high temperature superconductivity are reviewed before the theories by Bardeen, Cooper, and Schrieffer (BCS) and Ginzburg and Landau are briefly sketched. The last section gives excerpts of the by now vast literature on this subject, focussing on the role impurities play in this context. The second chapter develops the mathematical tools and the theoretical background for the description of many-body systems. Various Green's functions are introduced which are then used to describe scattering of quasiparticles off defects of arbitrary strength. They are also required to calculate the a.c. conductivity, for which an expression is derived using linear response theory. The convergence problems one encounters when actually calculating the conductivity are briefly discussed. Detailed calculations for the normal state are presented in the third chapter and in the appendix. The third Chapter begins with a detailed presentation of the tight binding model for the energy dispersion because this model appears to give a more accurate description of the electronic properties of high temperature superconductors than the nearly free electron model. The shape of the two-dimensional Fermi surface is calculated and displayed as function of band filling and the next-nearest neighbor hopping integral B, assuming a rigid band. B plays an important role in the formation of so-called hot spots. The quasiparticle density of states and its Hilbert transform F(ω) are solved by means of complete elliptic integrals formalism. These results are used to obtain impurity bound states. A simple model for the superconductivity in the cuprate materials is developed on the basis

  4. Breakdown of the Bardeen-Stephen law for free flux flow in Bi2Sr2CaCu2O8+δ

    Science.gov (United States)

    Pallinger, Á.; Sas, B.; Pethes, I.; Vad, K.; Williams, F. I. B.; Kriza, G.

    2008-09-01

    Pulsed high-current experiments in single crystals of the high- Tc superconductor Bi2Sr2CaCu2O8+δ in a c -axis-directed magnetic field H reveal that the ab -face resistance in the free flux flow regime is a solely logarithmic function of H , devoid of any power-law component. Reanalysis of published data confirms this result and leads to empirical analytical forms for the ab plane and c axis resistivities, ρab∝H3/4 , which does not obey the expected Bardeen-Stephen result for free flux flow and ρc∝H-3/4log2H .

  5. Social penalty promotes cooperation in a cooperative society.

    Science.gov (United States)

    Ito, Hiromu; Yoshimura, Jin

    2015-08-04

    Why cooperation is well developed in human society is an unsolved question in biological and human sciences. Vast studies in game theory have revealed that in non-cooperative games selfish behavior generally dominates over cooperation and cooperation can be evolved only under very limited conditions. These studies ask the origin of cooperation; whether cooperation can evolve in a group of selfish individuals. In this paper, instead of asking the origin of cooperation, we consider the enhancement of cooperation in a small already cooperative society. We ask whether cooperative behavior is further promoted in a small cooperative society in which social penalty is devised. We analyze hawk-dove game and prisoner's dilemma introducing social penalty. We then expand it for non-cooperative games in general. The results indicate that cooperation is universally favored if penalty is further imposed. We discuss the current result in terms of the moral, laws, rules and regulations in a society, e.g., criminology and traffic violation.

  6. Cooperative decision making in a stochastic environment

    NARCIS (Netherlands)

    Suijs, J.P.M.

    1998-01-01

    Cooperative game theory is a mathematical tool to analyze situations involving several individuals who can obtain certain benefits by cooperating. The main questions this theory addresses are who will cooperate with whom and how will the corresponding benefits be divided. Most results of cooperative

  7. Quantifying the Role of Homophily in Human Cooperation Using Multiplex Evolutionary Game Theory.

    Directory of Open Access Journals (Sweden)

    Alessandro Di Stefano

    Full Text Available Nature shows as human beings live and grow inside social structures. This assumption allows us to explain and explore how it may shape most of our behaviours and choices, and why we are not just blindly driven by instincts: our decisions are based on more complex cognitive reasons, based on our connectedness on different spaces. Thus, human cooperation emerges from this complex nature of social network. Our paper, focusing on the evolutionary dynamics, is intended to explore how and why it happens, and what kind of impact is caused by homophily among people. We investigate the evolution of human cooperation using evolutionary game theory on multiplex. Multiplexity, as an extra dimension of analysis, allows us to unveil the hidden dynamics and observe non-trivial patterns within a population across network layers. More importantly, we find a striking role of homophily, as the higher the homophily between individuals, the quicker is the convergence towards cooperation in the social dilemma. The simulation results, conducted both macroscopically and microscopically across the network layers in the multiplex, show quantitatively the role of homophily in human cooperation.

  8. Theory of superconductivity. II. Excited Cooper pairs. Why does sodium remain normal down to 0 K?

    International Nuclear Information System (INIS)

    Fujita, S.

    1992-01-01

    Based on a generalized BCS Hamiltonian in which the interaction strengths (V 11 , V 22 , V 12 ) among and between electron (12) and hole (2) Cooper pairs are differentiated, the thermodynamic properties of a type-I superconductor below the critical temperature T c are investigated. An expression for the ground-state energy, W - W 0 , relative to the unperturbed Block system is obtained. The usual BCS formulas are obtained in the limits: (all) V jl = V 0 , N 1 (0) = N 2 (0). Any excitations generated through the BCS interaction Hamiltonian containing V jl must involve Cooper pairs of antiparallel spins and nearly opposite momenta. The nonzero momentum or excited Cooper pairs below T c are shown to have an excitation energy band minimum lower than the quasi-electrons, which were regarded as the elementary excitations in the original BCS theory. The energy gap var-epsilon g (T) defined relative to excited and zero-momentum Copper pairs (when V jl > 0) decreases from var-epsilon g (0) to 0 as the temperature T is raised from 0 to T c . If electrons only are available as in a monovalent metal like sodium (V 12 = 0), the energy constant Δ 1 is finite but the energy gap vanishes identically for all T. In agreement with the BCS theory, the present theory predicts that a pure nonmagnetic metal in any dimensions should have a Cooper-pair ground state whose energy is lower than that of the Bloch ground state. Additionally it predicts that a monovalent metal should remain normal down to 0 K, and that there should be no strictly one-dimensional superconductor

  9. Combining evolutionary game theory and network theory to analyze human cooperation patterns

    International Nuclear Information System (INIS)

    Scatà, Marialisa; Di Stefano, Alessandro; La Corte, Aurelio; Liò, Pietro; Catania, Emanuele; Guardo, Ermanno; Pagano, Salvatore

    2016-01-01

    Highlights: • We investigate the evolutionary dynamics of human cooperation in a social network. • We introduce the concepts of “Critical Mass”, centrality measure and homophily. • The emergence of cooperation is affected by the spatial choice of the “Critical Mass”. • Our findings show that homophily speeds up the convergence towards cooperation. • Centrality and “Critical Mass” spatial choice partially offset the impact of homophily. - Abstract: As natural systems continuously evolve, the human cooperation dilemma represents an increasingly more challenging question. Humans cooperate in natural and social systems, but how it happens and what are the mechanisms which rule the emergence of cooperation, represent an open and fascinating issue. In this work, we investigate the evolution of cooperation through the analysis of the evolutionary dynamics of behaviours within the social network, where nodes can choose to cooperate or defect following the classical social dilemmas represented by Prisoner’s Dilemma and Snowdrift games. To this aim, we introduce a sociological concept and statistical estimator, “Critical Mass”, to detect the minimum initial seed of cooperators able to trigger the diffusion process, and the centrality measure to select within the social network. Selecting different spatial configurations of the Critical Mass nodes, we highlight how the emergence of cooperation can be influenced by this spatial choice of the initial core in the network. Moreover, we target to shed light how the concept of homophily, a social shaping factor for which “birds of a feather flock together”, can affect the evolutionary process. Our findings show that homophily allows speeding up the diffusion process and make quicker the convergence towards human cooperation, while centrality measure and thus the Critical Mass selection, play a key role in the evolution showing how the spatial configurations can create some hidden patterns, partially

  10. Co-Operative Learning and Development Networks.

    Science.gov (United States)

    Hodgson, V.; McConnell, D.

    1995-01-01

    Discusses the theory, nature, and benefits of cooperative learning. Considers the Cooperative Learning and Development Network (CLDN) trial in the JITOL (Just in Time Open Learning) project and examines the relationship between theories about cooperative learning and the reality of a group of professionals participating in a virtual cooperative…

  11. A Model for Cooperative Advertising and Pricing Decisions in Manufacturer-Retailer Supply Chain with Discount: A Game Theory Approach

    Directory of Open Access Journals (Sweden)

    Abolfazl Kazemi

    2016-02-01

    Full Text Available Coordinating the supply chain is among the most important subjects that is extensively addressed in the related literature. If a supply chain is to be coordinated, it is equivalent to say that we must solve a problem related to competition and cooperation. The game theory is obviously one of the most effective methods to solve such problems, in which the players of the supply chain are assumed to engage in cooperative and non-cooperative games. The current study aims to coordinate a two-level supply chain consisting of a manufacturer and a retailer. This will be achieved using cooperative advertisement along with pricing decisions such that the manufacturer offers a price discount to the retailer and the demand is affected by pricing and advertisement. Cooperative advertisement is a coordinated effort made by all the members of the supply chain to increase the customer demand, in which the retailer does the local advertisement and the manufacturer pays for a portion or all the costs of the retailer advertisement. We consider two models for manufacturer-retailer relation using the game theory: the manufacturer-Stackelberg and the retailer-Stackelberg games with asymmetric power distribution.

  12. Managing conflict in Dutch organizations: A test of the relevance of DeutschUs cooperation theory

    NARCIS (Netherlands)

    de Dreu, C.K.W.; Tjosvold, D.

    1997-01-01

    Deutsch's theory of cooperative and competitive conflict may be usefully extended to Dutch people. Results of LISREL analyses on data collected from interviews of Dutch employees in 2 companies indicate that competitive goals interfered with the open, constructive discussion of opposing views.

  13. Subgame consistent cooperation a comprehensive treatise

    CERN Document Server

    Yeung, David W K

    2016-01-01

    Strategic behavior in the human and social world has been increasingly recognized in theory and practice. It is well known that non-cooperative behavior could lead to suboptimal or even highly undesirable outcomes. Cooperation suggests the possibility of obtaining socially optimal solutions and the calls for cooperation are prevalent in real-life problems. Dynamic cooperation cannot be sustainable if there is no guarantee that the agreed upon optimality principle at the beginning is maintained throughout the cooperation duration. It is due to the lack of this kind of guarantees that cooperative schemes fail to last till its end or even fail to get started. The property of subgame consistency in cooperative dynamic games and the corresponding solution mechanism resolve this “classic” problem in game theory. This book is a comprehensive treatise on subgame consistent dynamic cooperation covering the up-to-date state of the art analyses in this important topic. It sets out to provide the theory, solution tec...

  14. Use of cooperative game theory in power system fixed-cost allocation

    International Nuclear Information System (INIS)

    Stamtsis, G.C.; Erlich, I.

    2004-01-01

    The use of cooperative game theory in power system fixed-cost allocation is investigated. The implementation of the allocation game in a bilateral transaction electricity market as well as in a pool market is discussed and the use of two well-known solution methods, nucleolus and the Shapley value, is explored. Conclusions are drawn which show that the Shapley value is a more preferable method when it is in the core of the game. For all the cases, results are illustrated in the IEEE 14-bus system. (author)

  15. Use of cooperative game theory in power system fixed-cost allocation

    Energy Technology Data Exchange (ETDEWEB)

    Stamtsis, G.C.; Erlich, I. [Duisburg-Essen Univ. (Germany). Inst. of Power Systems

    2004-05-01

    The use of cooperative game theory in power system fixed-cost allocation is investigated. The implementation of the allocation game in a bilateral transaction electricity market as well as in a pool market is discussed and the use of two well-known solution methods, nucleolus and the Shapley value, is explored. Conclusions are drawn which show that the Shapley value is a more preferable method when it is in the core of the game. For all the cases, results are illustrated in the IEEE 14-bus system. (author)

  16. Mass generation, the cosmological constant problem, conformal symmetry, and the Higgs boson

    Science.gov (United States)

    Mannheim, Philip D.

    2017-05-01

    In 2013 the Nobel Prize in Physics was awarded to Francois Englert and Peter Higgs for their work in 1964 along with the late Robert Brout on the mass generation mechanism (the Higgs mechanism) in local gauge theories. This mechanism requires the existence of a massive scalar particle, the Higgs boson, and in 2012 the Higgs boson was finally discovered at the Large Hadron Collider after being sought for almost half a century. In this article we review the work that led to the discovery of the Higgs boson and discuss its implications. We approach the topic from the perspective of a dynamically generated Higgs boson that is a fermion-antifermion bound state rather than an elementary field that appears in an input Lagrangian. In particular, we emphasize the connection with the Bardeen-Cooper-Schrieffer theory of superconductivity. We identify the double-well Higgs potential not as a fundamental potential but as a mean-field effective Lagrangian with a dynamical Higgs boson being generated through a residual interaction that accompanies the mean-field Lagrangian. We discuss what we believe to be the key challenge raised by the discovery of the Higgs boson, namely determining whether it is elementary or composite, and through study of a conformal invariant field theory model as realized with critical scaling and anomalous dimensions, suggest that the width of the Higgs boson might serve as a suitable diagnostic for discriminating between an elementary Higgs boson and a composite one. We discuss the implications of Higgs boson mass generation for the cosmological constant problem, as the cosmological constant receives contributions from the very mechanism that generates the Higgs boson mass in the first place. We show that the contribution to the cosmological constant due to a composite Higgs boson is more tractable and under control than the contribution due to an elementary Higgs boson, and is potentially completely under control if there is an underlying conformal

  17. A Model for Cooperative Advertising and Pricing Decisions in Manufacturer-Retailer Supply Chain with Discount: A Game Theory Approach

    OpenAIRE

    Abolfazl Kazemi; Zohreh SaeedMohammadi

    2016-01-01

    Coordinating the supply chain is among the most important subjects that is extensively addressed in the related literature. If a supply chain is to be coordinated, it is equivalent to say that we must solve a problem related to competition and cooperation. The game theory is obviously one of the most effective methods to solve such problems, in which the players of the supply chain are assumed to engage in cooperative and non-cooperative games. The current study aims to coordinate a two-level...

  18. Allocation of fixed transmission cost to wheeling transactions by cooperative game theory

    International Nuclear Information System (INIS)

    Tsukamoto, Yukitoki; Iyoda, Isao

    1996-01-01

    This paper describes a methodology to allocate the cost of transmission network facilities to wheeling transactions in decentralized power systems. The authors propose that the responsibility placed on transmission facilities involved in each transaction be according to the transmission usage pattern. Their proposal incorporates MW-mile method and considers economies of scale of transmission network facilities. The authors also incorporate a nucleolus scheme in the cooperative game theory to deal with matters of conflict. The applicability of their method is demonstrated in a numerical example

  19. Relativistic corrections to the Cooperon mass: BCS versus BEC picture

    Energy Technology Data Exchange (ETDEWEB)

    Lipavský, P., E-mail: lipavsky@karlov.mff.cuni.cz

    2017-02-15

    Highlights: • Tate's measurement of relativistic effects on the Cooper pair mass show the increase while a decrease was expected. • This disagreement raised a question whether it has fundamental significance or is due to the details of the particular physical system being studied. • The most fundamental were speculations about gravitomagnetic forces enhanced by the Higgs mechanism. • These were recently disproved experimentally. • This paper shows that the relativistic mass corrections might be sensitive to the pairing scenario: the predicted mass decrease corresponds to the Bose–Einstein condensation of preformed Cooper pairs, while the pairing in the Bardeen–Cooper–Schrieffer condensate leads to an increase of experimentally observed magnitude. - Abstract: Relativistic corrections to the Cooperon mass are discussed for preformed Cooper pairs that become superconductive via the Bose–Einstein condensation (BEC) and for Cooperons in the Bardeen–Copper–Schrieffer (BCS) condensate. The distinction explains experimental results of Tate et al. (1989).

  20. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2017-03-01

    Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q0(Bp) curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q0(Bp) .

  1. Exact tensor network ansatz for strongly interacting systems

    Science.gov (United States)

    Zaletel, Michael P.

    It appears that the tensor network ansatz, while not quite complete, is an efficient coordinate system for the tiny subset of a many-body Hilbert space which can be realized as a low energy state of a local Hamiltonian. However, we don't fully understand precisely which phases are captured by the tensor network ansatz, how to compute their physical observables (even numerically), or how to compute a tensor network representation for a ground state given a microscopic Hamiltonian. These questions are algorithmic in nature, but their resolution is intimately related to understanding the nature of quantum entanglement in many-body systems. For this reason it is useful to compute the tensor network representation of various `model' wavefunctions representative of different phases of matter; this allows us to understand how the entanglement properties of each phase are expressed in the tensor network ansatz, and can serve as test cases for algorithm development. Condensed matter physics has many illuminating model wavefunctions, such as Laughlin's celebrated wave function for the fractional quantum Hall effect, the Bardeen-Cooper-Schrieffer wave function for superconductivity, and Anderson's resonating valence bond ansatz for spin liquids. This thesis presents some results on exact tensor network representations of these model wavefunctions. In addition, a tensor network representation is given for the time evolution operator of a long-range one-dimensional Hamiltonian, which allows one to numerically simulate the time evolution of power-law interacting spin chains as well as two-dimensional strips and cylinders.

  2. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Pashupati Dhakal

    2017-03-01

    Full Text Available Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q_{0}(B_{p} curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q_{0}(B_{p}.

  3. Structural and physical properties of the metal (M) substituted YBa2Cu3√/sub x/M/sub x/O7√/sub y/ perovskite

    International Nuclear Information System (INIS)

    Tarascon, J.M.; Barboux, P.; Miceli, P.F.; Greene, L.H.; Hull, G.W.; Eibschutz, M.; Sunshine, S.A.

    1988-01-01

    The mixed YBa 2 Cu 3 √/sub x/M/sub x/O 7 √/sub y/ (M = Ni, Zn, Fe, Co, and Al) phases have been characterized for their structural, magnetic, and superconducting properties. The oxygen content in these phases is dependent on the nature and the amount of doping, especially for Co and Fe. The material remains orthorhombic when Cu is replaced by Ni or Zn whereas it evolves to tetragonal symmetry for the Fe-, Co-, and Al-doped compounds when x exceeds 0.05. Evidence for the major substitution of Co in the Cu-O chains only is obtained by means of thermogravimetric analysis and neutron diffraction measurements. The room-temperature Moessbauer spectra of the Fe-doped compounds consist of three doublets; their site assignments are proposed. dc resistance and ac susceptibility have shown that both magnetic and diamagnetic ions destroy T/sub c/ in a similar manner. At x = 0.2 the Fe and Co compounds are tetragonal, superconduct at 50 K, and show a Curie-type magnetic behavior associated with a magnetic moment of 3.4μ/sub B/ per doping atom. The origin of the orthorhombic-tetragonal transition and the importance of the Cu-O chains for superconductivity is discussed. The behavior of these materials with respect to magnetic impurities is apparently different from conventional Bardeen-Cooper-Schrieffer-type superconductors, and we believe that any new mechanism proposed must be mostly sensitive to local structural disorder

  4. Theory of Regression Apple Professional Cooperation Organization Research

    OpenAIRE

    Ouyang Bin

    2013-01-01

    In view of the enterprise ecological apple manor a variety of problems of existence, put forward to the enterprise management transformation, achieve enterprise, collective, individual integrated operation management and the use of regression mathematical model on apple professional cooperation organization analysis. Through the example, Apple professional economic cooperation organization innovation model of the input output ratio than the rural economic cooperation organization is much high...

  5. Reallocation of water in the state of New Mexico based on cooperative game theory

    Science.gov (United States)

    Rouhi Rad, M.

    2011-12-01

    Water allocation models often aim to maximize net benefits in the river basin based on the water rights, thus there is no motivation to use water efficiently by the users with lower marginal value for water. Water markets not only could help increase the net benefits over the basin but also will encourage the stakeholders to save the water and use it in transfer markets and increase their income. This issue can be viewed as a game in which stakeholders can play non-cooperatively and try to increase their own benefits using the amount of water assigned to them or they could cooperate and make coalitions in order to increase the total benefits in the coalition and the whole basin. The aim of this study is to reallocate the water based on cooperation among different stakeholders, namely agricultural, municipal and industrial and environmental, in the Upper Rio Grande river basin in the state of New Mexico in order to increase efficiency, sustainability and equity of water distribution in the basin using different game theory schemes such as Nucleolus and the Shapley Value.

  6. Evolution, epigenetics and cooperation.

    Science.gov (United States)

    Bateson, Patrick

    2014-04-01

    Explanations for biological evolution in terms of changes in gene frequencies refer to outcomes rather than process. Integrating epigenetic studies with older evolutionary theories has drawn attention to the ways in which evolution occurs. Adaptation at the level of the gene is givingway to adaptation at the level of the organism and higher-order assemblages of organisms. These ideas impact on the theories of how cooperation might have evolved. Two of the theories, i.e. that cooperating individuals are genetically related or that they cooperate for self-interested reasons, have been accepted for a long time. The idea that adaptation takes place at the level of groups is much more controversial. However, bringing together studies of development with those of evolution is taking away much of the heat in the debate about the evolution of group behaviour.

  7. Determination of covariant Schwinger terms in anomalous gauge theories

    International Nuclear Information System (INIS)

    Kelnhofer, G.

    1991-01-01

    A functional integral method is used to determine equal time commutators between the covariant currents and the covariant Gauss-law operators in theories which are affected by an anomaly. By using a differential geometrical setup we show how the derivation of consistent- and covariant Schwinger terms can be understood on an equal footing. We find a modified consistency condition for the covariant anomaly. As a by-product the Bardeen-Zumino functional, which relates consistent and covariant anomalies, can be interpreted as connection on a certain line bundle over all gauge potentials. Finally the commutator anomalies are calculated for the two- and four dimensional case. (Author) 13 refs

  8. Determination of covariant Schwinger terms in anomalous gauge theories

    International Nuclear Information System (INIS)

    Kelnhofer, G.

    1991-01-01

    A functional integral method is used to determine equal time commutators between the covariant currents and the covariant Gauss-law operators in theories which are affected by an anomaly. By using a differential geometrical setup we show how the derivation of consistent- and covariant Schwinger terms can be understood on an equal footing. We find a modified consistency condition for the covariant anomaly. As a by-product the Bardeen-Zumino functional, which relates consistent and covariant anomalies, can be interpreted as connection on a certain line bundle over all gauge potentials. Finally the covariant commutator anomalies are calculated for the two- and four dimensional case. (orig.)

  9. Sharing the cost of river basin adaptation portfolios to climate change: Insights from social justice and cooperative game theory

    Science.gov (United States)

    Girard, Corentin; Rinaudo, Jean-Daniel; Pulido-Velazquez, Manuel

    2016-10-01

    The adaptation of water resource systems to the potential impacts of climate change requires mixed portfolios of supply and demand adaptation measures. The issue is not only to select efficient, robust, and flexible adaptation portfolios but also to find equitable strategies of cost allocation among the stakeholders. Our work addresses such cost allocation problems by applying two different theoretical approaches: social justice and cooperative game theory in a real case study. First of all, a cost-effective portfolio of adaptation measures at the basin scale is selected using a least-cost optimization model. Cost allocation solutions are then defined based on economic rationality concepts from cooperative game theory (the Core). Second, interviews are conducted to characterize stakeholders' perceptions of social justice principles associated with the definition of alternatives cost allocation rules. The comparison of the cost allocation scenarios leads to contrasted insights in order to inform the decision-making process at the river basin scale and potentially reap the efficiency gains from cooperation in the design of river basin adaptation portfolios.

  10. Cooperative strategies European perspectives

    CERN Document Server

    Killing, J Peter

    1997-01-01

    Cooperative Strategies: European Perspectives is one of three geographically targeted volumes in which the contributors present the most current research on topics such as advances in theories of cooperative strategies, the formation of cooperative alliances, the dynamics of partner relationships, and the role of information and knowledge in cooperative alliances. Blending conceptual insights with empirical analyses, the contributors highlight commonalities and differences across national, cultural, and trade zones. The chapters in this volume are anchored in a wide set of theoretical approaches, conceptual frameworks, and models, illustrating how rich the area of cooperative strategies is for scholarly inquiry.

  11. Why do health and social care providers co-operate?

    Science.gov (United States)

    van Raak, Arno; Paulus, Aggie; Mur-Veeman, Ingrid

    2005-09-28

    Within Europe, although there are numerous examples of poor co-ordination in the delivery of integrated care, many providers do co-operate. We wanted to know why providers are moved to co-operate. In terms of systematic research, this is a new field; researchers have only begun to theorise about the rationales for co-operation. Practically, the issue of achieving co-operation attracts much attention from policymakers. Understanding the reasons for co-operation is a prerequisite for developing effective policy in support of integrated care. Our aim is to explore the comparative validity of different theoretical perspectives on the reasons for co-operation, to indicate directions for further study and for policy making. We used data from three successive studies to perform pattern matching with six established theoretical perspectives: transaction costs economics, strategic choice theory, resource dependence theory, learning theory, stakeholder theory and institutional theory. Insights from the studies were compared for validating purposes (triangulation). The first study concerned the evaluation of the Dutch 'National Home Health Care Programme' according to the case study methodology. The second and third studies were surveys among project directors: questionnaires were based on the concepts derived from the first study. Researchers should combine normative institutional theory, resource dependence theory and stakeholder theory into one perspective, in order to study relationship formation in health and social care. The concept of institutions (rules) is the linchpin between the theories. Policy makers must map the institutions of stakeholders and enable integrated care policy to correspond with these institutions as much as possible.

  12. A theory of leadership in human cooperative groups.

    Science.gov (United States)

    Hooper, Paul L; Kaplan, Hillard S; Boone, James L

    2010-08-21

    Two types of models aim to account the origins of rank differentiation and social hierarchy in human societies. Conflict models suggest that the formation of social hierarchies is synonymous with the establishment of relationships of coercive social dominance and exploitation. Voluntary or 'integrative' models, on the other hand, suggest that rank differentiation--the differentiation of leader from follower, ruler from ruled, or state from subject--may sometimes be preferred over more egalitarian social arrangements as a solution to the challenges of life in social groups, such as conflict over resources, coordination failures, and free-riding in cooperative relationships. Little formal theoretical work, however, has established whether and under what conditions individuals would indeed prefer the establishment of more hierarchical relationships over more egalitarian alternatives. This paper provides an evolutionary game theoretical model for the acceptance of leadership in cooperative groups. We propose that the effort of a leader can reduce the likelihood that cooperation fails due to free-riding or coordination errors, and that under some circumstances, individuals would prefer to cooperate in a group under the supervision of a leader who receives a share of the group's productivity than to work in an unsupervised group. We suggest, in particular, that this becomes an optimal solution for individual decision makers when the number of group members required for collective action exceeds the maximum group size at which leaderless cooperation is viable.

  13. Cooperativity of halogen, chalcogen, and pnictogen bonds in infinite molecular chains by electronic structure theory.

    Science.gov (United States)

    George, Janine; Deringer, Volker L; Dronskowski, Richard

    2014-05-01

    Halogen bonds (XBs) are intriguing noncovalent interactions that are frequently being exploited for crystal engineering. Recently, similar bonding mechanisms have been proposed for adjacent main-group elements, and noncovalent "chalcogen bonds" and "pnictogen bonds" have been identified in crystal structures. A fundamental question, largely unresolved thus far, is how XBs and related contacts interact with each other in crystals; similar to hydrogen bonding, one might expect "cooperativity" (bonds amplifying each other), but evidence has been sparse. Here, we explore the crucial step from gas-phase oligomers to truly infinite chains by means of quantum chemical computations. A periodic density functional theory (DFT) framework allows us to address polymeric chains of molecules avoiding the dreaded "cluster effects" as well as the arbitrariness of defining a "large enough" cluster. We focus on three types of molecular chains that we cut from crystal structures; furthermore, we explore reasonable substitutional variants in silico. We find evidence of cooperativity in chains of halogen cyanides and also in similar chalcogen- and pnictogen-bonded systems; the bonds, in the most extreme cases, are amplified through cooperative effects by 79% (I···N), 90% (Te···N), and 103% (Sb···N). Two experimentally known organic crystals, albeit with similar atomic connectivity and XB characteristics, show signs of cooperativity in one case but not in another. Finally, no cooperativity is observed in alternating halogen/acetone and halogen/1,4-dioxane chains; in fact, these XBs weaken each other by up to 26% compared to the respective gas-phase dimers.

  14. Coherence factors beyond the BCS expressions—a derivation

    International Nuclear Information System (INIS)

    Gorohovsky, G; Bettelheim, E

    2014-01-01

    We present a derivation of a previously announced result for matrix elements between exact eigenstates of the pairing Hamiltonian. Our results, which generalize the well-known Bardeen–Cooper–Schrieffer (BCS) (Bardeen et al 1957 Phys. Rev. 108 1175; 1957 Phys. Rev. 106 162) expressions for what are known as ‘coherence factors’, are derived based on the Slavnov (1989 Theor. Math. Phys. 79 502) formula for overlaps between Bethe-ansatz states, thus making use of the known connection between the exact diagonalization of the BCS Hamiltonian, due to Richardson (1963 Phys. Lett. 3 277; 1964 Nucl. Phys. A 52 221), and the algebraic Bethe ansatz. The resulting formula has a compact form after a suitable parameterization of the energy plane. Although we apply our method here to the pairing Hamiltonian, it may be adjusted to study what is termed the ‘Sutherland limit’ (Sutherland 1995 Phys. Rev. Lett. 74 816) for exactly solvable models, namely where a macroscopic number of rapidities form a large string. (paper)

  15. Game theory and fish wars

    DEFF Research Database (Denmark)

    Jensen, Frank; Frost, Hans Staby; Thøgersen, Thomas Talund

    2015-01-01

    of the mackerel crisis is based on a statistical estimation of relevant functional relations, and the behavior of the players is explained using a fully specified empirical model. Simple, non-cooperative game theory shows that all players have an incentive to act non-cooperatively, a result that is robust......Simple non-cooperative and cooperative game theory is used to explore the crisis involving the European Union (EU), Norway, Iceland and the Faroe Islands regarding the size and relative allocation of total allowable catches (TACs) in the mackerel fishery in the Northeast Atlantic. The analysis...... to changes in basic assumptions regarding demand and cost functions. Thus, using the estimated parameters and functions, simple, non-cooperative game theory cannot explain the cooperative behavior of EU and Norway during the mackerel crisis. Simple cooperative game theory shows that no player has...

  16. Cooperative strings and glassy interfaces.

    Science.gov (United States)

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-07

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

  17. Using Game Theory to Predict Supply Chain Cooperation

    Science.gov (United States)

    Lutz, Heather; Vang, David O.; Raffield, William D.

    2012-01-01

    The motivation for this research was to understand under what conditions supply chain cooperation might be feasible and under what circumstances it is not. Whereas previous research focuses on dyads in a supply chain, our research seeks to examine a possible factor that can explain why truly cooperative supply chains involving more than two firms…

  18. Parochial trust and cooperation across 17 societies

    Science.gov (United States)

    Romano, Angelo; Balliet, Daniel; Liu, James H.

    2017-01-01

    International challenges such as climate change, poverty, and intergroup conflict require countries to cooperate to solve these complex problems. However, the political tide in many countries has shifted inward, with skepticism and reluctance to cooperate with other countries. Thus, cross-societal investigations are needed to test theory about trust and cooperation within and between groups. We conducted an experimental study in 17 countries designed to test several theories that explain why, who, and where people trust and cooperate more with ingroup members, compared with outgroup members. The experiment involved several interactions in the trust game, either as a trustor or trustee. We manipulated partner group membership in the trust game (ingroup, outgroup, or unknown) and if their reputation was at stake during the interaction. In addition to the standard finding that participants trust and cooperate more with ingroup than outgroup members, we obtained findings that reputational concerns play a decisive role for promoting trust and cooperation universally across societies. Furthermore, men discriminated more in favor of their ingroup than women. Individual differences in cooperative preferences, as measured by social value orientation, predicted cooperation with both ingroup and outgroup members. Finally, we did not find support for three theories about the cross-societal conditions that influence the degree of ingroup favoritism observed across societies (e.g., material security, religiosity, and pathogen stress). We discuss the implications for promoting cooperation within and between countries. PMID:29133403

  19. The Right Tools for the Job: Cooperative Breeding Theory and an Evaluation of the Methodological Approaches to Understanding the Evolution and Maintenance of Sociality

    Directory of Open Access Journals (Sweden)

    Martin L. Hing

    2017-08-01

    Full Text Available Why do we observe so many examples in nature in which individuals routinely delay or completely forgo their own reproductive opportunities in order to join and remain within a group? Cooperative breeding theory provides a rich framework with which to study the factors that may influence the costs and benefits of remaining philopatric as a non-breeder. This is often viewed as an initial step in the development of costly helping behavior provided by non-breeding subordinates. Despite many excellent empirical studies testing key concepts of the theory, there is still debate regarding the relative importance of various evolutionary forces, suggesting that there may not be a general explanation but rather a dynamic and taxonomically varied combination of factors influencing the evolution and maintenance of sociality. Here, we explore two potential improvements in the study of sociality that could aid in the progress of this field. The first addresses the fact that empirical studies of social evolution are typically conducted using either comparative, observational or manipulative methodologies. Instead, we suggest a holistic approach, whereby observational and experimental studies are designed with the explicit view of advancing comparative analyses of sociality for the taxon, and in tandem, where comparative work informs targeted research effort on specific (usually understudied species within the lineage. A second improvement relates to the broadening of tests of cooperative breeding theory to include taxa where subordinates do not necessarily provide active cooperation within the group. The original bias toward “helpful subordinates” arose from a focus on terrestrial taxa. However, recent consideration of other taxa, especially marine taxa, is slowly revealing that the theory can and should encompass a continuum of cooperative social systems, including those where subordinates do not actively help. This review summarizes the major hypotheses

  20. Relativistic quasiparticle time blocking approximation: Dipole response of open-shell nuclei

    International Nuclear Information System (INIS)

    Litvinova, E.; Ring, P.; Tselyaev, V.

    2008-01-01

    The self-consistent relativistic quasiparticle random-phase approximation (RQRPA) is extended by the quasiparticle-phonon coupling (QPC) model using the quasiparticle time blocking approximation (QTBA). The method is formulated in terms of the Bethe-Salpeter equation (BSE) in the two-quasiparticle space with an energy-dependent two-quasiparticle residual interaction. This equation is solved either in the basis of Dirac states forming the self-consistent solution of the ground state or in the momentum representation. Pairing correlations are treated within the Bardeen-Cooper-Schrieffer (BCS) model with a monopole-monopole interaction. The same NL3 set of the coupling constants generates the Dirac-Hartree-BCS single-quasiparticle spectrum, the static part of the residual two-quasiparticle interaction and the quasiparticle-phonon coupling amplitudes. A quantitative description of electric dipole excitations in the chain of tin isotopes (Z=50) with the mass numbers A=100,106,114,116,120, and 130 and in the chain of isotones with (N=50) 88 Sr, 90 Zr, 92 Mo is performed within this framework. The RQRPA extended by the coupling to collective vibrations generates spectra with a multitude of 2q x phonon (two quasiparticles plus phonon) states providing a noticeable fragmentation of the giant dipole resonance as well as of the soft dipole mode (pygmy resonance) in the nuclei under investigation. The results obtained for the photo absorption cross sections and for the integrated contributions of the low-lying strength to the calculated dipole spectra agree very well with the available experimental data

  1. First-principles calculation of the superconducting gap function due to electron-electron interaction for YBa2Cu3O/sub 7-//sub x/

    International Nuclear Information System (INIS)

    Chui, S.T.; Kasowski, R.V.; Hsu, W.Y.

    1989-01-01

    We argue that because of the anisotropic nature of YBa 2 Cu 3 O/sub 7-//sub x/, one-dimensional-type charge- and spin-density fluctuations produce an effective attraction that overcomes the electron-electron Coulomb repulsion, but only at large distances. This effective attraction is further enhanced by band-structure effects such that a substantial superconducting transition temperature can be obtained. Without making any assumption of the symmetry of the gap function, we solve the Bardeen-Cooper-Schrieffer (BCS) superconducting gap equation for the six bands closest to the Fermi level. A highly anisotropic gap function with a maximum of about 0.11 eV is found. From the linearized gap equation, a transition temperature of about 0.035 eV is obtained. This is about one-quarter the maximum of the gap function, consistent with the experimental ratio of the transition temperature to the gap determined from tunneling, infrared, and nuclear quadrupole resonance measurements. The important participants to the superconducting pair come from electrons close to planar copper [Cu(2)] and chain oxygen [O(1) and O(4)] sites, consistent with recent quadrupole resonance measurements. Our calculation produces a coherence length of the order of 30 A in the xy direction, the same order of magnitude as the experimental result and considerably smaller than the conventional magnitude of ordinary BCS materials. Similar calculations for YBa 2 Cu 3 O/sub 6.5/ where periodic O vacancies are introduced along the one-dimensional Cu-O chains shows that the transition temperature is reduced by half

  2. Cooperative Control of Multi-Master-Slave Islanded Microgrid with Power Quality Enhancement Based on Conservative Power Theory

    DEFF Research Database (Denmark)

    Mortezaei, Ali; Simoes, Marcelo; Savaghebi, Mehdi

    2018-01-01

    Cooperative control of power converters in a microgrid offers power quality enhancement at sensitive load buses. Such cooperation is particularly important in the presence of reactive, nonlinear and unbalanced loads. In this paper, a multi-master-slave-based control of Distributed Generators (DGs...... in a selective control strategy able to share each current component with desired percentage among the microgrid inverters. Simulation results are presented to demonstrate the effectiveness of the proposed method.......) interface converters in a three-phase four-wire islanded microgrid using the Conservative Power Theory (CPT) is proposed. Inverters located in close proximity operate as a group in master-salve mode. Slaves inject the available energy and compensate selectively unwanted current components of local loads...

  3. Transmission expansion cost allocation based on cooperative game theory for congestion relief

    Energy Technology Data Exchange (ETDEWEB)

    Erli, Ge; Takahasi, Kazuhiro; Kurihara, Ikuo [Central Research Inst. of Electric Power Industry, Tokyo (Japan); Luonan Chen [Osaka Sangyo Univ., Osaka (Japan)

    2005-01-01

    In conventional power systems, upstream and downstream of power were distinct. However, due to the competition, power injection and sink can appear at unexpected locations, and cost sharing for such a new power system configuration must be considered. This paper proposes a scheme for transmission expansion cost allocation among electric market participants by using Core and Nucleolus concepts of game theory, which are developed particularly for the transmission users. A solution of the n-person cooperative game is adopted to distribute the line transmission expansion cost among the players. Congestion is assumed to be the transmission constraint, and expansion of transmission line is expected to relieve transmission congestion. A case study is illustrated to demonstrate the proposed method. (Author)

  4. Theory of muscle contraction mechanism with cooperative interaction among crossbridges.

    Science.gov (United States)

    Mitsui, Toshio; Ohshima, Hiroyuki

    2012-01-01

    The power stroke model was criticized and a model was proposed for muscle contraction mechanism (Mitsui, 1999). The proposed model was further developed and calculations based on the model well reproduced major experimental data on the steady filament sliding (Mitsui and Ohshima, 2008) and on the transient phenomena (Mitsui, Takai and Ohshima, 2011). In this review more weight is put on explanation of the basic ideas of the model, especially logical necessity of the model, leaving mathematical details to the above-mentioned papers. A thermodynamic relationship that any models based upon the sliding filament theory should fulfill is derived. The model which fulfills the thermodynamic relationship is constructed on the assumption that a myosin head bound to an actin filament forms a complex with three actin molecules. In shortening muscles, the complex moves along the actin filament changing the partner actin molecules with steps of about 5.5 nm. This process is made possible through cooperative interaction among cross-bridges. The ATP hydrolysis energy is liberated by fraction at each step through chemical reactions between myosin and actin molecules. The cooperativity among crossbridges disappears in length-clamped muscles, in agreement with experimental observations that the cross-bridge produces force independently in the isometric tetanus state. The distance of the head movement per ATP hydrolysis cycle is expected to be about 5.5 nm or a few times of it under the condition of the in vitro single head experiments. Calculation results are surveyed illustrating that they are in good agreement with major experimental observations.

  5. Addressing dysfunctional relations among healthcare teams: improving team cooperation through applied organizational theories.

    Science.gov (United States)

    Horwitz, Sujin K; Horwitz, Irwin B; Barshes, Neal R

    2011-01-01

    Previous research has demonstrated that communication failure and interpersonal conflicts are significant impediments among health-care teams to assess complex information and engage in the meaningful collaboration necessary for optimizing patient care. Despite the prolific research on the role of effective teamwork in accomplishing complex tasks, such findings have been traditionally applied to business organizations and not medical contexts. This chapter, therefore, reviews and applies four theories from the fields of organizational behavior (OB) and organization development (OD) as potential means for improving team interaction in health-care contexts. This study is unique in its approach as it addresses the long-standing problems that exist in team communication and cooperation in health-care teams by applying well-established theories from the organizational literature. The utilization and application of the theoretical constructs discussed in this work offer valuable means by which the efficacy of team work can be greatly improved in health-care organizations.

  6. Cooperation and cheating in microbes

    Science.gov (United States)

    Gore, Jeff

    2011-03-01

    Understanding the cooperative and competitive dynamics within and between species is a central challenge in evolutionary biology. Microbial model systems represent a unique opportunity to experimentally test fundamental theories regarding the evolution of cooperative behaviors. In this talk I will describe our experiments probing cooperation in microbes. In particular, I will compare the cooperative growth of yeast in sucrose and the cooperative inactivation of antibiotics by bacteria. In both cases we find that cheater strains---which don't contribute to the public welfare---are able to take advantage of the cooperator strains. However, this ability of cheaters to out-compete cooperators occurs only when cheaters are present at low frequency, thus leading to steady-state coexistence. These microbial experiments provide fresh insight into the evolutionary origin of cooperation.

  7. Spurious cooperativity in alkylated succinic acids

    Science.gov (United States)

    Ben-Naim, A.

    1998-03-01

    The proton-proton correlation, as measured by the ratio between the second and the first dissociation constants of dibasic acid, is sometimes very large and far beyond what could be explained by electrostatic theories. We propose a novel interpretation of this phenomenon based on the idea of spurious cooperativity. The general theoretical framework underlying the onset of spurious cooperativity is developed first. The basic result is that whenever a binding (or dissociating) two-site (or more) system splits into a mixture of noninterconverting isomers the binding isotherm (or the titration curve) behaves as if it is more negatively cooperative compared with the genuine cooperativities of the individual isomer. The theory is applied to a specific system of α-α' dialkyl succinic acid. It is known that the Meso form of these alkylated derivatives show a normal correlation of the same order of magnitude as in succinic acid. On the other hand, the Racemic form of these alkylated derivatives shows anomalous strong negative correlations when the alkyl groups become large (e.g., isopropyl and tert butyl). It is shown that the theory of spurious cooperativity can explain the different behavior of the Racemic and the Meso forms, as well as the onset of anomalous strong negative correlations when the alkyl groups become large.

  8. Cooperative Localization for Multi-AUVs Based on GM-PHD Filters and Information Entropy Theory

    Directory of Open Access Journals (Sweden)

    Lichuan Zhang

    2017-10-01

    Full Text Available Cooperative localization (CL is considered a promising method for underwater localization with respect to multiple autonomous underwater vehicles (multi-AUVs. In this paper, we proposed a CL algorithm based on information entropy theory and the probability hypothesis density (PHD filter, aiming to enhance the global localization accuracy of the follower. In the proposed framework, the follower carries lower cost navigation systems, whereas the leaders carry better ones. Meanwhile, the leaders acquire the followers’ observations, including both measurements and clutter. Then, the PHD filters are utilized on the leaders and the results are communicated to the followers. The followers then perform weighted summation based on all received messages and obtain a final positioning result. Based on the information entropy theory and the PHD filter, the follower is able to acquire a precise knowledge of its position.

  9. Isominkowskian theory of Cooper Pairs in superconductors

    International Nuclear Information System (INIS)

    Animalu, A.O.E.

    1993-01-01

    Via the use of Santilli's isominkowskian space, the author presents a relativistic extension of the author's recent treatment of the Cooper Pair in superconductivity based on the Lie-isotopic lifting of quantum mechanics known as Hadronic Mechanics. The isominkowskian treatment reduces the solution of the eiganvalue problem for the quasiparticle energy spectrum to a geometric problem of specifying the metric of the isominkowskian space inside the pair in various models of ordinary high T c superconductors. The use of an intriguing realization of the metric due to Dirac reduces the dimensionality of the interior space to two yielding a spin mutation from 1/2 to zero inside a Cooper pair in two-band BCS and Hubbard models. 12 refs

  10. Compromise in cooperative game and the VIKOR method

    Directory of Open Access Journals (Sweden)

    Opricović Serafim

    2009-01-01

    Full Text Available Five approaches in conflict resolution are distinguished, based on cooperativeness and aggressiveness in resolving conflict. Compromise based on cooperativeness is emphasized here as a solution in conflict resolution. Cooperative game theory oriented towards aiding the conflict resolution is considered and the compromise value for TU(transferable utility-game is presented. The method VIKOR could be applied to determine compromise solution of a multicriteria decision making problem with noncommensurable and conflicting criteria. Compromise is considered as an intermediate state between conflicting objectives or criteria reached by mutual concession. The applicability of the cooperative game theory and the VIKOR method for conflict resolution is illustrated.

  11. What Mothers Say and What They Do: The Relation between Parenting, Theory of Mind, Language and Conflict/Cooperation

    Science.gov (United States)

    Ruffman, Ted; Slade, Lance; Devitt, Kerry; Crowe, Elena

    2006-01-01

    We used a longitudinal study with 55 middle- and upper middle-class children to investigate the relation between early mother characteristics (e.g. mental state talk, general parenting style) and later child characteristics (e.g. theory of mind, conflict/cooperation). Children were tested once when they were around 3 years and then again around 4…

  12. Profit allocation of independent power producers based on cooperative Game theory

    International Nuclear Information System (INIS)

    Jia, N.X.; Yokoyama, R.

    2003-01-01

    With the development of deregulation, the retail market is being formed. The independent power producers (IPPs) can contact the customers and sell electric power to them directly to obtain the profits because IPPs can provide electricity at cheaper prices to the customers than the utilities can. If IPP can obtain further more profit through collaborating with other ones in some coalition, it will prefer to collaborate to form this coalition rather than participating individually. In coalition, also the problem of how to allocate profit rationally for each IPP should also be solved. In this paper, we discuss the cooperation of IPPs in retail market and give a formulation about the calculation of IPPs profits. After that, based on Game theory, we propose a scheme to decide the profit allocation of each IPP in the coalitions rationally and impartially. (author)

  13. Cooperation: the foundation of improvement.

    Science.gov (United States)

    Clemmer, T P; Spuhler, V J; Berwick, D M; Nolan, T W

    1998-06-15

    Cooperation--working together to produce mutual benefit or attain a common purpose--is almost inseparable from the quest for improvement. Although the case for cooperation can be made on ethical grounds, neither the motivation for nor the effects of cooperation need to be interpreted solely in terms of altruism. Cooperation can be a shrewd and pragmatic strategy for accomplishing personal goals in an interdependent system. Earlier papers in this series have explored the conceptual roots of modern approaches to improvement, which lie in systems theory. To improve systems, we must usually attend first and foremost to interactions. Among humans, "better interaction" is almost synonymous with "better cooperation." Physicians have ample opportunities and, indeed, an obligation to cooperate with other physicians in the same or different specialties, with nurses and other clinical workers, with administrators, and with patients and families. Many intellectual disciplines have made cooperation an object of study. These include anthropology; social psychology; genetics; biology; mathematics; game theory; linguistics; operations research; economics; and, of course, moral and rational philosophy. Scientifically grounded methods to enhance cooperation include developing a shared purpose; creating an open, safe environment; including all who share a common purpose and encouraging diverse viewpoints; negotiating agreement; and insisting on fairness and equity in the application of rules. These methods apply at the organizational level and at the level of the individual physician. This paper describes the application of these methods at the organizational level and focuses on one especially successful example of system-level cooperation in a care delivery site where interactions matter a great deal: the modern intensive care unit.

  14. South-South Development Cooperation and Soft Power. The case of Brazil's foreign policy and technical cooperation

    DEFF Research Database (Denmark)

    Bry, Sandra

    's participation in development cooperation and how these international political ambitions influence the project model of its South-South Development Cooperation, called technical cooperation. This was done by investigating the manifestations of ‘soft power’ in Brazilian development cooperation activities...... of the agent's attractive actions without which a country's soft power is non-existent. Therefore this thesis maintains that soft power theory should shift its current analytical focus from the agent to the subject and enhance the analysis on the role of subject's perceptions in the creation of ‘soft...

  15. High energy instanton induced processes in electroweak theory

    International Nuclear Information System (INIS)

    McLerran, L.

    1992-01-01

    It is well known that in electroweak theory, baryon plus lepton number is conserved by the classical equations of motion. This is of course consistent with the lack of experimental observation of such processes. It is a little less well known that when quantum corrections are included in electroweak theory, baryon plus lepton number is not conserved. This was first discovered as a consequence of the Adler-Bardeen-Bell-Jackiw triangle anomaly. It is perhaps most easily understood as a consequence of vacuum degeneracy, fermion energy level crossing and filling of the negative energy Dirac sea upon second quantization. To understand how baryon plus lepton number is not conserved upon second quantization, consider the situation shown in the energy of the system is shown as a function of a parameter which characterizes the gauge fields, the Chern-Simons charge. The Chern-Simons charge is a function only of the gauge fields, and the B + L change is equal to the change in Chern-Simons charge, ΔQ B+L = ΔQ CS

  16. Theory of tunneling in metal--superconductor devices: Supercurrents in the superconductor gap at zero temperature

    International Nuclear Information System (INIS)

    Garcia, N.; Flores, F.; Guinea, F.

    1988-01-01

    Tunneling experiments in metal-oxide superconductor have shown the existence of ''leakage'' currents for applied voltages V smaller than one-half of the superconductor gap Δ. These currents are independent of temperature T. Recently experiments with scanning tunneling microscopy (STM) and squeezable tunnel junctions have shown that the observation of the superconductor gap depends strongly on the resistance in the junction. In fact only for resistances larger than ∼10 6 Ω the gap is clearly observable. These experiments have been explained in terms of the perturbative Hamiltonian formalism of Bardeen. However, it may happen that this theory while applicable for very large resistances may not be so for small tunnel resistances. We present here a nonperturbative theory in all orders of the transmitivity chemical bondTochemical bond 2 and show the existence of supercurrents for values of V 2 . We believe that experiments in STM and other junctions should be interpreted in the frame of this theory

  17. Gauge invariant perturbation theory prediction of the sensitivity required for experimental measurement of quadrupole and higher moments of the cosmic microwave background radiation

    International Nuclear Information System (INIS)

    Wilson, K.E.

    1985-01-01

    The temperature variation of the cosmic microwave background radiation is computed in a spherical harmonic expansion for a 4 million term sum of perturbations. Each term has a different direction and a randomly chosen phase. The spherical harmonics are evaluated for values of the index l from 1 through 9. The computation was done by starting with the model for gauge invariant cosmological perturbations composed by James M. Bardeen (1980). This model does linear perturbation theory against a background Friedmann-Robertson-Walker general relativistic cosmological model. The Bardeen model was recomputed for a cosmological-time metric then solved for zero curvature and zero cosmological constant in the background for radiation and dust equations of state. Instantaneous decoupling was assumed. The model was solved for zero curvature, cosmological constant, and pressure in perturbation order. These solutions were used to compute the redshift equation, and then the temperature variation equation. The integral over the null geodesic (photon) path can be evaluated analytically under the zero curvature cosmological constant, and pressure assumption. Analytic equations are obtained for the temperature variation caused by an isothermal or adiabatic perturbation of a single mode (amplitude, wavelength, phase, and direction)

  18. Social heuristics shape intuitive cooperation.

    Science.gov (United States)

    Rand, David G; Peysakhovich, Alexander; Kraft-Todd, Gordon T; Newman, George E; Wurzbacher, Owen; Nowak, Martin A; Greene, Joshua D

    2014-04-22

    Cooperation is central to human societies. Yet relatively little is known about the cognitive underpinnings of cooperative decision making. Does cooperation require deliberate self-restraint? Or is spontaneous prosociality reined in by calculating self-interest? Here we present a theory of why (and for whom) intuition favors cooperation: cooperation is typically advantageous in everyday life, leading to the formation of generalized cooperative intuitions. Deliberation, by contrast, adjusts behaviour towards the optimum for a given situation. Thus, in one-shot anonymous interactions where selfishness is optimal, intuitive responses tend to be more cooperative than deliberative responses. We test this 'social heuristics hypothesis' by aggregating across every cooperation experiment using time pressure that we conducted over a 2-year period (15 studies and 6,910 decisions), as well as performing a novel time pressure experiment. Doing so demonstrates a positive average effect of time pressure on cooperation. We also find substantial variation in this effect, and show that this variation is partly explained by previous experience with one-shot lab experiments.

  19. The sound of cooperation: Musical influences on cooperative behavior.

    Science.gov (United States)

    Kniffin, Kevin M; Yan, Jubo; Wansink, Brian; Schulze, William D

    2017-03-01

    Music as an environmental aspect of professional workplaces has been closely studied with respect to consumer behavior while sparse attention has been given to its relevance for employee behavior. In this article, we focus on the influence of music upon cooperative behavior within decision-making groups. Based on results from two extended 20-round public goods experiments, we find that happy music significantly and positively influences cooperative behavior. We also find a significant positive association between mood and cooperative behavior. Consequently, while our studies provide partial support for the relevance of affect in relation to cooperation within groups, we also show an independently important function of happy music that fits with a theory of synchronous and rhythmic activity as a social lubricant. More generally, our findings indicate that music and perhaps other atmospheric variables that are designed to prime consumer behavior might have comparably important effects for employees and consequently warrant closer investigation. Copyright © 2016 The Authors Journal of Organizational Behavior Published by John Wiley & Sons Ltd.

  20. Cooperative behavior, competition and operations research

    NARCIS (Netherlands)

    Estevez Fernandez, M.A.

    2006-01-01

    Game theory is the mathematical tool to study cooperation and competition. Since the beginnings of operations research and game theory both fields have been closely related. This thesis further investigates this relationship. Costs or rewards sharing problems arising from scheduling problems,

  1. What we need is theory of human cooperation (and meta-analysis) to bridge the gap between the lab and the wild

    NARCIS (Netherlands)

    van Lange, P.A.M.; Balliet, D.P.; Ijzerman, H.

    2012-01-01

    This commentary seeks to clarify the potential discrepancy between lab-based and field data in the use and effectiveness of punishment to promote cooperation by recommending theory that outlines key differences between the lab and field, such as the shadow of the future and degree of information

  2. Non-Cooperative Regulation Coordination Based on Game Theory for Wind Farm Clusters during Ramping Events

    DEFF Research Database (Denmark)

    Qi, Yongzhi; Liu, Yutian; Wu, Qiuwei

    2017-01-01

    With increasing penetration of wind power in power systems, it is important to track scheduled wind power output as much as possible during ramping events to ensure security of the system. In this paper, a non‐cooperative coordination strategy based on the game theory is proposed for the regulation...... of the regulation revenue function according to the derived Nash equilibrium condition, the ER strategy is the Nash equilibrium of the regulation competition. Case studies were conducted with the power output data of wind farms from State Grid Jibei Electric Power Company Limited of China to demonstrate...

  3. Intergroup Cooperation in Common Pool Resource Dilemmas.

    Science.gov (United States)

    Sadowski, Jathan; Spierre, Susan G; Selinger, Evan; Seager, Thomas P; Adams, Elizabeth A; Berardy, Andrew

    2015-10-01

    Fundamental problems of environmental sustainability, including climate change and fisheries management, require collective action on a scale that transcends the political and cultural boundaries of the nation-state. Rational, self-interested neoclassical economic theories of human behavior predict tragedy in the absence of third party enforcement of agreements and practical difficulties that prevent privatization. Evolutionary biology offers a theory of cooperation, but more often than not in a context of discrimination against other groups. That is, in-group boundaries are necessarily defined by those excluded as members of out-groups. However, in some settings human's exhibit behavior that is inconsistent with both rational economic and group driven cooperation of evolutionary biological theory. This paper reports the results of a non-cooperative game-theoretic exercise that models a tragedy of the commons problem in which groups of players may advance their own positions only at the expense of other groups. Students enrolled from multiple universities and assigned to different multi-university identity groups participated in experiments that repeatedly resulted in cooperative outcomes despite intergroup conflicts and expressions of group identity. We offer three possible explanations: (1) students were cooperative because they were in an academic setting; (2) students may have viewed their instructors as the out-group; or (3) the emergence of a small number of influential, ethical leaders is sufficient to ensure cooperation amongst the larger groups. From our data and analysis, we draw out lessons that may help to inform approaches for institutional design and policy negotiations, particularly in climate change management.

  4. Designing Leadership models in a Three Level Unlimited Supply Chain: Non-Cooperative Game Theory Approach

    Directory of Open Access Journals (Sweden)

    Ahmad Jaafarnehad

    2015-09-01

    Full Text Available The role and importance of supply chain management, has faced with many challenges and problems. Although a comprehensive model of supply chain issues, has not been explained, we have to indicate that issues such as reviewing the theoretical foundations of information systems, marketing, financial management, logistical and organizational relations have been considered by many researchers. The objective of supply chain management is to improve various activities and components to increase overall supply chain system benefits. In order to achieve the overall objectives, many contradictions may occur between the components and different levels of supply chain and the contradictions that these disorders over time, result in decreased strength and competitiveness of the supply chain. Such conflicts, like marketing costs (advertising, pricing and inventory can occur during the supply chain life cycle. A Game Theory approach with respect to property is the appropriate tool for collaboration in the supply chain. This tool is used for collaborative making in any kind of supply chain such as cooperative supply chain and non-cooperative supply chain. In the present study and assuming a lack of cooperation between different levels of a supply chain, a dynamic game with complete information has been generated. In addition identifying appropriate leaders of various levels of the supply chain is considered. Non-Cooperative dynamic game mode (Stackelberg Game, for each of the three levels of supply chain including retailers, suppliers and manufacturers are modeled. Depending on the bargaining power and its position in the market, any level of supply chain can make a leader of the following rule. In the present study, the equilibrium model to play Stackelberg game may be led by a leader or leading players and ultimately identifying and modeling the appropriate unlimited three level supply chain are determined.

  5. INTERFIRM COOPERATION AND INFORMATION SHARING THROUGH INTERLOCKING DIRECTORATES

    Directory of Open Access Journals (Sweden)

    Mohammed Belal UDDIN

    2012-01-01

    Full Text Available When firms engage in cooperative efforts, interfirm relations get particular interest to be studied. A direct interlock occurs when an executive or director of one firm sits on the board of another firm, and an indirect interlock occurs when two firms have directors or executives who sit on the board of a third firm. The three commonly used theoretical models such as social network theory, learning theory, and theory of strategic choice are more relevant for the formation and management of interlocking directorates. Uncertainty, resource scarcity, mutual trust, dependency, etc. influence the formation of interlocking directorates. Consequently, interlocking directorates allow sharing of information and overall cooperation between partners through learning, collaboration, networking, and effective relationship, etc. Proper management of interlocking directorates requires communication and collaboration among partners that enhance exchange of knowledge and cooperation.

  6. Managing the evolution of cooperation

    OpenAIRE

    Dormann, Julian; Ehrmann, Thomas

    2008-01-01

    Management scholars have long stressed the importance of evolutionary processses for inter-firm cooperation but have mostly missed the promising opportunity to incorporate ideas from evolutionary theories into the analysis of collaborative arrangements. In this paper, we first present three rules for the evolution of cooperation - kinship selection, direct reciprocity, and indirect reciprocity. Second, we apply our theoretical considerations, enriched with ideas from cultural anthropology, to...

  7. Rationalizing Cooperation: Moroccan Craft, Politics, and Education

    Science.gov (United States)

    Nicholas, Claire

    2018-01-01

    State attempts to rationalize Moroccan craft education reflect the ambivalent status of traditional knowledge in a modern economy. Female artisans, recently organized as a cooperative, navigate this ambivalence in a weaving "theory" class and in their "occupation" of the cooperative structure itself. During performances of…

  8. Electronic properties of graphite

    International Nuclear Information System (INIS)

    Schneider, J.

    2010-10-01

    In this thesis, low-temperature magneto-transport (T ∼ 10 mK) and the de Haas-van Alphen effect of both natural graphite and highly oriented pyrolytic graphite (HOPG) are examined. In the first part, low field magneto-transport up to B = 11 T is discussed. A Fourier analysis of the background removed signal shows that the electric transport in graphite is governed by two types of charge carriers, electrons and holes. Their phase and frequency values are in agreement with the predictions of the SWM-model. The SWM-model is confirmed by detailed band structure calculations using the magnetic field Hamiltonian of graphite. The movement of the Fermi at B > 2 T is calculated self-consistently assuming that the sum of the electron and hole concentrations is constant. The second part of the thesis deals with high field magneto-transport of natural graphite in the magnetic field range 0 ≤ B ≤ 28 T. Both spin splitting of magneto-transport features in tilted field configuration and the onset of the charge density wave (CDW) phase for different temperatures with the magnetic field applied normal to the sample plane are discussed. Concerning the Zeeman effect, the SWM calculations including the Fermi energy movement require a g-factor of g* equal to 2.5 ± 0.1 to reproduce the spin spilt features. The measurements of the charge density wave state confirm that its onset magnetic field can be described by a Bardeen-Cooper-Schrieffer (BCS)-type formula. The measurements of the de Haas-van Alphen effect are in agreement with the results of the magneto-transport measurements at low field. (author)

  9. Structural and electronic properties of superconductor MgB sub 2 under high pressure

    CERN Document Server

    Tang, J; Gu, H W; Matsushita, A; Takano, Y; Togano, K; Kito, H; Ihara, H

    2002-01-01

    The superconductivity and the lattice properties of a sintered MgB sub 2 material have been investigated under high pressure up to 10 GPa. The transition temperature was found to decrease linearly with increasing hydrostatic pressure at a rate of 1.03 K GPa sup - sup 1 , which can be explained with the classical Bardeen-Cooper-Shrieffer theory based on an electron-phonon coupling mechanism. The crystal lattice exhibits an anisotropic compressibility characterized by a larger compressibility along the c-direction than the a/b-directions. The anisotropy is attributed to a weaker inter-plane bonding along the c-axis in comparison with a stronger intra-plane bonding perpendicular to the c-axis. The bulk modulus of the measured material was deduced to be 172 GPa.

  10. Cooperative Engineering as a Joint Action

    Science.gov (United States)

    Joffredo-Le Brun, Sophie; Morellato, Mireille; Sensevy, Gérard; Quilio, Serge

    2018-01-01

    This paper describes some elements of a specific kind of design-based research, cooperative engineering. In the first part of the paper, we argue that cooperative engineering can be analyzed through a joint action framework. We first present some conceptual tools that the Joint Action Theory in Didactics proposes in order to understand didactic…

  11. Political Ideology, Trust, and Cooperation

    Science.gov (United States)

    Balliet, Daniel; Tybur, Joshua M.; Wu, Junhui; Antonellis, Christian; Van Lange, Paul A. M.

    2016-01-01

    Theories suggest that political ideology relates to cooperation, with conservatives being more likely to pursue selfish outcomes, and liberals more likely to pursue egalitarian outcomes. In study 1, we examine how political ideology and political party affiliation (Republican vs. Democrat) predict cooperation with a partner who self-identifies as Republican or Democrat in two samples before (n = 362) and after (n = 366) the 2012 US presidential election. Liberals show slightly more concern for their partners’ outcomes compared to conservatives (study 1), and in study 2 this relation is supported by a meta-analysis (r = .15). However, in study 1, political ideology did not relate to cooperation in general. Both Republicans and Democrats extend more cooperation to their in-group relative to the out-group, and this is explained by expectations of cooperation from in-group versus out-group members. We discuss the relation between political ideology and cooperation within and between groups. PMID:29593363

  12. Worker cooperatives with particular reference to Malta : an educationist's theory and practice

    NARCIS (Netherlands)

    G. Baldacchino (Godfrey)

    1990-01-01

    textabstractThe issue of worker cooperation remains at the top of the agenda for workplace organization today, although the history of worker (or producer) cooperatives is littered with failures. Yet, despite the glaring and disappointing evidence, the establishment of cooperative forms of work

  13. The Teacher's Role in Implementing Cooperative Learning in the Classroom.

    NARCIS (Netherlands)

    Gillies, R.; Ashman, A.; Terwel, J.

    2008-01-01

    The teacher’s role in implementing cooperative learning in the classroom provides a comprehensive overview of the theories, research outcomes, challenges and issues in guided cooperative learning. In many chapters there are clear guidelines and discussion about how cooperative learning practices can

  14. Cooperative learning in 21st century

    Directory of Open Access Journals (Sweden)

    David W. Johnson

    2014-10-01

    Full Text Available The 21st century brings four important challenges in which cooperation plays a central role: (1 a rapidly increasing global interdependence that will result in increasing local diversity as well as more frequent and intense conflicts, (2 the increasing number of democracies throughout the world, (3 the need for creative entrepreneurs, and (4 the growing importance of interpersonal relationships that affect the development of personal identity. The tools for meeting these challenges include cooperative learning. In this article the nature of cooperative learning will be reviewed, the underlying theory of social interdependence will be discussed, and the results of the research on cooperative learning will be briefly reviewed. The way in which cooperative learning contributes to meeting the four challenges will then be discussed.

  15. Non-Cooperative Games

    NARCIS (Netherlands)

    van Damme, E.E.C.

    2014-01-01

    We describe non-cooperative game models and discuss game theoretic solution concepts. Some applications are also noted. Conventional theory focuses on the question ‘how will rational players play?’, and has the Nash equilibrium at its core. We discuss this concept and its interpretations, as well as

  16. Real Maths in Cooperative Groups in Secondary Education

    NARCIS (Netherlands)

    Terwel, J.; Davidson, N.

    1990-01-01

    This chapter describes author’s first encounters with cooperative learning and his personal viewpoint on education. In this view, education should be inclusive, adaptive and cooperative. This is followed by a rationale for a realistic mathematics curriculum and its main characteristics. The theory

  17. Signaling emotion and reason in cooperation.

    Science.gov (United States)

    Levine, Emma E; Barasch, Alixandra; Rand, David; Berman, Jonathan Z; Small, Deborah A

    2018-05-01

    We explore the signal value of emotion and reason in human cooperation. Across four experiments utilizing dyadic prisoner dilemma games, we establish three central results. First, individuals infer prosocial feelings and motivations from signals of emotion. As a result, individuals believe that a reliance on emotion signals that one will cooperate more so than a reliance on reason. Second, these beliefs are generally accurate-those who act based on emotion are more likely to cooperate than those who act based on reason. Third, individuals' behavioral responses towards signals of emotion and reason depend on their own decision mode: those who rely on emotion tend to conditionally cooperate (that is, cooperate only when they believe that their partner has cooperated), whereas those who rely on reason tend to defect regardless of their partner's signal. These findings shed light on how different decision processes, and lay theories about decision processes, facilitate and impede cooperation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  18. Designing a performance measurement system for supply chain using balanced scorecard, path analysis, cooperative game theory and evolutionary game theory: A Case Study

    Directory of Open Access Journals (Sweden)

    Seyed Hootan Eskafi

    2015-04-01

    Full Text Available In recent years, supply chain management is known as the key factor for achieving competitive advantage. Better customer service, revenue improvement and cost reduction are the results of this philosophy. Organizations can manage the performance of their firms by appropriate goal setting, identifying criteria and continuous performance measurement, which creates a good view for the business circumstances. Developing and defining appropriate indicators at different levels of chain is necessary for implementing a performance measurement system. In this study, we propose a new method to determine the measurement indicators and strategies of the company in term of balanced scorecard. The study is a combination of balanced scorecard, path analysis, evolutionary game theory and cooperative game theory for strategic planning. The study offers an appropriate program for future activities of organizations and determines the present status of the firm. The implementation of the proposed method is introduced for a food producer and the results are analyzed.

  19. Cooperative spontaneous emission from volume sources in layered media

    International Nuclear Information System (INIS)

    Nichelatti, E.

    2009-01-01

    The classical theory of radiation from a dipole located inside a microcavity is extended to the case of a volume source placed inside a layered medium. Cooperation phenomena that can take place in the spontaneous emission process are taken into account with an approach based on the theory of spatial coherence. Three cases are considered: noncooperation, long-range cooperation, and short-range cooperation. In all these cases, the expressions found for the out coupled power are analytical. As an application of the theory, an Alq 3 -based organic light emitting diode is analyzed. The optical properties of the device are evaluated and compared for two different types of cathode, one consisting of an Al layer, the other one consisting of an Al/LiF bi-layer. The results found show that the ultra-thin LiF layer significantly improves extraction efficiency [it

  20. Cooper Pairs in Insulators?

    International Nuclear Information System (INIS)

    Valles, James

    2008-01-01

    Nearly 50 years elapsed between the discovery of superconductivity and the emergence of the microscopic theory describing this zero resistance state. The explanation required a novel phase of matter in which conduction electrons joined in weakly bound pairs and condensed with other pairs into a single quantum state. Surprisingly, this Cooper pair formation has also been invoked to account for recently uncovered high-resistance or insulating phases of matter. To address this possibility, we have used nanotechnology to create an insulating system that we can probe directly for Cooper pairs. I will present the evidence that Cooper pairs exist and dominate the electrical transport in these insulators and I will discuss how these findings provide new insight into superconductor to insulator quantum phase transitions.

  1. Selfishness and Cooperation: Challenge for Social Life

    Directory of Open Access Journals (Sweden)

    Szocik Konrad

    2017-07-01

    Full Text Available Cooperation is a great challenge for natural selection. Some scholars assume that cooperation could not evolve within the framework of natural selection. It is undeniable that natural selection, at least at the individual level, favors selfishness and defectors. Nonetheless, this selfish tendency does not necessarily imply that cooperation could not evolve by means of natural selection. In this paper, we specifically acknowledge certain basic challenges for the evolution of the human ability to cooperate at the level of large groups. In this paper, we discuss topics like the human ability for “supercooperation,” the importance of repetition and reputation, and Multilevel Selection Theory as the basic mechanisms of evolution of cooperation.

  2. Correlated pay-offs are key to cooperation

    Science.gov (United States)

    Frommen, Joachim G.; Riehl, Christina

    2016-01-01

    The general belief that cooperation and altruism in social groups result primarily from kin selection has recently been challenged, not least because results from cooperatively breeding insects and vertebrates have shown that groups may be composed mainly of non-relatives. This allows testing predictions of reciprocity theory without the confounding effect of relatedness. Here, we review complementary and alternative evolutionary mechanisms to kin selection theory and provide empirical examples of cooperative behaviour among unrelated individuals in a wide range of taxa. In particular, we focus on the different forms of reciprocity and on their underlying decision rules, asking about evolutionary stability, the conditions selecting for reciprocity and the factors constraining reciprocal cooperation. We find that neither the cognitive requirements of reciprocal cooperation nor the often sequential nature of interactions are insuperable stumbling blocks for the evolution of reciprocity. We argue that simple decision rules such as ‘help anyone if helped by someone’ should get more attention in future research, because empirical studies show that animals apply such rules, and theoretical models find that they can create stable levels of cooperation under a wide range of conditions. Owing to its simplicity, behaviour based on such a heuristic may in fact be ubiquitous. Finally, we argue that the evolution of exchange and trading of service and commodities among social partners needs greater scientific focus. PMID:26729924

  3. Business Networks and Cooperation in International Business Relationships

    OpenAIRE

    Desirée Blankenburg Holm; Kent Eriksson; Jan Johanson

    1996-01-01

    Cooperative relationships between firms can be better understood if they are examined in the context of a network of connected business relationships. Based on research on business relationships and business networks, this paper formulates a LISREL model that analyses cooperation in international business relationships between suppliers and customer firms. Theory suggests that cooperation can raise the value of business relationships, and that business network connections have an impact on co...

  4. Solid State Technology Branch of NASA Lewis Research Center: Fifth Annual Digest

    International Nuclear Information System (INIS)

    1993-08-01

    An extensive characterization of Bi-Sr-Ca-Cu-O (BSCCO) thin films deposited by co-evaporation on LaAlO3 and SrTiO3 substrates was performed. The films had a T c (R = O) of approximately 78 K, and were predominantly c-axis oriented, with critical current densities (J c ) at 4.5 K of 1.6 x 10(exp 6) and 1.1 x 10(exp 6) A cm -2 , for the samples on SrTiO3 and LaAlO3, respectively. The microwave properties of the films were examined by three techniques. The complex conductivity sigma * = sigma 1 - j(sigma 2 ) and the magnetic penetration depth (A) were measured by power transmission at 30.6 GHz; the surface resistance (R s ) was measured using a cavity resonator at 58.9 GHz, and the transmission line losses were determined by measuring the quality factor (Q) of a linear microstrip resonator at 10.4 and 20.2 GHz. The complex conductivity for the film on LaAlO3 was determined to be (2.0-j10) x 10(exp 5) S/m at 77 K. It was observed that in the superconducting state sigma 1 deviates from both the Bardeen-Cooper-Schrieffer (BCS) theory and the two-fluid model. Values of lambda were found to be approximately 2.0 and 1.1 microns at 77 K and 20 K respectively, and were obtained for the film on LaAlO3. The value of lambda at 20 K was approximately three times larger than that of BSCCO single crystals. R s values of 865 and 1391 mOmega were obtained for the films on SrTiO3 and LaAlO3, respectively, at 77 K and 58.9 GHz. Unloaded Q factors at 20 K of approximately 1100 and 800 at 10.4 and 20.2 GHz respectively, were measured for the BSCCO resonator. Unloaded Q values of 290 and 405 at 20 K were obtained at 10.4 GHz and 20.2 GHz respectively, for an all gold (Au) resonator

  5. Investigation of the superconducting properties of niobium radio-frequency cavities

    Science.gov (United States)

    Ciovati, Gianluigi

    Radio-frequency (rf) superconducting cavities are widely used to increase the energy of a charged particle beam in particle accelerators. The maximum gradients of cavities made of bulk niobium have constantly improved over the last ten years and they are approaching the theoretical limit of the material. Nevertheless, rf tests of niobium cavities are still showing some "anomalous" losses (so-called "Q-drop"), characterized by a marked increase of the surface resistance at high rf fields, in absence of field emission. A low temperature "in-situ" baking under ultra-high vacuum has been successfully applied by several laboratories to reduce those losses and improve the cavity's quality factor. Several models have been proposed to explain the cause of the Q-drop and the baking effect. We investigated the effect of baking on niobium material parameters by measuring the temperature dependence of a cavity's surface impedance and comparing it with the Bardeen-Cooper-Schrieffer's theory of superconductivity. It was found that baking allows interstitial oxygen to diffuse from the surface deeper into the bulk. This produces a significant reduction of the normal electrons' mean free path, which causes an increase of the quality factor. The optimum baking parameters are 120°C for 24-48 h. We were also able to identify the origin of the Q-drop as due to a high magnetic field, rather then electric field, by measuring the quality factor of a cavity as function of the rf field in a resonant mode with only magnetic field present on the surface. With the aid of a thermometry system, we were able to localize the losses in the high magnetic field region. We measured the Q-drop in cavities which had undergone different treatments, such as anodization, electropolishing and post-purification, and with different metallurgical properties and we study the effectiveness of baking in each case. As a result, none of the models proposed so far can explain all the experimental observations. We

  6. Introduction to the theory of cooperative games

    CERN Document Server

    Peleg, Bezalel; Peleg, Bezalel

    2007-01-01

    This book systematically presents the main solutions of cooperative games: the core, bargaining set, kernel, nucleolus, and the Shapley value of TU games as well as the core, the Shapley value, and the ordinal bargaining set of NTU games. The authors devote a separate chapter to each solution, wherein they study its properties in full detail. In addition, important variants are defined or even intensively analyzed.

  7. The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems

    Science.gov (United States)

    Strinati, Giancarlo Calvanese; Pieri, Pierbiagio; Röpke, Gerd; Schuck, Peter; Urban, Michael

    2018-04-01

    This report addresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance. The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient

  8. Democratizing Rural Economy: Institutional Friction, Sustainable Struggle and the Cooperative Movement

    Science.gov (United States)

    Mooney, Patrick H.

    2004-01-01

    Sustainable development demands institutions manage the conflicts and struggles that inevitably arise over material and ideal interests. While current cooperative theory privileges the economic element, a political economy of cooperation emphasizes cooperatives' tentative bridging of economic and political spheres with a democratic ethos. The…

  9. Parochial cooperation in nested intergroup dilemmas is reduced when it harms out-groups.

    Science.gov (United States)

    Aaldering, Hillie; Ten Velden, Femke S; van Kleef, Gerben A; De Dreu, Carsten K W

    2018-06-01

    In intergroup settings, humans often contribute to their in-group at a personal cost. Such parochial cooperation benefits the in-group and creates and fuels intergroup conflict when it simultaneously hurts out-groups. Here, we introduce a new game paradigm in which individuals can display universal cooperation (which benefits both in- and out-group) as well as parochial cooperation that does, versus does not hurt the out-group. Using this set-up, we test hypotheses derived from group selection theory, social identity, and bounded generalized reciprocity theory. Across three experiments we find, first, that individuals choose parochial over universal cooperation. Second, there was no evidence for a motive to maximize differences between in- and out-group, which is central to both group selection and social identity theory. However, fitting bounded generalized reciprocity theory, we find that individuals with a prosocial value orientation display parochial cooperation, provided that this does not harm the out-group; individualists, in contrast, display parochialism whether or not nut it hurts the out-group. Our findings were insensitive to cognitive taxation (Experiments 2-3), and emerged even when universal cooperation served social welfare more than parochialism (Experiment 3). (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  10. Communication: Towards first principles theory of relaxation in supercooled liquids formulated in terms of cooperative motion

    Energy Technology Data Exchange (ETDEWEB)

    Freed, Karl F., E-mail: freed@uchicago.edu [James Franck Institute and Department of Chemistry, University of Chicago, 929 East 57 Street, Chicago, Illinois 60637 (United States)

    2014-10-14

    A general theory of the long time, low temperature dynamics of glass-forming fluids remains elusive despite the almost 20 years since the famous pronouncement by the Nobel Laureate P. W. Anderson, “The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition” [Science 267, 1615 (1995)]. While recent work indicates that Adam-Gibbs theory (AGT) provides a framework for computing the structural relaxation time of supercooled fluids and for analyzing the properties of the cooperatively rearranging dynamical strings observed in low temperature molecular dynamics simulations, the heuristic nature of AGT has impeded general acceptance due to the lack of a first principles derivation [G. Adam and J. H. Gibbs, J. Chem. Phys. 43, 139 (1965)]. This deficiency is rectified here by a statistical mechanical derivation of AGT that uses transition state theory and the assumption that the transition state is composed of elementary excitations of a string-like form. The strings are assumed to form in equilibrium with the mobile particles in the fluid. Hence, transition state theory requires the strings to be in mutual equilibrium and thus to have the size distribution of a self-assembling system, in accord with the simulations and analyses of Douglas and co-workers. The average relaxation rate is computed as a grand canonical ensemble average over all string sizes, and use of the previously determined relation between configurational entropy and the average cluster size in several model equilibrium self-associating systems produces the AGT expression in a manner enabling further extensions and more fundamental tests of the assumptions.

  11. Communication: Towards first principles theory of relaxation in supercooled liquids formulated in terms of cooperative motion.

    Science.gov (United States)

    Freed, Karl F

    2014-10-14

    A general theory of the long time, low temperature dynamics of glass-forming fluids remains elusive despite the almost 20 years since the famous pronouncement by the Nobel Laureate P. W. Anderson, "The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition" [Science 267, 1615 (1995)]. While recent work indicates that Adam-Gibbs theory (AGT) provides a framework for computing the structural relaxation time of supercooled fluids and for analyzing the properties of the cooperatively rearranging dynamical strings observed in low temperature molecular dynamics simulations, the heuristic nature of AGT has impeded general acceptance due to the lack of a first principles derivation [G. Adam and J. H. Gibbs, J. Chem. Phys. 43, 139 (1965)]. This deficiency is rectified here by a statistical mechanical derivation of AGT that uses transition state theory and the assumption that the transition state is composed of elementary excitations of a string-like form. The strings are assumed to form in equilibrium with the mobile particles in the fluid. Hence, transition state theory requires the strings to be in mutual equilibrium and thus to have the size distribution of a self-assembling system, in accord with the simulations and analyses of Douglas and co-workers. The average relaxation rate is computed as a grand canonical ensemble average over all string sizes, and use of the previously determined relation between configurational entropy and the average cluster size in several model equilibrium self-associating systems produces the AGT expression in a manner enabling further extensions and more fundamental tests of the assumptions.

  12. A house divided: cooperative and competitive recruitment in vital industries.

    Science.gov (United States)

    Willis, William K; Muslin, Ivan; Timko, Karlyn N

    2016-03-01

    To propose a theoretical based model approach to address the nursing shortage problem of recruiting qualified applicants. Vital industries such as nursing and trucking face a large labour shortage. A literature review focusing on recruitment and realistic job previews examines relevant theories and an indication of the focus of similar research. Game theory illustrates cooperative and competitive recruitment strategies in vital industries. Proposition and model development where cooperative or competitive strategies for recruitment can either increase or decrease the employee applicant pool. Institutional theory states that firms within a population become isomorphic in nature. Firms employing cooperative or competitive strategies for recruitment can change organisational practices through isomorphic processes. Industries facing a labour market shortage using cooperative strategy will use realistic job previews accurately to disseminate information about industry jobs. Realistic job previews will increase the applicant pool through individuals self-selecting into, rather than out of, the applicant pool. Recruitment in the nursing industry has been examined at the individual applicant and organisational level, yet the overall industry has been ignored. As nursing shortages continue, viewing recruitment at the macro level (the overall industry) is appropriate. Game theory as proposed provides opportunities for current research at the industry level. © 2015 John Wiley & Sons Ltd.

  13. Four Notions on the Qualities of Cooperating Music Teachers

    Science.gov (United States)

    Abramo, Joseph Michael; Campbell, Mark Robin

    2016-01-01

    This article develops criteria for the selection, professional development, and assessment of cooperating teachers through four "notions." These notions suggest that cooperating teachers might (1) possess knowledge of educational theory and practice; (2) understand the importance of context in education; (3) understand narrative's role…

  14. Cooperative effects in spherical spasers

    DEFF Research Database (Denmark)

    Bordo, Vladimir

    2017-01-01

    A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which...... a shell/core contains an arbitrarily large number of active molecules in the vicinity of a metallic core/shell. An essential aspect of the theory is an ab initio account of the feedback from the core/shell boundaries which significantly modifies the molecular dynamics. The theory provides rigorous, albeit...

  15. The role of physical space in labour–management cooperation

    DEFF Research Database (Denmark)

    Ilsøe, Anna; Felbo-Kolding, Jonas

    2018-01-01

    Many studies on labour–management relations have focused on formal cooperation in manufacturing. This calls for further research and theory development on labour–management interactions in private service companies, where cooperation practices appear to be less formal. In this article, a typology...... of cooperation between managers and employees is developed, based on a microsociological study conducted in the Danish retail trade in 2013. Drawing on six indepth case studies, the article identifies four different physical spaces of labour–management cooperation: open collective, closed collective, open...

  16. Robust Dynamic Cooperative Games

    NARCIS (Netherlands)

    Bauso, D.; Timmer, Judith B.

    2006-01-01

    Classical cooperative game theory is no longer a suitable tool for those situations where the values of coalitions are not known with certainty. Recent works address situations where the values of coalitions are modelled by random variables. In this work we still consider the values of coalitions as

  17. Cooperate without looking: Why we care what people think and not just what they do

    Science.gov (United States)

    Hoffman, Moshe; Yoeli, Erez; Nowak, Martin A.

    2015-01-01

    Evolutionary game theory typically focuses on actions but ignores motives. Here, we introduce a model that takes into account the motive behind the action. A crucial question is why do we trust people more who cooperate without calculating the costs? We propose a game theory model to explain this phenomenon. One player has the option to “look” at the costs of cooperation, and the other player chooses whether to continue the interaction. If it is occasionally very costly for player 1 to cooperate, but defection is harmful for player 2, then cooperation without looking is a subgame perfect equilibrium. This behavior also emerges in population-based processes of learning or evolution. Our theory illuminates a number of key phenomena of human interactions: authentic altruism, why people cooperate intuitively, one-shot cooperation, why friends do not keep track of favors, why we admire principled people, Kant’s second formulation of the Categorical Imperative, taboos, and love. PMID:25624473

  18. Cooperate without looking: why we care what people think and not just what they do.

    Science.gov (United States)

    Hoffman, Moshe; Yoeli, Erez; Nowak, Martin A

    2015-02-10

    Evolutionary game theory typically focuses on actions but ignores motives. Here, we introduce a model that takes into account the motive behind the action. A crucial question is why do we trust people more who cooperate without calculating the costs? We propose a game theory model to explain this phenomenon. One player has the option to "look" at the costs of cooperation, and the other player chooses whether to continue the interaction. If it is occasionally very costly for player 1 to cooperate, but defection is harmful for player 2, then cooperation without looking is a subgame perfect equilibrium. This behavior also emerges in population-based processes of learning or evolution. Our theory illuminates a number of key phenomena of human interactions: authentic altruism, why people cooperate intuitively, one-shot cooperation, why friends do not keep track of favors, why we admire principled people, Kant's second formulation of the Categorical Imperative, taboos, and love.

  19. Multilayered cuprate superconductor Ba2Ca5Cu6O12(O1-x,Fx) 2 studied by temperature-dependent scanning tunneling microscopy and spectroscopy

    Science.gov (United States)

    Sugimoto, Akira; Ekino, Toshikazu; Gabovich, Alexander M.; Sekine, Ryotaro; Tanabe, Kenji; Tokiwa, Kazuyasu

    2017-05-01

    Scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on a multilayered cuprate superconductor Ba2Ca5Cu6O12 (O1 -x,Fx )2. STM topography revealed random spot structures with the characteristic length ≤0.5 nm. The conductance spectra d I /d V (V ) show the coexistence of smaller gaps ΔS and large gaps (pseudogaps) ΔL. The pseudogap-related features in the superconducting state were traced with the spatial resolution of ˜0.07 nm. Here, I and V are the tunnel current and bias voltage, respectively. The temperature, T , dependence of ΔS follows the reduced Bardeen-Cooper-Schrieffer (BCS) dependence. The hallmark ratio 2 ΔS(T =0 ) /kBTc equals to 4.9, which is smaller than those of other cuprate superconductors. Here, Tc is the superconducting critical temperature and kB is the Boltzmann constant. The larger gap ΔL survives in the normal state and even increases with T above Tc. The T dependencies of the spatial distributions for both relevant gaps (Δ map), as well as for each gap separately (ΔS and ΔL), were obtained. From the histogram of Δ map, the averaged gap values were found to be Δ¯S=˜24 meV and Δ¯L=˜79 meV. The smaller gap ΔS shows a spatially homogeneous distribution while the larger gap ΔL is quite inhomogeneous, indicating that rather homogeneous superconductivity coexists with the patchy distributed pseudogap. The spatial variation length ξΔ L of ΔL correlates with the scale of the topography spot structures, being approximately 0.4 nm. This value is considerably smaller than the coherence length of this class of superconductors, suggesting that ΔL is strongly affected by the disorder of the apical O/F.

  20. SISL and SIRL: Two knowledge dissemination models with leader nodes on cooperative learning networks

    Science.gov (United States)

    Li, Jingjing; Zhang, Yumei; Man, Jiayu; Zhou, Yun; Wu, Xiaojun

    2017-02-01

    Cooperative learning is one of the most effective teaching methods, which has been widely used. Students' mutual contact forms a cooperative learning network in this process. Our previous research demonstrated that the cooperative learning network has complex characteristics. This study aims to investigating the dynamic spreading process of the knowledge in the cooperative learning network and the inspiration of leaders in this process. To this end, complex network transmission dynamics theory is utilized to construct the knowledge dissemination model of a cooperative learning network. Based on the existing epidemic models, we propose a new susceptible-infected-susceptible-leader (SISL) model that considers both students' forgetting and leaders' inspiration, and a susceptible-infected-removed-leader (SIRL) model that considers students' interest in spreading and leaders' inspiration. The spreading threshold λcand its impact factors are analyzed. Then, numerical simulation and analysis are delivered to reveal the dynamic transmission mechanism of knowledge and leaders' role. This work is of great significance to cooperative learning theory and teaching practice. It also enriches the theory of complex network transmission dynamics.

  1. Intention recognition, commitment and their roles in the evolution of cooperation from artificial intelligence techniques to evolutionary game theory models

    CERN Document Server

    Han, The Anh

    2013-01-01

    This original and timely monograph describes a unique self-contained excursion that reveals to the readers the roles of two basic cognitive abilities, i.e. intention recognition and arranging commitments, in the evolution of cooperative behavior. This book analyses intention recognition, an important ability that helps agents predict others’ behavior, in its artificial intelligence and evolutionary computational modeling aspects, and proposes a novel intention recognition method. Furthermore, the book presents a new framework for intention-based decision making and illustrates several ways in which an ability to recognize intentions of others can enhance a decision making process. By employing the new intention recognition method and the tools of evolutionary game theory, this book introduces computational models demonstrating that intention recognition promotes the emergence of cooperation within populations of self-regarding agents. Finally, the book describes how commitment provides a pathway to the evol...

  2. When Reputation Enforces Evolutionary Cooperation in Unreliable MANETs.

    Science.gov (United States)

    Tang, Changbing; Li, Ang; Li, Xiang

    2015-10-01

    In self-organized mobile ad hoc networks (MANETs), network functions rely on cooperation of self-interested nodes, where a challenge is to enforce their mutual cooperation. In this paper, we study cooperative packet forwarding in a one-hop unreliable channel which results from loss of packets and noisy observation of transmissions. We propose an indirect reciprocity framework based on evolutionary game theory, and enforce cooperation of packet forwarding strategies in both structured and unstructured MANETs. Furthermore, we analyze the evolutionary dynamics of cooperative strategies and derive the threshold of benefit-to-cost ratio to guarantee the convergence of cooperation. The numerical simulations verify that the proposed evolutionary game theoretic solution enforces cooperation when the benefit-to-cost ratio of the altruistic exceeds the critical condition. In addition, the network throughput performance of our proposed strategy in structured MANETs is measured, which is in close agreement with that of the full cooperative strategy.

  3. Upcrowding energy co-operatives - Evaluating the potential of crowdfunding for business model innovation of energy co-operatives.

    Science.gov (United States)

    Dilger, Mathias Georg; Jovanović, Tanja; Voigt, Kai-Ingo

    2017-08-01

    Practice and theory have proven the relevance of energy co-operatives for civic participation in the energy turnaround. However, due to a still low awareness and changing regulation, there seems an unexploited potential of utilizing the legal form 'co-operative' in this context. The aim of this study is therefore to investigate the crowdfunding implementation in the business model of energy co-operatives in order to cope with the mentioned challenges. Based on a theoretical framework, we derive a Business Model Innovation (BMI) through crowdfunding including synergies and differences. A qualitative study design, particularly a multiple-case study of energy co-operatives, was chosen to prove the BMI and to reveal barriers. The results show that although most co-operatives are not familiar with crowdfunding, there is strong potential in opening up predominantly local structures to a broader group of members. Building on this, equity-based crowdfunding is revealed to be suitable for energy co-operatives as BMI and to accompany other challenges in the same way. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. What we need is theory of human cooperation (and meta-analysis) to bridge the gap between the lab and the wild.

    Science.gov (United States)

    Van Lange, Paul A M; Balliet, Daniel P; IJzerman, Hans

    2012-02-01

    This commentary seeks to clarify the potential discrepancy between lab-based and field data in the use and effectiveness of punishment to promote cooperation by recommending theory that outlines key differences between the lab and field, such as the shadow of the future and degree of information availability. We also discuss a recent meta-analysis (Balliet et al. 2011) that does not support all conclusions outlined in Guala's target article.

  5. Firms, nonprofits, and cooperatives : A theory of organizational choice

    NARCIS (Netherlands)

    Herbst, Patrick; Prüfer, Jens

    We formalize the difference between profit-maximizing firms, nonprofits, and cooperatives and identify optimal organizational choice in a model of quality provision. Firms provide lowest and nonprofits highest levels of quality. Efficiency, however, depends on the competitive environment, the

  6. Firms, Nonprofits, and Cooperatives : A Theory of Organizational Choice

    NARCIS (Netherlands)

    Herbst, P.; Prüfer, J.

    2007-01-01

    Abstract This paper formalizes the difference between firms, nonprofits, and cooperatives and identifies optimal organizational choice. In a model of quality provision, we find a clear ranking of quality produced: Firms provide lowest and nonprofits highest levels of quality. Efficiency, however,

  7. Cooperation induces other cooperation: Fruiting bodies promote the evolution of macrocysts in Dictyostelium discoideum.

    Science.gov (United States)

    Shibasaki, Shota; Shirokawa, Yuka; Shimada, Masakazu

    2017-05-21

    Biological studies of the evolution of cooperation are challenging because this process is vulnerable to cheating. Many mechanisms, including kin discrimination, spatial structure, or by-products of self-interested behaviors, can explain this evolution. Here we propose that the evolution of cooperation can be induced by other cooperation. To test this idea, we used a model organism Dictyostelium discoideum because it exhibits two cooperative dormant phases, the fruiting body and the macrocyst. In both phases, the same chemoattractant, cyclic AMP (cAMP), is used to collect cells. This common feature led us to hypothesize that the evolution of macrocyst formation would be induced by coexistence with fruiting bodies. Before forming a mathematical model, we confirmed that macrocysts coexisted with fruiting bodies, at least under laboratory conditions. Next, we analyzed our evolutionary game theory-based model to investigate whether coexistence with fruiting bodies would stabilize macrocyst formation. The model suggests that macrocyst formation represents an evolutionarily stable strategy and a global invader strategy under this coexistence, but is unstable if the model ignores the fruiting body formation. This result indicates that the evolution of macrocyst formation and maintenance is attributable to coexistence with fruiting bodies. Therefore, macrocyst evolution can be considered as an example of evolution of cooperation induced by other cooperation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Kantian Optimization: An Approach to Cooperative Behavior

    OpenAIRE

    John E. Roemer

    2014-01-01

    Although evidence accrues in biology, anthropology and experimental economics that homo sapiens is a cooperative species, the reigning assumption in economic theory is that individuals optimize in an autarkic manner (as in Nash and Walrasian equilibrium). I here postulate a cooperative kind of optimizing behavior, called Kantian. It is shown that in simple economic models, when there are negative externalities (such as congestion effects from use of a commonly owned resource) or positive exte...

  9. Firms, Nonprofits, and Cooperatives : A Theory of Organizational Choice

    NARCIS (Netherlands)

    Herbst, P.; Prüfer, J.

    2007-01-01

    This paper formalizes the difference between firms, nonprofits, and cooperatives and identifies optimal organizational choice. In a model of quality provision, we find a clear ranking of quality produced: Firms provide lowest and nonprofits highest levels of quality. Efficiency, however, depends on

  10. Game theory : The next stage

    NARCIS (Netherlands)

    van Damme, E.E.C.

    1995-01-01

    This paper surveys some recent developments in (non-cooperative) game theory and provides an outlook on the near future of that theory. In particular, attention is focused on the limitations inherent in normative game theory and on attempts to construct a behavioral version of the theory that

  11. Team Learning: Through the Relational Dynamics of Co-operation and Rivalry in Team Communities

    OpenAIRE

    Lotz, Maja

    2008-01-01

    In this paper I explore the constructive links between co-operation, rivalry, and learning within the structure of team communities. Drawing upon social learning theory, the main purpose of this paper is to argue that both co-operation and rivalry are important triggers for mobilizing learning processes within and between teams. However, social learning theory tends to disregard the positive aspects of rivalry. Consequently, this paper will argue for the need to extend social learning theory ...

  12. Newton gauge cosmological perturbations for static spherically symmetric modifications of the de Sitter metric

    Science.gov (United States)

    Santa Vélez, Camilo; Enea Romano, Antonio

    2018-05-01

    Static coordinates can be convenient to solve the vacuum Einstein's equations in presence of spherical symmetry, but for cosmological applications comoving coordinates are more suitable to describe an expanding Universe, especially in the framework of cosmological perturbation theory (CPT). Using CPT we develop a method to transform static spherically symmetric (SSS) modifications of the de Sitter solution from static coordinates to the Newton gauge. We test the method with the Schwarzschild de Sitter (SDS) metric and then derive general expressions for the Bardeen's potentials for a class of SSS metrics obtained by adding to the de Sitter metric a term linear in the mass and proportional to a general function of the radius. Using the gauge invariance of the Bardeen's potentials we then obtain a gauge invariant definition of the turn around radius. We apply the method to an SSS solution of the Brans-Dicke theory, confirming the results obtained independently by solving the perturbation equations in the Newton gauge. The Bardeen's potentials are then derived for new SSS metrics involving logarithmic, power law and exponential modifications of the de Sitter metric. We also apply the method to SSS metrics which give flat rotation curves, computing the radial energy density profile in comoving coordinates in presence of a cosmological constant.

  13. The Impact of Cooperative Learning Methods on Elementary Preservice Education Teachers' Mathematics Achievement and Anxiety

    Science.gov (United States)

    Swift, Elijah Raford, Jr.

    2012-01-01

    The purpose of this study was to address the gap in research regarding the use of cooperative learning instructional methods in college mathematics courses to prepare future teachers. Bruner's constructivist theory and social interdependence theory guided this study. The research questions focused on the effects of the use of cooperative learning…

  14. Cooperation is fleeting in the world of transposable elements.

    Directory of Open Access Journals (Sweden)

    Andreas Wagner

    2006-12-01

    Full Text Available Composite transposons are key vehicles for the worldwide spreading of genes that allow bacteria to survive toxic compounds. Composite transposons consist of two smaller transposable elements called insertion sequences (ISs, which flank the genes that permit such survival. Each IS in a composite transposon can either transpose alone, selfishly, or it can transpose cooperatively, jointly with the other IS. Cooperative transposition can enhance an IS's chance of survival, but it also carries the risk of transposon destruction. I use game theory to show that the conditions under which cooperative transposition is an evolutionarily stable strategy (ESS are not biologically realistic. I then analyze the distribution of thousands of ISs in more than 200 bacterial genomes to test the following prediction of the game-theoretical model: if cooperative transposition was an ESS, then the closely spaced ISs that characterize composite transposons should be more abundant in genomes than expected by chance. The data show that this is not the case. Cooperativity can only be maintained in a transitional, far-from-equilibrium state shortly after a selection pressure first arises. This is the case in the spreading of antibiotic resistance, where we are witnessing a fleeting moment in evolution, a moment in which cooperation among selfish DNA molecules has provided a means of survival. Because such cooperation does not pay in the long run, the vehicles of such survival will eventually disappear again. My analysis demonstrates that game theory can help explain behavioral strategies even for mobile DNA.

  15. Emergence of cooperation in non-scale-free networks

    International Nuclear Information System (INIS)

    Zhang, Yichao; Aziz-Alaoui, M A; Bertelle, Cyrille; Zhou, Shi; Wang, Wenting

    2014-01-01

    Evolutionary game theory is one of the key paradigms behind many scientific disciplines from science to engineering. Previous studies proposed a strategy updating mechanism, which successfully demonstrated that the scale-free network can provide a framework for the emergence of cooperation. Instead, individuals in random graphs and small-world networks do not favor cooperation under this updating rule. However, a recent empirical result shows the heterogeneous networks do not promote cooperation when humans play a prisoner’s dilemma. In this paper, we propose a strategy updating rule with payoff memory. We observe that the random graphs and small-world networks can provide even better frameworks for cooperation than the scale-free networks in this scenario. Our observations suggest that the degree heterogeneity may be neither a sufficient condition nor a necessary condition for the widespread cooperation in complex networks. Also, the topological structures are not sufficed to determine the level of cooperation in complex networks. (paper)

  16. Theoretical and historical bases of formation of social and economic nature of consumer cooperation

    Directory of Open Access Journals (Sweden)

    Алла Іванівна Мілька

    2015-09-01

    Full Text Available The essence of cooperation and cooperative approaches to address these concepts and the importance of social and economic component at different stages of development of the cooperative movement and the theory of cooperation are described in the article. Opinions of the scientists about the non-profit nature of the cooperative are considered and researched. Based on the study the main conceptual provisions of cooperation are highlighted and proposed the author's definition of consumer cooperatives is proposed on the basis of the research 

  17. Promotion of cooperation by selective group extinction

    Science.gov (United States)

    Böttcher, Marvin A.; Nagler, Jan

    2016-06-01

    Multilevel selection is an important organizing principle that crucially underlies evolutionary processes from the emergence of cells to eusociality and the economics of nations. Previous studies on multilevel selection assumed that the effective higher-level selection emerges from lower-level reproduction. This leads to selection among groups, although only individuals reproduce. We introduce selective group extinction, where groups die with a probability inversely proportional to their group fitness. When accounting for this the critical benefit-to-cost ratio is substantially lowered. Because in game theory and evolutionary dynamics the degree of cooperation crucially depends on this ratio above which cooperation emerges, previous studies may have substantially underestimated the establishment and maintenance of cooperation.

  18. Performance measurement of the agricultural marketing cooperatives : The gap between theory and practice

    NARCIS (Netherlands)

    Soboh, R.A.M.E.; Oude Lansink, A.; Giesen, G.; Dijk, van G.

    2009-01-01

    The performance of agricultural cooperatives depends on their business objectives, which are defined in different ways in the literature. We review the theoretical literature on the performance of agricultural marketing cooperatives. Studies can be divided into two classes, those that assume a

  19. Visualising Actor Network for Cooperative Systems in Marine Technology

    DEFF Research Database (Denmark)

    Pan, Yushan; Finken, Sisse

    2016-01-01

    Awareness is a concept familiar to specialists within the field of Computer Supported Cooperative Work (CSCW). It is superior for analysing and describing some of the ad hoc work activities that unfold in cooperation. Such informal activities are outside the scope of engineers’ formal models, whi...... that shape computer systems. The aim, thus, is to portray cooperative work in a way that can be valuable for engineers implementing marine technology. We do so by way of presenting a transferring technique (2T) using insights from the CSCW field and Actor Network Theory (ANT)....

  20. Cooperative learning and academic achievement: why does groupwork work?

    Directory of Open Access Journals (Sweden)

    Robert E. Slavin

    2014-10-01

    Full Text Available Cooperative learning refers to instructional methods in which students work in small groups to help each other learn. Four major theoretical perspectives on achievement effects of cooperative learning are reviewed: Motivational, social cohesion, developmental, and cognitive elaboration. Evidence from practical classroom research primarily supports the motivational perspective, which emphasizes the use of group goals and individual accountability for group success. However, there are conditions under which methods derived from all four theoretical perspectives contribute to achievement gain. This chapter reconciles these perspectives in a unified theory of cooperative learning effects.

  1. Trust and Its Impact on Cooperation in Alliance Networks:Theory and Practice

    Directory of Open Access Journals (Sweden)

    Wlodzimierz SROKA

    2011-11-01

    Full Text Available At present we can observe the increasing role of cooperation among companies all around the world. Cooperation includes many forms, such as alliances, joint ventures, networks, clusters, outsourcing and others. Trust is one of the most important factors of success of any cooperation activity, because it can lower transaction costs, increase productivity and innovativeness, facilitate inter-organizational relationships and resolve conflicts. Therefore the paper discusses the basic problems of trust in alliance networks. The text consists of theoretical deliberations devoted to alliance networks and trust. The practical case of the company from machine industry that formed a portfolio of alliances based on trust is also an important part of the text. The conclusion of the paper is that portfolio of alliances based on trust is worth pursuing.

  2. Minefield Mapping Using Cooperative Multirobot Systems

    Directory of Open Access Journals (Sweden)

    Alaa Khamis

    2012-01-01

    Full Text Available This paper presents a team-theoretic approach to cooperative multirobot systems. The individual actions of the robots are controlled by the Belief-Desire-Intention model to endow the robots with the know-how needed to execute these actions deliberately. The cooperative behaviors between the heterogeneous robots are governed by the Team-Log theory to endow all the robots in the team with the know-how-to-cooperate and determine the team members’ commitments to each other despite their different types, properties, and goals. The proposed approach is tested for validity with the real life problem of minefield mapping. Different minefield sweeping strategies are studied to control the mobility of the mobile sweepers within the minefield in order to maximize the area coverage and improve picture compilation capability of the multirobot system.

  3. Judgments about Cooperators and Freeriders on a Shuar Work Team: An Evolutionary Psychological Perspective

    Science.gov (United States)

    Price, Michael E.

    2006-01-01

    Evolutionary biological theories of group cooperation predict that (1) group members will tend to judge cooperative co-members favorably, and freeriding co-members negatively and (2) members who themselves cooperate more frequently will be especially likely to make these social judgments. An experiment tested these predictions among Shuar…

  4. On renormalization of axial anomaly

    International Nuclear Information System (INIS)

    Efremov, A.V.; Teryaev, O.V.

    1989-01-01

    It is shown that multiplicative renormalization of the axial singlet current results in renormalization of the axial anomaly in all orders of perturbation theory. It is a necessary condition for the Adler - Bardeen theorem being valid. 10 refs.; 2 figs

  5. Linkage in the chain of care: a grounded theory of professional cooperation between antenatal care, postpartum care and child health care

    Directory of Open Access Journals (Sweden)

    Mia Barimani

    2008-12-01

    Full Text Available Purpose: The purpose of this article is to present a Swedish study exploring health care professionals’ cooperation in the chain of care for expectant and new parents between antenatal care (AC, postpartum care (PC and child health care (CHC. Furthermore, the rationale was to conceptualise barriers and facilitators of cooperation in order to generate a comprehensive theoretical model which may explain variations in the care providers’ experiences. Methods: Thirty-two midwives and CHC nurses were interviewed in five focus group – and two individual interviews in a suburb of a large Swedish city. Grounded Theory was applied as the research methodology. Results: One core category was discerned: linkage in the chain of care, including six categories with subcategories. Despite the fact that midwives as well as CHC nurses have common visions about linkage, cooperation is not achieved because of interacting barriers that have different influences on the three links in the chain. Conclusions: Barriers to linkage are lack of professional gain, link perspective and first or middle position in the chain, while facilitators are chain perspective, professional gain and last position in the chain. As the last link, CHC nurses promote a linkage most strongly and have the greatest gain from such linking.

  6. Cooperation induced by wise incentive allocation in spontaneous institution

    Science.gov (United States)

    Cong, Rui; Li, Kun; Wang, Long; Zhao, Qianchuan

    2016-08-01

    Institutional incentives such as punishment and rewarding have recently received wide attention in resolving issues of public goods provision that requires collective cooperation. In this letter, we are interested in exploring the effect on cooperation of a spontaneous institution, which rewards its participants exclusively and also takes the social responsibility of punishing interior and exterior free-riders. Drawing support from evolutionary game theory, our results indicate that the splitting ratio of such institution funds plays a decisive role in determining the evolutionary outcome. Rewarding is essential in sustaining the institution, while a certain intensity of punishment ensures a high overall cooperation level. Our results may provide more insights into understanding the roles institutional incentives play in promoting social cooperation.

  7. Cooperative networking in a heterogeneous wireless medium

    CERN Document Server

    Ismail, Muhammad

    2013-01-01

    This brief focuses on radio resource allocation in a heterogeneous wireless medium. It presents radio resource allocation algorithms with decentralized implementation, which support both single-network and multi-homing services. The brief provides a set of cooperative networking algorithms, which rely on the concepts of short-term call traffic load prediction, network cooperation, convex optimization, and decomposition theory. In the proposed solutions, mobile terminals play an active role in the resource allocation operation, instead of their traditional role as passive service recipients in the networking environment.

  8. The increased risk of predation enhances cooperation

    Science.gov (United States)

    Krams, Indrikis; Bērziņš, Arnis; Krama, Tatjana; Wheatcroft, David; Igaune, Kristīne; Rantala, Markus J.

    2010-01-01

    Theory predicts that animals in adverse conditions can decrease individual risks and increase long-term benefits by cooperating with neighbours. However, some empirical studies suggest that animals often focus on short-term benefits, which can reduce the likelihood that they will cooperate with others. In this experimental study, we tested between these two alternatives by evaluating whether increased predation risk (as a correlate of environmental adversity) enhances or diminishes the occurrence of cooperation in mobbing, a common anti-predator behaviour, among breeding pied flycatchers Ficedula hypoleuca. We tested whether birds would join their mobbing neighbours more often and harass a stuffed predator placed near their neighbours' nests more intensely in areas with a higher perceived risk of predation. Our results show that birds attended mobs initiated by their neighbours more often, approached the stuffed predator significantly more closely, and mobbed it at a higher intensity in areas where the perceived risk of predation was experimentally increased. In such high-risk areas, birds also were more often involved in between-pair cooperation. This study demonstrates the positive impact of predation risk on cooperation in breeding songbirds, which might help in explaining the emergence and evolution of cooperation. PMID:19846454

  9. Cooperation under indirect reciprocity and imitative trust.

    Science.gov (United States)

    Saavedra, Serguei; Smith, David; Reed-Tsochas, Felix

    2010-10-27

    Indirect reciprocity, a key concept in behavioral experiments and evolutionary game theory, provides a mechanism that allows reciprocal altruism to emerge in a population of self-regarding individuals even when repeated interactions between pairs of actors are unlikely. Recent empirical evidence show that humans typically follow complex assessment strategies involving both reciprocity and social imitation when making cooperative decisions. However, currently, we have no systematic understanding of how imitation, a mechanism that may also generate negative effects via a process of cumulative advantage, affects cooperation when repeated interactions are unlikely or information about a recipient's reputation is unavailable. Here we extend existing evolutionary models, which use an image score for reputation to track how individuals cooperate by contributing resources, by introducing a new imitative-trust score, which tracks whether actors have been the recipients of cooperation in the past. We show that imitative trust can co-exist with indirect reciprocity mechanisms up to a threshold and then cooperation reverses -revealing the elusive nature of cooperation. Moreover, we find that when information about a recipient's reputation is limited, trusting the action of third parties towards her (i.e. imitating) does favor a higher collective cooperation compared to random-trusting and share-alike mechanisms. We believe these results shed new light on the factors favoring social imitation as an adaptive mechanism in populations of cooperating social actors.

  10. Cooperation under indirect reciprocity and imitative trust.

    Directory of Open Access Journals (Sweden)

    Serguei Saavedra

    Full Text Available Indirect reciprocity, a key concept in behavioral experiments and evolutionary game theory, provides a mechanism that allows reciprocal altruism to emerge in a population of self-regarding individuals even when repeated interactions between pairs of actors are unlikely. Recent empirical evidence show that humans typically follow complex assessment strategies involving both reciprocity and social imitation when making cooperative decisions. However, currently, we have no systematic understanding of how imitation, a mechanism that may also generate negative effects via a process of cumulative advantage, affects cooperation when repeated interactions are unlikely or information about a recipient's reputation is unavailable. Here we extend existing evolutionary models, which use an image score for reputation to track how individuals cooperate by contributing resources, by introducing a new imitative-trust score, which tracks whether actors have been the recipients of cooperation in the past. We show that imitative trust can co-exist with indirect reciprocity mechanisms up to a threshold and then cooperation reverses -revealing the elusive nature of cooperation. Moreover, we find that when information about a recipient's reputation is limited, trusting the action of third parties towards her (i.e. imitating does favor a higher collective cooperation compared to random-trusting and share-alike mechanisms. We believe these results shed new light on the factors favoring social imitation as an adaptive mechanism in populations of cooperating social actors.

  11. Why Students Need to Be Prepared to Cooperate: A Cooperative Nudge in Statistics Learning at University

    Science.gov (United States)

    Buchs, Céline; Gilles, Ingrid; Antonietti, Jean-Philippe; Butera, Fabrizio

    2016-01-01

    Despite the potential benefits of cooperative learning at university, its implementation is challenging. Here, we propose a theory-based 90-min intervention with 185 first-year psychology students in the challenging domain of statistics, consisting of an exercise phase and an individual learning post-test. We compared three conditions that…

  12. Application of marginal calculation in managing a cooperative company

    Directory of Open Access Journals (Sweden)

    Danuta Mierzwa

    2011-01-01

    Full Text Available In the market economy the basic subject is a private enterprise dealing with the production of goods and services in order to maximize profit. The neoclassical microeconomics focuses on examining only these enterprises on the market, which strive to maximize profit within certain limitations in a rational way. Acc. to the act of September 1982 on the co-operative law (The Journal of Laws 1982, no 30, pos. 2010, a cooperative company belongs to a group of private enterprises. However, it is called a non-profit enterprise. Nevertheless, cooperative companies on the market are seldom confronted with capital companies. In the market economy it is a rare situation for a company not to be threatened by competition. And even if such a situation does happen, it is always connected with limited demand. Thus the following question may be asked: can a co-operative company, if it wants to become rational, utilize the marginalization theory in order to determine its general balance? The author is trying to answer this question in her article, selecting an agricultural supply co-operative for her analysis. Using the graphical method, she determines various types of optimums, at the same time stating what importance it has for the members and what position the co-perative holds on the market. In the conclusion she emphasizes that the difficulties with applying the marginalization theory in the co-operative companies are brought about by the way decisions are taken and these subjects are managed, and may be the reason why many of these enterprises are closed down.

  13. Stakeholders' Cooperation in the Study Programme Quality Assurance: Theory and Practice in Lithuania

    Science.gov (United States)

    Pileicikiene, Nora

    2011-01-01

    The cooperation of various stakeholders' groups is a prerequisite to develop and realise high-quality study programmes, i.e. during studies to develop skills that are relevant to the labour market and social life. In order to achieve effective stakeholders' cooperation, it is necessary to identify stakeholder's groups relevant to a study programme…

  14. Evolution is a cooperative process: the biodiversity-related niches differentiation theory (BNDT) can explain why.

    Science.gov (United States)

    Gatti, Roberto Cazzolla

    2011-01-01

    A. McFayden and G.E. Hutchinson defined a niche as a multidimensional space or hypervolume within the environment that allows an individual or a species to survive, we consider niches as a fundamental ecological variable that regulate species' composition and relation in ecosystems. Successively the niche concept has been associated to the genetic term "phenotype" by MacArthurstressing the importance on what a species or a genome can show outside, either in the environmental functions or in body characteristics. Several indexes have been developed to evaluate the grade of overlapping and similarities of species' niches, even utilizing the theory of information. However, which are the factors that determine the number of species that can coexist in a determinate environment and why a generalist species do not compete until the exclusion of the remaining species to maximize its fitness, is still quite unknown. Moreover, there are few studies and theories that clearly explain why the number of niches is so variable through ecosystems and how can several species live in the same basal niche, intended in a comprehensive sense as the range of basic conditions (temperature, humidity, food-guild, etc.). Here I show that the number of niches in an ecosystem depends on the number of species present in a particular moment and that the species themselves allow the enhancement of niches in terms of space and number. I found that using a three-dimensional model as hypervolume and testing the theory on a Mediterranean, temperate and tropical forest ecosystem it is possible to demonstrate that each species plays a fundamental role in facilitating the colonization by other species by simply modifying the environment and exponentially increasing the available niches' space and number. I resumed these hypothesis, after some preliminary empiric tests, in the Biodiversity-related Niches Differentiation Theory (BNDT), stressing with these definition that the process of niches

  15. Superfluid and antiferromagnetic phases in ultracold fermionic quantum gases

    International Nuclear Information System (INIS)

    Gottwald, Tobias

    2010-01-01

    In this thesis several models are treated, which are relevant for ultracold fermionic quantum gases loaded onto optical lattices. In particular, imbalanced superfluid Fermi mixtures, which are considered as the best way to realize Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states experimentally, and antiferromagnetic states, whose experimental realization is one of the next major goals, are examined analytically and numerically with the use of appropriate versions of the Hubbard model. The usual Bardeen-Cooper-Schrieffer (BCS) superconductor is known to break down in a magnetic field with a strength exceeding the size of the superfluid gap. A spatially inhomogeneous spin-imbalanced superconductor with a complex order parameter known as FFLO-state is predicted to occur in translationally invariant systems. Since in ultracold quantum gases the experimental setups have a limited size and a trapping potential, we analyze the realistic situation of a non-translationally invariant finite sized Hubbard model for this purpose. We first argue analytically, why the order parameter should be real in a system with continuous coordinates, and map our statements onto the Hubbard model with discrete coordinates defined on a lattice. The relevant Hubbard model is then treated numerically within mean field theory. We show that the numerical results agree with our analytically derived statements and we simulate various experimentally relevant systems in this thesis. Analogous calculations are presented for the situation at repulsive interaction strength where the N'eel state is expected to be realized experimentally in the near future. We map our analytical results obtained for the attractive model onto corresponding results for the repulsive model. We obtain a spatially invariant unit vector defining the direction of the order parameter as a consequence of the trapping potential, which is affirmed by our mean field numerical results for the repulsive case. Furthermore, we observe

  16. Superfluid and antiferromagnetic phases in ultracold fermionic quantum gases

    Energy Technology Data Exchange (ETDEWEB)

    Gottwald, Tobias

    2010-08-27

    In this thesis several models are treated, which are relevant for ultracold fermionic quantum gases loaded onto optical lattices. In particular, imbalanced superfluid Fermi mixtures, which are considered as the best way to realize Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states experimentally, and antiferromagnetic states, whose experimental realization is one of the next major goals, are examined analytically and numerically with the use of appropriate versions of the Hubbard model. The usual Bardeen-Cooper-Schrieffer (BCS) superconductor is known to break down in a magnetic field with a strength exceeding the size of the superfluid gap. A spatially inhomogeneous spin-imbalanced superconductor with a complex order parameter known as FFLO-state is predicted to occur in translationally invariant systems. Since in ultracold quantum gases the experimental setups have a limited size and a trapping potential, we analyze the realistic situation of a non-translationally invariant finite sized Hubbard model for this purpose. We first argue analytically, why the order parameter should be real in a system with continuous coordinates, and map our statements onto the Hubbard model with discrete coordinates defined on a lattice. The relevant Hubbard model is then treated numerically within mean field theory. We show that the numerical results agree with our analytically derived statements and we simulate various experimentally relevant systems in this thesis. Analogous calculations are presented for the situation at repulsive interaction strength where the N'eel state is expected to be realized experimentally in the near future. We map our analytical results obtained for the attractive model onto corresponding results for the repulsive model. We obtain a spatially invariant unit vector defining the direction of the order parameter as a consequence of the trapping potential, which is affirmed by our mean field numerical results for the repulsive case. Furthermore, we observe

  17. Game theory: applications for surgeons and the operating room environment.

    Science.gov (United States)

    McFadden, David W; Tsai, Mitchell; Kadry, Bassam; Souba, Wiley W

    2012-11-01

    Game theory is an economic system of strategic behavior, often referred to as the "theory of social situations." Very little has been written in the medical literature about game theory or its applications, yet the practice of surgery and the operating room environment clearly involves multiple social situations with both cooperative and non-cooperative behaviors. A comprehensive review was performed of the medical literature on game theory and its medical applications. Definitive resources on the subject were also examined and applied to surgery and the operating room whenever possible. Applications of game theory and its proposed dilemmas abound in the practicing surgeon's world, especially in the operating room environment. The surgeon with a basic understanding of game theory principles is better prepared for understanding and navigating the complex Operating Room system and optimizing cooperative behaviors for the benefit all stakeholders. Copyright © 2012 Mosby, Inc. All rights reserved.

  18. Relationships between Institutional Economics of Cooperation and the Political Economy of Trust

    Directory of Open Access Journals (Sweden)

    José Hernandéz

    2008-06-01

    Full Text Available The aim of this paper is to analyse the relationship between institutional economics of cooperation and the political economy of trust. Transactions costs, principal-agent theory, market power, increasing-returns theory and value creation, strategic management: competitive forces, resource-based theory, organisationtal knowledge and learning, strategic choice theory and collective efficiency theory are reviewed. Lastly, the political economy of trust is sustained.

  19. Cooperation, Coordination, and Trust in Virtual Teams: Insights from Virtual Games

    Science.gov (United States)

    Korsgaard, M. Audrey; Picot, Arnold; Wigand, Rolf T.; Welpe, Isabelle M.; Assmann, Jakob J.

    This chapter considers fundamental concepts of effective virtual teams, illustrated by research on Travian, a massively multiplayer online strategy game wherein players seek to build empires. Team inputs are the resources that enable individuals to work interdependently toward a common goal, including individual and collective capabilities, shared knowledge structures, and leadership style. Team processes, notably coordination and cooperation, transform team inputs to desired collective outcomes. Because the members of virtual teams are geographically dispersed, relying on information and communication technology, three theories are especially relevant for understanding how they can function effectively: social presence theory, media richness theory, and media synchronicity theory. Research in settings like Travian can inform our understanding of structures, processes, and performance of virtual teams. Such research could provide valuable insight into the emergence and persistence of trust and cooperation, as well as the impact of different communication media for coordination and information management in virtual organizations.

  20. A Study of Sino-Russian Energy Cooperation from the Perspective of Theories of International Relations

    Directory of Open Access Journals (Sweden)

    Chaoyue Yang

    2013-12-01

    Full Text Available Energy cooperation is an important component in the Sino-Russia relationship. After more than a decade of efforts, China and Russia have made great progress in their cooperation in the area of oil and natural gas, which has not only promoted the economic developments in both countries, but also expanded their common interests to a large extent, resulting in a tremendous improvement of the two countries’ international strategies towards each other. Nevertheless, constrained and influenced by the evolution of contemporary international politics and economies, the Sino-Russia energy cooperation is facing some problems and barriers. Therefore, the aim of this article is to analyze the multiple elements affecting the Sino-Russia energy cooperation through the prism of Neo-realism, Neo-liberalism and Social Constructivism, hence a clear account of the opportunities and challenges that constitute this cooperation will be gained.

  1. Spatial interaction models facility location using game theory

    CERN Document Server

    D'Amato, Egidio; Pardalos, Panos

    2017-01-01

    Facility location theory develops the idea of locating one or more facilities by optimizing suitable criteria such as minimizing transportation cost, or capturing the largest market share. The contributions in this book focus an approach to facility location theory through game theoretical tools highlighting situations where a location decision is faced by several decision makers and leading to a game theoretical framework in non-cooperative and cooperative methods. Models and methods regarding the facility location via game theory are explored and applications are illustrated through economics, engineering, and physics. Mathematicians, engineers, economists and computer scientists working in theory, applications and computational aspects of facility location problems using game theory will find this book useful.

  2. Determinants of public cooperation in multiplex networks

    Science.gov (United States)

    Battiston, Federico; Perc, Matjaž; Latora, Vito

    2017-07-01

    Synergies between evolutionary game theory and statistical physics have significantly improved our understanding of public cooperation in structured populations. Multiplex networks, in particular, provide the theoretical framework within network science that allows us to mathematically describe the rich structure of interactions characterizing human societies. While research has shown that multiplex networks may enhance the resilience of cooperation, the interplay between the overlap in the structure of the layers and the control parameters of the corresponding games has not yet been investigated. With this aim, we consider here the public goods game on a multiplex network, and we unveil the role of the number of layers and the overlap of links, as well as the impact of different synergy factors in different layers, on the onset of cooperation. We show that enhanced public cooperation emerges only when a significant edge overlap is combined with at least one layer being able to sustain some cooperation by means of a sufficiently high synergy factor. In the absence of either of these conditions, the evolution of cooperation in multiplex networks is determined by the bounds of traditional network reciprocity with no enhanced resilience. These results caution against overly optimistic predictions that the presence of multiple social domains may in itself promote cooperation, and they help us better understand the complexity behind prosocial behavior in layered social systems.

  3. Study on the Cooperative E-commerce Model between Enterprises based on the Value Chain

    Institute of Scientific and Technical Information of China (English)

    XU Jun[1,2; LIU Xiaoxing[1

    2015-01-01

    The real e-commerce between enterprises is based on the internal departments of enterprises and the cooperative interaction between enterprise and its partners. In this paper, on the basis of the theory of value chain, 11 cooperative e-commerce models between enterprises have been classified according to the activities of the cooperation between enterprises, and then every cooperative e-commerce model between enterprises is discussed. In practice, cooperative e-commerce between enterprises can be a combination of one or more e-commerce models between enterprises.

  4. Microscopy of 2D Fermi gases. Exploring excitations and thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Morgener, Kai Henning

    2014-12-08

    This thesis presents experiments on three-dimensional (3D) and two-dimensional (2D) ultracold fermionic {sup 6}Li gases providing local access to microscopic quantum many-body physics. A broad magnetic Feshbach resonance is used to tune the interparticle interaction strength freely to address the entire crossover between the Bose-Einstein-Condensate (BEC) and Bardeen-Cooper-Schrieffer (BCS) regime. We map out the critical velocity in the crossover from BEC to BCS superfluidity by moving a small attractive potential through the 3D cloud. We compare the results with theoretical predictions and achieve quantitative understanding in the BEC regime by performing numerical simulations. Of particular interest is the regime of strong correlations, where no theoretical predictions exist. In the BEC regime, the critical velocity should be closely related to the speed of sound, according to the Landau criterion and Bogolyubov theory. We measure the sound velocity by exciting a density wave and tracking its propagation. The focus of this thesis is on our first experiments on general properties of quasi-2D Fermi gases. We realize strong vertical confinement by generating a 1D optical lattice by intersecting two blue-detuned laser beams under a steep angle. The large resulting lattice spacing enables us to prepare a single planar quantum gas deeply in the 2D regime. The first measurements of the speed of sound in quasi-2D gases in the BEC-BCS crossover are presented. In addition, we present preliminary results on the pressure equation of state, which is extracted from in-situ density profiles. Since the sound velocity is directly connected to the equation of state, the results provide a crosscheck of the speed of sound. Moreover, we benchmark the derived sound from available equation of state predictions, find very good agreement with recent numerical calculations, and disprove a sophisticated mean field approach. These studies are carried out with a novel apparatus which has

  5. Small groups and long memories promote cooperation.

    Science.gov (United States)

    Stewart, Alexander J; Plotkin, Joshua B

    2016-06-01

    Complex social behaviors lie at the heart of many of the challenges facing evolutionary biology, sociology, economics, and beyond. For evolutionary biologists the question is often how group behaviors such as collective action, or decision making that accounts for memories of past experience, can emerge and persist in an evolving system. Evolutionary game theory provides a framework for formalizing these questions and admitting them to rigorous study. Here we develop such a framework to study the evolution of sustained collective action in multi-player public-goods games, in which players have arbitrarily long memories of prior rounds of play and can react to their experience in an arbitrary way. We construct a coordinate system for memory-m strategies in iterated n-player games that permits us to characterize all cooperative strategies that resist invasion by any mutant strategy, and stabilize cooperative behavior. We show that, especially when groups are small, longer-memory strategies make cooperation easier to evolve, by increasing the number of ways to stabilize cooperation. We also explore the co-evolution of behavior and memory. We find that even when memory has a cost, longer-memory strategies often evolve, which in turn drives the evolution of cooperation, even when the benefits for cooperation are low.

  6. Game theory and public policy

    CERN Document Server

    McCain, Roger A

    2015-01-01

    This book provides a critical, selective review of concepts from game theory and their applications in public policy, and further suggests some modifications for some of the models (chiefly in cooperative game theory) to improve their applicability to economics and public policy.

  7. Cooperative Game Study of Airlines Based on Flight Frequency Optimization

    Directory of Open Access Journals (Sweden)

    Wanming Liu

    2014-01-01

    Full Text Available By applying the game theory, the relationship between airline ticket price and optimal flight frequency is analyzed. The paper establishes the payoff matrix of the flight frequency in noncooperation scenario and flight frequency optimization model in cooperation scenario. The airline alliance profit distribution is converted into profit distribution game based on the cooperation game theory. The profit distribution game is proved to be convex, and there exists an optimal distribution strategy. The results show that joining the airline alliance can increase airline whole profit, the change of negotiated prices and cost is beneficial to profit distribution of large airlines, and the distribution result is in accordance with aviation development.

  8. Social networks and cooperation in hunter-gatherers.

    Science.gov (United States)

    Apicella, Coren L; Marlowe, Frank W; Fowler, James H; Christakis, Nicholas A

    2012-01-25

    Social networks show striking structural regularities, and both theory and evidence suggest that networks may have facilitated the development of large-scale cooperation in humans. Here, we characterize the social networks of the Hadza, a population of hunter-gatherers in Tanzania. We show that Hadza networks have important properties also seen in modernized social networks, including a skewed degree distribution, degree assortativity, transitivity, reciprocity, geographic decay and homophily. We demonstrate that Hadza camps exhibit high between-group and low within-group variation in public goods game donations. Network ties are also more likely between people who give the same amount, and the similarity in cooperative behaviour extends up to two degrees of separation. Social distance appears to be as important as genetic relatedness and physical proximity in explaining assortativity in cooperation. Our results suggest that certain elements of social network structure may have been present at an early point in human history. Also, early humans may have formed ties with both kin and non-kin, based in part on their tendency to cooperate. Social networks may thus have contributed to the emergence of cooperation.

  9. Explaining cooperation in the finitely repeated simultaneous and sequential prisoner's dilemma game under incomplete and complete information

    NARCIS (Netherlands)

    Dijkstra, Jacob; van Assen, Marcel A. L. M.

    2017-01-01

    Explaining cooperation in social dilemmas is a central issue in behavioral science, and the prisoner's dilemma (PD) is the most frequently employed model. Theories assuming rationality and selfishness predict no cooperation in PDs of finite duration, but cooperation is frequently observed. We

  10. Moderate intra-group bias maximizes cooperation on interdependent populations.

    Directory of Open Access Journals (Sweden)

    Changbing Tang

    Full Text Available Evolutionary game theory on spatial structures has received increasing attention during the past decades. However, the majority of these achievements focuses on single and static population structures, which is not fully consistent with the fact that real structures are composed of many interactive groups. These groups are interdependent on each other and present dynamical features, in which individuals mimic the strategy of neighbors and switch their partnerships continually. It is however unclear how the dynamical and interdependent interactions among groups affect the evolution of collective behaviors. In this work, we employ the prisoner's dilemma game to investigate how the dynamics of structure influences cooperation on interdependent populations, where populations are represented by group structures. It is found that the more robust the links between cooperators (or the more fragile the links between cooperators and defectors, the more prevalent of cooperation. Furthermore, theoretical analysis shows that the intra-group bias can favor cooperation, which is only possible when individuals are likely to attach neighbors within the same group. Yet, interestingly, cooperation can be even inhibited for large intra-group bias, allowing the moderate intra-group bias maximizes the cooperation level.

  11. Consultation and cooperation in NATO: nuclear planning, 1975-1987

    Energy Technology Data Exchange (ETDEWEB)

    Chernoff, F.B.

    1987-01-01

    This study looks at three types of explanation of international cooperation, which deal in different ways with communication and consultation. Themost-general theoretical explanation contrasts recent realist theories, like those of Waltz and Gilpin, with Keohane's functional theory of regimes. Secondly, the study looks at theories of information flow and processing (an element of consultation) within the alliance, like those of Deutsch and Steinbruner. Such theories explain governmental behavior using concepts like equilibrium of systems and feedback loop. Third, the study considers hypotheses that deal specifically with NATO and military alliances. The hypotheses relate alliance consultation processes to the cooperativeness of the cases' outcomes. Evidence is drawn from case studies of NATO decision-making. The cases include politically sensitive deployment issues, like the enhanced radiation warhead controversy in 1977-78 and the intermediate-range nuclear force deployment decision in 1979, and important, but less politically volatile arms-control decisions, including the 1975 option three proposal, the French plan for a conference on disarmament in Europe, approved in 1980, and the 1987 American zero-zero proposal on short- and intermediate-range nuclear forces in Europe.

  12. Stability Analysis of R&D Cooperation in a Supply Chain

    Directory of Open Access Journals (Sweden)

    Luyun Xu

    2015-01-01

    Full Text Available R&D outsourcing becomes the often-adopted strategy for firms to innovate. However, R&D cooperation often ends up with failure because of its inherent quality of instability. One of the main reasons for cooperation failure is the opportunistic behavior. As the R&D contract between firms is inherently incomplete, opportunistic behavior always cannot be avoided in the collaborative process. R&D cooperation has been divided into horizontal and vertical types. This paper utilizes game theory to study opportunistic behavior in the vertical R&D cooperation and analyzes the equilibrium of the cooperation. Based on the equilibrium and numerical results, it is found that the vertical R&D cooperation is inherently unstable, and the downstream firm is more likely to break the agreement. The level of knowledge spillovers and the cost of R&D efforts have different effects on firms’ payoffs. When the level of knowledge spillover is low or the cost of R&D efforts is high, mechanisms such as punishment for opportunism may be more effective to guarantee the stability of cooperation.

  13. Cooperation Dynamics on Mobile Crowd Networks of Device-to-Device Communications

    Directory of Open Access Journals (Sweden)

    Yong Deng

    2016-01-01

    Full Text Available The explosive use of smart devices enabled the emergence of collective resource sharing among mobile individuals. Mobile users need to cooperate with each other to improve the whole network’s quality of service. By modeling the cooperative behaviors in a mobile crowd into an evolutionary Prisoner’s dilemma game, we investigate the relationships between cooperation rate and some main influence factors, including crowd density, communication range, temptation to defect, and mobility attributes. Using evolutionary game theory, our analysis on the cooperative behaviors of mobile takes a deep insight into the cooperation promotion in a dynamical network with selfish autonomous users. The experiment results show that mobile user’s features, including speed, moving probability, and reaction radius, have an obvious influence on the formation of a cooperative mobile social network. We also found some optimal status when the crowd’s cooperation rate reaches the best. These findings are important if we want to establish a mobile social network with a good performance.

  14. An approach for leukemia classification based on cooperative game theory.

    Science.gov (United States)

    Torkaman, Atefeh; Charkari, Nasrollah Moghaddam; Aghaeipour, Mahnaz

    2011-01-01

    Hematological malignancies are the types of cancer that affect blood, bone marrow and lymph nodes. As these tissues are naturally connected through the immune system, a disease affecting one of them will often affect the others as well. The hematological malignancies include; Leukemia, Lymphoma, Multiple myeloma. Among them, leukemia is a serious malignancy that starts in blood tissues especially the bone marrow, where the blood is made. Researches show, leukemia is one of the common cancers in the world. So, the emphasis on diagnostic techniques and best treatments would be able to provide better prognosis and survival for patients. In this paper, an automatic diagnosis recommender system for classifying leukemia based on cooperative game is presented. Through out this research, we analyze the flow cytometry data toward the classification of leukemia into eight classes. We work on real data set from different types of leukemia that have been collected at Iran Blood Transfusion Organization (IBTO). Generally, the data set contains 400 samples taken from human leukemic bone marrow. This study deals with cooperative game used for classification according to different weights assigned to the markers. The proposed method is versatile as there are no constraints to what the input or output represent. This means that it can be used to classify a population according to their contributions. In other words, it applies equally to other groups of data. The experimental results show the accuracy rate of 93.12%, for classification and compared to decision tree (C4.5) with (90.16%) in accuracy. The result demonstrates that cooperative game is very promising to be used directly for classification of leukemia as a part of Active Medical decision support system for interpretation of flow cytometry readout. This system could assist clinical hematologists to properly recognize different kinds of leukemia by preparing suggestions and this could improve the treatment of leukemic

  15. Use of cooperative game theory concepts for loss allocation in bilateral electricity markets

    International Nuclear Information System (INIS)

    Satyaramesh, P.V.; Radhakrishna, C.

    2009-01-01

    The deregulation of electricity markets has resulted in changes in electricity pricing. Participants in a deregulated market require a fair and equitable pricing structure that reflects both the share of power produced and consumed in the network, as well as the cost of power loss caused by users. This paper focused on the allocation of losses using the cooperative game theory (CGT) where many transactions take place in a bilateral electricity market environment. A set of approaches documented in literature in the areas of application of CGT were first identified and their applicability to allocations of losses in bilateral electricity markets were then reviewed. The allocation methods can be classified into 3 broad categories, namely classical, new, and variants of nucleolus. The structure of the game and the concept of fairness behind it were the 2 points that were examined in detail in this study. The allocation concept of these methods was systematically analyzed and compared. Calculations were performed on a six-bus system sample and a standard IEEE 14-bus system. The variants of nucleolus were shown to be among the most plausible concepts. The power losses for each transaction were calculated using a power flow procedure. 16 refs., 4 tabs., 1 fig.

  16. Use of cooperative game theory concepts for loss allocation in bilateral electricity markets

    Energy Technology Data Exchange (ETDEWEB)

    Satyaramesh, P.V. [AP Transco, Hyderabad, AP (India); Radhakrishna, C. [Global Energy Consulting Engineers Private Ltd., Hyderabad, AP (India)

    2009-07-01

    The deregulation of electricity markets has resulted in changes in electricity pricing. Participants in a deregulated market require a fair and equitable pricing structure that reflects both the share of power produced and consumed in the network, as well as the cost of power loss caused by users. This paper focused on the allocation of losses using the cooperative game theory (CGT) where many transactions take place in a bilateral electricity market environment. A set of approaches documented in literature in the areas of application of CGT were first identified and their applicability to allocations of losses in bilateral electricity markets were then reviewed. The allocation methods can be classified into 3 broad categories, namely classical, new, and variants of nucleolus. The structure of the game and the concept of fairness behind it were the 2 points that were examined in detail in this study. The allocation concept of these methods was systematically analyzed and compared. Calculations were performed on a six-bus system sample and a standard IEEE 14-bus system. The variants of nucleolus were shown to be among the most plausible concepts. The power losses for each transaction were calculated using a power flow procedure. 16 refs., 4 tabs., 1 fig.

  17. Ignorance Is Bliss, But for Whom? The Persistent Effect of Good Will on Cooperation

    Directory of Open Access Journals (Sweden)

    Mike Farjam

    2016-10-01

    Full Text Available Who benefits from the ignorance of others? We address this question from the point of view of a policy maker who can induce some ignorance into a system of agents competing for resources. Evolutionary game theory shows that when unconditional cooperators or ignorant agents compete with defectors in two-strategy settings, unconditional cooperators get exploited and are rendered extinct. In contrast, conditional cooperators, by utilizing some kind of reciprocity, are able to survive and sustain cooperation when competing with defectors. We study how cooperation thrives in a three-strategy setting where there are unconditional cooperators, conditional cooperators and defectors. By means of simulation on various kinds of graphs, we show that conditional cooperators benefit from the existence of unconditional cooperators in the majority of cases. However, in worlds that make cooperation hard to evolve, defectors benefit.

  18. The nature of crime : Is cheating necessary for cooperation?

    Science.gov (United States)

    Machalek, R; Cohen, L E

    1991-09-01

    The classical social theorist Emile Durkheim proposed the counterintuitive thesis that crime is beneficial for society because it provokes punishment, which enhances social solidarity. His logic, however, is blemished by a reified view of society that leads to group-selectionist thinking and a teleological account of the causes of crime. Reconceptualization of the relationship between crime and punishment in terms of evolutionary game theory, however, suggests that crime (cheating) may confer benefits on cooperating individuals by promoting stability in their patterns of cooperation.

  19. Cognitive strategies take advantage of the cooperative potential of heterogeneous networks

    International Nuclear Information System (INIS)

    Vukov, Jeromos; Santos, Francisco C; Pacheco, Jorge M

    2012-01-01

    Understanding the emergence and maintenance of cooperation is one of the most challenging topics of our time. Evolutionary game theory offers a very flexible framework within which to address this challenge. Here we use the prisoner's dilemma game to investigate the performance of individuals who are capable of adopting reactive strategies in communities structurally organized by means of Barabási-Albert scale-free networks. We find that basic cognitive abilities, such as the capability to distinguish their partners and act according to their previous actions, enable cooperation to thrive. This result is particularly significant whenever fear is the leading social tension, as this fosters retaliation, thus enforcing and sustaining cooperation. Being able to simultaneously reward fellow cooperators and punish defectors proves instrumental in achieving cooperation and the welfare of the community. As a result, central individuals can successfully lead the community and turn defective players into cooperative ones. Finally, even when participation costs—known to be detrimental to cooperation in scale-free networks—are explicitly included, we find that basic cognitive abilities have enough potential to help cooperation to prevail. (paper)

  20. Explaining cooperation in the finitely repeated simultaneous and sequential prisoner’s dilemma game under incomplete and complete information

    NARCIS (Netherlands)

    Dijkstra, Jacob; Van Assen, M.A.L.M.

    2017-01-01

    Explaining cooperation in social dilemmas is a central issue in behavioral science, and the prisoner’s dilemma (PD) is the most frequently employed model. Theories assuming rationality and selfishness predict no cooperation in PDs of finite duration, but cooperation is frequently observed. We

  1. Explaining cooperation in the finitely repeated simultaneous and sequential prisoner’s dilemma game under incomplete and complete information

    NARCIS (Netherlands)

    Dijkstra, Jacob; van Assen, Marcel A L M

    2016-01-01

    Explaining cooperation in social dilemmas is a central issue in behavioral science, and the prisoner’s dilemma (PD) is the most frequently employed model. Theories assuming rationality and selfishness predict no cooperation in PDs of finite duration, but cooperation is frequently observed. We

  2. Social networks and cooperation: a bibliometric study

    Directory of Open Access Journals (Sweden)

    Ana Paula Lopes

    2013-05-01

    Full Text Available The social network analysis involves social and behavioral science. The decentralization of productive activities, such as the formation of "network organizations" as a result of downsizing of large corporate structures of the past, marked by outsoucing and formation of alliances, shows the importance of this theme. The main objective of this paper is to analyze the theory of cooperation and social networks over a period of 24 years. For this, was performed a bibliometric study with content analysis. The database chosen for the initial sample search was ISI Web of Science. The search topics were “social network” and “cooperation”. Were analyzed 97 articles and their references, through networks of citations. The main identified research groups dealing with issues related to trust, strategic alliances, natural cooperation, game theory, social capital, intensity of interaction, reciprocity and innovation. It was found that the publications occurred in a large number of journals, which indicates that the theme is multidisciplinary, and only five journals published at least three articles. Although the first publication has occurred in 1987, was from 2006 that the publications effectively increased. The areas most related to the theme of the research were performance, evolution, management, graphics, model and game theory.

  3. Novel superfluids

    CERN Document Server

    Ketterson, John B

    This book reports on the latest developments in the field of Superfluidity. The phenomenon has had a tremendous impact on the fundamental sciences as well as a host of technologies. It began with the discovery of superconductivity in mercury in 1911, which was ultimately described theoretically by the theory of Bardeen Cooper and Schriever (BCS) in 1957. The analogous phenomena, superfluidity, was discovered in helium in 1938 and tentatively explained shortly thereafter as arising from a Bose-Einstein Condensation (BEC) by London. But the importance of superfluidity, and the range of systems in which it occurs, has grown enormously. In addition to metals and the helium liquids the phenomena has now been observed for photons in cavities, excitons in semiconductors, magnons in certain materials, and cold gasses trapped in high vacuum. It very likely exist for neutrons in a neutron star and, possibly, in a conjectured quark state at their center. Even the Universe itself can be regarded as being in a kind of sup...

  4. Elastic effects behind cooperative bonding inβ-sheets

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Nørskov, Jens Kehlet; Jacobsen, Karsten Wedel

    2004-01-01

    We present extensive density functional theory calculations of the bonding between strands in â-sheets. We identify a significant cooperative effect whereby the interaction increases in strength with the number of strands. We show that the effect is related to a coupling between interstrand bonding...

  5. Temperament and self-based correlates of cooperative, competitive and individualistic learning preferences.

    Science.gov (United States)

    Gocłowska, Małgorzata A; Aldhobaiban, Nawal; Elliot, Andrew J; Murayama, Kou; Kobeisy, Ahmed; Abdelaziz, Ashraf

    2017-06-01

    People vary in the extent to which they prefer cooperative, competitive or individualistic achievement tasks. In this research, we conducted two studies designed to investigate correlates and possible roots of these social interdependence orientations, namely approach and avoidance temperament, general self-efficacy, implicit theories of intelligence, and contingencies of self-worth based in others' approval, competition and academic competence. The results indicated that approach temperament, general self-efficacy and incremental theory were positively related, and entity theory was negatively related to cooperative preferences (|r| range from .11 to .41); approach temperament, general self-efficacy, competition contingencies and academic competence contingencies were positively related to competitive preferences (|r| range from .16 to .46); and avoidance temperament, entity theory, competitive contingencies and academic competence contingencies were positively related, and incremental theory was negatively related to individualistic preferences (|r| range from .09 to .15). The findings are discussed with regard to the meaning of each of the three social interdependence orientations, cultural differences among the observed relations and implications for practitioners. © 2015 International Union of Psychological Science.

  6. Game Theory for Wireless Sensor Networks: A Survey

    Science.gov (United States)

    Shi, Hai-Yan; Wang, Wan-Liang; Kwok, Ngai-Ming; Chen, Sheng-Yong

    2012-01-01

    Game theory (GT) is a mathematical method that describes the phenomenon of conflict and cooperation between intelligent rational decision-makers. In particular, the theory has been proven very useful in the design of wireless sensor networks (WSNs). This article surveys the recent developments and findings of GT, its applications in WSNs, and provides the community a general view of this vibrant research area. We first introduce the typical formulation of GT in the WSN application domain. The roles of GT are described that include routing protocol design, topology control, power control and energy saving, packet forwarding, data collection, spectrum allocation, bandwidth allocation, quality of service control, coverage optimization, WSN security, and other sensor management tasks. Then, three variations of game theory are described, namely, the cooperative, non-cooperative, and repeated schemes. Finally, existing problems and future trends are identified for researchers and engineers in the field. PMID:23012533

  7. Game Theory for Wireless Sensor Networks: A Survey

    Directory of Open Access Journals (Sweden)

    Ngai-Ming Kwok

    2012-07-01

    Full Text Available Game theory (GT is a mathematical method that describes the phenomenon of conflict and cooperation between intelligent rational decision-makers. In particular, the theory has been proven very useful in the design of wireless sensor networks (WSNs. This article surveys the recent developments and findings of GT, its applications in WSNs, and provides the community a general view of this vibrant research area. We first introduce the typical formulation of GT in the WSN application domain. The roles of GT are described that include routing protocol design, topology control, power control and energy saving, packet forwarding, data collection, spectrum allocation, bandwidth allocation, quality of service control, coverage optimization, WSN security, and other sensor management tasks. Then, three variations of game theory are described, namely, the cooperative, non-cooperative, and repeated schemes. Finally, existing problems and future trends are identified for researchers and engineers in the field.

  8. Fashion, Cooperation, and Social Interactions

    Science.gov (United States)

    Cao, Zhigang; Gao, Haoyu; Qu, Xinglong; Yang, Mingmin; Yang, Xiaoguang

    2013-01-01

    Fashion plays such a crucial rule in the evolution of culture and society that it is regarded as a second nature to the human being. Also, its impact on economy is quite nontrivial. On what is fashionable, interestingly, there are two viewpoints that are both extremely widespread but almost opposite: conformists think that what is popular is fashionable, while rebels believe that being different is the essence. Fashion color is fashionable in the first sense, and Lady Gaga in the second. We investigate a model where the population consists of the afore-mentioned two groups of people that are located on social networks (a spatial cellular automata network and small-world networks). This model captures two fundamental kinds of social interactions (coordination and anti-coordination) simultaneously, and also has its own interest to game theory: it is a hybrid model of pure competition and pure cooperation. This is true because when a conformist meets a rebel, they play the zero sum matching pennies game, which is pure competition. When two conformists (rebels) meet, they play the (anti-) coordination game, which is pure cooperation. Simulation shows that simple social interactions greatly promote cooperation: in most cases people can reach an extraordinarily high level of cooperation, through a selfish, myopic, naive, and local interacting dynamic (the best response dynamic). We find that degree of synchronization also plays a critical role, but mostly on the negative side. Four indices, namely cooperation degree, average satisfaction degree, equilibrium ratio and complete ratio, are defined and applied to measure people’s cooperation levels from various angles. Phase transition, as well as emergence of many interesting geographic patterns in the cellular automata network, is also observed. PMID:23382799

  9. Assortment of encounters and evolution of cooperativeness.

    Science.gov (United States)

    Eshel, I; Cavalli-Sforza, L L

    1982-02-01

    The method of evolutionary stable strategies (ESS), in its current form, is confronted with a difficulty when it tries to explain how some social behaviors initiate their evolution. We show that this difficulty may be removed by changing the assumption made tacitly in game theory (and in ESS) of randomness of meetings or encounters. In reality, such randomness seems to be rare in nature. Family, population and social structure, customs, and habits impose various types of deviation from randomness. Introducing nonrandomness of meeting in a way formally similar to assortative mating, we show that the bar to initial increase of inherited cooperative or altruistic behaviors can be removed, provided there is sufficient assortment of meetings. Family structure may cause contacts predominantly between certain types of relatives, and one can reconstruct some results of classical kin selection in terms of evolutionary stable strategy with assortative meetings. Neighbor effects and group selection might be similarly treated. Assortment need not be a passive consequence of population and social structure, but it can also be actively pursued. Behaviors favoring the choice of cooperative companions will have the effect of favoring the evolution of cooperativeness. It can be shown that discrimination in the choice of companions, especially if combined with assortment, can favor the development of cooperativeness, making initial increase of cooperative behavior possible even at levels of assortment passively imposed which would not be adequate, per se, to guarantee the increase of cooperativeness. It is possible that, in some cases, cooperativeness and behavior favoring some type of assortment are coselected.

  10. NetCooperate: a network-based tool for inferring host-microbe and microbe-microbe cooperation.

    Science.gov (United States)

    Levy, Roie; Carr, Rogan; Kreimer, Anat; Freilich, Shiri; Borenstein, Elhanan

    2015-05-17

    Host-microbe and microbe-microbe interactions are often governed by the complex exchange of metabolites. Such interactions play a key role in determining the way pathogenic and commensal species impact their host and in the assembly of complex microbial communities. Recently, several studies have demonstrated how such interactions are reflected in the organization of the metabolic networks of the interacting species, and introduced various graph theory-based methods to predict host-microbe and microbe-microbe interactions directly from network topology. Using these methods, such studies have revealed evolutionary and ecological processes that shape species interactions and community assembly, highlighting the potential of this reverse-ecology research paradigm. NetCooperate is a web-based tool and a software package for determining host-microbe and microbe-microbe cooperative potential. It specifically calculates two previously developed and validated metrics for species interaction: the Biosynthetic Support Score which quantifies the ability of a host species to supply the nutritional requirements of a parasitic or a commensal species, and the Metabolic Complementarity Index which quantifies the complementarity of a pair of microbial organisms' niches. NetCooperate takes as input a pair of metabolic networks, and returns the pairwise metrics as well as a list of potential syntrophic metabolic compounds. The Biosynthetic Support Score and Metabolic Complementarity Index provide insight into host-microbe and microbe-microbe metabolic interactions. NetCooperate determines these interaction indices from metabolic network topology, and can be used for small- or large-scale analyses. NetCooperate is provided as both a web-based tool and an open-source Python module; both are freely available online at http://elbo.gs.washington.edu/software_netcooperate.html.

  11. The difference between teamwork and compliance: The application of game theory to real-world research teams

    Energy Technology Data Exchange (ETDEWEB)

    Frank, J.R.

    1994-04-01

    This study explores the relationships between cooperation, teamwork, and game theory in actual multidisciplinary research teams. Two types of cooperation have been differentiated as ``compliance`` (cooperation, which is enforced by short-term interest) and ``teamwork`` (in which team members give up short-term gains for longer-term gains). ``Compliance`` is best explained by the Principal Agent Theory and is best applied to routine activities. ``Teamwork`` is best explained by a modification of Axelrod`s Theory of Cooperation and is best applied to problem-solving, non-routine activities. These exploratory findings have important implications for organizational structure considerations and management policies.

  12. RECENT THEORIES OF THE FIRM: A CRITICAL APPROACH

    Directory of Open Access Journals (Sweden)

    Pacala Anca

    2012-07-01

    Full Text Available Besides the classical theories of the firms as complete or incomplete contract theories, in the last decades there were developed some new theories bringing new perspectives and approaches. Among these new perspectives we are presenting in this paper the evolutionary theory of the firm, the importance of resources and knowledge, and game theory. According to evolutionary theory the most important element for a firm is the company itself and its specific assets (physical and human. Evolutionist theories, in their diversity, are interested in issues such as the effects of changes in the long run within the firms, in terms of products, processes, decisions, analysis of the determinants of success. Resource and knowledge -based theories try to find a common point between transactions and organizational management analysis, focusing on development issues within companies, the importance of business strategy and achieving competitive advantages. Finally, cooperative game theory sees the firm as a coalition of various parts that compose it, emphasizing the importance of cooperative relations between employees and shareholders, risk sharing and effective collective skills, knowledge and funds using.

  13. Cutthroat cooperation : The effects of team role decisions on adaptation to alternative reward structures

    NARCIS (Netherlands)

    Beersma, Bianca; Hollenbeck, John R.; Conlon, Donald E.; Humphrey, Stephen E.; Moon, Henry; Ilgen, Daniel R.

    Structural Adaptation Theory proposes that it is more difficult for teams to change from competitive to cooperative reward conditions than it is for them to change in the opposite direction, and this has been labeled the cutthroat cooperation effect [Johnson, M. D., Hollenbeck, J. R., Ilgen, D. R.,

  14. Cutthroat cooperation: the effects of team role decisions on adaptation to alternative reward structures

    NARCIS (Netherlands)

    Beersma, B.; Hollenbeck, J.R.; Conlon, D.E.; Humphrey, S.E.; Moon, H.; Ilgen, D.R.

    2009-01-01

    Structural Adaptation Theory proposes that it is more difficult for teams to change from competitive to cooperative reward conditions than it is for them to change in the opposite direction, and this has been labeled the cutthroat cooperation effect [Johnson, M. D., Hollenbeck, J. R., Ilgen, D. R.,

  15. A Short Study on Cooperative Sector in Iran. Challenges and Issues

    Directory of Open Access Journals (Sweden)

    Hassan Danaee Fard

    2010-10-01

    Full Text Available This paper aims to study the issues of cooperative sector in Iran. According to the theories,among the three sectors i.e. Public, private and cooperative sector probably cooperative sectorbecause of participating people directly in its process, can work better for economic development andcan be considered as a country economic developer example by job creation and others, Prior Workbecause Islam religion has invited people for having cooperation and also Iranian is a Muslim countrythen there have been a lot work on cooperative sector and this work is among the others who looks forthe challenges and issues in this sector, Approach this paper looks for the challenges and issues ofthe cooperative sector in Iran to run effective cooperation, Results Cooperative sector in alldeveloped and undeveloped and developing countries has its own challenges and in Iran as a fastdeveloping country which want to speed the developing process then needs to consider thecooperative sector challenges in Iran and other countries as well, Implications Practitioners,academician and others who want to work on challenges and issues of cooperative sector in Iran andothers . Value among the other important variables in economic development, cooperative has thepriority because of its fast returned effects in economic development then this paper aims to study thechallenges of this sector.

  16. Attitudes of Economics and Sociology Students towards Cooperation. A Cross-Cultural Study

    Directory of Open Access Journals (Sweden)

    Joanna Dzionek-Kozlowska

    2017-12-01

    Full Text Available The impact of university education on the learners’ attitudes remains uncertain. Nevertheless, the Economics students’ unwillingness to cooperate is frequently attributed to the content of economic courses, and the theories of profit maximization. This article contributes to the discussion on students’ attitudes towards cooperation based on the survey of 341 Polish and Romanian students. Since these countries differ in terms of collectivism/individualism dimension, we focus on tracing the influence of cultures on cooperativeness. Specifically, we investigate three variables. First, the impact of culture on the willingness to cooperate, secondly, the influence of gender on collaboration, and finally, the differences in attitudes among the students of Sociology and Economics. We find significant differences between Polish and Romanian students’ attitudes towards cooperation, we also observe higher level cooperation among females than males. We detect a drop in cooperation from the first year to the subsequent years of undergraduate studies in Economics.

  17. Theory of cooperation in a micro-organismal snowdrift game

    Science.gov (United States)

    Wang, Zhenyu; Goldenfeld, Nigel

    2011-08-01

    We present a mean-field model for the phase diagram of a community of micro-organisms, interacting through their metabolism so that they are, in effect, engaging in a cooperative social game. We show that as a function of the concentration of the nutrients glucose and histidine, the community undergoes a phase transition separating a state in which one strain is dominant to a state which is characterized by coexisting populations. Our results are in good agreement with recent experimental results, correctly reproducing quantitative trends and predicting the phase diagram.

  18. Incipient cognition solves the spatial reciprocity conundrum of cooperation.

    Directory of Open Access Journals (Sweden)

    Jeromos Vukov

    Full Text Available BACKGROUND: From the simplest living organisms to human societies, cooperation among individuals emerges as a paradox difficult to explain and describe mathematically, although very often observed in reality. Evolutionary game theory offers an excellent toolbar to investigate this issue. Spatial structure has been one of the first mechanisms promoting cooperation; however, alone it only opens a narrow window of viability. METHODOLOGY/PRINCIPAL FINDINGS: Here we equip individuals with incipient cognitive abilities, and investigate the evolution of cooperation in a spatial world where retaliation, forgiveness, treason and mutualism may coexist, as individuals engage in Prisoner's Dilemma games. In the model, individuals are able to distinguish their partners and act towards them based on previous interactions. We show how the simplest level of cognition, alone, can lead to the emergence of cooperation. CONCLUSIONS/SIGNIFICANCE: Despite the incipient nature of the individuals' cognitive abilities, cooperation emerges for unprecedented values of the temptation to cheat, being also robust to invasion by cheaters, errors in decision making and inaccuracy of imitation, features akin to many species, including humans.

  19. Cooperative strategies in the LNG industry: is the rationalisation argument grounded?

    International Nuclear Information System (INIS)

    Massol, O.; Tchung-Ming, St.

    2009-02-01

    The authors are commenting the emergence of cooperative strategies between 12 LNG (liquefied natural gas) exporting countries which are part of the Gas Exporting Countries Forum (GECF). In this economic study, they more particularly examine the often evoked scenario of a cooperation only aimed at a logistic rationalisation, which has no impact of LNG prices. Using a simple static model calibrated with data from 2007, they assess the benefit of this cooperation. Numerical results suggest that, in absence of a redistribution policy, this cooperative strategy is likely not to be adopted. Without any redistribution, choosing cooperation would not be rational for some exporters. The issue of sharing this collective benefit is then formulated by using concepts of the cooperative game theory. Several redistribution policies are then studied, including the Shapley value and several concepts based on the nucleolus. The results reveal a relatively restrained choice for the redistribution policy. Among the used methods, only the 'per capita nucleolus', a rather sophisticated one, matches the both desirable properties: to belong to the cooperative game core and a monotony with respect to the aggregate

  20. An Approach for Leukemia Classification Based on Cooperative Game Theory

    Directory of Open Access Journals (Sweden)

    Atefeh Torkaman

    2011-01-01

    Full Text Available Hematological malignancies are the types of cancer that affect blood, bone marrow and lymph nodes. As these tissues are naturally connected through the immune system, a disease affecting one of them will often affect the others as well. The hematological malignancies include; Leukemia, Lymphoma, Multiple myeloma. Among them, leukemia is a serious malignancy that starts in blood tissues especially the bone marrow, where the blood is made. Researches show, leukemia is one of the common cancers in the world. So, the emphasis on diagnostic techniques and best treatments would be able to provide better prognosis and survival for patients. In this paper, an automatic diagnosis recommender system for classifying leukemia based on cooperative game is presented. Through out this research, we analyze the flow cytometry data toward the classification of leukemia into eight classes. We work on real data set from different types of leukemia that have been collected at Iran Blood Transfusion Organization (IBTO. Generally, the data set contains 400 samples taken from human leukemic bone marrow. This study deals with cooperative game used for classification according to different weights assigned to the markers. The proposed method is versatile as there are no constraints to what the input or output represent. This means that it can be used to classify a population according to their contributions. In other words, it applies equally to other groups of data. The experimental results show the accuracy rate of 93.12%, for classification and compared to decision tree (C4.5 with (90.16% in accuracy. The result demonstrates that cooperative game is very promising to be used directly for classification of leukemia as a part of Active Medical decision support system for interpretation of flow cytometry readout. This system could assist clinical hematologists to properly recognize different kinds of leukemia by preparing suggestions and this could improve the treatment

  1. [Does co-operation research provide approaches to explain the changes in the German hospital market?].

    Science.gov (United States)

    Raible, C; Leidl, R

    2004-11-01

    The German hospital market faces an extensive process of consolidation. In this change hospitals consider cooperation as one possibility to improve competitiveness. To investigate explanations of changes in the German hospital market by theoretical approaches of cooperation research. The aims and mechanism of the theories, their relevance in terms of contents and their potential for empirical tests were used as criteria to assess the approaches, with current and future trends in the German hospital market providing the framework. Based on literature review, six theoretical approaches were investigated: industrial organization, transaction cost theory, game theory, resource dependency, institutional theory, and co-operative investment and finance theory. In addition, the data needed to empirically test the theories were specified. As a general problem, some of the theoretical approaches set a perfect market as a precondition. This precondition is not met by the heavily regulated German hospital market. Given the current regulations and the assessment criteria, industrial organization as well as resource-dependency and institutional theory approaches showed the highest potential to explain various aspects of the changes in the hospital market. So far, none of the approaches investigated provides a comprehensive and empirically tested explanation of the changes in the German hospital market. However, some of the approaches provide a theoretical background for part of the changes. As this dynamic market is economically of high significance, there is a need for further development and empirical testing of relevant theoretical approaches.

  2. The ecology of cooperative breeding behaviour.

    Science.gov (United States)

    Shen, Sheng-Feng; Emlen, Stephen T; Koenig, Walter D; Rubenstein, Dustin R

    2017-06-01

    Ecology is a fundamental driving force for the evolutionary transition from solitary living to breeding cooperatively in groups. However, the fact that both benign and harsh, as well as stable and fluctuating, environments can favour the evolution of cooperative breeding behaviour constitutes a paradox of environmental quality and sociality. Here, we propose a new model - the dual benefits framework - for resolving this paradox. Our framework distinguishes between two categories of grouping benefits - resource defence benefits that derive from group-defended critical resources and collective action benefits that result from social cooperation among group members - and uses insider-outsider conflict theory to simultaneously consider the interests of current group members (insiders) and potential joiners (outsiders) in determining optimal group size. We argue that the different grouping benefits realised from resource defence and collective action profoundly affect insider-outsider conflict resolution, resulting in predictable differences in the per capita productivity, stable group size, kin structure and stability of the social group. We also suggest that different types of environmental variation (spatial vs. temporal) select for societies that form because of the different grouping benefits, thus helping to resolve the paradox of why cooperative breeding evolves in such different types of environments. © 2017 John Wiley & Sons Ltd/CNRS.

  3. Near quantum limited amplification from inelastic Cooper-pair tunneling

    Science.gov (United States)

    Hofheinz, Max; Jebari, Salha; Blanchet, Florian; Grimm, Alexander; Hazra, Dibyendu; Albert, Romain; Portier, Fabien

    Josephson parametric amplifiers approach quantum-limited noise performance but require strong external microwave pump tones which make them more difficult to use than DC powered amplifiers: The pump tone can affect the device under test and requires expensive room-temperature equipment. Inelastic Cooper pair tunneling processes through a small DC voltage-biased Josephson junction, where a tunneling Cooper pair dissipates its energy 2 eV in the form of two photons are reminiscent of parametric down conversion. We show that these processes can be used to provide amplification near the quantum limit without external microwave pump tone. We explain the measured gain and noise based on the P (E) theory of inelastic Cooper pair tunneling and general fluctuation-dissipation relations.

  4. Team Learning: Through the Relational Dynamics of Co-operation and Rivalry in Team Communities

    Science.gov (United States)

    Lotz, Maja

    2010-01-01

    This paper explores the constructive links between cooperation, rivalry, and learning within the structure of team communities. Drawing upon social learning theory and qualitative data from case studies conducted in Danish team-based firms, the main purpose is to argue that both cooperation and rivalry are important triggers for mobilizing…

  5. Use of AECC Directives and Cooperative Learning Theory in Introductory Accounting Classes.

    Science.gov (United States)

    Holt, Doris L.; Swanson, Janice Goodnow

    1995-01-01

    Explores how colleges and universities are responding to the directives of the Accounting Education Change Commission for introductory accounting classes and whether these classrooms use cooperative learning techniques. (Author/JOW)

  6. Unto Others: Illustrating the Human Capacity for Cooperation

    Science.gov (United States)

    Morris, J. Andrew; Urbanski, John; Hunt, Jason

    2011-01-01

    Research in both evolutionary economics and evolutionary psychology provides strong evidence that human behavior can be, and is, a complex mix of hedonism and altruism with a strong inclination toward cooperation under certain conditions. In this article, behavioral assumptions made in mainstream business theory are compared and contrasted with…

  7. From the lab to the field: Cooperation among fishermen

    NARCIS (Netherlands)

    J.T.R. Stoop (Jan); C. Noussair (Charles); D.P. van Soest (Daan)

    2012-01-01

    textabstractWe conduct a field experiment to measure cooperation among groups of recreational fishermen at a privately owned fishing facility. Group earnings are greater when group members catch fewer fish. Consistent with classical economic theory, though in contrast to prior results from

  8. Cooperation Performance Evaluation between Seaport and Dry Port; Case of Qingdao Port and Xi'an Port

    Directory of Open Access Journals (Sweden)

    Jian Li

    2014-12-01

    Full Text Available Along with the drastic competition among ports, the strive for the vast economic hinterland and the supply of goods have become strategic problems for port operators. At the same time, port enterprises are paying more and more attention to the construction of dry ports. This article establishes the port cooperation performance evaluation index based on the balanced score card method and uses the grey relational degree method to evaluate the cooperation performance between seaports and dry ports. Finally using Qingdao port and Xi'an port as an example, and Zhengzhou port and Lanzhou port as benchmarks, the application of this evaluation method is introduced in detail. The conclusion reveals that cooperation between Qingdao port and Xi'an port has deficiencies in customer satisfaction, financial cooperation and non-market tools. Alongside this, the author proposes related issues about information management in the supply chain, competition position and the scope of hinterland. This article, combined with the related theory of supply chain and performance evaluation, puts forward a set of relatively complete cooperation performance evaluations between seaports and dry ports, which provide scientific theory support for better cooperation.

  9. Cellular image segmentation using n-agent cooperative game theory

    Science.gov (United States)

    Dimock, Ian B.; Wan, Justin W. L.

    2016-03-01

    Image segmentation is an important problem in computer vision and has significant applications in the segmentation of cellular images. Many different imaging techniques exist and produce a variety of image properties which pose difficulties to image segmentation routines. Bright-field images are particularly challenging because of the non-uniform shape of the cells, the low contrast between cells and background, and imaging artifacts such as halos and broken edges. Classical segmentation techniques often produce poor results on these challenging images. Previous attempts at bright-field imaging are often limited in scope to the images that they segment. In this paper, we introduce a new algorithm for automatically segmenting cellular images. The algorithm incorporates two game theoretic models which allow each pixel to act as an independent agent with the goal of selecting their best labelling strategy. In the non-cooperative model, the pixels choose strategies greedily based only on local information. In the cooperative model, the pixels can form coalitions, which select labelling strategies that benefit the entire group. Combining these two models produces a method which allows the pixels to balance both local and global information when selecting their label. With the addition of k-means and active contour techniques for initialization and post-processing purposes, we achieve a robust segmentation routine. The algorithm is applied to several cell image datasets including bright-field images, fluorescent images and simulated images. Experiments show that the algorithm produces good segmentation results across the variety of datasets which differ in cell density, cell shape, contrast, and noise levels.

  10. Robust Nash Dynamic Game Strategy for User Cooperation Energy Efficiency in Wireless Cellular Networks

    Directory of Open Access Journals (Sweden)

    Shuhuan Wen

    2012-01-01

    Full Text Available Recently, there is an emerging trend of addressing “energy efficiency” aspect of wireless communications. It has been shown that cooperating users relay each other's information to improve data rates. The energy is limited in the wireless cellular network, but the mobile users refuse to relay. This paper presents an approach that encourages user cooperation in order to improve the energy efficiency. The game theory is an efficient method to solve such conflicts. We present a cellular framework in which two mobile users, who desire to communicate with a common base station, may cooperate via decode-and-forward relaying. In the case of imperfect information assumption, cooperative Nash dynamic game is used between the two users' cooperation to tackle the decision making problems: whether to cooperate and how to cooperate in wireless networks. The scheme based on “cooperative game theory” can achieve general pareto-optimal performance for cooperative games, and thus, maximize the entire system payoff while maintaining fairness.

  11. Quantum mechanics and the second law of thermodynamics: an insight gleaned from magnetic hysteresis in the first order phase transition of an isolated mesoscopic-size type I superconductor

    International Nuclear Information System (INIS)

    Keefe, Peter D

    2012-01-01

    J Bardeen proposed that the adiabatic phase transition of mesoscopic-size type I superconductors must be accompanied by magnetic hysteresis in the critical magnetic field of sufficient magnitude to satisfy the second law of thermodynamics, herein referred to as ‘Bardeen Hysteresis’. Bardeen Hysteresis remains speculative in that it has not been reported in the literature. This paper investigates Bardeen Hysteresis as a possible accompaniment to the adiabatic phase transition of isolated mesoscopic-size type I superconductors and its implications with respect to the second law of thermodynamics. A causal mechanism for Bardeen Hysteresis is discussed which contrasts with the long accepted causal mechanism of magnetic hysteresis, as first summarized by Pippard, herein referred to as ‘Pippard Hysteresis’. The paper offers guidance for an experimental verification and comments on how the existence of Bardeen Hysteresis has relation to a quantum mechanical basis for the second law of thermodynamics.

  12. Quantum mechanics and the second law of thermodynamics: an insight gleaned from magnetic hysteresis in the first order phase transition of an isolated mesoscopic-size type I superconductor

    Science.gov (United States)

    Keefe, Peter D.

    2012-11-01

    J Bardeen proposed that the adiabatic phase transition of mesoscopic-size type I superconductors must be accompanied by magnetic hysteresis in the critical magnetic field of sufficient magnitude to satisfy the second law of thermodynamics, herein referred to as ‘Bardeen Hysteresis’. Bardeen Hysteresis remains speculative in that it has not been reported in the literature. This paper investigates Bardeen Hysteresis as a possible accompaniment to the adiabatic phase transition of isolated mesoscopic-size type I superconductors and its implications with respect to the second law of thermodynamics. A causal mechanism for Bardeen Hysteresis is discussed which contrasts with the long accepted causal mechanism of magnetic hysteresis, as first summarized by Pippard, herein referred to as ‘Pippard Hysteresis’. The paper offers guidance for an experimental verification and comments on how the existence of Bardeen Hysteresis has relation to a quantum mechanical basis for the second law of thermodynamics.

  13. Gauge-invariant cosmic structures---A dynamic systems approach

    International Nuclear Information System (INIS)

    Woszczyna, A.

    1992-01-01

    Gravitational instability is expressed in terms of the dynamic systems theory. The gauge-invariant Ellis-Bruni equation and Bardeen's equation are discussed in detail. It is shown that in an open universe filled with matter of constant sound velocity the Jeans criterion does not adequately define the length scale of the gravitational structure

  14. Effects of information asymmetry on cooperation in the prisoners' dilemma game

    International Nuclear Information System (INIS)

    Wang Xi-Peng; Wang Bing-Hong; Jiang Luo-Luo

    2012-01-01

    Effects of information asymmetry on cooperation in the prisoners' dilemma game are investigated. The amplitude A is introduced to describe the degree of information asymmetry. It is found that there exists an optimal value of amplitude A opt at which the fraction of cooperation reaches its maximal value. The reason lies in that cooperators on the two-dimensional grid form large clusters at A opt . In addition, the theoretical analysis in terms of the meanfield theory is used to understand this kind of phenomenon. It is confirmed that the information asymmetry plays an important role in the dynamics of the dilemma games of spatial prisoners. (general)

  15. Cooperative institutions for sustainable common pool resource management: Application to groundwater

    Science.gov (United States)

    Madani, Kaveh; Dinar, Ariel

    2012-09-01

    Beneficiaries of common pool resources (CPRs) may select available noncooperative and regulatory exogenous institutions for managing the resource, as well as cooperative management institutions. All these institutions may increase the long-term gains, prolong the life of the resource, and help to escape the tragedy of the commons trap. Cooperative game theory approaches can serve as the backbone of cooperative CPR management institutions. This paper formulates and applies several commonly used cooperative game theoretic solution concepts, namely, the core, Nash-Harsanyi, Shapley, and nucleolus. Through a numerical groundwater example, we show how CPR users can share the gains obtained from cooperation in a fair and efficient manner based on these cooperative solution concepts (management institutions). Although, based on their fairness rationales, various cooperative management institutions may suggest different allocations that are potentially acceptable to the users, these allocation solutions may not be stable as some users may find them unfair. This paper discusses how different methods, such as application of the plurality rule and power index, stability index, and propensity to disrupt concepts, can help identify the most stable and likely solutions for enforcing cooperation among the CPR beneficiaries. Furthermore, how the noncooperative managerial characteristics of the CPR users can affect the stability and acceptability of the different cooperative CPR management institutions is discussed, providing valuable policy insights for cooperative CPR management at community levels.

  16. Social capital: its role in cooperation dilemmas and the coordination of actions

    Directory of Open Access Journals (Sweden)

    René Millán

    2015-05-01

    Full Text Available This work sustains the thesis that the concept of social capital must be understood as an element that helps to solve dilemmas of collective action. The concept is theoretically and in practice useful as it can be related to social cooperation problems. To sustain that statement, I present first the problem of cooperation as a dilemma between individual interest —or maximization strategies— and collective action. It is sustained that social capital confirms that, contrary to game theory, cooperate is rational and convenient. Then, it is established how it is conceived the relationship between social capital and cooperation in Coleman, Putnam and Ostrom. It is stressed the formation of incentives to overcome dilemmas of collective action. Finally, I develop a criticism to the critics made to social capital in order to establish its possibilities in generalizing social cooperation.

  17. Competition and Cooperation: The Wisdom to Know When

    Science.gov (United States)

    Berg, Roberta Wiig

    2010-01-01

    Both competition and cooperation are as necessary in business as they are in other aspects of people's lives. Unfortunately, highly educated professionals do not always make wise decisions about when to do what; even when they know in theory that competition is counterproductive, they still "choose" to compete. Organizations would be better served…

  18. Profit allocation among rational players in a cooperative game under ...

    Indian Academy of Sciences (India)

    research was carried out in two ways on dynamic coalition formation. .... see in a cooperative business that if an agent participates with low quality product then .... solve this question we further need to develop the theory by some definitions.

  19. To cooperate or not to cooperate

    DEFF Research Database (Denmark)

    Wessels, Josepha Ivanka

    To Cooperate or not to Cooperate...? discusses results of a research project to study the rehabilitation of 1500-year old water tunnels, so called "qanats", in Syria. Communities all over the world are using traditional technologies to extract drinkingwater, irrigate their lands and feed...... their livestock. But these often sustainable and ancient ways to make use of groundwater are in rapid decline worldwide. A research project started in 1999 to study the rehabilitation of 1500-year old water tunnels called "qanats"in Syria. To Cooperate or not to Cooperate...? discusses results and outcomes...

  20. Improved Sparse Channel Estimation for Cooperative Communication Systems

    Directory of Open Access Journals (Sweden)

    Guan Gui

    2012-01-01

    Full Text Available Accurate channel state information (CSI is necessary at receiver for coherent detection in amplify-and-forward (AF cooperative communication systems. To estimate the channel, traditional methods, that is, least squares (LS and least absolute shrinkage and selection operator (LASSO, are based on assumptions of either dense channel or global sparse channel. However, LS-based linear method neglects the inherent sparse structure information while LASSO-based sparse channel method cannot take full advantage of the prior information. Based on the partial sparse assumption of the cooperative channel model, we propose an improved channel estimation method with partial sparse constraint. At first, by using sparse decomposition theory, channel estimation is formulated as a compressive sensing problem. Secondly, the cooperative channel is reconstructed by LASSO with partial sparse constraint. Finally, numerical simulations are carried out to confirm the superiority of proposed methods over global sparse channel estimation methods.

  1. Cooperation Dilemma in Finite Populations under Fluctuating Environments

    Science.gov (United States)

    Assaf, Michael; Mobilia, Mauro; Roberts, Elijah

    2013-12-01

    We present a novel approach allowing the study of rare events like fixation under fluctuating environments, modeled as extrinsic noise, in evolutionary processes characterized by the dominance of one species. Our treatment consists of mapping the system onto an auxiliary model, exhibiting metastable species coexistence, that can be analyzed semiclassically. This approach enables us to study the interplay between extrinsic and demographic noise on the statistics of interest. We illustrate our theory by considering the paradigmatic prisoner’s dilemma game, whose evolution is described by the probability that cooperators fixate the population and replace all defectors. We analytically and numerically demonstrate that extrinsic noise may drastically enhance the cooperation fixation probability and even change its functional dependence on the population size. These results, which generalize earlier works in population genetics, indicate that extrinsic noise may help sustain and promote a much higher level of cooperation than static settings.

  2. Design method of redundancy of brace-anchor sharing supporting based on cooperative deformation

    Science.gov (United States)

    Liu, Jun-yan; Li, Bing; Liu, Yan; Cai, Shan-bing

    2017-11-01

    Because of the complicated environment requirement, the support form of foundation pit is diversified, and the brace-anchor sharing support is widely used. However, the research on the force deformation characteristics and the related aspects of the cooperative response of the brace-anchor sharing support is insufficient. The application of redundancy theory in structural engineering has been more mature, but there is little theoretical research on redundancy theory in underground engineering. Based on the idea of collaborative deformation, the paper calculates the ratio of the redundancy degree of the cooperative deformation by using the local reinforcement design method and the structural component redundancy parameter calculation formula based on Frangopol. Combined with the engineering case, through the calculation of the ratio of cooperative deformation redundancy in the joint of brace-anchor sharing support. This paper explores the optimal anchor distribution form under the condition of cooperative deformation, and through the analysis and research of displacement field and stress field, the results of the collaborative deformation are validated by comparing the field monitoring data. It provides theoretical basis for the design of this kind of foundation pit in the future.

  3. The role of cooperatives in the Georgian wine industry

    Directory of Open Access Journals (Sweden)

    Kvariani Levani

    2015-01-01

    Full Text Available The potential of the Georgian wine industry is not fully utilized. High fragmentation of agricultural land leads to limited production that restricts farmers' access to capital resources, finances, and markets, and prevents further development of the Georgian wine industry. Grape collectors and wine makers need help to join their capital and efforts, to gain economies of scale in production and marketing by jointly accessing agricultural inputs. This study aims to identify the importance of farmer cooperatives for grape producers in the Georgian wine industry in order to overcome inefficiency in the sector. Furthermore, this research project investigates the barriers and driving forces of smallholder grape farmers or wine makers to join cooperatives. Semi-structured interviews were conducted with stakeholders of the Georgian wine industry in order to assess different perspectives on the importance and benefits of farmer cooperatives in the local context. The interview results permit economic analysis of transaction costs, agency theory and property rights in the context of the nascent cooperative movement in the Georgian wine industry. The interviews revealed that development of agriculture cooperatives in the Georgian wine industry is strongly dependent on both farmer enthusiasm and governmental support.1

  4. Accurately bearing measurement in non-cooperative passive location system

    International Nuclear Information System (INIS)

    Liu Zhiqiang; Ma Hongguang; Yang Lifeng

    2007-01-01

    The system of non-cooperative passive location based on array is proposed. In the system, target is detected by beamforming and Doppler matched filtering; and bearing is measured by a long-base-ling interferometer which is composed of long distance sub-arrays. For the interferometer with long-base-line, the bearing is measured accurately but ambiguously. To realize unambiguous accurately bearing measurement, beam width and multiple constraint adoptive beamforming technique is used to resolve azimuth ambiguous. Theory and simulation result shows this method is effective to realize accurately bearing measurement in no-cooperate passive location system. (authors)

  5. 75 FR 10319 - Cooper Tools-Sumter, Cooper Tools Divisions, a Subsidiary of Cooper Industries, Inc., Including...

    Science.gov (United States)

    2010-03-05

    ... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-71,602] Cooper Tools--Sumter, Cooper Tools Divisions, a Subsidiary of Cooper Industries, Inc., Including On-Site Leased Workers From... January 26, 2010, applicable to workers of Cooper Tools--Sumter, Cooper Tools Division, a subsidiary of...

  6. Cooperation and control in multiplayer social dilemmas

    Science.gov (United States)

    Hilbe, Christian; Wu, Bin; Traulsen, Arne; Nowak, Martin A.

    2014-01-01

    Direct reciprocity and conditional cooperation are important mechanisms to prevent free riding in social dilemmas. However, in large groups, these mechanisms may become ineffective because they require single individuals to have a substantial influence on their peers. However, the recent discovery of zero-determinant strategies in the iterated prisoner’s dilemma suggests that we may have underestimated the degree of control that a single player can exert. Here, we develop a theory for zero-determinant strategies for iterated multiplayer social dilemmas, with any number of involved players. We distinguish several particularly interesting subclasses of strategies: fair strategies ensure that the own payoff matches the average payoff of the group; extortionate strategies allow a player to perform above average; and generous strategies let a player perform below average. We use this theory to describe strategies that sustain cooperation, including generalized variants of Tit-for-Tat and Win-Stay Lose-Shift. Moreover, we explore two models that show how individuals can further enhance their strategic options by coordinating their play with others. Our results highlight the importance of individual control and coordination to succeed in large groups. PMID:25349400

  7. Reinforcement Learning Explains Conditional Cooperation and Its Moody Cousin.

    Directory of Open Access Journals (Sweden)

    Takahiro Ezaki

    2016-07-01

    Full Text Available Direct reciprocity, or repeated interaction, is a main mechanism to sustain cooperation under social dilemmas involving two individuals. For larger groups and networks, which are probably more relevant to understanding and engineering our society, experiments employing repeated multiplayer social dilemma games have suggested that humans often show conditional cooperation behavior and its moody variant. Mechanisms underlying these behaviors largely remain unclear. Here we provide a proximate account for this behavior by showing that individuals adopting a type of reinforcement learning, called aspiration learning, phenomenologically behave as conditional cooperator. By definition, individuals are satisfied if and only if the obtained payoff is larger than a fixed aspiration level. They reinforce actions that have resulted in satisfactory outcomes and anti-reinforce those yielding unsatisfactory outcomes. The results obtained in the present study are general in that they explain extant experimental results obtained for both so-called moody and non-moody conditional cooperation, prisoner's dilemma and public goods games, and well-mixed groups and networks. Different from the previous theory, individuals are assumed to have no access to information about what other individuals are doing such that they cannot explicitly use conditional cooperation rules. In this sense, myopic aspiration learning in which the unconditional propensity of cooperation is modulated in every discrete time step explains conditional behavior of humans. Aspiration learners showing (moody conditional cooperation obeyed a noisy GRIM-like strategy. This is different from the Pavlov, a reinforcement learning strategy promoting mutual cooperation in two-player situations.

  8. A robust cooperative spectrum sensing scheme based on Dempster-Shafer theory and trustworthiness degree calculation in cognitive radio networks

    Science.gov (United States)

    Wang, Jinlong; Feng, Shuo; Wu, Qihui; Zheng, Xueqiang; Xu, Yuhua; Ding, Guoru

    2014-12-01

    Cognitive radio (CR) is a promising technology that brings about remarkable improvement in spectrum utilization. To tackle the hidden terminal problem, cooperative spectrum sensing (CSS) which benefits from the spatial diversity has been studied extensively. Since CSS is vulnerable to the attacks initiated by malicious secondary users (SUs), several secure CSS schemes based on Dempster-Shafer theory have been proposed. However, the existing works only utilize the current difference of SUs, such as the difference in SNR or similarity degree, to evaluate the trustworthiness of each SU. As the current difference is only one-sided and sometimes inaccurate, the statistical information contained in each SU's historical behavior should not be overlooked. In this article, we propose a robust CSS scheme based on Dempster-Shafer theory and trustworthiness degree calculation. It is carried out in four successive steps, which are basic probability assignment (BPA), trustworthiness degree calculation, selection and adjustment of BPA, and combination by Dempster-Shafer rule, respectively. Our proposed scheme evaluates the trustworthiness degree of SUs from both current difference aspect and historical behavior aspect and exploits Dempster-Shafer theory's potential to establish a `soft update' approach for the reputation value maintenance. It can not only differentiate malicious SUs from honest ones based on their historical behaviors but also reserve the current difference for each SU to achieve a better real-time performance. Abundant simulation results have validated that the proposed scheme outperforms the existing ones under the impact of different attack patterns and different number of malicious SUs.

  9. The Impact of Cooperative Learning on CHC Students' Achievements and Its Changes over the Past Decade

    Science.gov (United States)

    Chen, Qiuxian; Liu, Yuan

    2017-01-01

    Informed by emergent learning theories and multiple evidenced benefits, cooperative learning has developed into a widely accepted organization mode of class in the Western context. For the same reason, cooperative learning is transferred, during the past decade, into classrooms of Confucian Heritage Culture (CHC) contexts. Concerns, however, are…

  10. Cooperative effects in spherical spasers: Ab initio analytical model

    Science.gov (United States)

    Bordo, V. G.

    2017-06-01

    A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which a shell/core contains an arbitrarily large number of active molecules in the vicinity of a metallic core/shell. An essential aspect of the theory is an ab initio account of the feedback from the core/shell boundaries which significantly modifies the molecular dynamics. The theory provides rigorous, albeit simple and physically transparent, criteria for both plasmonic superradiance and surface plasmon generation.

  11. Importance-truncated no-core shell model for fermionic many-body systems

    Energy Technology Data Exchange (ETDEWEB)

    Spies, Helena

    2017-03-15

    The exact solution of quantum mechanical many-body problems is only possible for few particles. Therefore, numerical methods were developed in the fields of quantum physics and quantum chemistry for larger particle numbers. Configuration Interaction (CI) methods or the No-Core Shell Model (NCSM) allow ab initio calculations for light and intermediate-mass nuclei, without resorting to phenomenology. An extension of the NCSM is the Importance-Truncated No-Core Shell Model, which uses an a priori selection of the most important basis states. The importance truncation was first developed and applied in quantum chemistry in the 1970s and latter successfully applied to models of light and intermediate mass nuclei. Other numerical methods for calculations for ultra-cold fermionic many-body systems are the Fixed-Node Diffusion Monte Carlo method (FN-DMC) and the stochastic variational approach with Correlated Gaussian basis functions (CG). There are also such method as the Coupled-Cluster method, Green's Function Monte Carlo (GFMC) method, et cetera, used for calculation of many-body systems. In this thesis, we adopt the IT-NCSM for the calculation of ultra-cold Fermi gases at unitarity. Ultracold gases are dilute, strongly correlated systems, in which the average interparticle distance is much larger than the range of the interaction. Therefore, the detailed radial dependence of the potential is not resolved, and the potential can be replaced by an effective contact interaction. At low energy, s-wave scattering dominates and the interaction can be described by the s-wave scattering length. If the scattering length is small and negative, Cooper-pairs are formed in the Bardeen-Cooper-Schrieffer (BCS) regime. If the scattering length is small and positive, these Cooper-pairs become strongly bound molecules in a Bose-Einstein-Condensate (BEC). In between (for large scattering lengths) is the unitary limit with universal properties. Calculations of the energy spectra

  12. Cooperation and defection at the crossroads.

    Science.gov (United States)

    Abramson, Guillermo; Semeshenko, Viktoriya; Iglesias, José Roberto

    2013-01-01

    We study a simple traffic model with a non-signalized road intersection. In this model the car arriving from the right has precedence. The vehicle dynamics far from the crossing are governed by the rules introduced by Nagel and Paczuski, which define how drivers behave when braking or accelerating. We measure the average velocity of the ensemble of cars and its flow as a function of the density of cars on the roadway. An additional set of rules is defined to describe the dynamics at the intersection assuming a fraction of drivers that do not obey the rule of precedence. This problem is treated within a game-theory framework, where the drivers that obey the rule are cooperators and those who ignore it are defectors. We study the consequences of these behaviors as a function of the fraction of cooperators and defectors. The results show that cooperation is the best strategy because it maximizes the flow of vehicles and minimizes the number of accidents. A rather paradoxical effect is observed: for any percentage of defectors the number of accidents is larger when the density of cars is low because of the higher average velocity.

  13. Towards a unified theory of reciprocity.

    Science.gov (United States)

    Rosas, Alejandro

    2012-02-01

    In a unified theory of human reciprocity, the strong and weak forms are similar because neither is biologically altruistic and both require normative motivation to support cooperation. However, strong reciprocity is necessary to support cooperation in public goods games. It involves inflicting costs on defectors; and though the costs for punishers are recouped, recouping costs requires complex institutions that would not have emerged if weak reciprocity had been enough.

  14. Cooperative strategies in the LNG industry: is the rationalisation argument grounded?; Strategies cooperatives dans l'industrie du GNL: l'argument de la rationalisation est-il fonde?

    Energy Technology Data Exchange (ETDEWEB)

    Massol, O.; Tchung-Ming, St

    2009-02-15

    The authors are commenting the emergence of cooperative strategies between 12 LNG (liquefied natural gas) exporting countries which are part of the Gas Exporting Countries Forum (GECF). In this economic study, they more particularly examine the often evoked scenario of a cooperation only aimed at a logistic rationalisation, which has no impact of LNG prices. Using a simple static model calibrated with data from 2007, they assess the benefit of this cooperation. Numerical results suggest that, in absence of a redistribution policy, this cooperative strategy is likely not to be adopted. Without any redistribution, choosing cooperation would not be rational for some exporters. The issue of sharing this collective benefit is then formulated by using concepts of the cooperative game theory. Several redistribution policies are then studied, including the Shapley value and several concepts based on the nucleolus. The results reveal a relatively restrained choice for the redistribution policy. Among the used methods, only the 'per capita nucleolus', a rather sophisticated one, matches the both desirable properties: to belong to the cooperative game core and a monotony with respect to the aggregate.

  15. Cooperation prevails when individuals adjust their social ties.

    Directory of Open Access Journals (Sweden)

    Francisco C Santos

    2006-10-01

    Full Text Available Conventional evolutionary game theory predicts that natural selection favours the selfish and strong even though cooperative interactions thrive at all levels of organization in living systems. Recent investigations demonstrated that a limiting factor for the evolution of cooperative interactions is the way in which they are organized, cooperators becoming evolutionarily competitive whenever individuals are constrained to interact with few others along the edges of networks with low average connectivity. Despite this insight, the conundrum of cooperation remains since recent empirical data shows that real networks exhibit typically high average connectivity and associated single-to-broad-scale heterogeneity. Here, a computational model is constructed in which individuals are able to self-organize both their strategy and their social ties throughout evolution, based exclusively on their self-interest. We show that the entangled evolution of individual strategy and network structure constitutes a key mechanism for the sustainability of cooperation in social networks. For a given average connectivity of the population, there is a critical value for the ratio W between the time scales associated with the evolution of strategy and of structure above which cooperators wipe out defectors. Moreover, the emerging social networks exhibit an overall heterogeneity that accounts very well for the diversity of patterns recently found in acquired data on social networks. Finally, heterogeneity is found to become maximal when W reaches its critical value. These results show that simple topological dynamics reflecting the individual capacity for self-organization of social ties can produce realistic networks of high average connectivity with associated single-to-broad-scale heterogeneity. On the other hand, they show that cooperation cannot evolve as a result of "social viscosity" alone in heterogeneous networks with high average connectivity, requiring the

  16. Cooperation in the prisoner's dilemma game on tunable community networks

    Science.gov (United States)

    Liu, Penghui; Liu, Jing

    2017-04-01

    Community networks have attracted lots of attention as they widely exist in the real world and are essential to study properties of networks. As the game theory illustrates the competitive relationship among individuals, studying the iterated prisoner's dilemma games (PDG) on community networks is meaningful. In this paper, we focus on investigating the relationship between the cooperation level of community networks and that of their communities in the prisoner's dilemma games. With this purpose in mind, a type of tunable community networks whose communities inherit not only the scale-free property, but also the characteristic of adjustable cooperation level of Holme and Kim (HK) networks is designed. Both uniform and non-uniform community networks are investigated. We find out that cooperation enhancement of communities can improve the cooperation level of the whole networks. Moreover, simulation results indicate that a large community is a better choice than a small community to improve the cooperation level of the whole networks. Thus, improving the cooperation level of community networks can be divided into a number of sub-problems targeting at improving the cooperation level of individual communities, which can save the computation cost and deal with the problem of improving the cooperation level of huge community networks. Moreover, as the larger community is a better choice, it is reasonable to start with large communities, according to the greedy strategy when the number of nodes can participate in the enhancement is limited.

  17. A Novel Optimal Joint Resource Allocation Method in Cooperative Multicarrier Networks: Theory and Practice

    Directory of Open Access Journals (Sweden)

    Yuan Gao

    2016-04-01

    Full Text Available With the increasing demands for better transmission speed and robust quality of service (QoS, the capacity constrained backhaul gradually becomes a bottleneck in cooperative wireless networks, e.g., in the Internet of Things (IoT scenario in joint processing mode of LTE-Advanced Pro. This paper focuses on resource allocation within capacity constrained backhaul in uplink cooperative wireless networks, where two base stations (BSs equipped with single antennae serve multiple single-antennae users via multi-carrier transmission mode. In this work, we propose a novel cooperative transmission scheme based on compress-and-forward with user pairing to solve the joint mixed integer programming problem. To maximize the system capacity under the limited backhaul, we formulate the joint optimization problem of user sorting, subcarrier mapping and backhaul resource sharing among different pairs (subcarriers for users. A novel robust and efficient centralized algorithm based on alternating optimization strategy and perfect mapping is proposed. Simulations show that our novel method can improve the system capacity significantly under the constraint of the backhaul resource compared with the blind alternatives.

  18. Competitive Centipede Games: Zero-End Payoffs and Payoff Inequality Deter Reciprocal Cooperation

    Directory of Open Access Journals (Sweden)

    Eva M. Krockow

    2015-08-01

    Full Text Available Reciprocal cooperation can be studied in the Centipede game, in which two players alternate in choosing between a cooperative GO move and a non-cooperative STOP move. GO sustains the interaction and increases the player pair’s total payoff while incurring a small personal cost; STOP terminates the interaction with a favorable payoff to the defector. We investigated cooperation in four Centipede games differing in their payoffs at the game’s end (positive versus zero and payoff difference between players (moderate versus high difference. The games shared the same game-theoretic solution, therefore they should have elicited identical decision patterns, according to orthodox game theory. Nevertheless, both zero-end payoffs and high payoff inequality were found to reduce cooperation significantly. Contrary to previous predictions, combining these two factors in one game resulted in a slight weakening of their independent deterrent effects. These findings show that small changes in the payoff function have large and significant effects on cooperation, and that the effects do not combine synergistically.

  19. An Exploratory Study of Cooperative Survival: Strategic Adaptation to External Developments

    Directory of Open Access Journals (Sweden)

    Jasper Grashuis

    2018-02-01

    Full Text Available Farmer cooperatives have been portrayed in the literature as flawed and complex organizations with ambiguous objectives. However, research on the observed survival of farmer cooperatives in spite of their weaknesses and limitations is scarce, in part because academic attention to cooperative performance has been static and introspective. Using evidence collected from case studies and print media publications, this paper contributes to the literature with a qualitative study of farmer cooperatives which spurred survival and longevity by means of strategic adaptation in response to four current developments in the external environment: industry consolidation, consumer segmentation, price volatility, and policy change. The qualitative study concludes farmer cooperatives in general respond to such developments by means of organizational growth. Common strategies are vertical integration, geographic expansion, and portfolio diversification. While survival and longevity are promoted in theory, strategic adaptation also often facilitates the pursuit of investor-oriented as opposed to user-oriented objectives. In some scenarios, member ownership and control may become burdensome to the business and prompt conversion to another structure if further adaptation to internal and external developments is unsuccessful. More research is therefore needed to explore the dynamic and variable impact of strategy on cooperative survival.

  20. The decline of cooperation, the rise of competition: developmental effects of long-term social change in Mexico.

    Science.gov (United States)

    García, Camilo; Rivera, Natanael; Greenfield, Patricia M

    2015-02-01

    Using Greenfield's theory of sociocultural change and human development as a point of departure, we carried out two experimental studies exploring the implications of decades of globalised social change in Mexico for children's development of cooperation and competition. In rural San Vicente, Baja California, the baseline was 1970 and the historical comparison took place 40 years later. In Veracruz, the baseline was 1985 and the historical comparison took place 20 years later. In Veracruz, children were tested in both rural and urban settings. We hypothesized that cooperative behavior would decrease in all three settings as a result of the sociocultural transformations of the past decades in Mexico. The Madsen Marble Pull Game was used to assess cooperative and competitive behavior. As predicted by Greenfield's theory of social change and human development, the Marble Pull procedure revealed a striking decrease over time in levels of cooperative behavior, with a corresponding rise in competitive behavior, in all three settings. © 2015 International Union of Psychological Science.

  1. About Ginzburg-Landau, and a bit on others

    International Nuclear Information System (INIS)

    Maksimov, Evgenii G

    2011-01-01

    This note is a brief history of how the theory of Ginzburg and Landau came to be. Early publications on the macroscopic theory of superconductivity are reviewed in detail. Discussions that the two co-authors had with their colleagues and between themselves are described. The 1952 review by V L Ginzburg is discussed, in which a number of well-defined requirements on the yet-to-be-developed microscopic theory of superconductivity were formulated, constituting what J Bardeen called the 'Ginzburg energy gap model'. (from the history of physics)

  2. Reputation formation and the evolution of cooperation in anonymous online markets

    NARCIS (Netherlands)

    Diekmann, Andreas; Jann, Ben; Przepiorka, Wojtek|info:eu-repo/dai/nl/413317617; Wehrli, Stefan

    Theoretical propositions stressing the importance of trust, reciprocity, and reputation for cooperation in social exchange relations are deeply rooted in classical sociological thought. Today's online markets provide a unique opportunity to test these theories using unobtrusive data. Our study

  3. Facilitating Cooperative Learning in Online and Blended Courses: An Example from an Integrated Marketing Communications Course

    Science.gov (United States)

    Johnson, Katryna

    2013-01-01

    Employers today expect that students will be able to work in teams. Cooperative learning theory addresses how skills such as decision making, problem solving and communication can be learned by individuals in group settings. This paper discusses how cooperative learning can be used in an online and blended environment to increase active learning…

  4. Separating conditional and unconditional cooperation in a sequential Prisoner’s Dilemma game

    Science.gov (United States)

    Mieth, Laura; Buchner, Axel

    2017-01-01

    Most theories of social exchange distinguish between two different types of cooperation, depending on whether or not cooperation occurs conditional upon the partner’s previous behaviors. Here, we used a multinomial processing tree model to distinguish between positive and negative reciprocity and cooperation bias in a sequential Prisoner’s Dilemma game. In Experiments 1 and 2, the facial expressions of the partners were varied to manipulate cooperation bias. In Experiment 3, an extinction instruction was used to manipulate reciprocity. The results confirm that people show a stronger cooperation bias when interacting with smiling compared to angry-looking partners, supporting the notion that a smiling facial expression in comparison to an angry facial expression helps to construe a situation as cooperative rather than competitive. Reciprocity was enhanced for appearance-incongruent behaviors, but only when participants were encouraged to form expectations about the partners’ future behaviors. Negative reciprocity was not stronger than positive reciprocity, regardless of whether expectations were manipulated or not. Experiment 3 suggests that people are able to ignore previous episodes of cheating as well as previous episodes of cooperation if these turn out to be irrelevant for predicting a partner’s future behavior. The results provide important insights into the mechanisms of social cooperation. PMID:29121671

  5. Cooperative unfolding of apolipoprotein A-1 induced by chemical denaturation.

    Science.gov (United States)

    Eckhardt, D; Li-Blatter, X; Schönfeld, H-J; Heerklotz, H; Seelig, J

    2018-05-25

    Apolipoprotein A-1 (Apo A-1) plays an important role in lipid transfer and obesity. Chemical unfolding of α-helical Apo A-1 is induced with guanidineHCl and monitored with differential scanning calorimetry (DSC) and CD spectroscopy. The unfolding enthalpy and the midpoint temperature of unfolding decrease linearly with increasing guanidineHCl concentration, caused by the weak binding of denaturant. At room temperature, binding of 50-60 molecules guanidineHCl leads to a complete Apo A-1 unfolding. The entropy of unfolding decreases to a lesser extent than the unfolding enthalpy. Apo A-1 chemical unfolding is a dynamic multi-state equilibrium that is analysed with the Zimm-Bragg theory modified for chemical unfolding. The chemical Zimm-Bragg theory predicts the denaturant binding constant K D and the protein cooperativity σ. Chemical unfolding of Apo A-1 is two orders of magnitude less cooperative than thermal unfolding. The free energy of thermal unfolding is ~0.2 kcal/mol per amino acid residue and ~1.0 kcal/mol for chemical unfolding at room temperature. The Zimm-Bragg theory calculates conformational probabilities and the chemical Zimm-Bragg theory predicts stretches of α-helical segments in dynamic equilibrium, unfolding and refolding independently and fast. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  6. Surrounding information consideration promotes cooperation in Prisoner’s dilemma game

    International Nuclear Information System (INIS)

    Shu, Gang; Du, Xia; Li, Ya

    2016-01-01

    Highlights: • A new method of strategy updating is proposed in the Prisoner’s dilemma game. • The stochastic players only consider their neighbor’s payoff and update strategy by classical Fermi rule. • The advanced player would consider not only the neighbor’s payoff but also the neighbors’ local surrounding information. • The simulation result illustrates that with the increase of advanced players in the network, the fraction of cooperation increases. - Abstract: Evolutionary game theory provides a useful, integrative framework for studying the evolution of cooperation. A new strategy updating method is proposed in our model. Due to people with diversified thinking, players are divided into two categories based on their different strategy updating method: ordinary players and advanced players. The former players only consider their neighbor’s payoff and updating strategy by classical Fermi rule, while the latter players take both the neighbors’ surrounding information and payoff into account. The results show that the neighbors surrounding information consideration contributes to the evolution of cooperation and finds the fraction of cooperation grows evidently with the increase of advanced players numbers. Our model may provide a pragmatic approach to the research of cooperation in social network.

  7. Modeling and performance analysis of cooperative communications in cognitive radio networks

    KAUST Repository

    Khabazian, Mehdi; Aissa, Sonia

    2011-01-01

    as well as to relay the primary's traffic in a cooperative fashion. Taking a queuing theory approach, we find the probability generating functions of the numbers of packets in the queues of the primary and secondary users. Subsequently, we determine a

  8. Models of conflict and cooperation

    CERN Document Server

    Gillman, Rick

    2009-01-01

    Models of Conflict and Cooperation is a comprehensive, introductory, game theory text for general undergraduate students. As a textbook, it provides a new and distinctive experience for students working to become quantitatively literate. Each chapter begins with a "dialogue" that models quantitative discourse while previewing the topics presented in the rest of the chapter. Subsequent sections develop the key ideas starting with basic models and ending with deep concepts and results. Throughout all of the sections, attention is given to promoting student engagement with the material through re

  9. When does inferring reputation probability countervail temptation in cooperative behaviors for the prisoners’ dilemma game?

    International Nuclear Information System (INIS)

    Dai, Yu; Lu, Peng

    2015-01-01

    In evolutionary games, the temptation mechanism reduces cooperation percentage while the reputation mechanism promotes it. Inferring reputation theory proposes that agent's imitating neighbors with the highest reputation takes place with a probability. Although reputation promotes cooperation, when and how it enhances cooperation is still a question. This paper investigates the condition where the inferring reputation probability promotes cooperation. Hence, the effects of reputation and temptation on cooperation are explored under the spatial prisoners’ dilemma game, utilizing the methods of simulation and statistical analysis. Results show that temptation reduces cooperation unconditionally while reputation promotes it conditionally, i.e. reputation countervails temptation conditionally. When the inferring reputation probability is less than 0.5, reputation promotes cooperation substantially and thus countervails temptation. However, when the inferring reputation probability is larger than 0.5, its contribution to cooperation is relatively weak and cannot prevent temptation from undermining cooperation. Reputation even decreases cooperation together with temptation when the probability is higher than 0.8. It should be noticed that inferring reputation does not always succeed to countervail temptation and there is a specific interval for it to promote cooperation

  10. The concepts of asymmetric and symmetric power can help resolve the puzzle of altruistic and cooperative behaviour.

    Science.gov (United States)

    Phillips, Tim

    2018-02-01

    Evolutionary theory predicts competition in nature yet altruistic and cooperative behaviour appears to reduce the ability to compete in order to help others compete better. This evolutionary puzzle is usually explained by kin selection where close relatives perform altruistic and cooperative acts to help each other and by reciprocity theory (i.e. direct, indirect and generalized reciprocity) among non-kin. Here, it is proposed that the concepts of asymmetry and symmetry in power and dominance are critical if we are ever to resolve the puzzle of altruism and cooperation towards non-kin. Asymmetry in power and dominance is likely to emerge under competition in nature as individuals strive to gain greater access to the scarce resources needed to survive and reproduce successfully. Yet asymmetric power presents serious problems for reciprocity theory in that a dominant individual faces a temptation to cheat in interactions with subordinates that is likely to far outweigh any individual selective benefits gained through reciprocal mechanisms. Furthermore, action taken by subordinates to deter non-reciprocation by dominants is likely to prove prohibitively costly to their fitness, making successful enforcement of reciprocal mechanisms unlikely. It is also argued here that many apparently puzzling forms of cooperation observed in nature (e.g. cooperative breeding in which unrelated subordinates help dominants to breed) might be best explained by asymmetry in power and dominance. Once it is recognized that individuals in these cooperative interactions are subject to the constraints and opportunities imposed on them by asymmetric power then they can be seen as pursuing a 'least bad' strategy to promote individual fitness - one that is nevertheless consistent with evolutionary theory. The concept of symmetric power also provides important insights. It can inhibit reciprocal mechanisms in the sense that symmetric power makes it easier for a cheat to appropriate common

  11. Organizational structure and leadership styles in Savings and Credit Cooperatives of Pichincha

    Directory of Open Access Journals (Sweden)

    Sandra Patricia Galarza Torres

    2017-07-01

    Full Text Available Leadership studies are of great interest to organizations and management scientists, because of the diversity of theories and models that have been perfected over time. The objective of this research is to qualitatively determine the leadership styles used by the managers of the Savings and Credit Cooperatives of Pichincha province, and to relate them to the organizational structures through which these institutions operate. The methodology was based on the application of surveys to managers of 60 cooperatives, taking as reference the variables raised by Bass and Avolio in their "Multifactorial Questionnaire on MLQ Leadership" and the organizational structure was obtained by another methodologies. It is concluded that in the cooperatives studied the styles used by managers are: transactional, transformational and Laissez Faire, the latter being the predominant in the organizational structures of cooperatives.

  12. Toward a Theory of Entrepreneurial Rents: a Simulation of the Market Process

    NARCIS (Netherlands)

    Keyhani, M; Levesque, M.; Madhok, A.

    2015-01-01

    While strategy theory relies heavily on equilibrium theories of economic rents such as Ricardian and monopoly rents, we do not yet have a comprehensive theory of disequilibrium or entrepreneurial rents. We use cooperative game theory to structure computer simulations of the market process in which

  13. Goldstone and Higgs Hydrodynamics in the BCS–BEC Crossover

    Directory of Open Access Journals (Sweden)

    Luca Salasnich

    2017-06-01

    Full Text Available We discuss the derivation of a low-energy effective field theory of phase (Goldstone and amplitude (Higgs modes of the pairing field from a microscopic theory of attractive fermions. The coupled equations for Goldstone and Higgs fields are critically analyzed in the Bardeen–Cooper–Schrieffer (BCS-to-Bose–Einstein condensate (BEC crossover—both in three spatial dimensions and in two spatial dimensions. The crucial role of pair fluctuations is investigated, and the beyond-mean-field Gaussian theory of the BCS–BEC crossover is compared with available experimental data of the two-dimensional ultracold Fermi superfluid.

  14. International cooperation

    International Nuclear Information System (INIS)

    2008-01-01

    In this chapter international cooperation of the Division for Radiation Safety, NPP Decommissioning and Radwaste Management of the VUJE, a. s. is presented. Very important is cooperation with the International Atomic Energy Agency. This cooperation has various forms - national and regional projects of technical cooperation, coordinated research activities, participation of our experts in preparation of the IAEA documentation etc.

  15. Complex Cooperative Strategies in Group-Territorial African Lions

    Science.gov (United States)

    Heinsohn, Robert; Packer, Craig

    1995-09-01

    Female lions (Panthera leo) showed persistent individual differences in the extent to which they participated in group-territorial conflict. When intergroup encounters were simulated by playback of aggressive vocalizations, some individuals consistently led the approach to the recorded intruder, whereas others lagged behind and avoided the risks of fighting. The lead females recognized that certain companions were laggards but failed to punish them, which suggests that cooperation is not maintained by reciprocity. Modification of the "odds" in these encounters revealed that some females joined the group response when they were most needed, whereas other lagged even farther behind. The complexity of these responses emphasizes the great diversity of individual behavior in this species and the inadequacy of current theory to explain cooperation in large groups.

  16. Intelligent cooperation: A framework of pedagogic practice in the operating room.

    Science.gov (United States)

    Sutkin, Gary; Littleton, Eliza B; Kanter, Steven L

    2018-04-01

    Surgeons who work with trainees must address their learning needs without compromising patient safety. We used a constructivist grounded theory approach to examine videos of five teaching surgeries. Attending surgeons were interviewed afterward while watching cued videos of their cases. Codes were iteratively refined into major themes, and then constructed into a larger framework. We present a novel framework, Intelligent Cooperation, which accounts for the highly adaptive, iterative features of surgical teaching in the operating room. Specifically, we define Intelligent Cooperation as a sequence of coordinated exchanges between attending and trainee that accomplishes small surgical steps while simultaneously uncovering the trainee's learning needs. Intelligent Cooperation requires the attending to accurately determine learning needs, perform real-time needs assessment, provide critical scaffolding, and work with the learner to accomplish the next step in the surgery. This is achieved through intense, coordinated verbal and physical cooperation. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Cooperation among liquefied natural gas suppliers. Is rationalization the sole objective?

    International Nuclear Information System (INIS)

    Massol, Olivier; Tchung-Ming, Stephane

    2010-01-01

    This paper examines the development of cooperative strategies between countries exporting Liquefied Natural Gas (LNG) and members of the Gas Exporting Countries Forum (GECF). This economic study focuses specifically on an often-raised scenario: the emergence of a cooperative approach designed with the sole aim of logistic rationalization, and which would not have any effect on LNG prices. We first assess the annual gains that may result from this market-power-free cooperative approach using a simple static transportation model. The numerical results obtained suggest that, in the absence of a gain redistribution policy, this cooperative strategy will probably not be adopted because cooperation would not be a rational move for some exporters. The problem of gain sharing is then formulated using cooperative game theory concepts. Several gain-sharing methods have been studied, including the Shapley value and various nucleolus-inspired concepts. Our results suggest that the choice of a redistribution policy appears relatively restricted. Out of the methods studied, only one - per capita nucleolus - satisfies two key requirements. core belonging and monotonicity (in the aggregate). Lastly, we look at how cooperation may give rise to a coordination cost and try to determine the maximum amount of this cost. In view of the low level of this amount and the relative complexity of the sharing method implemented, we consider that the credibility of a logistic cooperation scenario exempt from market power should be reappraised. (author)

  18. Cooperation among liquefied natural gas suppliers: Is rationalization the sole objective?

    International Nuclear Information System (INIS)

    MASSOL, Olivier; TCHUNG-MING, Stephane

    2009-01-01

    This paper examines the development of cooperative strategies between 12 countries exporting Liquefied Natural Gas (LNG) and belonging to the Gas Exporting Countries Forum (GECF). This economic study is more specifically focused on a scenario often raised: that of the emergence of a cooperative approach designed with the sole aim of logistic rationalization, and which would not have any effect on LNG prices. As this is a standard transportation problem, we first assess the gains that may result from this cooperative approach using a simple static model calibrated on the year 2007. The numerical results obtained suggest that, in the absence of a gain redistribution policy, this cooperative strategy will probably not be adopted because cooperation would not be a rational move for some exporters. The problem of gain sharing is then formulated using cooperative game theory concepts. Several gain sharing methods have been studied, including the Shapley value and various nucleolus-inspired concepts. Our results suggest that the choice of a redistribution policy appears relatively restricted. Out of the methods studied, only one - the per capita nucleolus - satisfies two key requirements: core belonging and mono-tonicity (in the aggregate). Lastly, coordination costs are considered and we determine the maximum amount that can be tolerated by such a cooperation. In view of the low level of this amount and the relative complexity of the sharing method implemented, we consider that the credibility of a logistic cooperation scenario exempt from market power should be reappraised. (authors)

  19. Cooperation among liquefied natural gas suppliers. Is rationalization the sole objective?

    Energy Technology Data Exchange (ETDEWEB)

    Massol, Olivier [Center for Economics and Management, IFP School, 228-232 av. Napoleon Bonaparte, F-92852 Rueil-Malmaison (France); Department of Economics, City University, Northampton Square, London EC1V 0HB (United Kingdom); Tchung-Ming, Stephane [Economic Studies Division, IFP, 1-4 av. de Bois-Preau, F-92852 Rueil Malmaison (France); CREDEN, Universite Montpellier I, Av. de la mer, BP 9606, F-34054, Montpellier (France)

    2010-07-15

    This paper examines the development of cooperative strategies between countries exporting Liquefied Natural Gas (LNG) and members of the Gas Exporting Countries Forum (GECF). This economic study focuses specifically on an often-raised scenario: the emergence of a cooperative approach designed with the sole aim of logistic rationalization, and which would not have any effect on LNG prices. We first assess the annual gains that may result from this market-power-free cooperative approach using a simple static transportation model. The numerical results obtained suggest that, in the absence of a gain redistribution policy, this cooperative strategy will probably not be adopted because cooperation would not be a rational move for some exporters. The problem of gain sharing is then formulated using cooperative game theory concepts. Several gain-sharing methods have been studied, including the Shapley value and various nucleolus-inspired concepts. Our results suggest that the choice of a redistribution policy appears relatively restricted. Out of the methods studied, only one - per capita nucleolus - satisfies two key requirements. core belonging and monotonicity (in the aggregate). Lastly, we look at how cooperation may give rise to a coordination cost and try to determine the maximum amount of this cost. In view of the low level of this amount and the relative complexity of the sharing method implemented, we consider that the credibility of a logistic cooperation scenario exempt from market power should be reappraised. (author)

  20. Multiple Vehicle Cooperative Localization with Spatial Registration Based on a Probability Hypothesis Density Filter

    Directory of Open Access Journals (Sweden)

    Feihu Zhang

    2014-01-01

    Full Text Available This paper studies the problem of multiple vehicle cooperative localization with spatial registration in the formulation of the probability hypothesis density (PHD filter. Assuming vehicles are equipped with proprioceptive and exteroceptive sensors (with biases to cooperatively localize positions, a simultaneous solution for joint spatial registration and state estimation is proposed. For this, we rely on the sequential Monte Carlo implementation of the PHD filtering. Compared to other methods, the concept of multiple vehicle cooperative localization with spatial registration is first proposed under Random Finite Set Theory. In addition, the proposed solution also addresses the challenges for multiple vehicle cooperative localization, e.g., the communication bandwidth issue and data association uncertainty. The simulation result demonstrates its reliability and feasibility in large-scale environments.

  1. A Test of Evolutionary Policing Theory with Data from Human Societies

    Science.gov (United States)

    Kümmerli, Rolf

    2011-01-01

    In social groups where relatedness among interacting individuals is low, cooperation can often only be maintained through mechanisms that repress competition among group members. Repression-of-competition mechanisms, such as policing and punishment, seem to be of particular importance in human societies, where cooperative interactions often occur among unrelated individuals. In line with this view, economic games have shown that the ability to punish defectors enforces cooperation among humans. Here, I examine a real-world example of a repression-of-competition system, the police institutions common to modern human societies. Specifically, I test evolutionary policing theory by comparing data on policing effort, per capita crime rate, and similarity (used as a proxy for genetic relatedness) among citizens across the 26 cantons of Switzerland. This comparison revealed full support for all three predictions of evolutionary policing theory. First, when controlling for policing efforts, crime rate correlated negatively with the similarity among citizens. This is in line with the prediction that high similarity results in higher levels of cooperative self-restraint (i.e. lower crime rates) because it aligns the interests of individuals. Second, policing effort correlated negatively with the similarity among citizens, supporting the prediction that more policing is required to enforce cooperation in low-similarity societies, where individuals' interests diverge most. Third, increased policing efforts were associated with reductions in crime rates, indicating that policing indeed enforces cooperation. These analyses strongly indicate that humans respond to cues of their social environment and adjust cheating and policing behaviour as predicted by evolutionary policing theory. PMID:21909429

  2. A test of evolutionary policing theory with data from human societies.

    Science.gov (United States)

    Kümmerli, Rolf

    2011-01-01

    In social groups where relatedness among interacting individuals is low, cooperation can often only be maintained through mechanisms that repress competition among group members. Repression-of-competition mechanisms, such as policing and punishment, seem to be of particular importance in human societies, where cooperative interactions often occur among unrelated individuals. In line with this view, economic games have shown that the ability to punish defectors enforces cooperation among humans. Here, I examine a real-world example of a repression-of-competition system, the police institutions common to modern human societies. Specifically, I test evolutionary policing theory by comparing data on policing effort, per capita crime rate, and similarity (used as a proxy for genetic relatedness) among citizens across the 26 cantons of Switzerland. This comparison revealed full support for all three predictions of evolutionary policing theory. First, when controlling for policing efforts, crime rate correlated negatively with the similarity among citizens. This is in line with the prediction that high similarity results in higher levels of cooperative self-restraint (i.e. lower crime rates) because it aligns the interests of individuals. Second, policing effort correlated negatively with the similarity among citizens, supporting the prediction that more policing is required to enforce cooperation in low-similarity societies, where individuals' interests diverge most. Third, increased policing efforts were associated with reductions in crime rates, indicating that policing indeed enforces cooperation. These analyses strongly indicate that humans respond to cues of their social environment and adjust cheating and policing behaviour as predicted by evolutionary policing theory.

  3. A test of evolutionary policing theory with data from human societies.

    Directory of Open Access Journals (Sweden)

    Rolf Kümmerli

    Full Text Available In social groups where relatedness among interacting individuals is low, cooperation can often only be maintained through mechanisms that repress competition among group members. Repression-of-competition mechanisms, such as policing and punishment, seem to be of particular importance in human societies, where cooperative interactions often occur among unrelated individuals. In line with this view, economic games have shown that the ability to punish defectors enforces cooperation among humans. Here, I examine a real-world example of a repression-of-competition system, the police institutions common to modern human societies. Specifically, I test evolutionary policing theory by comparing data on policing effort, per capita crime rate, and similarity (used as a proxy for genetic relatedness among citizens across the 26 cantons of Switzerland. This comparison revealed full support for all three predictions of evolutionary policing theory. First, when controlling for policing efforts, crime rate correlated negatively with the similarity among citizens. This is in line with the prediction that high similarity results in higher levels of cooperative self-restraint (i.e. lower crime rates because it aligns the interests of individuals. Second, policing effort correlated negatively with the similarity among citizens, supporting the prediction that more policing is required to enforce cooperation in low-similarity societies, where individuals' interests diverge most. Third, increased policing efforts were associated with reductions in crime rates, indicating that policing indeed enforces cooperation. These analyses strongly indicate that humans respond to cues of their social environment and adjust cheating and policing behaviour as predicted by evolutionary policing theory.

  4. Integrating Dynamic Mathematics Software into Cooperative Learning Environments in Mathematics

    Science.gov (United States)

    Zengin, Yilmaz; Tatar, Enver

    2017-01-01

    The aim of this study was to evaluate the implementation of the cooperative learning model supported with dynamic mathematics software (DMS), that is a reflection of constructivist learning theory in the classroom environment, in the teaching of mathematics. For this purpose, a workshop was conducted with the volunteer teachers on the…

  5. Finnish Cooperating Physics Teachers' Conceptions of Physics Teachers' Teacher Knowledge

    Science.gov (United States)

    Asikainen, Mervi A.; Hirvonen, Pekka E.

    2010-01-01

    This article examines Finnish cooperating physics teachers' conceptions of teacher knowledge in physics. Six experienced teachers were interviewed. The data was analyzed to form categories concerning the basis of teacher knowledge, and the tradition of German Didaktik and Shulman's theory of teacher knowledge were used in order to understand the…

  6. Cooperative Advertising in a Supply Chain with Horizontal Competition

    Directory of Open Access Journals (Sweden)

    Yi He

    2013-01-01

    Full Text Available Cooperative advertising programs are usually provided by manufacturers to stimulate retailers investing more in local advertising to increase the sales of their products or services. While previous literature on cooperative advertising mainly focuses on a “single-manufacturer single-retailer” framework, the decision-making framework with “multiple-manufacturer single-retailer” becomes more realistic because of the increasing power of retailers as well as the increased competition among the manufacturers. In view of this, in this paper we investigate the cooperative advertising program in a “two-manufacturer single-retailer” supply chain in three different scenarios; that is, (i each channel member makes decisions independently; (ii the retailer is vertically integrated with one manufacturer; (iii two manufacturers are horizontally integrated. Utilizing differential game theory, the open-loop equilibrium-advertising strategies of each channel member are obtained and compared. Also, we investigate the effects of competitive intensity on the firm’s profit in three different scenarios by using the numerical analysis.

  7. The game theory in thoracic surgery: from the intuitions of Luca Pacioli to the operating rooms management.

    Science.gov (United States)

    Ciocci, Argante; Viti, Andrea; Terzi, Alberto; Bertolaccini, Luca

    2015-11-01

    Game theory is a formal way to analyze the interactions among groups of subjects who behave each other. It has historically been of great interest in the economic fields in which decisions are made in a competitive environment. Game theory has fascinating potential if applied in the medical science. Few papers have been written about the application of game theory in surgery. The majority of scenarios of game theory in surgery fall into two main groups: cooperative and no cooperative games.

  8. Designing for cooperation - cooperating in design

    DEFF Research Database (Denmark)

    Kyng, Morten

    1991-01-01

    This article will discuss how to design computer applications that enhance the quality of work and products, and will relate the discussion to current themes in the field of Computer-Supported Cooperative Work (CSCW). Cooperation is a key element of computer use and work practice, yet here...... a specific "CSCW approach is not taken." Instead the focus is cooperation as an important aspect of work that should be integrated into most computer support efforts in order to develop successful computer support, however, other aspects such as power, conflict and control must also be considered....

  9. Cooperation, norms, and revolutions: a unified game-theoretical approach.

    Directory of Open Access Journals (Sweden)

    Dirk Helbing

    Full Text Available BACKGROUND: Cooperation is of utmost importance to society as a whole, but is often challenged by individual self-interests. While game theory has studied this problem extensively, there is little work on interactions within and across groups with different preferences or beliefs. Yet, people from different social or cultural backgrounds often meet and interact. This can yield conflict, since behavior that is considered cooperative by one population might be perceived as non-cooperative from the viewpoint of another. METHODOLOGY AND PRINCIPAL FINDINGS: To understand the dynamics and outcome of the competitive interactions within and between groups, we study game-dynamical replicator equations for multiple populations with incompatible interests and different power (be this due to different population sizes, material resources, social capital, or other factors. These equations allow us to address various important questions: For example, can cooperation in the prisoner's dilemma be promoted, when two interacting groups have different preferences? Under what conditions can costly punishment, or other mechanisms, foster the evolution of norms? When does cooperation fail, leading to antagonistic behavior, conflict, or even revolutions? And what incentives are needed to reach peaceful agreements between groups with conflicting interests? CONCLUSIONS AND SIGNIFICANCE: Our detailed quantitative analysis reveals a large variety of interesting results, which are relevant for society, law and economics, and have implications for the evolution of language and culture as well.

  10. Game Theory An Introduction

    CERN Document Server

    Barron, E N

    2008-01-01

    A fundamental introduction to modern game theory from a mathematical viewpoint. Game theory arises in almost every fact of human and inhuman interaction since oftentimes during these communications objectives are opposed or cooperation is viewed as an option. From economics and finance to biology and computer science, researchers and practitioners are often put in complex decision-making scenarios, whether they are interacting with each other or working with evolving technology and artificial intelligence. Acknowledging the role of mathematics in making logical and advantageous decisions, Game

  11. Collaborative Learning or Cooperative Learning? The Name Is Not Important; Flexibility Is

    Directory of Open Access Journals (Sweden)

    George M. Jacobs

    2015-06-01

    Full Text Available Abstract A great deal of theory and research, not to mention students’ and teachers’ practical experience, supports the use of group activities in education. Collaborative learning and cooperative learning are two terms commonly used in discussions of how and why to use group activities. This article looks at the issue of whether the two terms collaborative learning and cooperative learning are synonymous or whether they represent different conceptualisations of how and why students should interact as part of their learning. Those scholars who differentiate the two terms often see collaborative learning as more student centred and cooperative learning as a more teacher centred way to facilitate student-student interaction. The present article argues that collaborative and cooperative learning should be seen as synonymous student centric approaches, and that teachers and students, regardless of which of the two terms they use, should and will vary the ways they shape their learning environments in order to best facilitate the cognitive and affective benefits that student-student interaction offers. Keywords: Collaborative learning, cooperative learning, flexibility

  12. Egoism, altruism, and social justice : theory and experiments on cooperation in social dilemmas

    NARCIS (Netherlands)

    Vries, Sjerp de

    1991-01-01

    Cooperative or altruistic behavior in the absence of egoistic incentives is an issue that has puzzled many social scientists. In this book an attempt is made to gain more insight into such behavior for a specific type of situation: the social dilemma. ...

  13. Recent characterizations of generalized convexity in convexity in cooperative game thoery

    Energy Technology Data Exchange (ETDEWEB)

    Driessen, T.

    1994-12-31

    The notion of convexity for a real-valued function on the power set of the finite set N (the so-called cooperative game with player set N) is defined as in other mathematical fields. The study of convexity plays an important role within the field of cooperative game theory because the application of the solution part of game theory to convex games provides elegant results for the solution concepts involved. Especially, the well known solution concept called core is, for convex games, very well characterized. The current paper focuses on a notion of generalized convexity, called k- convexity, for cooperative n-person games. Due to very recent characterizations of convexity for cooperative games, the goal is to provide similar new characterizations of k-convexity. The main characterization states that for the k-convexity of an n-person game it is both necessary and sufficient that half of all the so-called marginal worth vectors belong to the core of the game. Here it is taken into account whether a marginal worth vector corresponds to an even or odd ordering of k elements of the n-person player set N. Another characterization of k-convexity is presented in terms of a so-called finite min-modular decomposition. That is, some specific cover game of a k-convex game can be decomposed as the minimum of a finite number of modular (or additive) games. Finally it is established that the k-convexity of a game can be characterized in terms of the second order partial derivates of the so-called multilinear extension of the game.

  14. A coalition formation game for transmitter cooperation in OFDMA uplink communications

    KAUST Repository

    Chelli, Ali; Tembine, Hamidou; Alouini, Mohamed-Slim

    2014-01-01

    the nodes is modelled using coalitional game theory. In this game, each coalition tries to maximize its utility in terms of rate. In the absence of cooperation cost, it can be shown that the grand coalition is sum-rate optimal and stable, i.e., the mobile

  15. Alternative banking: theory and evidence from Europe

    Directory of Open Access Journals (Sweden)

    Kurt Von Mettenheim

    2012-12-01

    Full Text Available Since financial liberalization in the 1980s, non-profit maximizing, stakeholder-oriented banks have outperformed private banks in Europe. This article draws on empirical research, banking theory and theories of the firm to explain this apparent anomaly for neo-liberal policy and contemporary market-based banking theory. The realization of competitive advantages by alternative banks (savings banks, cooperative banks and development banks has significant implications for conceptions of bank change, regulation and political economy.

  16. No place to hide: when shame causes proselfs to cooperate.

    Science.gov (United States)

    Declerck, Carolyn Henriette; Boone, Christophe; Kiyonari, Toko

    2014-01-01

    Shame is considered a social emotion with action tendencies that elicit socially beneficial behavior. Yet, unlike other social emotions, prior experimental studies do not indicate that incidental shame boosts prosocial behavior. Based on the affect as information theory, we hypothesize that incidental feelings of shame can increase cooperation, but only for self-interested individuals, and only in a context where shame is relevant with regards to its action tendency. To test this hypothesis, cooperation levels are compared between a simultaneous prisoner's dilemma (where "defect" may result from multiple motives) and a sequential prisoner's dilemma (where "second player defect" is the result of intentional greediness). As hypothesized, shame positively affected proselfs in a sequential prisoner's dilemma. Hence ashamed proselfs become inclined to cooperate when they believe they have no way to hide their greediness, and not necessarily because they want to make up for earlier wrong-doing.

  17. Assessing instructor intervention upon the perceptions, attitudes, and anxieties of community college biology students toward cooperative learning

    Science.gov (United States)

    Gafford, Kenneth Allen

    The differences between two experimental groups using cooperative learning activities were examined during the initial eight weeks of a biology course. While both groups participated in the same cooperative learning activities, only one group received deliberate instructor interventions. These interventions were designed to help students think positively about working in cooperative learning groups while alleviating anxiety toward cooperative learning. Initially, all students were uncomfortable and reported trouble staying focused during cooperative learning. The final quantitative results indicated that the group who received the interventions had more positive perceptions toward cooperative learning but their attitudes and anxiety levels showed no significant difference from the non-intervention group; advantages occurred specifically for thinking on task, student engagement, perceptions of task importance, and best levels of challenge and skill. Intervention participants had a higher mean score on the class exam administered during the eight-week study but it was not significantly different. Qualitative data revealed that the intervention participants experienced greater overall consequence, mainly in the areas of engagement, believed skill, and self-worth. According to flow theory, when students are actively engaged, the probability of distraction by fears and unrelated ideas is reduced, for instance, how they are perceived by others. These findings corroborate constructivist theories, particularly the ones relative to students working in cooperative groups. Researchers should continue to use appropriate methods to further explore how students of various abilities and developmental levels are affected by their perceptions, attitudes, and anxieties relative to different instructional contexts. Given the highly contextual nature of students' learning and motivation, researchers need to examine a number of meaningful questions by comparing students' perceptions

  18. Cooperation between parents and school nurses in primary schools: parents' perceptions.

    Science.gov (United States)

    Mäenpää, Tiina; Astedt-Kurki, Päivi

    2008-03-01

    Cooperation between pupils' parents and school nurses is an important part of health promotion in primary schools. Developing frank and trusting relationships contributes to easy and uninhibited cooperation. Cooperation between parents and school nurses has not been widely researched internationally. This article reports on parents' views on cooperation with school nurses in primary schools. The study aims at contributing to school nurses' work so that instead of focusing only on the children, family nursing approaches could be improved. Nineteen parents from 13 families from southern Finland were interviewed for the study in 2004. The data were analysed by grounded theory and the constant comparative method was utilized. Six concepts describing parents' views on cooperation were generated on the basis of the data. Cooperation consists of supporting the child's well-being. School nurses take children's and parents' concerns seriously and intervene effectively if the child's health is threatened. School nurses' expertise is not very visible within school communities. Hoping to receive information and desiring parental involvement are important concepts of cooperation with the school nurse. The child's family is not sufficiently known or taken holistically into consideration when the child's health is promoted. Parents are the initiators of cooperation within school health care and parents describe this by the concept of one-sided communication. Parents do not know about school nurses' work and school health services. They would like to be more involved in school nursing activities. When developing children's health services, parents' expertise in their children's well-being should be paid more attention. This study enhances the knowledge of family nursing by describing Finnish parents' perceptions of cooperation with school nurses. The findings facilitate the understanding of cooperation in school health services.

  19. Co-operative Education in the Pulp and Paper Sector in Quebec.

    Science.gov (United States)

    Savoie-Zajc, Lorraine; Dolbec, Andre

    2003-01-01

    A cooperative education program involved student practica in Quebec pulp and paper mills. Using the concept of community of practice and a typology of work experience, data from 175 students indicated that schools and workplaces placed traditional roles regarding theory and practice. Organizational cultures remained separate and opportunities for…

  20. Two-agent cooperative search using game models with endurance-time constraints

    Science.gov (United States)

    Sujit, P. B.; Ghose, Debasish

    2010-07-01

    In this article, the problem of two Unmanned Aerial Vehicles (UAVs) cooperatively searching an unknown region is addressed. The search region is discretized into hexagonal cells and each cell is assumed to possess an uncertainty value. The UAVs have to cooperatively search these cells taking limited endurance, sensor and communication range constraints into account. Due to limited endurance, the UAVs need to return to the base station for refuelling and also need to select a base station when multiple base stations are present. This article proposes a route planning algorithm that takes endurance time constraints into account and uses game theoretical strategies to reduce the uncertainty. The route planning algorithm selects only those cells that ensure the agent will return to any one of the available bases. A set of paths are formed using these cells which the game theoretical strategies use to select a path that yields maximum uncertainty reduction. We explore non-cooperative Nash, cooperative and security strategies from game theory to enhance the search effectiveness. Monte-Carlo simulations are carried out which show the superiority of the game theoretical strategies over greedy strategy for different look ahead step length paths. Within the game theoretical strategies, non-cooperative Nash and cooperative strategy perform similarly in an ideal case, but Nash strategy performs better than the cooperative strategy when the perceived information is different. We also propose a heuristic based on partitioning of the search space into sectors to reduce computational overhead without performance degradation.

  1. Modeling and performance analysis of cooperative communications in cognitive radio networks

    KAUST Repository

    Khabazian, Mehdi

    2011-09-01

    In this paper, we study the performance of a network comprised of a primary user and a secondary user with the latter having cognitive radio capabilities. The secondary node uses the empty slots of the primary user to transmit its own traffic as well as to relay the primary\\'s traffic in a cooperative fashion. Taking a queuing theory approach, we find the probability generating functions of the numbers of packets in the queues of the primary and secondary users. Subsequently, we determine a number of performance measures such as the average queues\\' lengths, average packet transmission delays and secondary user\\'s queue surcharge due to cooperation. The numerical results along with the simulations show the importance of controlling the number of primary user packets admitted by the secondary user for cooperation and its impacts on the other performance measures. © 2011 IEEE.

  2. Theory of cooperation in a micro-organismal snow-drift game

    Science.gov (United States)

    Wang, Zhenyu; Goldenfeld, Nigel

    2011-03-01

    We present a mean field model for the phase diagram of a community of micro-organisms, interacting through their metabolism so that they are, in effect, engaging in a cooperative social game. We show that as a function of the concentration of the nutrients glucose and histidine, the community undergoes a phase transition separating a state in which one strain is dominant to a state which is characterized by coexisting populations. Our results are in good agreement with recent experimental results, correctly predicting quantitative trends and the phase diagram. We thank Jeff Gore for sharing with us his experimental data. This work was supported in part by the National Science Foundation through grant number NSF-EF-0526747.

  3. Theory of coherent resonance energy transfer

    International Nuclear Information System (INIS)

    Jang, Seogjoo; Cheng, Y.-C.; Reichman, David R.; Eaves, Joel D.

    2008-01-01

    A theory of coherent resonance energy transfer is developed combining the polaron transformation and a time-local quantum master equation formulation, which is valid for arbitrary spectral densities including common modes. The theory contains inhomogeneous terms accounting for nonequilibrium initial preparation effects and elucidates how quantum coherence and nonequilibrium effects manifest themselves in the coherent energy transfer dynamics beyond the weak resonance coupling limit of the Foerster and Dexter (FD) theory. Numerical tests show that quantum coherence can cause significant changes in steady state donor/acceptor populations from those predicted by the FD theory and illustrate delicate cooperation of nonequilibrium and quantum coherence effects on the transient population dynamics.

  4. International cooperation

    International Nuclear Information System (INIS)

    1996-01-01

    In 1995, Nuclear Regulatory Authority of the Slovak Republic (NRA SR) ensured foreign cooperation particularly in the frame of the Slovak Republic is membership in the IAEA, as well as cooperation with the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD NEA), cooperation with European Union in the frame of PHARE programmes, and intergovernmental cooperation and cooperation among nuclear regulatory authorities. With respect to an international importance, prestige and a wide-scope possibilities of a technical assistance , either a direct one (expert assessments, technology supplies, work placement, scientific trips, training courses) or indirect one (participation at various conferences, seminars, technical committees, etc), the most important cooperation with the IAEA in Vienna. In 1994, the Slovak Republic, was elected to the Board Governors, the represent the group of Eastern European countries. The Slovak Government entrusted the NRA SR's Chairman with representing the Slovak Republic in the Board of Governors. Owing to a good name of Slovakia was elected to the one of two Vice-Chairmen of the Board of Governors at the 882-nd session on the Board. IAEA approved and developed 8 national projects for Slovakia in 1995. Generally, IAEA is contracting scientific contracts with research institutes, nuclear power plants and other organizations. Slovak organizations used these contracts as complementary funding of their tasks. In 1995, there were 12 scientific contracts in progress, or approved respectively. Other international activities of the NRA SR, international co-operations as well as foreign affairs are reported

  5. EU — Russia energy cooperation: major development trends and the present state

    Directory of Open Access Journals (Sweden)

    Romanova Tatyana

    2013-09-01

    Full Text Available The article analyzes the development of EU — Russia energy relations through the lens of the evolution of three parameters: the political agenda (the Energy Dialogue, the institutional structure, and the legal modalities. The identification of these three aspects for assessing the evolution of EU — Russia energy relations is the novelty in the author’s approach. This study aims to identify the previous stages and assess the current state of EU — Russia energy dialogue, since they set out conditions for energy cooperation in the Baltic Sea region. This research is based on a political and legal analysis of various documents and employs various international relations theories (including integration theories. The article demonstrates that the EU nd Russia have made a transition to the integration agenda manifested in the Energy Dialogue (its current goal is the creation of a common European energy market. The author describes the process of gradual consolidation of transgovernmental and transnational institutions, which leads to depoliticization of cooperation and mutual socialization of the partners. Finally, legal discussions on the development of common rules have become more constructive. In sum, the current situation in EU — Russia energy relations is favourable and positively affects cooperation in the Baltic Sea region.

  6. Gossip Versus Punishment: The Efficiency of Reputation to Promote and Maintain Cooperation

    Science.gov (United States)

    Wu, Junhui; Balliet, Daniel; Van Lange, Paul A. M.

    2016-01-01

    Prior theory suggests that reputation spreading (e.g., gossip) and punishment are two key mechanisms to promote cooperation in groups, but no behavioral research has yet examined their relative effectiveness and efficiency in promoting and maintaining cooperation. To examine these issues, we observed participants interacting in a four-round public goods game (PGG) with or without gossip and punishment options, and a subsequent two-round trust game (TG). We manipulated gossip as the option to send notes about other group members to these members’ future partners, and punishment as the option to assign deduction points to reduce other group members’ outcomes with a fee-to-fine ratio of 1:3. Findings revealed that in the four-round PGG, the option to gossip increased both cooperation and individual earnings, whereas the option to punish had no overall effect on cooperation (but a positive effect on cooperation in the last two rounds of the PGG) and significantly decreased individual earnings. Importantly, the initial option to gossip made people more trusting and trustworthy in the subsequent TG when gossip was no longer possible, compared to the no-gossip condition. Thus, we provide some initial evidence that gossip may be more effective and efficient than punishment to promote and maintain cooperation. PMID:27039896

  7. Gossip Versus Punishment: The Efficiency of Reputation to Promote and Maintain Cooperation.

    Science.gov (United States)

    Wu, Junhui; Balliet, Daniel; Van Lange, Paul A M

    2016-04-04

    Prior theory suggests that reputation spreading (e.g., gossip) and punishment are two key mechanisms to promote cooperation in groups, but no behavioral research has yet examined their relative effectiveness and efficiency in promoting and maintaining cooperation. To examine these issues, we observed participants interacting in a four-round public goods game (PGG) with or without gossip and punishment options, and a subsequent two-round trust game (TG). We manipulated gossip as the option to send notes about other group members to these members' future partners, and punishment as the option to assign deduction points to reduce other group members' outcomes with a fee-to-fine ratio of 1:3. Findings revealed that in the four-round PGG, the option to gossip increased both cooperation and individual earnings, whereas the option to punish had no overall effect on cooperation (but a positive effect on cooperation in the last two rounds of the PGG) and significantly decreased individual earnings. Importantly, the initial option to gossip made people more trusting and trustworthy in the subsequent TG when gossip was no longer possible, compared to the no-gossip condition. Thus, we provide some initial evidence that gossip may be more effective and efficient than punishment to promote and maintain cooperation.

  8. Distributed Cooperative Optimal Control for Multiagent Systems on Directed Graphs: An Inverse Optimal Approach.

    Science.gov (United States)

    Zhang, Huaguang; Feng, Tao; Yang, Guang-Hong; Liang, Hongjing

    2015-07-01

    In this paper, the inverse optimal approach is employed to design distributed consensus protocols that guarantee consensus and global optimality with respect to some quadratic performance indexes for identical linear systems on a directed graph. The inverse optimal theory is developed by introducing the notion of partial stability. As a result, the necessary and sufficient conditions for inverse optimality are proposed. By means of the developed inverse optimal theory, the necessary and sufficient conditions are established for globally optimal cooperative control problems on directed graphs. Basic optimal cooperative design procedures are given based on asymptotic properties of the resulting optimal distributed consensus protocols, and the multiagent systems can reach desired consensus performance (convergence rate and damping rate) asymptotically. Finally, two examples are given to illustrate the effectiveness of the proposed methods.

  9. On cooperative and efficient overlay network evolution based on a group selection pattern.

    Science.gov (United States)

    Nakao, Akihiro; Wang, Yufeng

    2010-04-01

    In overlay networks, the interplay between network structure and dynamics remains largely unexplored. In this paper, we study dynamic coevolution between individual rational strategies (cooperative or defect) and the overlay network structure, that is, the interaction between peer's local rational behaviors and the emergence of the whole network structure. We propose an evolutionary game theory (EGT)-based overlay topology evolution scheme to drive a given overlay into the small-world structure (high global network efficiency and average clustering coefficient). Our contributions are the following threefold: From the viewpoint of peers' local interactions, we explicitly consider the peer's rational behavior and introduce a link-formation game to characterize the social dilemma of forming links in an overlay network. Furthermore, in the evolutionary link-formation phase, we adopt a simple economic process: Each peer keeps one link to a cooperative neighbor in its neighborhood, which can slightly speed up the convergence of cooperation and increase network efficiency; from the viewpoint of the whole network structure, our simulation results show that the EGT-based scheme can drive an arbitrary overlay network into a fully cooperative and efficient small-world structure. Moreover, we compare our scheme with a search-based economic model of network formation and illustrate that our scheme can achieve the experimental and analytical results in the latter model. In addition, we also graphically illustrate the final overlay network structure; finally, based on the group selection model and evolutionary set theory, we theoretically obtain the approximate threshold of cost and draw the conclusion that the small value of the average degree and the large number of the total peers in an overlay network facilitate the evolution of cooperation.

  10. Trust in Effective International Business Cooperation: Mediating Effect of Work Engagement

    Directory of Open Access Journals (Sweden)

    Małgorzata Chrupała-Pniak

    2017-06-01

    Full Text Available Objective: This study aims to analyse the relationships between relational competence and its trust-building processes with individuals’ traits considered as psychological antecedents of inter-organizational relationships (IORs, outcomes. We hypothesize that organizational trust-building competence, situational trust, trust propensity, and autonomous motivation of cooperating teams and their managers influence IORs outcomes through work engagement of cooperating people. Research Design & Methods: We addressed 210 managers and 982 employees responsible for inter-organizational cooperation from medium and big companies. As explanatory model we adopted the job resources-demands (JR-D model. Correlation, regression, mediation analyses with bootstrapping, and structural equations modelling (SEM were used. Findings: Our analyses confirmed positive role of both organizational competences and psychological states of individuals, as valuable mediators in translating the potential of personal traits of teams and managers into IORs outcomes. Implications & Recommendations: As both psychological variables of people responsible for the course of IORs and relational competences of organizations play a vital role in reaching outcomes in IORs attention should be paid simultaneously to both aspects. Our findings highlight the necessity for interdisciplinary research in the field of IORs. Contribution & Value Added: We expose the multilevel and multifactor character of relationships between the antecedents of firms success in IORs, with the use of relationships theory in organization science, and theories proposed by psychology of work and organization.

  11. Applications of the Theory of Technical Systems

    DEFF Research Database (Denmark)

    Andreasen, Mogens Myrup; McAloone, Timothy Charles

    2008-01-01

    of Vladimir Hubka and a short historical sketch of the incidental nature of our group’s introduction to Vladimir Hubka, which led to life long cooperation and academic development. Results have been obtained in the areas of DFX, workbench-based design, mechatronics, product development, and multi......This paper uses the development and applications of Hubka’s Theory of Technical Systems (TTS) at DTU as an example of the power of the theory, the necessity of detailing and fitting the theory, and the role of a theory as a basis for research.At the same time the paper is a balance of the influence...

  12. Incentive Model Based on Cooperative Relationship in Sustainable Construction Projects

    Directory of Open Access Journals (Sweden)

    Guangdong Wu

    2017-07-01

    Full Text Available Considering the cooperative relationship between owners and contractors in sustainable construction projects, as well as the synergistic effects created by cooperative behaviors, a cooperative incentive model was developed using game theory. The model was formulated and analyzed under both non-moral hazard and moral hazard situations. Then, a numerical simulation and example were proposed to verify the conclusions derived from the model. The results showed that the synergistic effect increases the input intensity of one party’s resource transfer into the increase of marginal utility of the other party, thus the owner and contractor are willing to enhance their levels of effort. One party’s optimal benefit allocation coefficient is positively affected by its own output efficiency, and negatively affected by the other party’s output efficiency. The effort level and expected benefits of the owner and contractor can be improved by enhancing the cooperative relationship between the two parties, as well as enhancing the net benefits of a sustainable construction project. The synergistic effect cannot lower the negative effect of moral hazard behaviors during the implementation of sustainable construction projects. Conversely, the higher levels of the cooperative relationship, the wider the gaps amongst the optimal values under both non-moral hazard and moral hazard situations for the levels of effort, expected benefits and net project benefits. Since few studies to date have emphasized the effects of cooperative relationship on sustainable construction projects, this study constructed a game-based incentive model to bridge the gaps. This study contributes significant theoretical and practical insights into the management of cooperation amongst stakeholders, and into the enhancement of the overall benefits of sustainable construction projects.

  13. Design and Implementation of a Cooperative Learning System for Digital Content Design Curriculum: Investigation on Learning Effectiveness and Social Presence

    Science.gov (United States)

    Huang, Ming-Shang; Hsiao, Wei-Hung; Chang, Tsung-Sheng; Hu, Mei-Huei

    2012-01-01

    The purpose of this paper is to investigate the learning effectiveness of cooperative learning system based on social presence theory. We develop a web-based cooperative learning system which contains personal module, admin module, course module, communication module, and learning records module to support the implementation of cooperative…

  14. A Comparative Study on Cooperative Learning in Multimedia and Network Environment Used by English Majors between China Mainland and Taiwan

    Science.gov (United States)

    Xue, Gong; Lingling, Liu

    2018-01-01

    This paper first based on the theory of cooperative learning research. It analyses the characteristics and advantages of cooperative learning under the multimedia network environment. And then take China Three Gorges University and Taiwan I-Shou University English major students for example, using questionnaires and interviews to investigate the…

  15. International cooperation

    International Nuclear Information System (INIS)

    Prieto, F.E.

    1984-01-01

    It looks doubtless that the need for an international cooperation to solve the worldwide energy problems is already a concern of individuals, institutions, and governments. This is an improvement. But there is something lacking. The author refers to the Atoms for Peace speech, the origin of the IAEA and of the subsequent spreading of the nuclear option. He also refers back to the call made by the Mexican government for a worldwide energy cooperation. He stresses the need for governments to cooperate, so that this international cooperation on energy can be put into operation for the benefit of mankind

  16. Cooperation for a competitive position: The impact of hospital cooperation behavior on organizational performance.

    Science.gov (United States)

    Büchner, Vera Antonia; Hinz, Vera; Schreyögg, Jonas

    2015-01-01

    Several public policy initiatives, particularly those involving managed care, aim to enhance cooperation between partners in the health care sector because it is expected that such cooperation will reduce costs and generate additional revenue. However, empirical evidence regarding the effects of cooperation on hospital performance is scarce, particularly with respect to creating a comprehensive measure of cooperation behavior. The aim of this study is to investigate the impact of hospital cooperation behavior on organizational performance. We differentiate between horizontal and vertical cooperation using two alternative measures-cooperation depth and cooperation breadth-and include the interaction effects between both cooperation directions. Data are derived from a survey of German hospitals and combined with objective performance information from annual financial statements. Generalized linear regression models are used. The study findings provide insight into the nature of hospitals' cooperation behavior. In particular, we show that there are negative synergies between horizontal administrative cooperation behavior and vertical cooperation behavior. Whereas the depth and breadth of horizontal administrative cooperation positively affect financial performance (when there is no vertical cooperation), vertical cooperation positively affects financial performance (when there is no horizontal administrative cooperation) only when cooperation is broad (rather than deep). Horizontal cooperation is generally more effective than vertical cooperation at improving financial performance. Hospital managers should consider the negative interaction effect when making decisions about whether to recommend a cooperative relationship in a horizontal or vertical direction. In addition, managers should be aware of the limited financial benefit of cooperation behavior.

  17. Behavior of Collective Cooperation Yielded by Two Update Rules in Social Dilemmas: Combining Fermi and Moran Rules

    International Nuclear Information System (INIS)

    Xia Chengyi; Wang Lei; Wang Jinsong; Wang Juan

    2012-01-01

    We combine the Fermi and Moran update rules in the spatial prisoner's dilemma and snowdrift games to investigate the behavior of collective cooperation among agents on the regular lattice. Large-scale simulations indicate that, compared to the model with only one update rule, the cooperation behavior exhibits the richer phenomena, and the role of update dynamics should be paid more attention in the evolutionary game theory. Meanwhile, we also observe that the introduction of Moran rule, which needs to consider all neighbor's information, can markedly promote the aggregate cooperation level, that is, randomly selecting the neighbor proportional to its payoff to imitate will facilitate the cooperation among agents. Current results will contribute to further understand the cooperation dynamics and evolutionary behaviors within many biological, economic and social systems.

  18. Behavior of Collective Cooperation Yielded by Two Update Rules in Social Dilemmas: Combining Fermi and Moran Rules

    Science.gov (United States)

    Xia, Cheng-Yi; Wang, Lei; Wang, Juan; Wang, Jin-Song

    2012-09-01

    We combine the Fermi and Moran update rules in the spatial prisoner's dilemma and snowdrift games to investigate the behavior of collective cooperation among agents on the regular lattice. Large-scale simulations indicate that, compared to the model with only one update rule, the cooperation behavior exhibits the richer phenomena, and the role of update dynamics should be paid more attention in the evolutionary game theory. Meanwhile, we also observe that the introduction of Moran rule, which needs to consider all neighbor's information, can markedly promote the aggregate cooperation level, that is, randomly selecting the neighbor proportional to its payoff to imitate will facilitate the cooperation among agents. Current results will contribute to further understand the cooperation dynamics and evolutionary behaviors within many biological, economic and social systems.

  19. Choosing the cooperative option

    Energy Technology Data Exchange (ETDEWEB)

    English, G. (National Rural Electric Cooperative Association (United States))

    1999-06-01

    Cooperatives do not ask to be exempted from the law. They do ask that laws and regulations be designed to allow them to meet the needs of their consumer-owners in accordance with cooperative principles, at a time that the marginal consumers being abandoned by for-profit utilities may be ready to gravitate toward cooperatives. The cooperative principles are worth reviewing because they explain the focus on the consumer and the cooperative concept of service: cooperatives are voluntary organizations, open to all persons able to use their services and willing to accept the responsibilities of membership; cooperatives are democratic organizations controlled by their members, who actively participate in setting policies and making decisions, the elected representatives are accountable to the membership; members contribute equitably to, and democratically control, the capital of their cooperative; cooperatives are autonomous, self-help organizations controlled by their members, if they enter into agreements with other organizations, including governments, they do so on terms that ensure democratic control by their members and maintain their cooperative autonomy; cooperatives provide education and training for their members, elected representatives, managers, and employees so they can contribute effectively to the development of their cooperatives, they inform the general public, particularly young people and opinion leaders, about the nature and benefits of cooperation; cooperatives serve their members most effectively and strength the cooperative movement by working together through local, national, regional, and international structures; and while focusing on member needs, cooperatives work for the sustainable development of their communities through policies accepted by their members.

  20. International co-operation

    International Nuclear Information System (INIS)

    1998-01-01

    In this part the are reviewed: Co-operation with IAEA; Participation of the Slovakia on the 41 st session of the General Conference; The comprehensive Nuclear-Test-Ban Treaty Organization; Co-operation with the Organization for Economic Co-operation and Development; co-operation with the European Commission; Fulfillment of obligations resulting from the international contracting documents

  1. Imitating winner or sympathizing loser? Quadratic effects on cooperative behavior in prisoners' dilemma games

    Science.gov (United States)

    Lu, Peng

    2015-10-01

    Cooperation is vital in human societies and therefore is widely investigated in the evolutionary game theory. Varieties of mechanisms have been proposed to overcome temptation and promote cooperation. Existing studies usually believe that agents are rational, but irrationalism such as emotions and feelings matters as well. Winner and loser are defined by their payoffs. In addition to admiring and imitating winners, the mechanism of sympathizing and imitating losers is introduced into the model as an alternative action rule, and each one plays the prisoners' dilemma game with eight neighbors under the influence of both irrationalism and rationalism. Rationalism refers to imitating winner to get highest payoff, and irrationalism means that people sympathize and adopt the actions of losers. As it is widely recognized that temptation reduces cooperation, this study focuses on the effect of sympathy on cooperation within a certain group or society. If it overcomes temptation that leads to defection, sympathy will be a powerful mechanism to promote cooperative behavior. Simulation results indicate that sympathy and temptation shares similar quadratic relationships with cooperation. Both sympathy and temptation undermine cooperation below their thresholds, and they both promote cooperation above their thresholds. Temptation not only reduces cooperation but also promote it as temptation goes beyond the threshold. Although sympathy is a good merit or human nature that is beneficial to society, a crisis or collapse of cooperation is inevitable when the sympathy propensity is relatively smaller. After cooperation reaches a minimal bottom, it then rises increasingly and dramatically, which brings a much brighter future of the society.

  2. Third-party punishment increases cooperation in children through (misaligned) expectations and conditional cooperation.

    Science.gov (United States)

    Lergetporer, Philipp; Angerer, Silvia; Glätzle-Rützler, Daniela; Sutter, Matthias

    2014-05-13

    The human ability to establish cooperation, even in large groups of genetically unrelated strangers, depends upon the enforcement of cooperation norms. Third-party punishment is one important factor to explain high levels of cooperation among humans, although it is still somewhat disputed whether other animal species also use this mechanism for promoting cooperation. We study the effectiveness of third-party punishment to increase children's cooperative behavior in a large-scale cooperation game. Based on an experiment with 1,120 children, aged 7 to 11 y, we find that the threat of third-party punishment more than doubles cooperation rates, despite the fact that children are rarely willing to execute costly punishment. We can show that the higher cooperation levels with third-party punishment are driven by two components. First, cooperation is a rational (expected payoff-maximizing) response to incorrect beliefs about the punishment behavior of third parties. Second, cooperation is a conditionally cooperative reaction to correct beliefs that third party punishment will increase a partner's level of cooperation.

  3. Failures of Corporate Governance in Housing Cooperatives – Case Study

    Directory of Open Access Journals (Sweden)

    Waldemar Walczak

    2013-09-01

    Full Text Available Purpose: The purpose of this paper is a discussion and in-depth analysis of the legal and organizational circumstances associated with the activities of Supervisory Boards in housing cooperatives.Methodology: A critical analysis of the existing legislation, own analytical analysis of the source documents, supplemented by conclusions and observations formulated on the basis of a case study, for the preparation of which information has been used obtained from primary sources in the form of documents of the analyzed housing cooperative and information obtained through participant observation.Findings: What has a decisive impact on the mechanisms of corporate governance in housing cooperatives are the direct behaviors of Supervisory Board members, as well as the lack of awareness and involvement of the residents, who do not want to actively participate in the life of the cooperative. A diagnosis is presented of the most important factors that infl uence the actual operations of the analyzed Supervisory Board. While the current legal regulations make it possible to ensure effective and proper control as well as adequate supervision over the activities of cooperatives.Originality: The paper enriches the theory of management sciences in terms of a wider perception of the term corporate governance in relation to other organizations than companies. The presented methodological approach that is the basis for a comprehensive and thorough inspection of the activities of the Management Board can be used in other cooperatives as well. In the literature on the subject no similar analysis, supported by the results of own analytical research, had been found.

  4. Educational Interpretations of General Systems Theory.

    Science.gov (United States)

    Hug, William E.; King, James E.

    This chapter discusses General Systems Theory as it applies to education, classrooms, innovations, and instructional design. The principles of equifinality, open and closed systems, the individual as the key system, hierarchical structures, optimization, stability, cooperation, and competition are discussed, and their relationship to instructional…

  5. The Effects of Temperature Priming on Cooperation in the Iterated Prisoner's Dilemma

    Directory of Open Access Journals (Sweden)

    Simon Storey

    2013-01-01

    Full Text Available Based on initial research findings by Williams and Bargh (2008 and Kang, Williams, Clark, Gray and Bargh (2011 on the interaction between interpersonal and physical warmth, theoretical models such as cognitive scaffolding and the importance of evaluations of interpersonal warmth in trust-based decisions, this experiment investigated the effect of temperature priming on 30 pairs of British university students with hot and cold objects on frequency of cooperation in a game of iterated Prisoner's Dilemma. Participants were found to cooperate significantly more frequently when primed with hot objects than with cold objects, supporting the assertion that physical warmth sensation positively affects interpersonal trust evaluation. No support was found for the prediction that male-male pairs would cooperate less than female-female pairs. The implications of these findings to evolutionary and developmental theories of interpersonal warmth are discussed.

  6. An analysis of the transformational leadership theory | Moradi ...

    African Journals Online (AJOL)

    An analysis of the transformational leadership theory. ... at all levels of the organization also feel the need to cooperate with others to achieve the desired results. ... intellectual stimulation; inspirational motivation; personal considerations ...

  7. Toward a behavioural theory of cooperation between managers and employee representatives in works councils

    NARCIS (Netherlands)

    Van der Brempt, O.; Boone, C.; van Witteloostuijn, Arjen|info:eu-repo/dai/nl/072825855; van den Berg, Annette|info:eu-repo/dai/nl/079405169

    This article builds a comprehensive behavioural framework of cooperation between management and employee representatives in a works council setting. The authors do so by applying insights from organizational behaviour in the works council setting in the belief that this discipline’s long-standing

  8. Toward a behavioral theory of cooperation between managers and employee representatives in works councils

    NARCIS (Netherlands)

    Van der Brempt, O.; Boone, C.; van Witteloostuijn, A.; Van den Berg, A.

    2017-01-01

    This article builds a comprehensive behavioural framework of cooperation between management and employee representatives in a works council setting. The authors do so by applying insights from organizational behaviour in the works council setting in the belief that this discipline’s long-standing

  9. Theory Z: The Promise for U.S. Schools.

    Science.gov (United States)

    Miller, William C.; Sparks, Dennis

    1984-01-01

    Elaborates Ouchi's Theory Z--organizations characterized by genuine concern for employee welfare, development of a philosophy, and a cooperative team approach. Applies these precepts to the improvement of individual schools and school districts. (SK)

  10. Sorting and sustaining cooperation

    DEFF Research Database (Denmark)

    Vikander, Nick

    2013-01-01

    This paper looks at cooperation in teams where some people are selfish and others are conditional cooperators, and where lay-offs will occur at a fixed future date. I show that the best way to sustain cooperation prior to the lay-offs is often in a sorting equilibrium, where conditional cooperators...... can identify and then work with one another. Changes to parameters that would seem to make cooperation more attractive, such as an increase in the discount factor or the fraction of conditional cooperators, can reduce equilibrium cooperation if they decrease a selfish player's incentive to sort....

  11. Theory of itinarant ferromagnetism in superconducting semimetals. Theorie du ferromagnetisme itinerant dans des semimetaux supraconducteurs

    Energy Technology Data Exchange (ETDEWEB)

    Do Tran, C; Nguyen Van, C [Groupe de Physique Theorique, Inst. National Polytechnique de Hanoi (Viet Nam); Nguyen Manh, D [Groupe de Physique Theorique, Inst. National Polytechnique de Hanoi (Viet Nam) Centre National de la Recherche Scientifique, Lab. d' Etudes des Proprietes Electroniques des Solides, 38 - Grenoble (France)

    1991-11-01

    A theory of itinerant ferromagnetism in superconducting semimetals is proposed. A nonzero mean magnetisation appears in the superconducting state due to the interaction (interference) of spin density wave (SDW), charge density wave (CDW) and Cooper pair wave. Phase diagram and physical properties of the states considered are investigated analytically and numerically. (orig.).

  12. Political Ideology, Trust, and Cooperation: In-group Favoritism among Republicans and Democrats during a US National Election.

    Science.gov (United States)

    Balliet, Daniel; Tybur, Joshua M; Wu, Junhui; Antonellis, Christian; Van Lange, Paul A M

    2018-04-01

    Theories suggest that political ideology relates to cooperation, with conservatives being more likely to pursue selfish outcomes, and liberals more likely to pursue egalitarian outcomes. In study 1, we examine how political ideology and political party affiliation (Republican vs. Democrat) predict cooperation with a partner who self-identifies as Republican or Democrat in two samples before ( n = 362) and after ( n = 366) the 2012 US presidential election. Liberals show slightly more concern for their partners' outcomes compared to conservatives (study 1), and in study 2 this relation is supported by a meta-analysis ( r = .15). However, in study 1, political ideology did not relate to cooperation in general. Both Republicans and Democrats extend more cooperation to their in-group relative to the out-group, and this is explained by expectations of cooperation from in-group versus out-group members. We discuss the relation between political ideology and cooperation within and between groups.

  13. Innovation diffusion and development in a Third World setting: the cooperative movement in Sierra Leone

    Energy Technology Data Exchange (ETDEWEB)

    Brown, L.A. (Ohio State Univ., Columbus); Schneider, R.; Harvey, M.E.; Riddell, J.B.

    1979-09-01

    The interface between innovation diffusion and economic development and social change in Third World settings is investigated. The paper first presents a conceptual framework linking diffusion processes and development and then exemplifies a portion of that framework by examining the diffusion of agricultural cooperatives in Sierra Leone from 1948 through 1967. Attention is then turned to elements of the historical development of a cooperative movement in Sierra Leone which are important for understanding the processes underlying that diffusion. The temporal and spatial patterns of diffusion are discussed and the statistical analyses that assess (1) which variables provide a basis for distinguishing political units with cooperatives from those without, and (2) which variables account for the differences in the time at which cooperatives were established are examined. The findings are integrated with the theory presented. 41 references.

  14. Encouraging Second Language Use in Cooperative Learning Groups

    Directory of Open Access Journals (Sweden)

    George M Jacobs

    2013-11-01

    Full Text Available This article presents, explains and organizes ideas for promoting students’ use of their second language (this term includes foreign language when they work together in cooperative learning groups. The first part of the article reviews arguments as to whether students of second languages should be encouraged to use their second language with classmates when doing group activities. These arguments are discussed with reference to Second Language Acquisition (SLA theory. Practical issues are also explored. Next, the majority of the article presents ideas on how to promote second language use during peer interaction. Twenty-nine of these ideas are explained. The ideas are organized into five categories: a role for the L1; understanding the issue; creating a conducive climate; providing language support; and the task. It is recommended that teachers use ideas from the literature on cooperative learning when they ask students to interact.

  15. A Game-Theoretic Model to Analyze Value Creation with Simultaneous Cooperation and Competition of Supply Chain Partners

    Directory of Open Access Journals (Sweden)

    F. Kafi

    2014-01-01

    Full Text Available There is a rising trend in supplying chain management to employ simultaneous cooperation and competition (coopetition among supply chain partners as an efficient strategy to create value. There exist, however, few models which analyze coopetitive situations mathematically. Cooperative game theory is the common tool in analyzing cooperative situations. However, the term “cooperative” in “cooperative game theory” is absolutely misleading since it ultimately leads to competition analysis and ignores the internal structure of the cooperation. Coopetition, however, results in structural transformations in players. Therefore, we require a mathematical modeling approach which takes into account the internal structural changes due to cooperation among competitors. In so doing, in this paper we propose, we assume that those parameters of each firm’s profit function are subject to transformation by cooperation as a function of cooperation level so as to determine the right level of cooperation and production of firms while considering technical cooperation between them. Furthermore, we demonstrate the results of applying the idea to a supply chain situation where two similar suppliers participate. We conclude that under intuitive conditions coopetition strategy is superior to the pure competitive relationship between the suppliers in terms of profitability which validates the previous empirical results mathematically.

  16. Distributed Cooperative Search Control Method of Multiple UAVs for Moving Target

    Directory of Open Access Journals (Sweden)

    Chang-jian Ru

    2015-01-01

    Full Text Available To reduce the impact of uncertainties caused by unknown motion parameters on searching plan of moving targets and improve the efficiency of UAV’s searching, a novel distributed Multi-UAVs cooperative search control method for moving target is proposed in this paper. Based on detection results of onboard sensors, target probability map is updated using Bayesian theory. A Gaussian distribution of target transition probability density function is introduced to calculate prediction probability of moving target existence, and then target probability map can be further updated in real-time. A performance index function combining with target cost, environment cost, and cooperative cost is constructed, and the cooperative searching problem can be transformed into a central optimization problem. To improve computational efficiency, the distributed model predictive control method is presented, and thus the control command of each UAV can be obtained. The simulation results have verified that the proposed method can avoid the blindness of UAV searching better and improve overall efficiency of the team effectively.

  17. Analysis of safety supervision effect on coal mine using game theory

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Min; Xiao Zhong-hai [China University of Mining & Technology, Xuzhou (China). School of Management

    2006-07-01

    A two-phase game model was constructed based on economic game theory to improve the inefficient supervision conditions of coalmining enterprises' safety production. The inner mechanism of safety supervision system was carefully studied. The strategy set of the dynamic game-theory relations between colliery proprietor and safety supervision department and the strict competitive game-theory relations between safety supervision department and workers at the production line was analyzed. The conditions of achieving the dominant-strategy equilibrium were revealed. Upon this basis, the possible solution set of safety benefit distribution for the cooperative game-theory of triple party was obtained and the effective and cooperative fair solution was formed. Finally, conclusions are drawn as follows: the combination of necessary penalty to supervisors and operators with the fair distribution of safety benefits can realize the zero-defect of operational violation, so that the violation behavior can be completely avoided. 10 refs., 7 figs.

  18. Cooperatives as Entrants

    OpenAIRE

    Richard J. Sexton; Terri A. Sexton

    1987-01-01

    A potential shortcoming of game-theoretic models in industrial organization is their failure to consider consumers as players. We introduce a customer coalition --- a cooperative -- as a potential entrant and compare the cooperative entry threat with that posed by the usual for-profit entrant. We identify four fundamental distinctions between cooperative and for-profit entrants and demonstrate that the strategic interplay between a cooperative and an incumbent firm may differ markedly from th...

  19. Emotion and the construal of social situations: inferences of cooperation versus competition from expressions of anger, happiness, and disappointment.

    Science.gov (United States)

    Van Doorn, Evert A; Heerdink, Marc W; Van Kleef, Gerben A

    2012-01-01

    The notion that emotional expressions regulate social life by providing information is gaining popularity. Prior research on the effects of emotional expressions on observers' inferential processes has focused mostly on inferences regarding the personality traits of the expresser, such as dominance and affiliation. We extend this line of research by exploring the possibility that emotional expressions shape observers' construal of social situations. Across three vignette studies, an interaction partner's expressions of anger, compared to expressions of happiness or disappointment, led observers to construe hypothetical situations as less cooperative, both in dyads and groups. These effects occurred even when factual information regarding the cooperativeness or competitiveness of the situation was provided, attesting to the power of emotional expressions in shaping the construal of social situations. Results are discussed in relation to appraisal theory, reverse appraisals, emotions as social information theory, and the emergence of cooperation in groups and cultures.

  20. Lewin's Impact on Education: Instilling Cooperation and Conflict Management Skills in School Children.

    Science.gov (United States)

    Maruyama, Geoffrey

    1992-01-01

    A Lewinian orientation to educational problems fits current innovative thinking in education (e.g., models for making education multicultural), and provides the bases of important applied work on cooperative learning techniques and constructive ways of structuring conflict within educational settings. Lewinian field theory provides a broad…

  1. Security-Based Mechanism for Proactive Routing Schema Using Game Theory Model

    Directory of Open Access Journals (Sweden)

    Hicham Amraoui

    2016-01-01

    Full Text Available Game theory may offer a useful mechanism to address many problems in mobile ad hoc networks (MANETs. One of the key concepts in the research field of such networks with Optimized Link State Routing Protocol (OLSR is the security problem. Relying on applying game theory to study this problem, we consider two strategies during this suggested model: cooperate and not-cooperate. However, in such networks, it is not easy to identify different actions of players. In this paper, we have essentially been inspired from recent advances provided in game theory to propose a new model for security in MANETs. Our proposal presents a powerful tool with a large number of players where interactions are played multiple times. Moreover, each node keeps a cooperation rate (CR record of other nodes to cope with the behaviors and mitigate aggregate effect of other malicious devices. Additionally, our suggested security mechanism does not only take into consideration security requirements, but also take into account system resources and network performances. The simulation results using Network Simulator 3 are presented to illustrate the effectiveness of the proposal.

  2. Learning to Cooperate: The Evolution of Social Rewards in Repeated Interactions.

    Science.gov (United States)

    Dridi, Slimane; Akçay, Erol

    2018-01-01

    Understanding the behavioral and psychological mechanisms underlying social behaviors is one of the major goals of social evolutionary theory. In particular, a persistent question about animal cooperation is to what extent it is supported by other-regarding preferences-the motivation to increase the welfare of others. In many situations, animals adjust their behaviors through learning by responding to the rewards they experience as a consequence of their actions. Therefore, we may ask whether learning in social situations can be driven by evolved other-regarding rewards. Here we develop a mathematical model in order to ask whether the mere act of cooperating with a social partner will evolve to be inherently rewarding. Individuals interact repeatedly in pairs and adjust their behaviors through reinforcement learning. We assume that individuals associate with each game outcome an internal reward value. These perceived rewards are genetically evolving traits. We find that conditionally cooperative rewards that value mutual cooperation positively but the sucker's outcome negatively tend to be evolutionarily stable. Purely other-regarding rewards can evolve only under special parameter combinations. On the other hand, selfish rewards that always lead to pure defection are also evolutionarily successful. These findings are consistent with empirical observations showing that humans tend to display conditionally cooperative behavior and also exhibit a diversity of preferences. Our model also demonstrates the need to further integrate multiple levels of biological causation of behavior.

  3. Cooperation and Defection in Ghetto

    Science.gov (United States)

    Kułakowski, Krzysztof

    We consider ghetto as a community of people ruled against their will by an external power. Members of the community feel that their laws are broken. However, attempts to leave ghetto makes their situation worse. We discuss the relation of the ghetto inhabitants to the ruling power in context of their needs, organized according to the Maslow hierarchy. Decisions how to satisfy successive needs are undertaken in cooperation with or defection the ruling power. This issue allows to construct the tree of decisions and to adopt the pruning technique from the game theory. Dynamics of decisions can be described within the formalism of fundamental equations. The result is that the strategy of defection is stabilized by the estimated payoff.

  4. In Search of the Political Value of the Federalism Cooperative

    Directory of Open Access Journals (Sweden)

    Marcos Silva Marinho

    2016-11-01

    Full Text Available This article aims to analyze the constitutional affirmation of cooperative federalism as an organizational model of the Brazilian state and the difficulties of its implementation. To do so, were used the post- positivist theories, that defend the indispensability of moral values for the legitimation of institutional practices, and some sociological theories that, analyzing the consolidation of the nation-state as the archetype of social organization of modernity, were able to distinguish the categories "state" and "nation" as not necessarily complementary elements. Through this distinction, the article tried to discuss the relationship among these categories in the construction of Brazil's social fabric.

  5. Collaborative Learning or Cooperative Learning? The Name Is Not Important; Flexibility Is

    Science.gov (United States)

    Jacobs, George M.

    2015-01-01

    A great deal of theory and research, not to mention students' and teachers' practical experience, supports the use of group activities in education. Collaborative learning and cooperative learning are two terms commonly used in discussions of how and why to use group activities. This article looks at the issue of whether the two…

  6. Enhancing Empathy and Theory of Mind

    Science.gov (United States)

    Goldstein, Thalia R.; Winner, Ellen

    2012-01-01

    Social cognitive skills such as empathy and theory of mind are crucial for everyday interactions, cooperation, and cultural learning, and deficits in these skills have been implicated in pathologies such as autism spectrum disorder, sociopathy, and nonverbal learning disorders. Little research has examined how these skills develop after early…

  7. How grandparents matter. Support for the cooperative breeding hypothesis in a contemporary Dutch population

    NARCIS (Netherlands)

    Kaptijn, R.; Thomese, G.C.F.; van Tilburg, T.G.; Liefbroer, A.C.

    2010-01-01

    Low birth rates in developed societies reflect women's difficulties in combining work and motherhood. While demographic research has focused on the role of formal childcare in easing this dilemma, evolutionary theory points to the importance of kin. The cooperative breeding hypothesis states that

  8. Interaction between Dutch soccer teams and fans: a mathematical analysis through cooperative game theory

    NARCIS (Netherlands)

    Hou, D.; Driessen, Theo

    2012-01-01

    Inspired by the first lustrum of the Club Positioning Matrix (CPM) for professional Dutch soccer teams, we model the interaction between soccer teams and their potential fans as a cooperative cost game based on the annual voluntary sponsorships of fans in order to validate their fan registration in

  9. Alternative vision or utopian fantasy? Cooperation, empowerment and women's cooperative development in India.

    Science.gov (United States)

    Mayoux, L

    1995-01-01

    The discussion addresses the costs and benefits of working in cooperatives in India, imposed participation, methods for increasing incomes, preconceived models, the importance of meeting the actual needs of women, and participatory options. This author evaluated 10 producer cooperatives in West Bengal, Karnataka, and Tamil Nadu during 1984-92. It is argued that more discussion is needed on how ideals of cooperation and empowerment of women can occur simultaneous with the context in which cooperatives must operate. The ten study cooperatives were all officially registered cooperatives. Cooperatives varied in size, organizational structure, and forms of support. Four were determined to be successful in economic and participatory terms. Three were successful because of the efforts of the women themselves. All three cases were based on earning goals that were higher than the women could have achieved on their own. Six failed in terms of participatory decision making and cooperative operations. Lack of sufficient support and/or excessive bureaucratic red tape were involved in the six failures, but to varying degrees. Type of support and means of implementation were important in the six failures. All women used cooperatives as a means of increasing income. Participation rules were imposed by outside agencies. Women were given "cooperative" training. Disputes occurred because women selected to power positions were powerful leaders outside the cooperative. Consensus was difficult to reach. There were conflicts of interest between different departments. Quality control was made difficult by women's inability to provide discipline. Personal conflicts from outside were carried on within the cooperative. Incomes could be improved by training women in local marketing and networking, insuring adequate resources and capital, and providing savings schemes. Gender inequalities were a key factor limiting income for women, but cooperatives did not address this issue. Gains for women

  10. On the Usefulness of Cooperation in N Person Games

    Directory of Open Access Journals (Sweden)

    Mikhail Sergeevich Nikolskii

    2016-01-01

    Full Text Available The N person games in which each player maximizes his payoff function are considered. We have studied an interesting question for the cooperative game theory about the usefulness of uniting the N players in a union. The aim of such cooperation is for each player to get a positive increase to his guaranteed payoff. We have obtained some effective sufficient conditions under which the joining of the players in union is useful for each player. The linear case, specially, is being considered. In the second part of the paper, we have studied the question about the usefulness of cooperation of the N players in the presence of the (N+1th player, an ill-intentioned destructive player, whose whole aim is not to win but to harm each player individually, and also the union of these players, for example, global terrorism. It should be noted that the considered situation in the second part is related to A. V. Kryazhimskiy’s talk delivered in the summer of 2014. We obtain constructive conditions under which the union of the players is beneficial in this situation as well.

  11. Productive Systems and the Structuring Role of Economic and Social Theories

    OpenAIRE

    Frank Wilkinson

    2002-01-01

    The institutions of productive systems are structured by mutual interests and relative power. Securing mutually beneficial cooperation in production requires resolving distributional differences. These objectives are secured in liberal economic theory by the working of markets which mediate the power of individuals and reward individual success. The centrality of individuals and hierarchies in market theory contrasts with developments in labour management theory which identifies group activit...

  12. Effect of initial fraction of cooperators on cooperative behavior in evolutionary prisoner's dilemma game.

    Directory of Open Access Journals (Sweden)

    Keizo Shigaki

    Full Text Available We investigate the influence of initial fraction of cooperators on the evolution of cooperation in spatial prisoner's dilemma games. Compared with the results of heterogeneous networks, we find that there is a relatively low initial fraction of cooperators to guarantee higher equilibrium cooperative level. While this interesting phenomenon is contrary to the commonly shared knowledge that higher initial fraction of cooperators can provide better environment for the evolution of cooperation. To support our outcome, we explore the time courses of cooperation and find that the whole course can be divided into two sequent stages: enduring (END and expanding (EXP periods. At the end of END period, thought there is a limited number of cooperator clusters left for the case of low initial setup, these clusters can smoothly expand to hold the whole system in the EXP period. However, for high initial fraction of cooperators, superfluous cooperator clusters hinder their effective expansion, which induces many remaining defectors surrounding the cooperator clusters. Moreover, through intensive analysis, we also demonstrate that when the tendency of three cooperation cluster characteristics (cluster size, cluster number and cluster shape are consistent within END and EXP periods, the state that maximizes cooperation can be favored.

  13. Punishment does not promote cooperation under exploration dynamics when anti-social punishment is possible.

    Science.gov (United States)

    P Hauser, Oliver; A Nowak, Martin; G Rand, David

    2014-11-07

    It has been argued that punishment promotes the evolution of cooperation when mutation rates are high (i.e. when agents engage in 'exploration dynamics'). Mutations maintain a steady supply of agents that punish free-riders, and thus free-riders are at a disadvantage. Recent experiments, however, have demonstrated that free-riders sometimes also pay to punish cooperators. Inspired by these empirical results, theoretical work has explored evolutionary dynamics where mutants are rare, and found that punishment does not promote the evolution of cooperation when this 'anti-social punishment' is allowed. Here we extend previous theory by studying the effect of anti-social punishment on the evolution of cooperation across higher mutation rates, and by studying voluntary as well as compulsory Public Goods Games. We find that for intermediate and high mutation rates, adding punishment does not promote cooperation in either compulsory or voluntary public goods games if anti-social punishment is possible. This is because mutations generate agents that punish cooperators just as frequently as agents that punish defectors, and these two effects cancel each other out. These results raise questions about the effectiveness of punishment for promoting cooperation when mutations are common, and highlight how decisions about which strategies to include in the strategy set can have profound effects on the resulting dynamics. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Bistable traveling waves for a competitive-cooperative system with nonlocal delays

    Science.gov (United States)

    Tian, Yanling; Zhao, Xiao-Qiang

    2018-04-01

    This paper is devoted to the study of bistable traveling waves for a competitive-cooperative reaction and diffusion system with nonlocal time delays. The existence of bistable waves is established by appealing to the theory of monotone semiflows and the finite-delay approximations. Then the global stability of such traveling waves is obtained via a squeezing technique and a dynamical systems approach.

  15. Network coding and evolutionary theory for performance enhancement in wireless cooperative clusters

    DEFF Research Database (Denmark)

    Militano, Leonardo; Fitzek, Frank; Iera, Antonio

    2010-01-01

    Cooperation over short-range wireless links among user devices, which download remote contents through cellular links, is a paradigm quickly gaining ground, given that it can answer several technological and design issues that next-generation wireless applications will raise. Among others, energy...... are investigated and an ad hoc conceived Genetic Algorithm (GA) designed. Either the service time (the time needed for all nodes to receive the complete file) or the energy consumption for the nodes is used as objective function, showing in both cases the fast convergence for the algorithm that makes it preferable...

  16. A note on cooperative versus non-cooperative strategies in international pollution control

    Energy Technology Data Exchange (ETDEWEB)

    Rubio, Santiago J.; Casino, Begona [Department of Economic Analysis, University of Valencia, Avda. de los Naranjos s/n, Edificio Departamental Oriental, 46022 Valencia (Spain)

    2002-06-01

    In this note, we evaluate the scope of Dockner and Long's [Journal of Environment Economics and Management 24 (1993) 13] conclusion on the efficiency of the non-cooperative outcome in a differential game of international pollution control. We also complete the study of the different equilibria the differential game can present. Our results show that their conclusion requires that the initial value of the stock of pollution be higher than the Pareto-efficient pollution stock so that the equilibrium path of emissions involves a decreasing stock of pollution. Our results also show that the application of the procedure proposed by Tsutsui and Mino [Journal of Economic Theory 52 (1990) 136] to construct a Markov-perfect equilibrium using non-linear strategies is problematic when the initial pollution stock is lower than the Pareto-efficient pollution stock.

  17. Commitment to Cooperation and Peer Punishment: Its Evolution

    Directory of Open Access Journals (Sweden)

    Tatsuya Sasaki

    2015-11-01

    Full Text Available Theoretical and empirical studies have generally weighed the effect of peer punishment and pool punishment for sanctioning free riders separately. However, these sanctioning mechanisms often pose a puzzling tradeoff between efficiency and stability in detecting and punishing free riders. Here, we combine the key aspects of these qualitatively different mechanisms in terms of evolutionary game theory. Based on the dilemmatic donation game, we introduce a strategy of commitment to both cooperation and peer punishment. To make the commitment credible, we assume that those willing to commit have to make a certain deposit. The deposit will be refunded as long as the committers faithfully cooperate in the donation game and punish free riders and non-committers. It turns out that the deposit-based commitment offers both the efficiency of peer punishment and the stability of pool punishment and that the replicator dynamics lead to transitions of different systems: pool punishment to commitment to peer punishment.

  18. NATO-EU PARTNERSHIP: FOSTERING RESILIENCE FOR A COOPERATIVE SECURITY SPACE

    Directory of Open Access Journals (Sweden)

    Octavia MOISE

    2017-12-01

    Full Text Available Present events indicate an encompassing process of multi-level changes - political, military, economic, and technological that highlights the idea that we are going through a phase of transition at systemic level that is redesigning the structure of power of the 21st century. This paper will try to find out first if the cooperative security concept can be seen as a security theory according to Baldwin’s criteria and second if NATO’s partnership policy in general and the NATO EU partnership in particular can foster resilience. The objectives of this article are to envisage the role of the NATO-EU partnership in the future by: reviewing the theoretical approaches on cooperative security, analysing NATO’s partnership policy, analysing the ability of NATO-EU partnership to foster resilience.

  19. Consensus based on learning game theory with a UAV rendezvous application

    Directory of Open Access Journals (Sweden)

    Zhongjie Lin

    2015-02-01

    Full Text Available Multi-agent cooperation problems are becoming more and more attractive in both civilian and military applications. In multi-agent cooperation problems, different network topologies will decide different manners of cooperation between agents. A centralized system will directly control the operation of each agent with information flow from a single centre, while in a distributed system, agents operate separately under certain communication protocols. In this paper, a systematic distributed optimization approach will be established based on a learning game algorithm. The convergence of the algorithm will be proven under the game theory framework. Two typical consensus problems will be analyzed with the proposed algorithm. The contributions of this work are threefold. First, the designed algorithm inherits the properties in learning game theory for problem simplification and proof of convergence. Second, the behaviour of learning endows the algorithm with robustness and autonomy. Third, with the proposed algorithm, the consensus problems will be analyzed from a novel perspective.

  20. International co-operation

    International Nuclear Information System (INIS)

    Klinda, J.; Lieskovska, Z.

    1998-01-01

    Within the Union Nations (UN) framework, the Slovak Republic participated in following activities on environment protection co-operation: UN European Economic Commission, UN Industrial Development Organization, UN Development Programme, UN Human Habitat Organization, UN Environment Programme, and UN Commission on Sustainable Development. Relevant activities of the Slovak Republic in these co-operations as well as in European Union and OECD activities are reviewed. International conventions and other forms of multilateral co-operation, bilateral co-operation, and international programmes and projects in which the Slovak Republic took participate are presented