570 research outputs found

    A Sidetrack-Based Algorithm for Finding the k Shortest Simple Paths in a Directed Graph

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    We present an algorithm for the k shortest simple path problem on weighted directed graphs (kSSP) that is based on Eppstein's algorithm for a similar problem in which paths are allowed to contain cycles. In contrast to most other algorithms for kSSP, ours is not based on Yen's algorithm and does not solve replacement path problems. Its worst-case running time is on par with state-of-the-art algorithms for kSSP. Using our algorithm, one may find O(m) simple paths with a single shortest path tree computation and O(n + m) additional time per path in well-behaved cases, where n is the number of nodes and m is the number of edges. Our computational results show that on random graphs and large road networks, these well-behaved cases are quite common and our algorithm is faster than existing algorithms by an order of magnitude. Further, the running time is far better predictable due to very small dispersion

    K-Best Solutions of MSO Problems on Tree-Decomposable Graphs

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    We show that, for any graph optimization problem in which the feasible solutions can be expressed by a formula in monadic second-order logic describing sets of vertices or edges and in which the goal is to minimize the sum of the weights in the selected sets, we can find the k best solution values for n-vertex graphs of bounded treewidth in time O(n + k log n). In particular, this applies to finding the k shortest simple paths between given vertices in directed graphs of bounded treewidth, giving an exponential speedup in the per-path cost over previous algorithms

    Core-coupled states and split proton-neutron quasi-particle multiplets in 122-126Ag

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    Neutron-rich silver isotopes were populated in the fragmentation of a 136Xe beam and the relativistic fission of 238U. The fragments were mass analyzed with the GSI Fragment separator and subsequently implanted into a passive stopper. Isomeric transitions were detected by 105 HPGe detectors. Eight isomeric states were observed in 122-126Ag nuclei. The level schemes of 122,123,125Ag were revised and extended with isomeric transitions being observed for the first time. The excited states in the odd-mass silver isotopes are interpreted as core-coupled states. The isomeric states in the even-mass silver isotopes are discussed in the framework of the proton-neutron split multiplets. The results of shell-model calculations, performed for the most neutron-rich silver nuclei are compared to the experimental data

    Single-particle isomeric states in 121Pd and 117Ru

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    Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states

    Single-particle isomeric states in 121Pd and 117Ru

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    Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states

    Single-particle isomeric states in 121Pd and 117Ru

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    Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states

    ő≤Delayed ő≥Ray spectroscopy of heavy neutron rich nuclei ‚Äúsouth‚ÄĚ of lead

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    Relativistic projectile fragmentation of a 208Pb primary beam has been used to produce neutron-rich nuclei with proton-holes relative to the Z = 82 shell closure, i.e., ‚Äúsouth‚ÄĚ of Pb. ő≤Delayed ő≥Ray spectroscopy allows to investigate the structural properties of such nuclei with A ~ 195 ‚Üí 205. The current work presents transitions de-exciting excited states in 204Au, which are the first spectroscopic information on this N = 125 isotone.Agramunt Ros, Jorge, [email protected] ; Algora, Alejandro, [email protected] ; Molina Palacios, Francisco Manuel, [email protected] ; Rubio Barroso, Berta, [email protected]

    Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

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    We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

    ő≤-Delayed and isomer spectroscopy of neutron-rich Ta and W isotopes

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    Decays of neutron-rich A ~ 190 nuclei have been studied following projectile fragmentation of a 208Pb beam on a 9Be target at the GSI Fragment Separator. Gamma-ray decays from previously reported isomeric states in 188Ta, 190W and 192, 193Re were used as internal calibrations for the particle identification analysis, together with the identification of previously unreported isomeric decays in 189Ta and 191W. The current work also identifies ő≤-delayed ő≥ rays following the decay of 188Ta to 188W for the first time.Algora, Alejandro, [email protected] ; Molina Palacios, Francisco Manuel, [email protected]; Rubio Barroso, Berta, [email protected]
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