6,265 research outputs found

    Causal connectivity of evolved neural networks during behavior

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    To show how causal interactions in neural dynamics are modulated by behavior, it is valuable to analyze these interactions without perturbing or lesioning the neural mechanism. This paper proposes a method, based on a graph-theoretic extension of vector autoregressive modeling and 'Granger causality,' for characterizing causal interactions generated within intact neural mechanisms. This method, called 'causal connectivity analysis' is illustrated via model neural networks optimized for controlling target fixation in a simulated head-eye system, in which the structure of the environment can be experimentally varied. Causal connectivity analysis of this model yields novel insights into neural mechanisms underlying sensorimotor coordination. In contrast to networks supporting comparatively simple behavior, networks supporting rich adaptive behavior show a higher density of causal interactions, as well as a stronger causal flow from sensory inputs to motor outputs. They also show different arrangements of 'causal sources' and 'causal sinks': nodes that differentially affect, or are affected by, the remainder of the network. Finally, analysis of causal connectivity can predict the functional consequences of network lesions. These results suggest that causal connectivity analysis may have useful applications in the analysis of neural dynamics

    Summary of Experimental Meson Physics

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    A summary of the present experimental status of meson physics is presented. The presentation includes the new results presented at the MESON06 workshop, as well as other recent experimental developments in the field.Comment: 15 pages, 6 figures, presented at 9th International Workshop on Meson Production, Properties and Interaction, Krakow, Poland, June 200

    A Comprehensive Study of the Radiative Decays of J/ψJ/\psi and ψ(2S)\psi(2S) to Pseudoscalar Meson Pairs, and Search for Glueballs

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    Using 53 pb−1^{-1} of e+e−e^+e^- annihilation data taken at s=3.686\sqrt{s}=3.686 GeV, a comprehensive study has been made of the radiative decays of samples of 5.1 million J/ψJ/\psi and 24.5 million ψ(2S)\psi(2S) into pairs of pseudoscalar mesons, π+π−\pi^+\pi^-, π0π0\pi^0\pi^0, K+K−K^+K^-, KS0KS0K_S^0K_S^0, and ηη\eta\eta. Product branching fractions for the radiative decays of J/ψJ/\psi and ψ(2S)\psi(2S) to scalar resonances f0(1370,1500,1710,2100,and2200)f_0(1370,1500,1710,2100, \text{and} 2200), and tensor resonances f2(1270,1525,and2230)f_2(1270,1525, \text{and} 2230) have been determined, and are discussed in relation to predicted glueballs. For ψ(2S)\psi(2S) radiative decays the search for glueballs has been extended to masses between 2.5 GeV and 3.3 GeV.Comment: 21 pages, 14 figures, published in PR

    Quantum Pumping with Ultracold Atoms on Microchips: Fermions versus Bosons

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    We present a design for simulating quantum pumping of electrons in a mesoscopic circuit with ultra-cold atoms in a micro-magnetic chip trap. We calculate theoretical results for quantum pumping of both bosons and fermions, identifying differences and common features, including geometric behavior and resonance transmission. We analyze the feasibility of experiments with bosonic 87^{87}Rb and fermionic 40^{40}K atoms with an emphasis on reliable atomic current measurements.Comment: 4 pages; 4 figure

    New Results From CLEO and BES

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    Latest experimental results from BES in the charmonium mass region, and those from CLEO in the bottomonium and charmonium spectroscopy are reviewed.Comment: 12 pages, 12 figures, Presented at First Meeting of the APS Topical Group on Hadron Physics, Fermilab, Batavia, Illinois, Oct 24-26, 200

    Light Quark Resonances in pbar p Annihilations at 5.2 GeV/c

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    Data from the Fermilab E835 experiment have been used to study the reaction pbar p -> eta eta pi0 at 5.2 GeV/c. A sample of 22 million six photons events has been analyzed to construct the Dalitz plot containing ~80k eta eta pi0 events. A partial wave analysis of the data has been done. Six f_J-states decaying into eta eta and five a_J-states decaying into eta pi0 are identified in the mass region ~1.3 and 2.4 GeV, and their masses, widths and spins are determined by maximum likelihood analysis of the data. Two f_0 states are identified with the popular candidates for the lightest scalar glueball, f_0(1500) and f_0(1710).Comment: 7 pages, 6 figure

    Generation and detection of NOON states in superconducting circuits

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    NOON states, states between two modes of light of the form ∣N,0⟩+eiϕ∣0,N⟩|N,0\rangle+e^{i\phi}|0,N\rangle allow for super-resolution interformetry. We show how NOON states can be efficiently produced in circuit quntum electrodynamics using superconducting phase qubits and resonators. We propose a protocol where only one interaction between the two modes is required, creating all the necessary entanglement at the start of the procedure. This protocol makes active use of the first three states of the phase qubits. Additionally, we show how to efficiently verify the success of such an experiment, even for large NOON states, using randomly sampled measurements and semidefinite programming techniques.Comment: 15 pages and 3 figure
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