(An)isotropy of the Hubble diagram: comparing hemispheres

We test the isotropy of the Hubble diagram. At small redshifts, this is possible without assumptions on the cosmic inventory and provides a fundamental test of the cosmological principle. At higher redshift we check for the self-consistency of the LambdaCDM model. At small redshifts, we use public supernovae (SNe) Ia data to determine the deceleration parameter q_0 and the SN calibration on opposite hemispheres. For the complete data sets we fit Omega_M and the SN calibration on opposite hemispheres. A statistically significant anisotropy of the Hubble diagram at redshifts z 95% C.L.). While data from the North Galactic hemisphere favour the accelerated expansion of the Universe, data from the South Galactic hemisphere are not conclusive. The hemispheric asymmetry is maximal toward a direction close to the equatorial poles. The discrepancy between the equatorial North and South hemispheres shows up in the SN calibration. For the LambdaCDM model fitted to all available SNe, we find the same asymmetry. The alignment of discrepancies between hemispheric Hubble diagrams with the equatorial frame seems to point toward a systematic error in the SN search, observation, analysis or data reduction. We also find that our model independent test cannot exclude the case of the deceleration of the expansion at a statistically significant level.Comment: 13 pages, 8 figures; several corrections - conclusions unchanged; matches published versio

Verallgemeinerte Turbulenzmodelle zur Beschreibung von "field line random walk" und Teilchentransport

Diese Arbeit handelt von astrophysikalischer Turbulenz, dem Transport magnetischer Feldlinien und energetischer Teilchen. Da sich geladene Teilchen näherungsweise entlang magnetischer Feldlinien bewegen, ist die genaue Behandlung dieser Felder ein wichtiger Bestandteil des Weges zum Verständnis des Verhaltens der Teilchen. Im ersten Abschnitt wird kurz das physikalische Szenario und die verwendeten Modelle vorgestellt. Im zweiten Teil werden diese Modelle verallgemeinert und gezeigt, dass Messungen von den neu entwickelten Modellen sehr viel besser beschrieben werden. Dabei werden Korrelationstensoren und Diffusionskoeffizienten berechnet, welche zur Beschreibung der gemessenen Anisotropie der turbulenten Magnetfelder benötigt werden. Im letzten Kapitel werden die Ergebnisse diskutiert und ein Ausblick auf weiterführende Arbeiten gegeben

Design status of the ITER core CXRS diagnostic setup

The Charge eXchange Recombination Spectroscopy diagnostic system on the ITER plasma core (CXRS core) will provide spatially resolved measurements of plasma parameters. The optical front-end is located in upper port 3 and the light of 460–665 nm is routed to spectrometers housed in the tritium building. This paper describes the layout of the optical system in the port plug, cell and interspace areas. The layout is a continuation of the developments described in [1] and takes into account changes in the design of the upper port plug, considerations for the system lifetime as well as internal and external tolerances on the optical chain. The layout was selected also with a number of additional criteria, including optical performance, radiation shielding, maintainability and robustness. A free-space optical chain was added pushing the optical fibres to the port cell. A line-of-sight finder imaging apertures and masks in the optical chain was added to enable determination of deviations within the optical chain and stabilise the image on the fibres. Where feasible, existing solutions for sub-systems such as the shutter were adapted to the layout