The randomly driven Ising ferromagnet, Part I: General formalism and mean field theory

We consider the behavior of an Ising ferromagnet obeying the Glauber dynamics under the influence of a fast switching, random external field. After introducing a general formalism for describing such systems, we consider here the mean-field theory. A novel type of first order phase transition related to spontaneous symmetry breaking and dynamic freezing is found. The non-equilibrium stationary state has a complex structure, which changes as a function of parameters from a singular-continuous distribution with Euclidean or fractal support to an absolutely continuous one.Comment: 12 pages REVTeX/LaTeX format, 12 eps/ps figures. Submitted to Journal of Physics

Liquid 4He near the superfluid transition in the presence of a heat current and gravity

The effects of a heat current and gravity in liquid 4He near the superfluid transition are investigated for temperatures above and below T_lambda. We present a renormalization-group calculation based on model F for the Green's function in a self-consistent approximation which in quantum many-particle theory is known as the Hartree approximation. The approach can handle a zero average order parameter above and below T_lambda and includes effects of vortices. We calculate the thermal conductivity and the specific heat for all temperatures T and heat currents Q in the critical regime. Furthermore, we calculate the temperature profile. Below T_lambda we find a second correlation length which describes the dephasing of the order parameter field due to vortices. We find dissipation and mutual friction of the superfluid-normal fluid counterflow and calculate the Gorter-Mellink coefficient A. We compare our theoretical results with recent experiments.Comment: 26 pages, 9 figure

The Dynamics of Nestedness Predicts the Evolution of Industrial Ecosystems

In economic systems, the mix of products that countries make or export has been shown to be a strong leading indicator of economic growth. Hence, methods to characterize and predict the structure of the network connecting countries to the products that they export are relevant for understanding the dynamics of economic development. Here we study the presence and absence of industries at the global and national levels and show that these networks are significantly nested. This means that the less filled rows and columns of these networks' adjacency matrices tend to be subsets of the fuller rows and columns. Moreover, we show that nestedness remains relatively stable as the matrices become more filled over time and that this occurs because of a bias for industries that deviate from the networks' nestedness to disappear, and a bias for the missing industries that reduce nestedness to appear. This makes the appearance and disappearance of individual industries in each location predictable. We interpret the high level of nestedness observed in these networks in the context of the neutral model of development introduced by Hidalgo and Hausmann (2009). We show that, for the observed fills, the model can reproduce the high level of nestedness observed in these networks only when we assume a high level of heterogeneity in the distribution of capabilities available in countries and required by products. In the context of the neutral model, this implies that the high level of nestedness observed in these economic networks emerges as a combination of both, the complementarity of inputs and heterogeneity in the number of capabilities available in countries and required by products. The stability of nestedness in industrial ecosystems, and the predictability implied by it, demonstrates the importance of the study of network properties in the evolution of economic networks.Comment: 26 page

Etablierung einer Methode zur Phänotypisierung der Schwarzfäule (Guignardia bidwellii) resistenz in der Weinrebe (Vitis spec.)

Development of a method for phenotyping Black Rot (Guignardia bidwellii) resistance on grapevine (Vitis spec.)ZusammenfassungDer Erreger der Schwarzfäule Guignardia bidwellii wurde im 19. Jahrhundert aus Nordamerika nach Europa eingeschleppt. Seit 2002 wird der Ascomycet vermehrt in deutschen Weinanbaugebieten beobachtet und führt gebietsweise zu erheblicher Ertragsminderung. Dies gibt Anlass, in Zukunft Schwarzfäule resistente Reben zu züchten. Für die Züchtung ist eine Methode erforderlich, um eine große Anzahl an Reben schnell und zuverlässig bezüglich ihrer Anfälligkeit gegen die Schwarzfäule zu charakterisieren. Vorgestellt wird ein Verfahren der Phänotypisierung der Resistenz in der Rebe, sowie die Durchführung der Bonitur und deren Ergebnisse. Die Bonituren sind darauf ausgerichtet, Daten zu erheben, die für genetische Analysen (hier QTL) verwendbar sind. Letztendlich werden molekulare Marker entwickelt, die eng mit dem Merkmal Schwarzfäule Resistenz gekoppelt sind und daher in der Züchtung zur Frühselektion von Reben verwendet werden können. Stichwörter: Schwarzfäule, Weinrebe, ZüchtungAbstractBlack Rot of grapevine is caused by the Ascomycet Guignardia bidwellii. The pathogen was introduced from North America to Europe in the 19th century. Since 2002 increased effects of the disease have been noticed, causing significant yield losses in the region of Mosel and infections in all German wine-growing regions. For that reason, it is important to breed Black Rot resistant grapevine cultivars. A method has been developed to characterize lots of vines in a fast and reliable way concerning their susceptibility. First data have been collected and can be used for genetic analysis (here QTL). The aim of the project is to develop a molecular marker correlating with Black Rot resistance which can be used to select juvenile plants and therefore supporting the breeding of resistant cultivars.Keywords: Black Rot, Grapevine, Breedin

Orbifold projection in supersymmetric QCD at N_f\leq N_c

Supersymmetric orbifold projection of N=1 SQCD with relatively small number of flavors (not larger than the number of colors) is considered. The purpose is to check whether orbifolding commutes with the infrared limit. On the one hand, one considers the orbifold projection of SQCD and obtains the low-energy description of the resulting theory. On the other hand, one starts with the low-energy effective theory of the original SQCD, and only then perfoms orbifolding. It is shown that at finite N_c the two low-energy theories obtained in these ways are different. However, in the case of stabilized run-away vacuum these two theories are shown to coincide in the large N_c limit. In the case of quantum modified moduli space, topological solitons carrying baryonic charges are present in the orbifolded low-energy theory. These solitons may restore the correspondence between the two theories provided that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde

A robust, scanning quantum system for nanoscale sensing and imaging

Controllable atomic-scale quantum systems hold great potential as sensitive tools for nanoscale imaging and metrology. Possible applications range from nanoscale electric and magnetic field sensing to single photon microscopy, quantum information processing, and bioimaging. At the heart of such schemes is the ability to scan and accurately position a robust sensor within a few nanometers of a sample of interest, while preserving the sensor's quantum coherence and readout fidelity. These combined requirements remain a challenge for all existing approaches that rely on direct grafting of individual solid state quantum systems or single molecules onto scanning-probe tips. Here, we demonstrate the fabrication and room temperature operation of a robust and isolated atomic-scale quantum sensor for scanning probe microscopy. Specifically, we employ a high-purity, single-crystalline diamond nanopillar probe containing a single Nitrogen-Vacancy (NV) color center. We illustrate the versatility and performance of our scanning NV sensor by conducting quantitative nanoscale magnetic field imaging and near-field single-photon fluorescence quenching microscopy. In both cases, we obtain imaging resolution in the range of 20 nm and sensitivity unprecedented in scanning quantum probe microscopy

Beta-decay of nuclei around Se-90. Search for signatures of a N=56 sub-shell closure relevant the r-process

Nuclear structure plays a significant role on the rapid neutron capture process (r-process) since shapes evolve with the emergence of shells and sub-shells. There was some indication in neighboring nuclei that we might find examples of a new N=56 sub-shell, which may give rise to a doubly magic Se-90 nucleus. Beta-decay half lives of nuclei around Se-90 have been measured to determine if this nucleus has in fact a doubly-magic character. The fragmentation of Xe-136 beam at the National Superconducting Cyclotron Laboratory at Michigan State University was used to create a cocktail of nuclei in the A=90 region. We have measured the half lives of twenty-two nuclei near the r-process path in the A=90 region. The half lives of As-88 and Se-90 have been measured for the first time. The values were compared with theoretical predictions in the search for nuclear-deformation signatures of a N=56 sub-shell, and its possible role in the emergence of a potential doubly-magic Se-90. The impact of such hypothesis on the synthesis of heavy nuclei, particularly in the production of Sr, Y and Zr elements was investigated with a weak r-process network. The new half lives agree with results obtained from a standard global QRPA model used in r-process calculations, indicating that Se-90 has a quadrupole shape incompatible with a closed N=56 sub-shell in this region. The impact of the measured Se-90 half-life in comparison with a former theoretical predication associated with a spherical half-life on the weak-r-process is shown to be strong