Animation and Boundlessness

East Asian Languages and Civilization

Bödeker's Effective Theory: From Langevin Dynamics to Dyson-Schwinger Equations

The dynamics of weakly coupled, non-abelian gauge fields at high temperature is non-perturbative if the characteristic momentum scale is of order |k| \sim g^2 T. Such a situation is typical for the processes of electroweak baryon number violation in the early Universe. Bödeker has derived an effective theory that describes the dynamics of the soft field modes to leading logarithmic order by means of a Langevin equation. This effective theory has been used for lattice calculations so far. In this work we provide a complementary, more analytic approach based on Dyson-Schwinger equations. Using methods known from stochastic quantisation, we recast Bödeker's Langevin equation in the form of a field theoretic path integral. We argue that a physically reasonable truncation of the Dyson-Schwinger equations requires the introduction of gauge ghosts, which in general is not mandatory in stochastic quantisation. This leads to a BRST symmetric formulation and to corresponding Ward-Takahashi identities. A second BRST symmetry reflecting the origin in a stochastic differential equation has to be sacrificed to establish the gauge BRST symmetry. The (stochastic) Ward identities can still be obtained by referring to the underlying structure and are shown to produce a cancellation among several terms of the gauge Ward identity. To clarify some issues, we derive the Feynman rules and perform some perturbative calculations. Finally, we deduce the Dyson-Schwinger equations and suggest a truncation scheme that approximately respects the gauge and stochastic Ward identities

Resummed effective action in the world-line formalism

Using the world-line method we resum the scalar one-loop effective action. This is based on an exact expression for the one-loop action obtained for a background potential and a Taylor expansion of the potential up to quadratic order in x-space. We thus reproduce results of Masso and Rota very economically. An alternative resummation scheme is suggested using ``center of mass'' based loops which is equivalent under the assumption of vanishing third and higher derivatives in the Taylor expansion but leads to simplified expressions. In an appendix some general issues concerning the relation between world-line integrals with fixed end points versus integrals with fixed center are clarified. We finally note that this method is also very valuable for gauge field effective actions where it is based on the Euler--Heisenberg type resummation.Comment: 15 page

Induction of Krüppel-Like Factor 4 Mediates Polymorphonuclear Neutrophil Activation in Streptococcus pneumoniae Infection

The recruitment and activation of polymorphonuclear neutrophils (PMNs) are of central importance for the elimination of pathogens in bacterial infections. We investigated the Streptococcus pneumoniae-dependent induction of the transcription factor Kruppel-like factor (KLF) 4 in PMNs as a potential regulator of PMN activation. We found that KLF4 expression is induced in human blood-derived PMNs in a time- and dose-dependent manner by wild-type S. pneumoniae and capsule knockout mutants. Unencapsulated knockout mutants induced stronger KLF4 expression than encapsulated wild types. The presence of autolysin LytA-competent (thus viable) pneumococci and LytA-mediated bacterial autolysis were required for KLF4 induction in human and murine PMNs. LyzMcre-mediated knockdown of KLF4 in murine blood-derived PMNs revealed that KLF4 influences pneumococci killing and increases the release of the proinflammatory cytokines tumor necrosis factor alpha and keratinocyte chemoattractant and decreases the release of the anti-inflammatory cytokine interleukin-10. Thus, S. pneumoniae induces KLF4 expression in PMNs, which contributes to PMN activation in S. pneumoniae infection

Digitalization in Construction, Computer-based Design for Structural Elements, PArt 2: Analyses and Validation of Compliance to EuroCodes

A classic structural analysis is characterized by the usage of a wide spectrum of manual, specialized analysis methods. An engineer has to break down the complex problem into small manageable sub-problems. This procedure will be completely superseded by the advent of numerical methods. A full model of the spatial structure will be built up. A similar revolution has already begun by the introduction of finite shell and volume elements into commercially available FE software. The idea is that these models are closer to reality and allow us to capture both global and local effects in one single comprehensive model. This, however, introduces modelling questions and numerical effects, which are explicitly excluded from simplified theory, and questions arise regarding the trustworthiness of these results. Shell elements have already been fairly well established in practical engineering. The next step could be the use of volume elements to overcome certain restriction inherent in shell formulations. One driving force for this tendency is BIM (Building Information Modelling). Here the geometrical model is, like nature itself, fully 3D. It can be directly translated into the Finite Element Method (FEM). However, structural design in the 27 EU member states and 4 EFTA countries has to be performed according to the Eurocodes (EC), representing harmonized European Standards (EN) for the structural design. These design codes regulate essential requirements regarding mechanical resistance and stability as well as safety aspects. The current Eurocodes essentially stipulate engineering design models which can easily be transferred to classical structural analyses, but often do not give comprehensive references to the application and evaluation of advanced numerical simulations. The application of associated software products is not regulated by norms. This situation often results in discussions and different interpretations of the design results. Ultimately, false computational assumptions and misinterpretations can lead to damages and unsafe designs. Guidance for the verification of the software results is required and the link to the current and upcoming second generation of Eurocodes is also presented by the project. In parallel the possibilities by digitalization in construction by Building Information Modelling and the transfer of data from the architectural model to the structural model have been investigatedAugutst 202