40,017 research outputs found

    Effects of thermal conduction in sonoluminescence

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    We show by numerical hydrodynamic calculations that there are two important effects of thermal conduction in sonoluminescence: (i) the bubble remains close to being isothermal during the expansion phase; and (ii) a cold, dense layer of air is formed at the bubble wall during the contraction phase. These conclusions are not sensitive to the particular equation of state used, although details of the dynamical evolution of the bubble are

    Temperature dependence of instantons in QCD

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    We investigate the temperature dependence of the instanton contents of gluon fields, using unquenched lattice QCD and the cooling method. The instanton size parameter deduced from the correlation function decreases from 0.44fm below the phase-transition temperature TcT_c (‚Čą150\approx 150MeV) to 0.33fm at 1.3 TcT_c. The instanton charge distribution is Poissonian above TcT_c, but it deviates from the convoluted Poisson at low temperature. The topological susceptibility decreases rapidly below TcT_c, showing the apparent restoration of the U(1)AU(1)_A symmetry already at T‚ČąTcT \approx T_c.Comment: 8 pages TEX, 3 Postscript figures available at http://www.krl.caltech.edu/preprints/MAP.htm

    Evidence for the Role of Instantons in Hadron Structure from Lattice QCD

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    Cooling is used as a filter on a set of gluon fields sampling the Wilson action to selectively remove essentially all fluctuations of the gluon field except for the instantons. The close agreement between quenched lattice QCD results with cooled and uncooled configurations for vacuum correlation functions of hadronic currents and for density-density correlation functions in hadronic bound states provides strong evidence for the dominant role of instantons in determining light hadron structure and quark propagation in the QCD vacuum.Comment: 26 pages in REVTeX, plus 10 figures, uuencoded. Submitted to Physical Review D. MIT-CTP-226
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