3,146 research outputs found

    Dissipate locally, couple globally: a sharp transition from decoupling to infinite range coupling in Josephson arrays with on-site dissipation

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    We study the T=0 normal to superconducting transition of Josephson arrays with {\it on-site} dissipation. A perturbative renormalization group solution is given. Like the previously studied case of {\it bond} dissipation (BD), this is a "floating" to coupled (FC) phase transition. {\it Unlike} the BD transition, at which {\it only} nearest-neighbor couplings become relevant, here {\it all} inter-grain couplings, out to {\it infinitely} large distances, do so simultaneously. We predict, for the first time in an FC transition, a diverging spatial correlation length. Our results show the robustness of floating phases in dissipative quantum systems.Comment: 7+ pages, 3 eps figures, Europhysics Letters preprint format, as publishe

    Ground state of Li and Be+^+ using explicitly correlated functions

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    We compare the explicitly correlated Hylleraas and exponential basis sets in the evaluations of ground state of Li and Be+^+. Calculations with Hylleraas functions are numerically stable and can be performed with the large number of basis functions. Our results for ground state energies −7.47806032391010(32)-7.478 060 323 910 10(32), −14.32476317679043(22)-14.324 763 176 790 43(22) of Li and Be+^+ correspondingly, are the most accurate to date. When small basis set is considered, explicitly correlated exponential functions are much more effective. With only 128 functions we obtained about 10−910^{-9} relative accuracy, but the severe numerical instabilities make this basis costly in the evaluation.Comment: 15 page
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