Heavy quark and gluino potentials to two loops

The static potentials for systems of a heavy quark and anti-quark, two gluinos and a quark and a gluino are computed for all possible colour configurations of a $SU(N_c)$ gauge group.Comment: 6 pages, v2: figure with Feynman diagrams added; typos fixed; version to appear in Phys. Lett.

The higher spin Laplace operator in several vector variables

In this paper, an explicit expression is obtained for the conformally invariant higher spin Laplace operator $\mathcal{D}_{\lambda}$, which acts on functions taking values in an arbitrary (finite-dimensional) irreducible representation for the orthogonal group with integer valued highest weight. Once an explicit expression is obtained, a special kind of (polynomial) solutions of this operator is determined

Do Religious Factors Impact Armed Conflict? Empirical Evidence from Sub-Saharan Africa

Theoretically, the “mobilization hypothesis” establishes a link between religion and conflict by arguing that religious structures such as overlapping ethnic and religious identities are prone to mobilization; once politicized, escalation to violent conflict becomes likelier. Yet, despite the religious diversity in sub-Saharan Africa and the religious overtones in a number of African armed conflicts, this assumption has not yet been backed by systematic empirical research on the religion–conflict nexus in the region. The following questions thus remain: Do religious factors significantly impact the onset of (religious) armed conflict? If so, do they follow the logic of the mobilization hypothesis and, if yes, in which way? To answer these questions, this paper draws on a unique data inventory of all sub-Saharan countries for the period 1990–2008, particularly including data on mobilization-prone religious structures (e.g. demographic changes, parallel ethno-religious identities) as well as religious factors indicating actual politicization of religion (e.g. inter-religious tensions, religious discrimination, incitement by religious leaders). Based on logit regressions, results suggest that religion indeed plays a significant role in African armed conflicts. The findings are compatible with the mobilization hypothesis: Overlaps of religious and ethnic identities and religious dominance are conflict-prone; religious polarization is conflict-prone only if combined with religious discrimination and religious tensions.Armed conflict, religion, sub-Saharan Africa, mobilization

Regularized Newton Methods for X-ray Phase Contrast and General Imaging Problems

Like many other advanced imaging methods, x-ray phase contrast imaging and tomography require mathematical inversion of the observed data to obtain real-space information. While an accurate forward model describing the generally nonlinear image formation from a given object to the observations is often available, explicit inversion formulas are typically not known. Moreover, the measured data might be insufficient for stable image reconstruction, in which case it has to be complemented by suitable a priori information. In this work, regularized Newton methods are presented as a general framework for the solution of such ill-posed nonlinear imaging problems. For a proof of principle, the approach is applied to x-ray phase contrast imaging in the near-field propagation regime. Simultaneous recovery of the phase- and amplitude from a single near-field diffraction pattern without homogeneity constraints is demonstrated for the first time. The presented methods further permit all-at-once phase contrast tomography, i.e. simultaneous phase retrieval and tomographic inversion. We demonstrate the potential of this approach by three-dimensional imaging of a colloidal crystal at 95 nm isotropic resolution.Comment: (C)2016 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibite

Sharing One Biographical Detail Elicits Priming between Famous Names: Empirical and Computational Approaches

In this paper three experiments and corresponding model simulations are reported that investigate the priming of famous name recognition in order to explore the structure of the part of the semantic system dealing with people. Consistent with empirical findings, novel computational simulations using Burton et al.’s interactive activation and competition model point to a conceptual distinction between how priming is initiated in single- and double-familiarity tasks, indicating that priming should be weaker or non-existent for the single-familiarity task. Experiment 1 demonstrates that, within a double-familiarity framework using famous names, categorical, and associative priming are reliable effects. Pushing the model to the limit, it predicts that pairs of celebrities who are neither associatively nor categorically related but who share single biographical features, both died in a car crash for example, should prime each other. Experiment 2 investigated this in a double-familiarity task but the effect was not observed. We therefore simulated and realized a pairwise learning task that was conceptually similar to the double-familiarity-decision task but allowed to strengthen the underlying connections. Priming based on a single biographical feature could be found both in simulations and the experiment. The effect was not due to visual or name similarity which were controlled for and participants did not report using the biographical links between the people to learn the pairs. The results are interpreted to lend further support to structural models of the memory for persons. Furthermore, the results are consistent with the idea that episodic features known about people are stored in semantic memory and are automatically activated when encountering that person