Thermal photons in QGP and non-ideal effects

We investigate the thermal photon production-rates using one dimensional boost-invariant second order relativistic hydrodynamics to find proper time evolution of the energy density and the temperature. The effect of bulk-viscosity and non-ideal equation of state are taken into account in a manner consistent with recent lattice QCD estimates. It is shown that the \textit{non-ideal} gas equation of state i.e $\epsilon-3\,P\,\neq 0$ behaviour of the expanding plasma, which is important near the phase-transition point, can significantly slow down the hydrodynamic expansion and thereby increase the photon production-rates. Inclusion of the bulk viscosity may also have similar effect on the hydrodynamic evolution. However the effect of bulk viscosity is shown to be significantly lower than the \textit{non-ideal} gas equation of state. We also analyze the interesting phenomenon of bulk viscosity induced cavitation making the hydrodynamical description invalid. We include the viscous corrections to the distribution functions while calculating the photon spectra. It is shown that ignoring the cavitation phenomenon can lead to erroneous estimation of the photon flux.Comment: 11 pages, 13 figures; accepted for publication in JHE

Critical roles of molecular dynamics in the superior mechanical properties of isotactic-poly (1-butene) elucidated by solid-state NMR

Isotactic-poly(1-butene) (iPB1) shows superior mechanical properties after crystal–crystal transitions. Recently, Miyoshi et al. found that crystalline stems in metastable tetragonal crystal perform uniaxial rotational diffusions accompanying side-chain conformational transitions in the fast motional limit (correlation time, 〈τc〉 10 s). In addition, lamellar thickness, 〈l〉 of iPB1 and a low isotacticity iPB1 (low_iPB1) with 〈mmmm〉=78%, respectively, were investigated by small-angle X-ray scattering. The low_iPB1 sample shows very week supercooling dependence of 〈l〉 (∼5 nm), whereas iPB1 shows strong supercooling dependence of 〈l〉 (10–28 nm). On the basis of molecular dynamics and 〈l〉 results, molecular dynamics effects on structures and unique mechanical property of iPB1 are discussed