Generalized parton distributions of the pion in a Bethe-Salpeter approach

We calculate generalized parton distribution functions in a field theoretic formalism using a covariant Bethe-Salpeter approach for the determination of the bound-state wave function. We describe the procedure in an exact calculation in scalar Electrodynamics proving that the relevant corrections outside our scheme vanish. We extend the formalism to the Nambu--Jona-Lasinio model, a realistic theory of the pion. We go in both cases beyond all previous calculations and discover that all important features required by general physical considerations, like symmetry properties, sum rules and the polynomiality condition, are explicitly verified. We perform a numerical study of their behavior in the weak and strong coupling limits.Comment: 19 pages, 21 eps figures, accepted for publication in EPJ

Electric and magnetic form factors of strange baryons

Predictions for the electromagnetic form factors of the Lambda$, Sigma and Xi hyperons are presented. The numerical calculations are performed within the framework of the fully relativistic constituent-quark model developed by the Bonn group. The computed magnetic moments compare favorably with the experimentally known values. Most magnetic form factors G_M(Q^2) can be parametrized in terms of a dipole with cutoff masses ranging from 0.79 to 1.14 GeV.Comment: 15 pages, 8 figures, 3 tables, submitted to Eur. Phys. J.

Borromean Binding of Three or Four Bosons

We estimate the ratio $R=g_{3}/g_{2}$ of the critical coupling constants $g_{2}$ and $g_{3}$ which are required to achieve binding of 2 or 3 bosons, respectively, with a short-range interaction, and examine how this ratio depends on the shape of the potential. Simple monotonous potentials give $R\simeq 0.8$. A wide repulsive core pushes this ratio close to R=1. On the other hand, for an attractive well protected by an external repulsive barrier, the ratio approaches the rigorous lower bound $R=2/3$. We also present results for N=4 bosons, sketch the extension to $N>4$, and discuss various consequences.Comment: 12 pages, RevTeX, 5 Figures in tex include

How to derive consensus among various marketing journal rankings?

Despite the increasing popularity of journal rankings to evaluate the quality of research contributions, the individual rankings for journals that ranked below the top tier of publications usually feature only modest agreement. Attempts to merge rankings into meta-rankings suffer from some methodological issues, such as mixed measurement scales and incomplete data. This paper addresses the issue of how to construct suitable aggregates of individual journal rankings, using an optimization-based consensus ranking approach. The authors apply the proposed method to a subset of marketing-related journals from a list of collected journal rankings. Next, the paper studies the stability of the derived consensus solution, and the degeneration effects that occur when excluding journals and/or rankings. Finally, the authors investigate the similarities/dissimilarities of the consensus with a naive meta-ranking and with individual rankings. The results show that, even though journals are not uniformly ranked, one may derive a consensus ranking with considerably high agreement with the individual rankings. © 2013 Elsevier Inc. All rights reserved

Isosurfaces on Optimal Regular Samples

Volumetric samples on Cartesian lattices are less efficient than samples on body-centred cubic (BCC) lattices. We show how to construct isosurfaces on BCC lattices using several different algorithms. Since the mesh that arises from BCC lattices involves a large number of cells, we show two alternate methods of reducing the number of cells by clumping tetrahedra into either octahedra or hexahedra. We also propose a theoretical model for estimating triangle counts for various algorithms, and present experimental results to show that isosurfaces generated using one of our algorithms can be competitive with isosurfaces generated using Marching Cubes on similar Cartesian grids. 1