Multi-band implications of external-IC flares

Very fast variability on scales of minutes is regularly observed in Blazars. The assumption that these flares are emerging from the dominant emission zone of the very high energy (VHE) radiation within the jet challenges current acceleration and radiation models. In this work we use a spatially resolved and time dependent synchrotron-self-Compton (SSC) model that includes the full time dependence of Fermi-I acceleration. We use the (apparent) orphan $\gamma$-ray flare of \textit{Mrk501} during MJD 54952 and test various flare scenarios against the observed data. We find that a rapidly variable external radiation field can reproduce the high energy lightcurve best. However, the effect of the strong inverse Compton (IC) cooling on other bands and the X-ray observations are constraining the parameters to rather extreme ranges. Then again other scenarios would require parameters even more extreme or stronger physical constraints on the rise and decay of the source of the variability which might be in contradiction with constraints derived from the size of the black hole's ergosphere.Comment: accepted for publication in Astroparticle Physic

The radio morphology of a spatially resolved SSC model

One of the main, unresolved questions about the nature of quasars is the position of the acceleration site responsible for the highest energies. The attempt to investigate this question in the energy regime with the highest resolution, the radio band, has the downside that no theoretical model exists that can connect these two regimes. The model in this work tries to shrink this gap by extending the general synchrotron self Compton (SSC) model up to length scales in the order of the resolution of radio observations. The resulting spectral energy distributions (SED) show a qualitative improvement in the representation of the radio spectrum. Furthermore the obtained emission morphology shows similar properties to the radio structures observed in jets of quasars. A complete and quantitative connection will however need either much higher numerical effort or an improved methodology

A spatially resolved SSC Shock-in-Jet model

In this paper a spatially resolved, fully self-consistent SSC model is presented. The observable spectral energy distribution (SED) evolves entirely from a low energetic delta distribution of injected electrons by means of the implemented microphysics of the jet. These are in particular the properties of the shock and the ambient plasma, which can be varied along the jet axis. Hence a large variety of scenarios can be computed, e.g. the acceleration of particles via multiple shocks. Two acceleration processes, shock acceleration and stochastic acceleration, are taken into account. From the resulting electron distribution the SED is calculated taking into account synchrotron radiation, inverse Compton scattering (full cross section) and synchrotron self absorption. The model can explain SEDs where cooling processes are crucial. It can verify high variability results from acausal simulations and produce variability not only via injection of particles, but due to the presence of multiple shocks. Furthermore a fit of the data, obtained in the 2010 multi-frequency campaign of Mrk501, is presented.Comment: 4 pages, 2 figures; appeared in the proceedings of the conference: "High Energy Phenomena in Relativistic Outflows (HEPRO) III", held in Barcelona, Spain, June 27th-July 1st 2011 (IJMPCS

Winner Picking in Urban Revitalization Policies: Empirical Evidence from Berlin

Urban revitalization programs are widespread used but empirically understudied place-based policy instruments which attract increasing attention in recent years. This study adds to the existing literature by evaluating the selection process which led to the designation of a set of five urban revitalization areas in Berlin, Germany in the beginning of 2010. Moreover, the study addresses the question whether the choice of the location of potential urban revitalization areas is influenced by a winner picking strategy, i.e. whether policy makers select areas that would prosper even in absence of the policy to make the policy seem more successful. We attempt to model this hypothesis by evaluating the influence of long run past trends of selected key characteristics (the unemployment rate and the share of residents with immigration background) on the probability of being selected as a target area of the revitalization policy, conditional on the current levels of these characteristics and a comprehensive set of housing and location controls. The empirical evidence is in line with our expectations and is quite stable across different specifications and several estimation approaches: we find evidence that policy makers indeed seem to base their choice to some extent on their expectation of the future performance of the areas. Specifically, they seem to choose the target areas from a pool of areas, which have high levels of unemployment and a high share of residents with immigration background. From this pool, however, they preferably choose areas which have undergone a positive development in the past years. While high current levels of the unemployment rate and the share of residents with an immigration background increase the probability of being selected as a target area, an increase in the six year change of the unemployment rate and the share of residents with immigration background, i.e. a further negative development, decreases the probability of being selected into a target area. This effect is interpreted as a winner picking strategy, as the local authorities do not simply choose the areas which have the greatest need for revitalization, but instead prefer areas which show first signs of a revitalization or gentrification process

Winner Picking in Urban Revitalization Policies: Empirical Evidence from Berlin

This study addresses the question whether policy makers strategically pick winners when selecting the targets for place-based revitalization policies. It evaluates the influence of long-term trends of the unemployment rate and the share of residents of immigrant background on the probability of being selected as a target area, conditional on the current levels of these attributes. The empirical evidence is in line with the expectations: policy makers base their choice to some extent on the future performance expected of the areas. While high current levels of the unemployment rate increase the probability of being designated, increases in the unemployment rate over time decrease the probability of being selected. This effect is interpreted as winner picking: local authorities do not simply choose the most deprived areas, but instead prefer areas which show first signs of a gentrification process

Main Memory Adaptive Indexing for Multi-core Systems

Adaptive indexing is a concept that considers index creation in databases as a by-product of query processing; as opposed to traditional full index creation where the indexing effort is performed up front before answering any queries. Adaptive indexing has received a considerable amount of attention, and several algorithms have been proposed over the past few years; including a recent experimental study comparing a large number of existing methods. Until now, however, most adaptive indexing algorithms have been designed single-threaded, yet with multi-core systems already well established, the idea of designing parallel algorithms for adaptive indexing is very natural. In this regard only one parallel algorithm for adaptive indexing has recently appeared in the literature: The parallel version of standard cracking. In this paper we describe three alternative parallel algorithms for adaptive indexing, including a second variant of a parallel standard cracking algorithm. Additionally, we describe a hybrid parallel sorting algorithm, and a NUMA-aware method based on sorting. We then thoroughly compare all these algorithms experimentally; along a variant of a recently published parallel version of radix sort. Parallel sorting algorithms serve as a realistic baseline for multi-threaded adaptive indexing techniques. In total we experimentally compare seven parallel algorithms. Additionally, we extensively profile all considered algorithms. The initial set of experiments considered in this paper indicates that our parallel algorithms significantly improve over previously known ones. Our results suggest that, although adaptive indexing algorithms are a good design choice in single-threaded environments, the rules change considerably in the parallel case. That is, in future highly-parallel environments, sorting algorithms could be serious alternatives to adaptive indexing.Comment: 26 pages, 7 figure

Precision Muon Tracking at Future Hadron Colliders with sMDT Chambers

Small-diameter muon drift tube (sMDT) chambers are a cost-effective technology for high-precision muon tracking. The rate capability of the sMDT chambers has been extensively tested at the Gamma Irradiation Facility at CERN in view of expected rates at future high-energy hadron colliders. Results show that it fulfills the requirements over most of the acceptance of muon detectors. The optimization of the read-out electronics to further increase the rate capability of the detectors is discussed. Chambers of this type are under construction for upgrades of the muon spectrometer of the ATLAS detector at high LHC luminosities. Design and construction procedures have been optimized for mass production while providing a precision of better than 10 micrometers in the sense wire positions and the mechanical stability required to cover large areas.Comment: 5 pages, 12 figures; conference proceedings for IEEE NSS & MIC conference, San Diego, 201

Exports and olympic games: Is there a signal effect?

Rose & Spiegel (2011) find that Olympic Games host countries experience significant positive, lasting effects on exports. They interpret their results as an indication that countries use the hosting of such events to signal openness and competitiveness. We challenge these empirical findings on the grounds that a comparison of structurally different and non-matching groups of countries might suffer from a selection bias. We demonstrate that with an appropriate matching and treatment methodology, the significant Olympic effect disappears.Version: January 201

The Olympic effect: A reply

Rose & Spiegel (2011) find that Olympic Games host countries experience significant positive and lasting effects on exports. They interpret their results as an indication that countries use the hosting of such an event as a signal of their (new) openness and competitiveness. We challenge these empirical findings on the grounds that the comparison of structurally different and non-matching groups might suffer from a selection bias. We demonstrate that with an appropriately applied matching and treatment methodology, the significant Olympic export effect disappears