3,558 research outputs found

    Recent Developments in Parallelization of the Multidimensional Integration Package DICE

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    DICE is a general purpose multidimensional numerical integration package. There can be two ways in the parallelization of DICE, "distributing random numbers into workers" and "distributing hypercubes into workers". Furthermore, there can be the combination of both ways. So far, we had developed the parallelization code using the former way and reported it in ACAT2002 in Moscow. Here, we will present the recent developments of parallelized DICE in the latter way as the 2nd stage of our parallelization activities.Comment: 5 pages, 2 figures, Talk given at the X International Workshop on Advanced Computing and Analysis Techniques in Physics Research, ACAT 2005, DESY-Zeuthen, Germany, 22-27 May 200

    Monte Carlo integration on GPU

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    We use a graphics processing unit (GPU) for fast computations of Monte Carlo integrations. Two widely used Monte Carlo integration programs, VEGAS and BASES, are parallelized on GPU. By using W+W^{+} plus multi-gluon production processes at LHC, we test integrated cross sections and execution time for programs in FORTRAN and C on CPU and those on GPU. Integrated results agree with each other within statistical errors. Execution time of programs on GPU run about 50 times faster than those in C, and more than 60 times faster than the original FORTRAN programs.Comment: 6 pages, 2 figure

    Magnetic effects in heavy-ion collisions at intermediate energies

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    The time-evolution and space-distribution of internal electromagnetic fields in heavy-ion reactions at beam energies between 200 and 2000 MeV/nucleon are studied within an Isospin-dependent Boltzmann-Uhling-Uhlenbeck transport model IBUU11. While the magnetic field can reach about 7×10167\times 10^{16} G which is significantly higher than the estimated surface magnetic field (1015\sim 10^{15} G) of magnetars, it has almost no effect on nucleon observables as the Lorentz force is normally much weaker than the nuclear force. Very interestingly, however, the magnetic field generated by the projectile-like (target-like) spectator has a strong focusing/diverging effect on positive/negative pions at forward (backward) rapidities. Consequently, the differential π/π+\pi^-/\pi^+ ratio as a function of rapidity is significantly altered by the magnetic field while the total multiplicities of both positive and negative pions remain about the same. At beam energies above about 1 GeV/nucleon, while the integrated ratio of total π\pi^- to π+\pi^+ multiplicities is not, the differential π/π+\pi^-/\pi^+ ratio is sensitive to the density dependence of nuclear symmetry energy Esym(ρ)E_{\rm{sym}}(\rho). Our findings suggest that magnetic effects should be carefully considered in future studies of using the differential π/π+\pi^-/\pi^+ ratio as a probe of the Esym(ρ)E_{\rm{sym}}(\rho) at supra-saturation densities.Comment: 12 pages including 8 figures and 1 tabl

    Potential Disregard of the Corporate Entity & U.S. Subsidiary Invocation of Japanese Parent\u27s Treaty Rights

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    U.S. corporate subsidiaries of Japanese parent companies enjoy the same advantages of incorporation (e.g., liability limited to the amount of investment) and the same legal protections extended to domestically-held U.S. corporations (e.g., access to courts and various legal remedies). Thus, it would be a natural and logical assumption that U.S. subsidiaries of Japanese parent companies are required to comply with U.S. law in the same manner as domestically-held corporations. However, some U.S. subsidiaries, by asserting that they are, in reality, inseparable from their Japanese parent companies, have been allowed to avail themselves of exceptions to U.S. law under the U.S.-Japan Friendship, Commerce and Navigation Treaty ( FCN Treaty ). Thus, the paradox arises where Japanese subsidiaries are not required to comply with provisions of the U.S. legal system, but enjoy the same advantages of incorporation and legal protection as domestically-held U.S. corporations. A notable example of such use (or misuse) of the FCN Treaty is the avoidance of liability for discriminatory practices in employment, in particular, wrongful discharge. However, as this Article explains, such use of the FCN Treaty is not without consequence, as the invocation of Treaty rights by a U.S. subsidiary poses the potential danger of disregard of the corporate entity and thus unlimited liability to the Japanese parent company

    A massive star origin for an unusual helium-rich supernova in an elliptical galaxy

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    The unusual helium-rich (type Ib) supernova SN 2005E is distinguished from any supernova hitherto observed by its faint and rapidly fading light curve, prominent calcium lines in late-phase spectra and lack of any mark of recent star formation near the supernova location. These properties are claimed to be explained by a helium detonation in a thin surface layer of an accreting white dwarf (Perets et al. 2010). Here we report on observations of SN 2005cz appeared in an elliptical galaxy, whose observed properties resemble those of SN 2005E in that it is helium-rich and unusually faint, fades rapidly, shows much weaker oxygen emission lines than those of calcium in the well-evolved spectrum. We argue that these properties are best explained by a core-collapse supernova at the low-mass end (812M8-12 M_{\odot}) of the range of massive stars that explode (Smartt 2009). Such a low mass progenitor had lost its hydrogen-rich envelope through binary interaction, having very thin oxygen-rich and silicon-rich layers above the collapsing core, thus ejecting a very small amount of radioactive 56^{56}Ni and oxygen. Although the host galaxy NGC 4589 is an elliptical, some studies have revealed evidence of recent star-formation activity (Zhang et al. 2008), consistent with the core-collapse scenario.Comment: Accepted by Nature (24 March 2010), 32 pages including Supplementary Informatio

    Spin-charge mixing effects on resonant tunneling in a polarized Luttinger Liquid

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    We investigate spin-charge mixing effect on resonant tunneling in spin-polarized Tomonaga-Luttinger liquid with double impurities. The mixing arises from Fermi velocity difference between two spin species due to Zeeman effect. Zero bias conductance is calculated as a function of gate voltage VgV_{\rm g}, gate magnetic field BgB_{\rm g}, temperature and magnetic field applied to the system. Mixing effect is shown to cause rotation of the lattice pattern of the conductance peaks in (Vg,Bg)(V_{\rm g},B_{\rm g}) plane, which can be observed in experiments. At low temperatures, the contour shapes are classified into three types, reflecting the fact that effective barrier potential is renormalized towards ``perfect reflection'', ``perfect transmission'' and magnetic field induced ``spin-filtering'', respectively.Comment: 10 pages, 4 figures, Sec.I and references largely changed, results for a strong barrier limit added in a new section Sec.I

    The Unique Type Ib Supernova 2005bf at Nebular Phases: A Possible Birth Event of A Strongly Magnetized Neutron Star

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    Late phase nebular spectra and photometry of Type Ib Supernova (SN) 2005bf taken by the Subaru telescope at ~ 270 and ~ 310 days since the explosion are presented. Emission lines ([OI]6300, 6363, [CaII]7291, 7324, [FeII]7155) show the blueshift of ~ 1,500 - 2,000 km s-1. The [OI] doublet shows a doubly-peaked profile. The line luminosities can be interpreted as coming from a blob or jet containing only ~ 0.1 - 0.4 Msun, in which ~ 0.02 - 0.06 Msun is 56Ni synthesized at the explosion. To explain the blueshift, the blob should either be of unipolar moving at the center-of-mass velocity v ~ 2,000 - 5,000 km s-1, or suffer from self-absorption within the ejecta as seen in SN 1990I. In both interpretations, the low-mass blob component dominates the optical output both at the first peak (~ 20 days) and at the late phase (~ 300 days). The low luminosity at the late phase (the absolute R magnitude M_R ~ -10.2 mag at ~ 270 days) sets the upper limit for the mass of 56Ni < ~ 0.08 Msun, which is in contradiction to the value necessary to explain the second, main peak luminosity (M_R ~ -18.3 mag at ~ 40 days). Encountered by this difficulty in the 56Ni heating model, we suggest an alternative scenario in which the heating source is a newly born, strongly magnetized neutron star (a magnetar) with the surface magnetic field Bmag ~ 10^{14-15} gauss and the initial spin period P0 ~ 10 ms. Then, SN 2005bf could be a link between normal SNe Ib/c and an X-Ray Flash associated SN 2006aj, connected in terms of Bmag and/or P0.Comment: 16 pages, 12 figures. Accepted by the Astrophysical Journa
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