Semiclassical Prediction of Large Spectral Fluctuations in Interacting Kicked Spin Chains

While plenty of results have been obtained for single-particle quantum systems with chaotic dynamics through a semiclassical theory, much less is known about quantum chaos in the many-body setting. We contribute to recent efforts to make a semiclassical analysis of many-body systems feasible. This is nontrivial due to both the enormous density of states and the exponential proliferation of periodic orbits with the number of particles. As a model system we study kicked interacting spin chains employing semiclassical methods supplemented by a newly developed duality approach. We show that for this model the line between integrability and chaos becomes blurred. Due to the interaction structure the system features (non-isolated) manifolds of periodic orbits possessing highly correlated, collective dynamics. As with the invariant tori in integrable systems, their presence lead to significantly enhanced spectral fluctuations, which by order of magnitude lie in-between integrable and chaotic cases.Comment: 42 pages, 19 figure

Collectivity and Periodic Orbits in a Chain of Interacting, Kicked Spins

The field of quantum chaos originated in the study of spectral statistics for interacting many-body systems, but this heritage was almost forgotten when single-particle systems moved into the focus. In recent years new interest emerged in many-body aspects of quantum chaos. We study a chain of interacting, kicked spins and carry out a semiclassical analysis that is capable of identifying all kinds of genuin many-body periodic orbits. We show that the collective many-body periodic orbits can fully dominate the spectra in certain cases.Comment: 6 pages, 6 figures, accepted for publication in Acta Physica Polonica A. arXiv admin note: substantial text overlap with arXiv:1611.0574

Post-growth perspectives in Economic Geography

No abstract necessar

The moral branding of Fairtrade: Opportunities and pitfalls of visual representations in the Fairtrade system – empirical insights on the perspectives of German consumers

The Fairtrade system can be considered as one of the most successful real-world experiments of alternative economies. However, Fairtrade more than other alternative economic approaches relies on mass market mechanisms and the sale of its products via conventional distribution channels and retail outlets. To gradually transform the ‘unfair’ mechanisms of world trade and to achieve its social and environmental goals, Fairtrade requires a constant growth in sales. This also means that the marketing of Fairtrade goods in the consumer countries is subject to established capitalist mechanisms of advertising and demand creation. Although Fairtrade’s brand building aims at differentiation through alternative values of cooperation, trust, and fairness, it also works within the constraints of simplified and abridged advertising messages. More often than not, contrasts and stereotypes are over-emphasized – a phenomenon that critics call the ‘exploitation of difference’. In this way, new forms of ‘distancing’ and ‘othering’ are constantly built up and reinforced. Individuals, livelihoods, production practices, and entire landscapes in the Global South become commodified and are used for brand development and sales promotion. This paper examines these issues based on interviews and a questionnaire survey among German consumers. Our empirical insights indicate that the visual language used for Fairtrade marketing has to be targeted to critical consumers, who are increasingly skeptical of overly moralizing and simplified images with exaggerated contrasts between the ‘different worlds’ of producers in the South and consumers in the North. However, it should also be noted that Fairtrade Germany is increasingly aware of challenges in its visual communication and is intensively reflecting on its visual language

The paradox of formalization and informalization in South-North value chains

The internationalization of value chains and the broad proliferation of different public and private standards have led to a formalization and standardization of value chains, production systems and their constitutional actors and linkages in the Global South. Recent studies on the integration of Southern production systems in international value chains, however, show that this is only partly the case. These studies identify limits and insufficiencies of formal and standardized coordination and control systems as well as a neglect of regional peculiarities, individual aims and capabilities of the embedded stakeholders in the South by the coordinating lead firms from the North. As a result, informal actors and arrangements continue to be, and even continue to develop as, important parts of Southern production systems. With reference to the concept of informality, principal-agent theory and convention theory, this study aims to contribute to the recent conceptual debate on global value chains and global production networks in outlining the importance of informal arrangements and non-industrial conventions as well as the limits to upgrading in South-North relationships. The empirical base are case studies on export-oriented primary production systems in Kenya (horticulture), Bangladesh (shrimps) and India/Bangladesh (leather)

How compatible are Western European dietary patterns to climate targets? : Accounting for uncertainty of life cycle assessments by applying a probabilistic approach

The food system plays a crucial role in mitigating climate change. Even if fossil fuel emissions are halted immediately, current trends in global food systems may prevent the achieving of the Paris Agreement's climate targets. The high degree of variability and uncertainty involved in calculating diet-related greenhouse gas emissions limits the ability to evaluate reduction potentials to remain below a global warming of 1.5 or 2 degrees. This study assessed Western European dietary patterns while accounting for uncertainty and variability. An extensive literature review provided value ranges for climate impacts of animal-based foods to conduct an uncertainty analysis via Monte Carlo simulation. The resulting carbon footprints were assessed against food system-specific greenhouse gas emission thresholds. The range and absolute value of a diet carbon footprint become larger the higher the amount of products with highly varying emission values in the diet. All dietary pattern carbon footprints overshoot the 1.5 degrees threshold. The vegan, vegetarian, and diet with low animal-based food intake were predominantly below the 2 degrees threshold. Omnivorous diets with more animal-based product content trespassed them. Reducing animal-based foods is a powerful strategy to decrease emissions. However, further mitigation strategies are required to achieve climate goals

Regge asymptotics and color suppressed heavy meson decays

We discuss a possible generation of color suppressed B-decays amplitudes through a soft final state interaction. As a typical example, we consider in detail the decay $\bar{B}^{0} \rightarrow D^{0} \pi^{0}$ (and also $\bar{B}^{0} \rightarrow 2 \pi^{0}$). We show that in the approximation of the two particle unitarity and at zero order in $\alpha_{s}$ this process can be related to the weak decay $\bar{B}^{0} \rightarrow D^{+} \pi^{-}$ followed by the strong charge exchange scattering in the Regge kinematics. We estimate the amplitude of this process using the light cone QCD sum rule technique and find that it is supppressed as a power of $1/m_{B}$ in comparison to the amplitude generated by the effective non-leptonic Hamiltonian, but remains important for the physical value of $m_{B}$.Comment: 14 pages,Latex,no figure