10,424 research outputs found

    Charmonium properties at finite temperature on quenched anisotropic lattices

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    We study charmonium properties below and above TcT_c up to 1.8TcT_c, on quenched anisotropic lattices. Information of the spectral functions is extracted using the maximum entropy method and the constrained curve fitting. We also calculate the color singlet and averaged free energies and evaluate the charmonium spectrum with the potential model analysis. The relation between the lattice result of the spectral function analysis and the potential model is discussed.Comment: Lattice2004(non-zero), 3 pages, 4 figure

    Charmonium near the deconfining transition on the lattice

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    We study the charmonium properties at finite temperature using quenched lattice QCD simulations. Although a simple potential model analysis indicates no bound state at T>1.05TcT>1.05T_c, our analyses of the spatial correlation between quark and anti-quark and the spectral function indicate that a bound-state-like structure may survive even above TcT_c.Comment: 4 pages, 3 figures, Talk presented at the PANIC02 conference, Sept. 30 - Oct. 4, 2002, Osaka, Japa

    Nucleosynthesis in High-Entropy Hot-Bubbles of SNe and Abundance Patterns of Extremely Metal-Poor Stars

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    There have been suggestions that the abundance of Extremely Metal-Poor (EMP) stars can be reproduced by Hypernovae (HNe), not by normal supernovae (SNe). However, recently it was also suggested that if the innermost neutron-rich or proton-rich matter is ejected, the abundance patterns of ejected matter are changed, and normal SNe may also reproduce the observations of EMP stars. In this letter, we calculate explosive nucleosynthesis with various Ye and entropy, and investigate whether normal SNe with this innermost matter, which we call "hot-bubble" component, can reproduce the abundance of EMP stars. We find that neutron-rich (Ye = 0.45-0.49) and proton-rich (Ye = 0.51-0.55) matter can increase Zn/Fe and Co/Fe ratios as observed, but tend to overproduce other Fe-peak elements. In addition to it, we find that if slightly proton-rich matter with 0.50 <= Ye < 0.501 with s/kb ~ 15-40 is ejected as much as ~ 0.06 Msolar, even normal SNe can reproduce the abundance of EMP stars, though it requires fine-tuning of Ye. On the other hand, HNe can more easily reproduce the observations of EMP stars without fine-tuning. Our results imply that HNe are the most possible origin of the abundance pattern of EMP stars.Comment: 10 pages, 3 figures, Accepted to ApJL; modified reference

    Quarkonium at finite temperature

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    Lattice QCD studies on charmonium at finite temperature are presented After a discussion about problems for the Maximum Entropy Method applied to finite temperature lattice QCD, I show several results on charmonium spectral functions. The ``wave function'' of charmonium is also discussed to study the spatial correlation between quark and anti-quark in deconfinement phase.Comment: 8pages, 4figures, talk presented at Hard Probes 200

    Two-dimensional full particle simulation of a perpendicular collisionless shock with a shock-rest-frame model

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    A two-dimensional (2D) shock-rest-frame model for particle simulations is developed. Then full kinetic dynamics of a perpendicular collisionless shock is examined by means of a 2D full particle simulation. We found that in the 2D simulation there are fewer nonthermal electrons due to surfing acceleration which was seen in the previous 1D simulations of a high Mach number perpendicular shock in a low-beta and weakly magnetized plasma. This is because the particle motion along the ambient magnetic field disturbs the formation of coherent electrostatic solitary structures which is necessary for electron surfing acceleration.Comment: 4 pages, 4 figures, ApJL in press. The paper with full resolution images is http://theo.phys.sci.hiroshima-u.ac.jp/~ryo/papers/shock_rest_2D.pd
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