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In the context of cosmological structure formation sheets, filaments and eventually halos form due to gravitational instabilities. It is noteworthy, that at all times, the majority of the baryons in the universe does not reside in the dense halos but in the filaments and the sheets of the intergalactic medium. While at higher redshifts of z > 2, these baryons can be detected via the absorption of light (originating from more distant sources) by neutral hydrogen at temperatures of T ~ 10^4 K (the Lyman-alpha forest), at lower redshifts only about 20 % can be found in this state. The remain (about 50 to 70 % of the total baryons mass) is unaccounted for by observational means. Numerical simulations predict that these missing baryons could reside in the filaments and sheets of the cosmic web at high temperatures of T = 10^4.5 - 10^7 K, but only at low to intermediate densities, and constitutes the warm-hot intergalactic medium (WHIM). The high temperatures of the WHIM are caused by the formation of shocks and the subsequent shock-heating of the gas. This results in a high degree of ionization and renders the reliable detection of the WHIM a challenging task. Recent high-resolution hydrodynamical simulations indicate that, at redshifts of z ~ 2, filaments are able to provide very massive galaxies with a significant amount of cool gas at temperatures of T ~ 10^4 K. This could have an important impact on the star-formation in those galaxies. It is therefore of principle importance to investigate the particular hydro- and thermodynamical conditions of these large filament structures. Density and temperature profiles, and velocity fields, are expected to leave their special imprint on spectroscopic observations. A potential multiphase structure may act as tracer in observational studies of the WHIM. In the context of cold streams, it is important to explore the processes, which regulate the amount of gas transported by the streams. This includes the time evolution of filaments, as well as possible quenching mechanisms. In this context, the halo mass range in which cold stream accretion occurs is of particular interest. In order to address these questions, we perform particular hydrodynamical simulations of very high resolution, and investigate the formation and evolution of prototype structures representing the typical filaments and sheets of the WHIM. We start with a comprehensive study of the one-dimensional collapse of a sinusoidal density perturbation (pancake formation) and examine the influence of radiative cooling, heating due to an UV background, thermal conduction, and the effect of small-scale perturbations given by the cosmological power spectrum. We use a set of simulations, parametrized by the wave length of the initial perturbation L. For L ~ 2 Mpc/h the collapse leads to shock-confined structures. As a result of radiative cooling and of heating due to an UV background, a relatively cold and dense core forms. With increasing L the core becomes denser and more concentrated. Thermal conduction enhances this trend and may lead to an evaporation of the core at very large L ~ 30 Mpc/h. When extending our simulations into three dimensions, instead of a pancake structure, we obtain a configuration consisting of well-defined sheets, filaments, and a gaseous halo. For L > 4 Mpc/h filaments form, which are fully confined by an accretion shock. As with the one-dimensional pancakes, they exhibit an isothermal core. Thus, our results confirm a multiphase structure, which may generate particular spectral tracers. We find that, after its formation, the core becomes shielded against further infall of gas onto the filament, and its mass content decreases with time. In the vicinity of the halo, the filament's core can be attributed to the cold streams found in other studies. We show, that the basic structure of these cold streams exists from the very beginning of the collapse process. Further on, the cross section of the streams is constricted by the outwards moving accretion shock of the halo. Thermal conduction leads to a complete evaporation of the cold stream for L > 6 Mpc/h. This corresponds to halos with a total mass higher than M_halo = 10^13 M_sun, and predicts that in more massive halos star-formation can not be sustained by cold streams. Far away from the gaseous halo, the temperature gradients in the filament are not sufficiently strong for thermal conduction to be effective.
We study boundary value problems for linear elliptic differential operators of order one. The underlying manifold may be noncompact, but the boundary is assumed to be compact. We require a symmetry property of the principal symbol of the operator along the boundary. This is satisfied by Dirac type operators, for instance. We provide a selfcontained introduction to (nonlocal) elliptic boundary conditions, boundary regularity of solutions, and index theory. In particular, we simplify and generalize the traditional theory of elliptic boundary value problems for Dirac type operators. We also prove a related decomposition theorem, a general version of Gromov and Lawson's relative index theorem and a generalization of the cobordism theorem.
We consider orthogonal connections with arbitrary torsion on compact Riemannian manifolds. For the induced Dirac operators, twisted Dirac operators and Dirac operators of Chamseddine-Connes type we compute the spectral action. In addition to the Einstein-Hilbert action and the bosonic part of the Standard Model Lagrangian we find the Holst term from Loop Quantum Gravity, a coupling of the Holst term to the scalar curvature and a prediction for the value of the Barbero-Immirzi parameter.
We introduce renormalized integrals which generalize conventional measure theoretic integrals. One approximates the integration domain by measure spaces and defines the integral as the limit of integrals over the approximating spaces. This concept is implicitly present in many mathematical contexts such as Cauchy's principal value, the determinant of operators on a Hilbert space and the Fourier transform of an L^p function. We use renormalized integrals to define a path integral on manifolds by approximation via geodesic polygons. The main part of the paper is dedicated to the proof of a path integral formula for the heat kernel of any self-adjoint generalized Laplace operator acting on sections of a vector bundle over a compact Riemannian manifold.
A linear differential operator L is called weakly hypoelliptic if any local solution u of Lu = 0 is smooth. We allow for systems, i.e. the coefficients may be matrices, not necessarily of square size. This is a huge class of important operators which covers all elliptic, overdetermined elliptic, subelliptic and parabolic equations. We extend several classical theorems from complex analysis to solutions of any weakly hypoelliptic equation: the Montel theorem providing convergent subsequences, the Vitali theorem ensuring convergence of a given sequence, and Riemann's first removable singularity theorem. In the case of constant coefficients we show that Liouville's theorem holds, any bounded solution must be constant and any L^p solution must vanish.
Für Stefan Zweig war Brasilien 1941 "ein Land der Zukunft". Die Realität sieht anders aus: Bis heute ist es ein Land der Gegensätze, geprägt vor allem durch jenen von Arm und Reich. Was Gini-Koeffizienten nüchtern in Zahlen ausdrücken, kann man in Metropolen mit hypermodernen Zentren und Favelas an Berghängen auf engstem Raum erleben. Vor allem die Verteilung von Land resultiert in Auseinandersetzungen. Experten analysieren im Thema die Lage eines Staates, der in seinen Widersprüchlichkeiten gefangen ist.
Die Freiheit des Geldes
(2012)
We present 3D zero-beta ideal MHD simulations of the solar flare/CME event that occurred in Active Region 11060 on 2010 April 8. The initial magnetic configurations of the two simulations are stable nonlinear force-free field and unstable magnetic field models constructed by Su et al. (2011) using the flux rope insertion method. The MHD simulations confirm that the stable model relaxes to a stable equilibrium, while the unstable model erupts as a CME. Comparisons between observations and MHD simulations of the CME are also presented.
Although all bilinguals encounter cross-language interference (CLI), some bilinguals are more susceptible to interference than others. Here, we report on language performance of late bilinguals (Russian/German) on two bilingual tasks (interview, verbal fluency), their language use and switching habits. The only between-group difference was CLI: one group consistently produced significantly more errors of CLI on both tasks than the other (thereby replicating our findings from a bilingual picture naming task). This striking group difference in language control ability can only be explained by differences in cognitive control, not in language proficiency or language mode.
We present the new multi-threaded version of the state-of-the-art answer set solver clasp. We detail its component and communication architecture and illustrate how they support the principal functionalities of clasp. Also, we provide some insights into the data representation used for different constraint types handled by clasp. All this is accompanied by an extensive experimental analysis of the major features related to multi-threading in clasp.
Much of our knowledge about the solar dynamo is based on sunspot observations. It is thus desirable to extend the set of positional and morphological data of sunspots into the past. Gustav Spörer observed in Germany from Anklam (1861–1873) and Potsdam (1874–1894). He left detailed prints of sunspot groups, which we digitized and processed to mitigate artifacts left in the print by the passage of time. After careful geometrical correction, the sunspot data are now available as synoptic charts for almost 450 solar rotation periods. Individual sunspot positions can thus be precisely determined and spot areas can be accurately measured using morphological image processing techniques. These methods also allow us to determine tilt angles of active regions (Joy’s law) and to assess the complexity of an active region.
Inhalt: Editorial (Dr. Roswitha Lohwaßer) ; Auf Veränderungen reagieren. Herausforderungen an Beratungs- und Unterstützungssysteme im Kontext der Anforderungen an Schule
(Dr. Götz Bieber, Bernd Jankofsky) ; Lehrer qualifizieren, Kräfte bündeln. Überlegungen zur Enwicklung universitätsnaher Lehrerfortbildung in Niedersachsen (Dr. Jens Winkel, Ulrike Heinrichs) ; Nicht nur fachlich, auch didaktisch vorbereitet sein. Wann ist eine Fortbildung für Lehrkräfte eine gelungene Fortbildung (Elke Dengler) ; Der Lehrer - TÜV Qualitätscheck aus Schülersicht (Jorid Engler) ; Zusammenbringen, was zusammen gehört - universitäre Forschung und LehrerInnenfortbildung - (Dr. Charlotte Gemsa, Martina Rode) ; Wissensvermittlung spannend gestalten. Faszinierende numerische Experimente mit Polynomen - Fortbildung für Mathematiklehrer (Dr. Wolfgang Schöbel) ; Wow-Effekt, der Spaß an Mathe weckt. Erwartungen an eine Fortbildung für Mathematiklehrer (Jörg Schulz); Gemeinsames Lernen von Studierenden und Lehrenden. Was Potsdam von der Oldenburger Teamforschung lernen kann (Dr. Benjamin Apelojg) ; Design Thinking - Innovationsmethode für Projektarbeit. Ein Experiment im Helmholtz-Gymnasium (Andrea Scheer, Johannes Erdmann) ; Entwicklungen als Chance begreifen.
Lernkulturen und Portfolioarbeit in der Lehrerbildung (Dr. Mark-Oliver Carl) ; Rückblick auf die Tage der Lehrerbildung 2012
Inhalt: I. Megatrend Rekommunalisierung II. Rechtstatsächliche Befundnahmen 1. Der „Fall Potsdam“ 2. Weitere Rekommunalisierungsszenarien 3. Relativierungen III. Rekommunalisierungsbegriff, -gegenstände und -motive IV. Zu Rechtsregime und rechtsdogmatischen Herausforderungen 1. Zum Rechtsregime 2. Zu rechtsdogmatischen Herausforderungen V. Entwicklungsperspektiven jenseits von Privatisierung und Rekommunalisierung
In der aktuellen Performance-Management-Forschung wurden bereits eine Vielzahl von Einflussfaktoren untersucht, die eine zielgerichtete Verwendung von Kennzahlen beeinflussen. Verwaltungskultur spielte hierbei nur eine nachgeordnete Rolle. Die vorliegende Untersuchung verwendet die Daten einer Umfrage in allen kreisfreien Städten Deutschlands, um den Zusammenhang zwischen verschiedenen Kulturtypen und der Verwendung von Kennzahlen zu untersuchen. Als Analyseschema für Verwaltungskultur wird die Grid/Group-Analysis verwendet. Die Ergebnisse sind zum Teil überraschend. Individualistische Kulturen scheinen einen negativen, hierarchistische Kulturen einen positiven Einfluss zu haben. Dennoch wird das Fehlen eines geeigneten Operationalisierungsschemas bemängelt.
Wissenschaft hat einen großen Anteil daran, internationale Umweltprobleme auf die politische Tagesordnung zu bringen und Maßnahmen zu ihrer technischen Lösung zu entwerfen. Dies gilt sowohl für den Abbau der Ozonschicht als auch für den Klimawandel. So relevant die Generierung von wissenschaftlichen Erkenntnissen in diesen Feldern ist, so komplex ist die Interaktion zwischen Wissenschaft und Politik und so schwierig ist es, Verlässliches darüber zu sagen. Thomas Hickmann analysiert das Verhältnis von Wissenschaft und Politik in internationalen Umweltregimen aus einer neuen Perspektive. Er untersucht nicht den Einfluss wissenschaftlicher Erkenntnisse auf die Politik, sondern rückt die Frage in den Fokus, inwieweit Regierungen Einfluss auf die Wissenschaft nehmen, um nationale Interessen durchzusetzen. Diese Perspektive wurde in der Forschung bislang weitgehend vernachlässigt, weshalb eine systematische Analyse dieser Frage in der Literatur fehlt.