Mean Field Dynamics in Non-Abelian Plasmas from Classical Transport Theory

Based on classical transport theory, we present a general set of covariant equations describing the dynamics of mean fields and their statistical fluctuations in a non-Abelian plasma in or out-of-equilibrium. A procedure to obtain the collision integrals for the Boltzmann equation from the microscopic theory is described. As an application, we study a hot non-Abelian plasma close to equilibrium, where the fluctuations are integrated out explicitly. For soft fields, and at logarithmic accuracy, we obtain B\"odeker's effective theory.Comment: 4 pages, revtex, no figures. Typo removed, a reference updated, version as to appear in Phys. Rev. Let

Polarization transfer in the 4^{4}He(e⃗,e′p⃗3(\vec{e},e' \vec{p}^{3}H reaction

Polarization transfer in the 4He(e,e'p)3H reaction at a Q^2 of 0.4 (GeV/c)^2 was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.Comment: 5 pages, Latex, 2 postscript figures, submitted to Physics Letters

Kinetic Equation for Gluons in the Background Gauge of QCD

We derive the quantum kinetic equation for a pure gluon plasma, applying the background field and closed-time-path method. The derivation is more general and transparent than earlier works. A term in the equation is found which, as in the classical case, corresponds to the color charge precession for partons moving in the gauge field.Comment: RevTex 4, 4 pages, no figure, PRL accepted versio

Entropy Production in Relativistic Hydrodynamics

The entropy production occurring in relativistic hydrodynamical systems such as the quark-gluon plasma (QGP) formed in high-energy nuclear collisions is explored. We study mechanisms which change the composition of the fluid, i.e. particle production and/or chemical reactions, along with chemo- and thermo-diffusion. These effects complement the conventional dissipative effects of shear viscosity, bulk viscosity, and heat conductivity.Comment: 15 pages; LaTex. Accepted for publication in Physics Letters B. - Two typos corrected and one reference adde

Microstructural characterization of AISI 431 martensitic stainless steel laser-deposited coatings

High cooling rates during laser cladding of stainless steels may alter the microstructure and phase constitution of the claddings and consequently change their functional properties. In this research, solidification structures and solid state phase transformation products in single and multi layer AISI 431 martensitic stainless steel coatings deposited by laser cladding at different processing speeds are investigated by optical microscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), orientation imaging microscopy (OIM), ternary phase diagram, Schaeffler and TTT diagrams. The results of this study show how partitionless solidification and higher solidification rates alter the microstructure and phase constitution of martensitic stainless steel laser deposited coatings. In addition, it is shown that while different cladding speeds have no effect on austenite–martensite orientation relationship in the coatings, increasing the cladding speed has resulted in a reduction of hardness in deposited coatings which is in contrast to the common idea about obtaining higher hardness values at higher cladding speeds.

Facing the Beast Apart Together: Fear in Boys and Girls after Processing Information about Novel Animals Individually or in a Duo

In this experimental study, we made an attempt to examine gender-related peer influences on childhood fear. Nine- to 12-year-old boys and girls were provided with ambiguous and positive information about novel animals and then asked to provide a subjective fear rating of the animals under two conditions: fear of one animal was assessed individually by the child on its own, whereas fear of the other animal was measured after a brief discussion on fear-related issues with a same-gender peer. Results indicated that children who completed the FBQ after a discussion with a same-gender peer displayed lower fear beliefs scores than children who completed the questionnaire fully on their own. This fear-suppression effect was mainly evident in boys after hearing ambiguous information about the novel animals. The implications of these findings are briefly discussed

Hard Loop Approach to Anisotropic Systems

Anisotropic systems of quarks and gluons, which at least for sufficiently short space-time intervals can be treated as homogeneous and static, are considered. The gluon polarization tensor of such a system is explicitly computed within the semiclassical kinetic and Hard Loop diagrammatic theories. The equivalence of the two approaches is demonstrated. The quark self energy is computed as well, and finally, the dispersion relations of quarks and gluons in the anisotropic medium are discussed.Comment: 10 pages, revised to appear in Phys. Rev.

The problem of nonlinear Landau damping in quark-gluon plasma

On the basis of the semiclassical equations for quark-gluon plasma (QGP) and Yang-Mills equation, the generalized kinetic equation for waves with regard to its interaction is obtained. The physical mechanisms defining nonlinear scattering of a plasmon by QGP particles are analysed. The problem on a connection of nonlinear Landau damping rate of longitudinal oscillation with damping rate, obtained on the basis of hard thermal loops approximation, is considered.Comment: 33 page

Transport Theory of Massless Fields

Using the Schwinger-Keldysh technique we discuss how to derive the transport equations for the system of massless quantum fields. We analyse the scalar field models with quartic and cubic interaction terms. In the $\phi^4$ model the massive quasiparticles appear due to the self-interaction of massless bare fields. Therefore, the derivation of the transport equations strongly resembles that one of the massive fields, but the subset of diagrams which provide the quasiparticle mass has to be resummed. The kinetic equation for the finite width quasiparticles is found, where, except the mean-field and collision terms, there are terms which are absent in the standard Boltzmann equation. The structure of these terms is discussed. In the massless $\phi^3$ model the massive quasiparticles do not emerge and presumably there is no transport theory corresponding to this model. It is not surprising since the $\phi^3$ model is anyhow ill defined.Comment: 32 pages, no macro

Ferromagnetic/superconducting proximity effect in La0.7Ca0.3MnO3 / YBa2Cu3O7 superlattices

We study the interplay between magnetism and superconductivity in high quality YBa2Cu3O7 (YBCO) / La0.7Ca0.3MnO3(LCMO)superlattices. We find evidence for the YBCO superconductivity depression in presence of the LCMO layers. We show that due to its short coherence length superconductivity survives in the YBCO down to much smaller thickness in presence of the magnetic layer than in low Tc superconductors. We also find that for a fixed thickness of the superconducting layer, superconductivity is depressed over a thickness interval of the magnetic layer in the 100 nm range. This is a much longer length scale than that predicted by the theory of ferromagnetic/superconducting proximity effect.Comment: 10 pages + 5 figures, submitted to Phys. Rev.