Mathematics of complexity in experimental high energy physics

Mathematical ideas and approaches common in complexity-related fields have been fruitfully applied in experimental high energy physics also. We briefly review some of the cross-pollination that is occurring.Comment: 7 pages, 3 figs, latex; Second International Conference on Frontier Science: A Nonlinear World: The Real World, Pavia, Italy, 8-12 September 200

Spectral Dependence of Polarized Radiation due to Spatial Correlations

We study the polarization of light emitted by spatially correlated sources. We show that in general polarization acquires nontrivial spectral dependence due to spatial correlations. The spectral dependence is found to be absent only for a special class of sources where the correlation length scales as the wavelength of light. We further study the cross correlations between two spatially distinct points that are generated due to propagation. It is found that such cross correlation leads to sufficiently strong spectral dependence of polarization which can be measured experimentally.Comment: 5 pages, 4 figure

Dilepton Production in Nucleon-Nucleon Interactions

Starting from a realistic one--boson--exchange--model fitted to the amplitudes of elastic nucleon--nucleon scattering and the process $NN\rightarrow N\Delta$ we perform a fully relativistic and gauge invariant calculation for the dilepton production in nucleon--nucleon collisions, including the important effect of propagating the $\Delta$--resonance. We compare the results of our calculations with the latest experimental data on dilepton production. We also show how to implement various electromagnetic formfactors for the hadrons in our calculations without loosing gauge--invariance and discuss their influence on dilepton spectra.Comment: 24 pages, figures will be sent on reques

Quantum Interference between Impurities: Creating Novel Many-Body States in s-wave Superconductors

We demonstrate that quantum interference of electronic waves that are scattered by multiple magnetic impurities in an s-wave superconductor gives rise to novel bound states. We predict that by varying the inter-impurity distance or the relative angle between the impurity spins, the states' quantum numbers, as well as their distinct frequency and spatial dependencies, can be altered. Finally, we show that the superconductor can be driven through multiple local crossovers in which its spin polarization, $$, changes between $=0, 1/2$ and 1.Comment: 4 pages, 4 figure

Interfaces with a single growth inhomogeneity and anchored boundaries

The dynamics of a one dimensional growth model involving attachment and detachment of particles is studied in the presence of a localized growth inhomogeneity along with anchored boundary conditions. At large times, the latter enforce an equilibrium stationary regime which allows for an exact calculation of roughening exponents. The stochastic evolution is related to a spin Hamiltonian whose spectrum gap embodies the dynamic scaling exponent of late stages. For vanishing gaps the interface can exhibit a slow morphological transition followed by a change of scaling regimes which are studied numerically. Instead, a faceting dynamics arises for gapful situations.Comment: REVTeX, 11 pages, 9 Postscript figure

Vraaggestuurde ketens

This report by Animal Sciences Group, Agrotechnology & Food Innovations and LEI looks at demand pull in chains and aims to find an answer to the question: 'What can the government leave to market forces (under certain conditions) and what action does it need to take itself?' After a 'quick scan' of the existing literature, originating both from the Netherlands and else-where in the world, the literature on demand pull and transparency was explored more intensively and the gaps in the knowledge were indicated. Lastly, in the third phase, the research examined the purchasing behaviour of consumers and retailers in greater depth, for instance by means of interviews with buyers (retailers and bulk consumers) of fresh meat

A versatile method for simulating pp -> ppe+e- and dp -> pne+e-p_spec reactions

We have developed a versatile software package for the simulation of di-electron production in $pp$ and $dp$ collisions at SIS energies. Particular attention has been paid to incorporate different descriptions of the Dalitz decay $\Delta \to N e^+e^-$ via a common interface. In addition, suitable parameterizations for the virtual bremsstrahlung process $NN \to NN e^+e^-$ based on one-boson exchange models have been implemented. Such simulation tools with high flexibility of the framework are important for the interpretation of the di-electron data taken with the HADES spectrometer and the design of forthcoming experiments

The Seven-sphere and its Kac-Moody Algebra

We investigate the seven-sphere as a group-like manifold and its extension to a Kac-Moody-like algebra. Covariance properties and tensorial composition of spinors under $S^7$ are defined. The relation to Malcev algebras is established. The consequences for octonionic projective spaces are examined. Current algebras are formulated and their anomalies are derived, and shown to be unique (even regarding numerical coefficients) up to redefinitions of the currents. Nilpotency of the BRST operator is consistent with one particular expression in the class of (field-dependent) anomalies. A Sugawara construction is given.Comment: 22 pages. Macropackages used: phyzzx, epsf. Three epsf figure files appende

Proximity induced metal/insulator transition in YBa2Cu3O7/La2/3Ca1/3MnO3Y Ba_2 Cu_3 O_7 / La_{2/3} Ca_{1/3} Mn O_3 superlattices

The far-infrared dielectric response of superlattices (SL) composed of superconducting YBa$_{2}$Cu$_{3}$O$_{7}$ (YBCO) and ferromagnetic La$_{0.67}$% Ca$_{0.33}$MnO$_{3}$ (LCMO) has been investigated by ellipsometry. A drastic decrease of the free carrier response is observed which involves an unusually large length scale of d$^{crit}\approx$20 nm in YBCO and d$^{crit}\approx$10 nm in LCMO. A corresponding suppression of metallicity is not observed in SLs where LCMO is replaced by the paramagnetic metal LaNiO$_{3}$. Our data suggest that either a long range charge transfer from the YBCO to the LCMO layers or alternatively a strong coupling of the charge carriers to the different and competitive kind of magnetic correlations in the LCMO and YBCO layers are at the heart of the observed metal/insulator transition. The low free carrier response observed in the far-infrared dielectric response of the magnetic superconductor RuSr$_{2}$GdCu$_{2}$O$_{8}$ is possibly related to this effect

Perspectieven bedrijfsmaatregelen voor duurzaambodemgebruik : kosten en effectiviteit van vijf maatregelen

In dit onderzoek zijn de kosten en baten en de effectiviteit op duurzaam bodemgebruik beoordeeld van vijf bedrijfsmaatregelen: aanpassing van vruchtwisseling, preventie van bodemverdichting, optimalisering van ontwatering en flexibel peilbeheer, grondruil en landhuur/-verhuur en omzanden en diepploegen. De effecten op duurzaam bodemgebruik zijn beoordeeld op de aspecten organische stof, bodemstructuur, erosiegevoeligheid en bodemgezondheid. Verruiming van vruchtwisseling met meer maaivruchten en minder rooivruchten gaat meestal ten koste van het bedrijfsinkomen. Bij vruchtwisseling is bodemgezondheid een belangrijk aspect. Bodemverdichting kan worden verminderd. Dit vraagt meestal flinke investeringen. Met een goed management en goede voorlichting kan nog veel worden bereikt. Veranderingen in water- en peilbeheer gaan deels vaak ten koste van een optimale landbouwkundige productie. Er kunnen echter ook maatregelen worden toegepast die niet of nauwelijks nadelig zijn vanuit landbouwkundig oogpunt, maar wel gunstig zijn voor natuur en maatschappi