1,302 research outputs found

    Modeling and Aiding Intuition: Introduction to the Commentary Section

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    This section of JARMAC includes a series of commentaries on articles published in the September, 2015, special issue of JARMAC: "Modeling and aiding intuition in organizational decision making" (Marewski & Hoffrage, 2015). The commentaries focus on research programs such as naturalistic decision making, heuristics-and-biases, ACT-R, and CLARION. They feature topics ranging from evolution to decision styles. In this introduction, we provide a brief overview of those contributions, alongside with concluding words on this project of pulling together multiple and very different strands of research on intuition

    Soluble `Supersymmetric' Quantum XY Model

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    We present a `supersymmetric' modification of the dd-dimensional quantum rotor model whose ground state is exactly soluble. The model undergoes a vortex-binding transition from insulator to metal as the rotor coupling is varied. The Hamiltonian contains three-site terms which are relevant: they change the universality class of the transition from that of the (d+1d+1)--- to the dd-dimensional classical XY model. The metallic phase has algebraic ODLRO but the superfluid density is identically zero. Variational wave functions for single-particle and collective excitations are presented.Comment: 12 pages, REVTEX 3.0, IUCM93-00

    Universality of the Crossing Probability for the Potts Model for q=1,2,3,4

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    The universality of the crossing probability πhs\pi_{hs} of a system to percolate only in the horizontal direction, was investigated numerically by using a cluster Monte-Carlo algorithm for the qq-state Potts model for q=2,3,4q=2,3,4 and for percolation q=1q=1. We check the percolation through Fortuin-Kasteleyn clusters near the critical point on the square lattice by using representation of the Potts model as the correlated site-bond percolation model. It was shown that probability of a system to percolate only in the horizontal direction πhs\pi_{hs} has universal form πhs=A(q)Q(z)\pi_{hs}=A(q) Q(z) for q=1,2,3,4q=1,2,3,4 as a function of the scaling variable z=[b(q)L1Îœ(q)(p−pc(q,L))]ζ(q)z= [ b(q)L^{\frac{1}{\nu(q)}}(p-p_{c}(q,L)) ]^{\zeta(q)}. Here, p=1−exp⁥(−ÎČ)p=1-\exp(-\beta) is the probability of a bond to be closed, A(q)A(q) is the nonuniversal crossing amplitude, b(q)b(q) is the nonuniversal metric factor, ζ(q)\zeta(q) is the nonuniversal scaling index, Îœ(q)\nu(q) is the correlation length index. The universal function Q(x)≃exp⁥(−z)Q(x) \simeq \exp(-z). Nonuniversal scaling factors were found numerically.Comment: 15 pages, 3 figures, revtex4b, (minor errors in text fixed, journal-ref added

    The Bose-Hubbard model is QMA-complete

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    The Bose-Hubbard model is a system of interacting bosons that live on the vertices of a graph. The particles can move between adjacent vertices and experience a repulsive on-site interaction. The Hamiltonian is determined by a choice of graph that specifies the geometry in which the particles move and interact. We prove that approximating the ground energy of the Bose-Hubbard model on a graph at fixed particle number is QMA-complete. In our QMA-hardness proof, we encode the history of an n-qubit computation in the subspace with at most one particle per site (i.e., hard-core bosons). This feature, along with the well-known mapping between hard-core bosons and spin systems, lets us prove a related result for a class of 2-local Hamiltonians defined by graphs that generalizes the XY model. By avoiding the use of perturbation theory in our analysis, we circumvent the need to multiply terms in the Hamiltonian by large coefficients

    Feynman's Propagator Applied to Network Models of Localization

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    Network models of dirty electronic systems are mapped onto an interacting field theory of lower dimensionality by intepreting one space dimension as time. This is accomplished via Feynman's interpretation of anti-particles as particles moving backwards in time. The method developed maps calculation of the moments of the Landauer conductance onto calculation of correlation functions of an interacting field theory of bosons and fermions. The resulting field theories are supersymmetric and closely related to the supersymmetric spin-chain representations of network models recently discussed by various authors. As an application of the method, the two-edge Chalker-Coddington model is shown to be Anderson localized, and a delocalization transition in a related two-edge network model (recently discussed by Balents and Fisher) is studied by calculation of the average Landauer conductance.Comment: Latex, 14 pages, 2 fig

    High resolution studies of low-energy electron attachment to SF5Cl: Product anions and absolute cross sections

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    Low energy electron attachment to SF5_5Cl was studied at high energy resolution by mass spectrometric detection of the product anions. Two variants of the laser photoelectron attachment (LPA) technique (Kaiserslautern) were used for determining the threshold behaviour of the yield for SF5−_5^- formation at about 1 meV resolution, and to investigate the relative cross sections for Cl−^-, FCl−^-, and SF5−_5^- formation towards higher energies (up to 1 eV) at about 20 meV resolution. Thermal swarm measurements (Birmingham) were used to place the relative LPA cross sections on an absolute scale. A trochoidal electron monochromator (Innsbruck) was used for survey measurements of the relative cross sections for the different product anions over the energy range of 0-14 eV with a resolution of 0.30 eV. Combined with earlier beam data (taken at Berlin, J. Chem. Phys. 88 (1988) 149), the present experimental results provide a detailed set of partial cross sections for anion formation in low-energy electron collisions with SF5_5Cl

    Response to Comment on “Mycorrhizal association as a primary control of the CO 2 fertilization effect”

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    Norby et al. center their critique on the design of the data set and the response variable used. We address these criticisms and reinforce the conclusion that plants that associate with ectomycorrhizal fungi exhibit larger biomass and growth responses to elevated CO2 compared with plants that associate with arbuscular mycorrhizae

    Variational theory of flux-line liquids

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    We formulate a variational (Hartree like) description of flux line liquids which improves on the theory we developed in an earlier paper [A.M. Ettouhami, Phys. Rev. B 65, 134504 (2002)]. We derive, in particular, how the massive term confining the fluctuations of flux lines varies with temperature and show that this term vanishes at high enough temperatures where the vortices behave as freely fluctuating elastic lines.Comment: 10 pages, 1 postscript figur

    Application of Minimal Subtraction Renormalization to Crossover Behavior near the 3^3He Liquid-Vapor Critical Point

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    Parametric expressions are used to calculate the isothermal susceptibility, specific heat, order parameter, and correlation length along the critical isochore and coexistence curve from the asymptotic region to crossover region. These expressions are based on the minimal-subtraction renormalization scheme within the ϕ4\phi^4 model. Using two adjustable parameters in these expressions, we fit the theory globally to recently obtained experimental measurements of isothermal susceptibility and specific heat along the critical isochore and coexistence curve, and early measurements of coexistence curve and light scattering intensity along the critical isochore of 3^3He near its liquid-vapor critical point. The theory provides good agreement with these experimental measurements within the reduced temperature range ∣tâˆŁâ‰€2×10−2|t| \le 2\times 10^{-2}

    Scaling in the Lattice Gas Model

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    A good quality scaling of the cluster size distributions is obtained for the Lattice Gas Model using the Fisher's ansatz for the scaling function. This scaling identifies a pseudo-critical line in the phase diagram of the model that spans the whole (subcritical to supercritical) density range. The independent cluster hypothesis of the Fisher approach is shown to describe correctly the thermodynamics of the lattice only far away from the critical point.Comment: 4 pages, 3 figure
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