Relativistic description of the charmonium mass spectrum

The charmonium mass spectrum is considered in the framework of the constituent quark model with the relativistic treatment of the c quark. The obtained masses are in good agreement with the existing experimental data including the mass of eta_c(2S).Comment: 5 page

Bosonization in Particle Physics

Path integral techniques in collective fields are shown to be a useful analytical tool to reformulate a field theory defined in terms of microscopic quark (gluon) degrees of freedom as an effective theory of collective boson (meson) fields. For illustrations, the path integral bosonization approach is applied to derive a (non)linear sigma model from a Nambu-Jona-Lasinio (NJL) quark model. The method can be extended to include higher order derivative terms in meson fields or heavy-quark symmetries. It is also approximately applicable to QCD.Comment: 12 pages, LaTeX, uses lamuphys.sty, 5 LaTeX figures, talk given at the Workshop "Field Theoretical Tools in Polymer and Particle Physics", University Wuppertal, June 17-19, 199

Spin projection and spin current density within relativistic electronic transport calculations

A spin projection scheme is presented which allows the decomposition of the electric conductivity into two different spin channels within fully relativistic $ab$ $initio$ transport calculations that account for the impact of spin-orbit coupling. This is demonstrated by calculations of the spin-resolved conductivity of Fe$_{1-x}$Cr$_x$ and Co$_{1-x}$Pt$_x$ disordered alloys on the basis of the corresponding Kubo-Greenwood equation implemented using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band structure method. In addition, results for the residual resistivity of diluted Ni-based alloys are presented that are compared to theoretical and experimental ones that rely on Mott's two-current model for spin-polarized systems. The application of the scheme to deal with the spin-orbit induced spin Hall effect is discussed in addition

Excited heavy tetraquarks with hidden charm

The masses of the excited heavy tetraquarks with hidden charm are calculated within the relativistic diquark-antidiquark picture. The dynamics of the light quark in a heavy-light diquark is treated completely relativistically. The diquark structure is taken into account by calculating the diquark-gluon form factor. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that X(3872), Y(4260), Y(4360), Z(4248), Z(4433) and Y(4660) could be tetraquark states with hidden charm.Comment: 11 page

Ab-initio calculation of the Gilbert damping parameter via linear response formalism

A Kubo-Greenwood-like equation for the Gilbert damping parameter $\alpha$ is presented that is based on the linear response formalism. Its implementation using the fully relativistic Korringa-Kohn-Rostoker (KKR) band structure method in combination with Coherent Potential Approximation (CPA) alloy theory allows it to be applied to a wide range of situations. This is demonstrated with results obtained for the bcc alloy system Fe$_x$Co$_{1-x}$ as well as for a series of alloys of permalloy with 5d transition metals. To account for the thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. The corresponding calculations for Ni correctly describe the rapid change of $\alpha$ when small amounts of substitutional Cu are introduced

High order fluid model for streamer discharges. II. Numerical solution and investigation of planar fronts

The high order fluid model developed in the preceding paper is employed here to study the propagation of negative planar streamer fronts in pure nitrogen. The model consists of the balance equations for electron density, average electron velocity, average electron energy and average electron energy flux. These balance equations have been obtained as velocity moments of Boltzmann's equation and are here coupled to the Poisson equation for the space charge electric field. Here the results of simulations with the high order model, with a PIC/MC (Particle in cell/Monte Carlo) model and with the first order fluid model based on the hydrodynamic drift-diffusion approximation are presented and compared. The comparison with the MC model clearly validates our high order fluid model, thus supporting its correct theoretical derivation and numerical implementation. The results of the first order fluid model with local field approximation, as usually used for streamer discharges, show considerable deviations. Furthermore, we study the inaccuracies of simulation results caused by an inconsistent implementation of transport data into our high order fluid model. We also demonstrate the importance of the energy flux term in the high order model by comparing with results where this term is neglected. Finally, results with an approximation for the high order tensor in the energy flux equation is found to agree well with the PIC/MC results for reduced electric fields up to 1000 Townsend, as considered in this work.Comment: 26 pages, 11 figure

Coherent description of the intrinsic and extrinsic anomalous Hall effect in disordered alloys on an abab initioinitio level

A coherent description of the anomalous Hall effect (AHE) is presented that is applicable to pure as well as disordered alloy systems by treating all sources of the AHE on equal footing. This is achieved by an implementation of the Kubo-St\v{r}eda equation using the fully relativistic Korringa-Kohn-Rostoker (KKR) Green's function method in combination with the Coherent Potential Approximation (CPA) alloy theory. Applications to the pure elemental ferromagnets bcc-Fe and fcc-Ni led to results in full accordance with previous work. For the alloy systems fcc-Fe$_x$Pd$_{1-x}$ and fcc-Ni$_x$Pd$_{1-x}$ very satisfying agreement with experiment could be achieved for the anomalous Hall conductivity (AHC) over the whole range of concentration. To interpret these results an extension of the definition for the intrinsic AHC is suggested. Plotting the corresponding extrinsic AHC versus the longitudinal conductivity a linear relation is found in the dilute regimes, that allows a detailed discussion of the role of the skew and side-jump scattering processes.Comment: * shortened manuscript * slight rewordings * changed line style in Fig 1 * corrected misprinted S (skewness) factor * merged Fig. 3 with Fig. 1 * new citation introduce