Abstract involutions of algebraic groups and of Kac-Moody groups

Based on the second author's thesis in this article we provide a uniform treatment of abstract involutions of algebraic groups and of Kac-Moody groups using twin buildings, RGD systems, and twisted involutions of Coxeter groups. Notably we simultaneously generalize the double coset decompositions established by Springer and by Helminck-Wang for algebraic groups and by Kac-Wang for certain Kac-Moody groups, we analyze the filtration studied by Devillers-Muhlherr in the context of arbitrary involutions, and we answer a structural question on the combinatorics of involutions of twin buildings raised by Bennett-Gramlich-Hoffman-Shpectorov

A Study of Assimilation Bias in Name-Based Sampling of Migrants

The use of personal names for screening is an increasingly popular sampling technique for migrant populations. Although this is often an effective sampling procedure, very little is known about the properties of this method. Based on a large German survey, this article compares characteristics of respondents whose names have been correctly classified as belonging to a migrant population with respondentswho aremigrants and whose names have not been classified as belonging to a migrant population. Although significant differences were found for some variables even with some large effect sizes, the overall bias introduced by name-based sampling (NBS) is small as long as procedures with small false-negative rates are employed

Ein neues Verfahren für namensbasierte Zufallsstichproben von Migranten

The set of best methods for sampling mi- grant populations includes name-based sampling. So far this is done using either ad-hoc lists or onomastic dictionaries for the classi cation of names. This paper pro- poses a new name-based procedure, which uses a Bayes-classi er for the n-grams of the name. The new procedure is fault-tol- erant of alternate spellings, and also allows the classi cation of names that are not found in dictionaries. It was tested using the names of about 1.600 foreigners in the PASS panel. Finally, a CATI survey based on the new method in Hesse is described

The relationship of alignment hyperacuity to stereopsis

Human ability to monocularly detect spatial misalignment is functionally more precise than predicted by the diameter of one foveal cone. The spatial thresholds for vernier alignment are approximately 8 to 13 arc seconds of visual angle, which is more sensitive than expected. Although threshold stereopsis (another hyperacuity) seems to be approximately double alignment hyperacuity values, studies have not conclusively shown a definite relationship to ex1st. Additionally, these measurements have not been widely tested in clinical settings. This study examines the correlation between threshold stereoacuity and the monocular alignment hyperacuity measures. Twenty six subjects were evaluated measuring threshold stereopsis with the Mentor BVAT II Visual Acuity Tester and monocular alignment hyperacuity with software designed at Pacific University College of Optometry. This study supports a relationship of sum of one standard deviation of hyperacuity data distributed for each eye with stereopsis. However, the relationship is not statistically significant, most likely due to the lack of testing precision and variability in individual performance, specifically in binocular function and appreciation of stereopsis. Increased knowledge in the areas of monocular alignment hyperacuity and threshold stereopsis may aid optometric practitioners to better understand how these two factors play a role in such clinical conditions as unexplained asthenopia, amblyopia, strabismus and stereoacuity potential. However, clinical testing of an individual patient would not seem appropriate with this testing paradigm

Loops under Strategies ... Continued

While there are many approaches for automatically proving termination of term rewrite systems, up to now there exist only few techniques to disprove their termination automatically. Almost all of these techniques try to find loops, where the existence of a loop implies non-termination of the rewrite system. However, most programming languages use specific evaluation strategies, whereas loop detection techniques usually do not take strategies into account. So even if a rewrite system has a loop, it may still be terminating under certain strategies. Therefore, our goal is to develop decision procedures which can determine whether a given loop is also a loop under the respective evaluation strategy. In earlier work, such procedures were presented for the strategies of innermost, outermost, and context-sensitive evaluation. In the current paper, we build upon this work and develop such decision procedures for important strategies like leftmost-innermost, leftmost-outermost, (max-)parallel-innermost, (max-)parallel-outermost, and forbidden patterns (which generalize innermost, outermost, and context-sensitive strategies). In this way, we obtain the first approach to disprove termination under these strategies automatically.Comment: In Proceedings IWS 2010, arXiv:1012.533

Electronic properties of alkali-metal loaded zeolites -- a "supercrystal" Mott insulator

First-principles band calculations are performed for the first time for an open-structured zeolite (LTA) with guest atoms (potassium) introduced in their cages. A surprisingly simple band structure emerges, which indicates that this system may be regarded as a "supercrystal", where each cluster of guest atoms with diameter $\sim$10\AA acts as a "superatom" with well-defined $s$- and $p$-like orbitals, which in turn form the bands around the Fermi energy. The calculated Coulomb and exchange energies for these states turn out to be in the strongly-correlated regime. With the dynamical mean-field theory we show the system should be on the Mott-insulator side, and, on a magnetic phase diagram for degenerate-orbital systems, around the ferromagnetic regime, in accord with experimental results. We envisage this class of systems can provide a new avenue for materials design.Comment: 4 pages, 4 figure

On the distortion of twin building lattices

We show that twin building lattices are undistorted in their ambient group; equivalently, the orbit map of the lattice to the product of the associated twin buildings is a quasi-isometric embedding. As a consequence, we provide an estimate of the quasi-flat rank of these lattices, which implies that there are infinitely many quasi-isometry classes of finitely presented simple groups. In an appendix, we describe how non-distortion of lattices is related to the integrability of the structural cocycle

Certification of nontermination proofs using strategies and nonlooping derivations

© 2014 Springer International Publishing Switzerland. The development of sophisticated termination criteria for term rewrite systems has led to powerful and complex tools that produce (non)termination proofs automatically. While many techniques to establish termination have already been formalized—thereby allowing to certify such proofs—this is not the case for nontermination. In particular, the proof checker CeTA was so far limited to (innermost) loops. In this paper we present an Isabelle/HOL formalization of an extended repertoire of nontermination techniques. First, we formalized techniques for nonlooping nontermination. Second, the available strategies include (an extended version of) forbidden patterns, which cover in particular outermost and context-sensitive rewriting. Finally, a mechanism to support partial nontermination proofs further extends the applicability of our proof checker