Coulomb effects on electromagnetic pair production in ultrarelativistic heavy-ion collisions

We calculate the asymptotic high-energy amplitude for electrons scattering at one ion, as well as at two colliding ions, by means of perturbation theory. We show that the interaction with one ion eikonalizes and that the interaction with two ions causally decouples. We are able to put previous results on perturbative grounds and propose further applications for the obtained rules for interactions on the light cone. We discuss the implications of the eikonal amplitude on the pair production probability in ultrarelativistic peripheral heavy-ion collisions. In this context the Weizsäcker-Williams method is shown to be exact in the ultrarelativistic limit, irrespective of the produced particles’ mass. A new equivalent single-photon distribution is derived, which correctly accounts for Coulomb distortions. The impact on single-photon induced processes is discussed

Europe is in desperate need of a ‘Schumanian moment’ for EU asylum politics

The EU has formulated a new Pact on Migration and Asylum, which seeks to make EU asylum politics more realistic, efficient and crisis-proof. Ulrich Krotz and Lucas Schramm argue that for such an asylum regime to become a reality, a ‘Schumanian moment’ will be required, with a number of determined member states coming together and taking concrete steps in this direction. Ultimately, France and Germany must lead the way

An Old Couple in a New Setting: Franco-German Leadership in the Post-Brexit EU

What are the implications of Brexit for the nature, role, and potential of Franco-German leadership in the EU? Brexit, we contend, is both an expression and a further cause of two broader underlying developments in the contemporary EU: First, a stronger and more prominent German part and position, and second, disintegrative tendencies in several EU policy fields and the EU polity as a whole. This, in turn, has major implications for Franco-German bilateralism and for Franco-German leadership in the EU. In light of a stronger Germany, a relatively weaker France, and significant centrifugal forces, the two largest EU member states must not only realign their bilateral relationship but must also act as a stabilizer in and for the EU. We show that during the EU’s recent crises, not least during the Brexit negotiations and the recovery from the Covid-19 pandemic, France and Germany did exercise joint leadership. We also show, however, that major discrepancies persist between the two countries in particular policy fields and with regard to longer-term European objectives. Brexit, with its numerous calamities and implications, thus once again moves Franco-German leadership—and its shortcomings—to center stage in Europe. When it comes to leadership in the EU, there remains no viable alternative to the Franco-German duo. Yet, in order to provide constructive leadership and successfully shape the EU, the two countries must bridge substantial differences and be ready to carry disproportionately high burdens

Quantitatively consistent computation of coherent and incoherent radiation in particle-in-cell codes - a general form factor formalism for macro-particles

Quantitative predictions from synthetic radiation diagnostics often have to consider all accelerated particles. For particle-in-cell (PIC) codes, this not only means including all macro-particles but also taking into account the discrete electron distribution associated with them. This paper presents a general form factor formalism that allows to determine the radiation from this discrete electron distribution in order to compute the coherent and incoherent radiation self-consistently. Furthermore, we discuss a memory-efficient implementation that allows PIC simulations with billions of macro-particles. The impact on the radiation spectra is demonstrated on a large scale LWFA simulation.Comment: Proceedings of the EAAC 2017, This manuscript version is made available under the CC-BY-NC-ND 4.0 licens

Embedded bilateralism, integration theory, and European crisis politics : France, Germany, and the birth of the EU corona recovery fund

Published online: 16 September 2021What explains the creation of the EU corona recovery fund? Why did the Union agree on a large-scale financial response to the corona pandemic, despite member states' very different immediate reactions to the crisis and their opposing attitudes towards common debt? This article argues for the decisiveness of France and Germany's role within the Union and their tight bilateral political cooperation. The ‘embedded bilateralism’ approach to European integration and EU politics explains how and why France and Germany, starting from different poles, came together and established joint positions, paving the way for an overall European compromise. Focusing on these two countries' particular leadership role advances the theoretical debate about the actors most crucial for driving European integration, especially in times of severe crisis.This article was published Open Access with the support from the EUI Library through the CRUI - Wiley Transformative Agreement (2020-2023

Fourteen-Year Long-Term Results after Gastric Banding

Background. Gastric banding (GB) is a common bariatric procedure that is performed worldwide. Weight loss can be substantial after this procedure, but it is not sufficient in a significant portion of patients. Long-term rates for associated complications increase with every year of follow up, and only a few long-term studies have been published that examine these rates. We present our results after 14 years of postoperative follow up. Methods. Two hundred patients were operated upon form 01.02.1995 to 31.01.2009. Data collection was performed prospectively. In retrospective analysis, we analyzed weight loss, short- and long-term complications, amelioration of comorbidities and long-term outcome. Results. The mean postoperative follow up time was 94.4 months (range 2–144). The follow up rate was 83.5%. The incidence of postoperative complications for slippage was 2.5%, for pouch dilatation was 9.5%, for band migration was 5.5% and 12.0% for overall band removal. After 14 years, the reoperation rate was 30.5% with a reoperation rate of 2.2% for every year of follow up. Excess weight loss was 40.2% after 1 year, 46.3% after 2 years, 45.9% after 3 years, 41.9% after five years, 33.3% after 8 years, 30.8% after 10 years, 33.3% after 12 years and 15.6% after 14 years of follow up. Conclusion. The complication and reoperation rate after GB is high. Nevertheless, GB is still a therapeutic option in morbid obese patients, but the criteria for patient selection should be carefully evaluated