Effective theory for the cosmological generation of structure

The current understanding of structure formation in the early universe is mainly built on a magnification of quantum fluctuations in an initial vacuum state during an early phase of accelerated universe expansion. One usually describes this process by solving equations for a quantum state of matter on a given expanding background space-time, followed by decoherence arguments for the emergence of classical inhomogeneities from the quantum fluctuations. Here, we formulate the coupling of quantum matter fields to a dynamical gravitational background in an effective framework which allows the inclusion of back-reaction effects. It is shown how quantum fluctuations couple to classical inhomogeneities and can thus manage to generate cosmic structure in an evolving background. Several specific effects follow from a qualitative analysis of the back-reaction, including a likely reduction of the overall amplitude of power in the cosmic microwave background, the occurrence of small non-Gaussianities, and a possible suppression of power for odd modes on large scales without parity violation.Comment: 8 pages, 1 figur

Edge Enhancement Investigations by Means of Experiments and Simulations

Standard neutron imaging procedures are based on the “shadow” of the transmitted radiation, attenuated by the sample material. Under certain conditions significant deviations from pure transmission can be found in the form of enhancement or depression at the edges of the samples. These effects can limit the quantification process in the related regions. Otherwise, an enhancement and improvement of visibility can be achieved e.g. in defect analysis. In systematic studies we investigated the dependency of these effects on the specific material (mainly for common metals), such as the sample-to-detector distance, the beam collimation, the material thickness and the neutron energy. The beam lines ICON and BOA at PSI and ANTARES at TU München were used for these experiments due to their capability for neutron imaging with highest possible spatial resolution (6.5 to 13.5 micro-meter pixel size, respectively) and their cold beam spectrum. Next to the experimental data we used a McStas tool for the description of refraction and reflection features at edges for comparison. Even if minor contributions by coherent in-line propagation phase contrast are underlined, the major effect can be described by refraction of the neutrons at the sample-void interface. Ways to suppress and to magnify the edge effects can be derived from these findings.Fil: Lehmann, E.. Paul Scherrer Institut; SuizaFil: Schulz, M.. Technische Universitat Munchen; AlemaniaFil: Wang, Y.. China Insititute of Atomic Energy; ChinaFil: Tartaglione, Aureliano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Decavanadate: a journey in a search of a role

Currently, efforts have been directed towards using decavanadate as a tool for the understanding of several biochemical processes such as muscle contraction, calcium homeostasis, in vivo changes of oxidative stress markers, mitochondrial oxygen consumption, mitochondrial membrane depolarization, actin polymerization and glucose uptake, among others. In addition, studies have been conducted in order to make vanadium available and safe for clinical use, for instance with decavanadate compounds that present interesting pharmacological properties, eventually useful for the treatment of diabetes. Here, recent contributions of decavanadate to the effects of vanadium in biological systems, not only in vitro, but also in vivo, are analysed