On the Landau gauge matter-gluon vertex in scalar QCD in a functional approach

Recently the quark-gluon vertex has been investigated in Landau gauge using a combined Dyson-Schwinger and nPI effective action approach. We present here a numerical analysis of a simpler system where the quarks have been replaced by charged scalar fields. We solve the coupled system of Dyson-Schwinger equations for the scalar propagator, the scalar-gluon vertex and the Yang-Mills propagators in a truncation related to earlier studies. The calculations have been performed for scalars both in the fundamental and the adjoint representation. A clear suppression of the Abelian diagram is found in both cases. Thus, within the used truncation the suppression of the Abelian diagram predominantly happens dynamically and is to a high degree independent of the colour structure. The numerical techniques developed here can directly be applied to the fermionic case.Comment: 8 pages, 4 figures, presented by MH at Excited QCD 2013, 3rd - 9th February 2013, Bjelasnica Mountain, Sarajevo, Bosnia-Herzegovin

The Quark-Gluon Vertex in Landau gauge QCD

The coupled system of the quark-gluon vertex and quark propagator Dyson-Schwinger equations (DSEs) is investigated within Landau gauge QCD. The aim is to get a deeper insight into the mechanisms of quark confinement and dynamical chiral symmetry breaking and into a possible relation between these two phenomena. To this end an earlier study is extended by improving systematically on the truncations imposed on the quark-gluon vertex DSE. A clear infrared enhancement for all tensor structures of the quark-gluon vertex is obtained.Comment: 8 pages, Confinement X proceeding

Center Phase Transition from Fundamentally Charged Matter Propagators

The center phase transition at non-vanishing temperatures is investigated in Landau gauge Quantum Chromodynamics (QCD) and scalar QCD. For each theory novel order parameters for the transition are introduced. The matter-gluon vertex which occurs in the Dyson-Schwinger equations of the propagators has to be modeled in contemporary studies. It is found that the nature of the phase transition depends strongly on the detailed structure of this vertex. Our investigation motivates a precise determination of the matter-gluon vertex at non-vanishing temperatures.Comment: 8 pages, Confinement X proceeding

On propagators and three-point functions in Landau gauge QCD and QCD-like theories

Recent progress in our studies of propagators and three-point functions in Landau gauge for QCD and QCD-like theories is presented. Special emphasis is put on the properties of the three-gluon vertex and the quark-gluon vertex. The effect of unquenching is investigated. Furthermore, an exploratory study for a large number of light flavours is described, from where clear evidence for the qualitative behaviour of propagators in the so-called conformal window can be extracted.Comment: 13 pages, 9 figures; Proceedings of the workshop QCD-TNT-III, ECT* Trento, Sept. 2-6, 2013; references update

Generalized helicity formalism, higher moments, and the B→KJK(→Kπ)¯¯¯ℓ1ℓ2 angular distributions

We generalise the Jacob-Wick helicity formalism, which applies to sequential decays, to effective field theories of rare decays of the type $B \to K_{J_K}(\to K \pi) \bar{\ell}_1 \ell_2$. This is achieved by reinterpreting local interaction vertices $\bar b \Gamma'_{\mu_1 ..\mu_n} s \bar \ell \Gamma^{\mu_1 ..\mu_n} \ell$ as a coherent sum of $1 \to 2$ processes mediated by particles whose spin ranges between zero and $n$. We illustrate the framework by deriving the full angular distributions for $B \to K\bar{\ell}_1 \ell_2$ and $B \to K^*(\to K \pi) \bar{\ell}_1 \ell_2$ for the complete dimension-six effective Hamiltonian for non-equal lepton masses. Amplitudes and decay rates are expressed in terms of Wigner rotation matrices, leading naturally to the method of moments in various forms. We discuss how higher-spin operators and QED corrections alter the standard angular distribution used throughout the literature, potentially leading to differences between the method of moments and the likelihood fits. We propose to diagnose these effects by assessing higher angular moments. These could be relevant in investigating the nature of the current LHCb anomalies in $R_K = {\cal B}( B \to K \mu^+\mu^-) /{\cal B}( B \to K e^+e^-)$ as well as angular observables in $B \to K^* \mu^+\mu^-$.Comment: identical to version appeared in PRD. typo in Eq below C.9 corrected, includes Mathematica notebook with angular distribution same as v

Silent recovery of native kidney function after transplantation in a patient with membranous nephropathy

Recurrence of membranous nephropathy (MN) is frequently seen after transplantation. However, there are no published data about the course of MN in the native kidneys after transplantation. Disease progression in almost all cases is assumed to be the ‘natural' course after transplantation. We report on a patient suffering from end-stage renal disease due to MN. Eight years after transplantation, nephrectomy was performed due to chronic rejection and unexpectedly, partial recovery of native kidney function was noted. As far as we know, there is no other similar case reported in the literature. The potential impact of the immunosuppression, especially of calcineurin inhibitors, is discusse

Solving the Ghost-Gluon System of Yang-Mills Theory on GPUs

We solve the ghost-gluon system of Yang-Mills theory using Graphics Processing Units (GPUs). Working in Landau gauge, we use the Dyson-Schwinger formalism for the mathematical description as this approach is well-suited to directly benefit from the computing power of the GPUs. With the help of a Chebyshev expansion for the dressing functions and a subsequent appliance of a Newton-Raphson method, the non-linear system of coupled integral equations is linearized. The resulting Newton matrix is generated in parallel using OpenMPI and CUDA(TM). Our results show, that it is possible to cut down the run time by two orders of magnitude as compared to a sequential version of the code. This makes the proposed techniques well-suited for Dyson-Schwinger calculations on more complicated systems where the Yang-Mills sector of QCD serves as a starting point. In addition, the computation of Schwinger functions using GPU devices is studied.Comment: 19 pages, 7 figures, additional figure added, dependence on block-size is investigated in more detail, version accepted by CP

The quark propagator in QCD and G

QCD-like theories provide testing grounds for truncations of functional equations at non-zero density, since comparisons with lattice results are possible due to the absence of the sign problem. As a first step towards such a comparison, we determine for QCD and $G_2$ QCD the chiral and confinement/deconfinement transitions from the quark propagator Dyson-Schwinger equation at zero chemical potential by calculating the chiral and dual chiral condensates, respectively.Comment: 7 pages, 6 figures, submitted to proceedings of 'XIIth Quark Confinement and the Hadron Spectrum', August 28-September 04, 2016, Thessaloniki, Greec