Single-channel fits and K-matrix constraints

A K-matrix formalism is used to relate single-channel and multi-channel fits. We show how the single-channel formalism changes as new hadronic channels become accessible. These relations are compared to those commonly used to fit pseudoscalar meson photoproduction data.Comment: 9 pages, 2 figures. A numerical example has been adde

Conformal field theories and compact curves in moduli spaces

We show that there are many compact subsets of the moduli space $M_g$ of Riemann surfaces of genus $g$ that do not intersect any symmetry locus. This has interesting implications for $\mathcal{N}=2$ supersymmetric conformal field theories in four dimensions.Comment: Update acknowledging recent development

How does Labour Mobility affect the Performance of Plants? The importance of relatedness and geographical proximity

This paper analyses the impact of skill portfolios and labour mobility on plant performance by means of a unique database that connects attributes of individuals to features of plants for the whole Swedish economy. We found that a portfolio of related competences at the plant level increases significantly productivity growth of plants, in contrast to plant portfolios consisting of either similar or unrelated competences. Based on the analysis of 101,093 job moves, we found that inflows of skills that are related to the existing knowledge base of the plant had a positive effect on plant performance, while the inflow of new employees with skills that are already present in the plant had a negative impact. Our analyses also show that geographical proximity influences the effect of different skill inflows. Inflows of unrelated skills only contribute positively to plant performance when these are recruited in the same region. Labour mobility across regions only has a positive effect on productivity growth of plants when this concerns new employees with related skills.Labour mobility; related variety; skill portfolio; plant performance; geographical proximi

Renormalization group maps for Ising models in lattice gas variables

Real space renormalization group maps, e.g., the majority rule transformation, map Ising type models to Ising type models on a coarser lattice. We show that each coefficient of the renormalized Hamiltonian in the lattice gas variables depends on only a finite number of values of the renormalized Hamiltonian. We introduce a method which computes the values of the renormalized Hamiltonian with high accuracy and so computes the coefficients in the lattice gas variables with high accuracy. For the critical nearest neighbor Ising model on the square lattice with the majority rule transformation, we compute over 1,000 different coefficients in the lattice gas variable representation of the renormalized Hamiltonian and study the decay of these coefficients. We find that they decay exponentially in some sense but with a slow decay rate. We also show that the coefficients in the spin variables are sensitive to the truncation method used to compute them.Comment: 22 pages, 9 color postscript figures; minor revisions in version

Storing images in warm atomic vapor

Reversible and coherent storage of light in atomic medium is a key-stone of future quantum information applications. In this work, arbitrary two-dimensional images are slowed and stored in warm atomic vapor for up to 30 $\mu$s, utilizing electromagnetically induced transparency. Both the intensity and the phase patterns of the optical field are maintained. The main limitation on the storage resolution and duration is found to be the diffusion of atoms. A techniqueanalogous to phase-shift lithography is employed to diminish the effect of diffusion on the visibility of the reconstructed image

Some reports of snowfall from fog during the UK winter of 2008/09

Snowfall during anticyclonic, non-frontal, and foggy conditions is surprising. Because it is often not forecast, it can present a hazard to transport and modify the surface albedo. In this report, we present some observations of snowfall during conditions of freezing fog in the UK during the winter of 2008/09

The motif problem

Fix a choice and ordering of four pairwise non-adjacent vertices of a parallelepiped, and call a motif a sequence of four points in R^3 that coincide with these vertices for some, possibly degenerate, parallelepiped whose edges are parallel to the axes. We show that a set of r points can contain at most r^2 motifs. Generalizing the notion of motif to a sequence of L points in R^p, we show that the maximum number of motifs that can occur in a point set of a given size is related to a linear programming problem arising from hypergraph theory, and discuss some related questions.Comment: 17 pages, 1 figur