Color Coulomb Potential in Yang-Mills Theory from Hamiltonian Flows

We consider the Hamiltonian formulation of Yang-Mills theory in the Coulomb gauge and apply the recently developed technique of Hamiltonian flows. We formulate a flow equation for the color Coulomb potential which allows for a scaling solution that results in an almost linearly rising confining potential.Comment: 6 pages, 4 figure

Formin1 disruption confers oligodactylism and alters Bmp signaling

Proper limb development requires concerted communication between cells within the developing limb bud. Several molecules have been identified which contribute to the formation of a circuitry loop consisting in large part of secreted proteins. The intracellular actin nucleator, Formin 1 (Fmn1), has previously been implicated in limb development, but questions remain after the identification of a Gremlin transcriptional enhancer within the 3′ end of the Fmn 1 locus. To resolve this issue, a knockout mouse devoid of Fmn1 protein was created and characterized. The mice exhibit a reduction of digit number to four, a deformed posterior metatarsal, phalangeal soft tissue fusion as well as the absence of a fibula to 100% penetrance in the FVB genetic background. Importantly, this mutant allele does not genetically disrupt the characterized Gremlin enhancer, and indeed Gremlin RNA expression is upregulated at the 35 somite stage of development. Our data reveal increased Bone Morphogenetic Protein (Bmp) activity in mice which carry a disruption in Fmn1, as evidenced by upregulation of Msx1 and a decrease in Fgf4 within the apical ectodermal ridge. Additionally, these studies show enhanced activity downstream of the Bmp receptor in cells where Fmn1 is perturbed, suggesting a role for Fmn1 in repression of Bmp signalin

Fermion loop simulation of the lattice Gross-Neveu model

We present a numerical simulation of the Gross-Neveu model on the lattice using a new representation in terms of fermion loops. In the loop representation all signs due to Pauli statistics are eliminated completely and the partition function is a sum over closed loops with only positive weights. We demonstrate that the new formulation allows to simulate volumes which are two orders of magnitude larger than those accessible with standard methods

Parallel computation of radio listening rates

Obtaining the listening rates of radio stations in function of time is an important instrument for determining the impact of publicity. Since many radio stations are financed by publicity, the exact determination of radio listening rates is vital to their existence and to further development. Existing methods of determining radio listening rates are based on face to face interviews or telephonic interviews made with a sample population. These traditional methods however require the cooperation and compliance of the participants. In order to significantly improve the determination of radio listening rates, special watches were created which incorporate a custom integrated circuit sampling the ambient sound during a few seconds every minutes. Each watch accumulates these compressed sound samples during one full week. Watches are then sent to an evaluation center, where the sound samples are matched with the sound samples recorded from candidate radio stations. The present paper describes the processing steps necessary for computing the radio listening rates, and shows how this application was parallelized on a cluster of PCs using the CAP Computer-aided parallelization framework. Since the application must run in a production environment, the paper describes also the support provided for graceful degradation in case of transient or permanent failure of one of the system's components. The parallel sound matching server offers a linear speedup up to a large number of processing nodes thanks to the fact that disk access operations across the network are done in pipeline with computations

Formin 1-Isoform IV Deficient Cells Exhibit Defects in Cell Spreading and Focal Adhesion Formation

Background: Regulation of the cytoskeleton is a central feature of cell migration. The formin family of proteins controls the rate of actin nucleation at its barbed end. Thus, formins are predicted to contribute to several important cell processes such as locomotion, membrane ruffling, vesicle endocytosis, and stress fiber formation and disassociation. Methodology/Principal Findings: In this study we investigated the functional role of Formin1-isoform4 (Fmn1-IV) by using genetically null primary cells that displayed augmented protrusive behaviour during wound healing and delayed cell spreading. Cells deficient of Fmn1-IV also showed reduced efficiency of focal adhesion formation. Additionally, we generated an enhanced green fluorescence protein (EGFP)-fused Fmn1-IV knock-in mouse to monitor the endogenous subcellular localization of Fmn1-IV. Its localization was found within the cytoplasm and along microtubules, yet it was largely excluded from adherens junctions. Conclusions/Significance: It was determined that Fmn1-IV, as an actin nucleator, contributes to protrusion of the cell’s leading edge and focal adhesion formation, thus contributing to cell motility

Renormierungsgruppenflüsse der Hamiltonschen QCD in Coulomb-Eichung

In this thesis, Yang-Mills theory in Coulomb gauge in its Hamiltonian formulation is investigated by applying the method of the functional renormalization group. Yang-Mills theories form the basis of the Standard Model of elementary particle physics. The focus of this work is in particular on quantum chromodynamics, which describes the strong interaction. In Chap. 1, the method of the functional renormalization group is introduced. At first, it is presented in its usual formulation in Lagrangian quantum field theory. The flow equation for the propagator of scalar quantum field theory is derived. Chap. 2 contains an overview of Yang-Mills theory in Coulomb gauge in its Hamiltonian formulation as opposed to the Lagrangian approach. In Chap. 3 the functional renormalization group is transferred to the Hamiltonian setting of Yang-Mills theory in Coulomb gauge. With this new tool, the flow equations for the gluon and ghost propagators are derived. The equations are solved numerically using two different approximations. The results are compared to those obtained in the variational approach. Chap. 4 deals with the derivation and solution of a flow equation for the colour Coulomb potential between two heavy colour charges. The corresponding Dyson-Schwinger equation is derived and the conditions for the existence of solutions are examined. The inclusion of dynamic quarks into this formalism is the subject of Chap. 5. The static quark propagator is calculated in order to obtain the mass function, which shows the dynamic generation of the constituent quark mass. The influence of the gluon propagator and of the quark four-point function on the mass function are examined. In the last chapter, a short summary and an outlook are given. Some definitions and several longer calculations are presented in the appendices.In der vorliegenden Dissertation wird die Yang-Mills-Theorie in Coulombeichung in der Hamilton-Formulierung unter Anwendung der Funktionalen Renormierungsgruppenflüsse untersucht. Yang-Mills-Theorien bilden die Grundlage des Standardmodells der Elementarteilchenphysik. Der Fokus dieser Arbeit liegt insbesondere auf der Quantenchromodynamik, die die Starke Wechselwirkung beschreibt. In Kap. 1 wird die Methode der Funktionalen Renormierungsgruppe eingeführt. Sie wird dabei zunächst in ihrer üblichen Formulierung innerhalb des Lagrange-Zugangs zur Quantenfeldtheorie präsentiert. Die Flussgleichung für den Propagator der skalaren Quantenfeldtheorie wird hergeleitet. Kap. 2 enthält einen Überblick über die Yang-Mills-Theorie in Coulombeichung in der Hamilton-Formulierung, als Gegensatz Lagrange-Formulierung. In Kap. 3 wird die Funktionale Renormierungsgruppe auf den Hamilton-Zugang zur Yang-Mills-Theorie in Coulombeichung übertragen. Mit diesem neuen Werkzeug werden die Flussgleichungen für den Gluon- und den Geistpropagator hergeleitet. Die Gleichungen werden numerisch unter Benutzung zweier verschiedener Näherungen gelöst und die Ergebnisse mit jenen aus dem Variationszugang verglichen. Kap. 4 hat die Herleitung und Lösung einer Flussgleichung für das Farb-Coulomb-Potential zwischen zwei schweren Farbladungen zum Thema. Die entsprechende Dyson-Schwinger-Gleichung wird hergeleitet und die Bedingungen für die Existenz von Lösungen für diese Gleichung werden untersucht. Die Einbeziehung dynamischer Quarks in diesen Formalismus wird in Kap. 5 behandelt. Der statische Quark-Propagator wird berechnet, um die Massenfunktion zu erhalten, die die dynamische Erzeugung der Konstituentenquarkmasse beschreibt. Der Einfluss des Gluonpropagators und der Quark-Vier-Punkt-Funktion auf die Massenfunktion werden untersucht. Im letzten Kapitel werden eine kurze Zusammenfassung und ein Ausblick gegeben. Einige Definitionen und mehrere längere Rechnungen werden in den Anhängen dargestellt

Hamiltonian flow in Coulomb gauge Yang-Mills theory

We derive a new functional renormalization group equation for Hamiltonian Yang-Mills theory in Coulomb gauge. The flow equations for the static gluon and ghost propagators are solved under the assumption of ghost dominance within different diagrammatic approximations. The results are compared to those obtained in the variational approach and the reliability of the approximations is discussed.Comment: 17 pages, 10 figure