The Colour of Quarks

It is shown that colour can only be defined on gauge invariant states. Since the ability to associate colour with constituent quarks is an integral part of the constituent quark model, this means that, if we want to extract constituent quarks from QCD, we need to dress Lagrangian quarks with gluons so that the result is gauge invariant. We further prove that gauge fixings can be used to construct such dressings. Gauge invariant dressed quark states are presented and a direct approach to the interquark potential is discussed. Some further aspects of dressing quarks are briefly discussed.Comment: Extended version, to appear in Phys. Lett B., 7 pages, Te

Initial States: IR and Collinear Divergences

The standard approach to the infra-red problem is to use the Bloch-Nordsieck trick to handle soft divergences and the Lee-Nauenberg (LN) theorem for collinear singularities. We show that this is inconsistent in the presence of massless initial particles. Furthermore, we show that using the LN theorem with such initial states introduces a non-convergent infinite series of diagrams at any fixed order in perturbation theory.Comment: 4 pages, talk given at Montpellier meeting QCD'06 (to appear in the proceedings

Soil biodiversity: functions, threats and tools for policy makers

Human societies rely on the vast diversity of benefits provided by nature, such as food, fibres, construction materials, clean water, clean air and climate regulation. All the elements required for these ecosystem services depend on soil, and soil biodiversity is the driving force behind their regulation. With 2010 being the international year of biodiversity and with the growing attention in Europe on the importance of soils to remain healthy and capable of supporting human activities sustainably, now is the perfect time to raise awareness on preserving soil biodiversity. The objective of this report is to review the state of knowledge of soil biodiversity, its functions, its contribution to ecosystem services and its relevance for the sustainability of human society. In line with the definition of biodiversity given in the 1992 Rio de Janeiro Convention, soil biodiversity can be defined as the variation in soil life, from genes to communities, and the variation in soil habitats, from micro-aggregates to entire landscapes. Bio Intelligence Service, IRD, and NIOO, Report for European Commission (DG Environment

Charges in Gauge Theories

In this article we investigate charged particles in gauge theories. After reviewing the physical and theoretical problems, a method to construct charged particles is presented. Explicit solutions are found in the Abelian theory and a physical interpretation is given. These solutions and our interpretation of these variables as the true degrees of freedom for charged particles, are then tested in the perturbative domain and are demonstrated to yield infra-red finite, on-shell Green's functions at all orders of perturbation theory. The extension to collinear divergences is studied and it is shown that this method applies to the case of massless charged particles. The application of these constructions to the charged sectors of the standard model is reviewed and we conclude with a discussion of the successes achieved so far in this programme and a list of open questions.Comment: 47 pages, LaTeX, 14 figures, uses feynmp, necessary Metapost files included. Review to appear in Pramana, Journal of Physics. Minor LaTeX change to make page numbers visible on "Letter" paper forma

Estudo de caso : identificação de patógenos e condenações de carcaças de perus por aspecto repugnante

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, 2018.Objetivou-se relacionar a ocorrência de diagnósticos positivos para determinadas bactérias durante a criação de perus com número de condenações de carcaças por aspecto repugnante ao abate. O levantamento de dados foi realizado a partir dos dados coletados no ano de 2017 em uma empresa produtora de carne de perus localizada na região Sul do Brasil, com abatedouro dotado de Sistema de Inspeção Federal (SIF). Os dados foram compilados, agrupados e analisados com o auxílio de ferramentas eletrônicas e estatísticas (histograma e média ponderada). Com base nos dados coletados, foi verificado que cerca de 21% das aves descartadas por aspecto repugnante eram provenientes de lotes que possuíam laudos laboratoriais positivos para alguma infecção bacteriana. Dentre os lotes positivos, 88% foram associados a infecções relacionadas às salmonelas. Destes, 80% estavam relacionados aos sorovares S. Schwarzengrund, S. Heidelberg, além da Salmonella spp. Em conclusão, a melhoria contínua do manejo sanitário nas granjas de perus e durante o abate, deve visar não somente a redução do volume de condenações, mas também o seu possível impacto na saúde pública.The aim of this study was to relate the occurrence of positive diagnoses of certain bacteria during the breeding of turkeys with the number of carcass condemnations due to a disgusting aspect at the slaughter. Data analyses was done based on the data collected in 2017 in a company that produces turkey meat located in the southern region of Brazil, with a slaughterhouse provided with the Federal Inspection System (SIF). The data was compiled, grouped and analyzed with the aid of electronic and statistical tools (histogram and weighted mean). Based on the data collected, it was verified that about 21% of the birds discarded by repugnant aspect came from lots that had laboratory reports positive for some bacterial infection. Among the positive lots, 88% were associated with Salmonella-related infections. Of these, 80% were related to sorovars S. Schwarzengrund, S. Heidelberg, as well as Salmonella spp. In conclusion, the continuous improvement of health management in turkey farms and during the slaughter should aim not only to reduce the volume of convictions, but also their possible impact on public health

Generalized Random Phase Approximation and Gauge Theories

Mean-field treatments of Yang-Mills theory face the problem of how to treat the Gauss law constraint. In this paper we try to face this problem by studying the excited states instead of the ground state. For this purpose we extend the operator approach to the Random Phase Approximation (RPA) well-known from nuclear physics and recently also employed in pion physics to general bosonic theories with a standard kinetic term. We focus especially on conservation laws, and how they are translated from the full to the approximated theories, demonstrate that the operator approach has the same spectrum as the RPA derived from the time-dependent variational principle, and give - for Yang-Mills theory - a discussion of the moment of inertia connected to the energy contribution of the zero modes to the RPA ground state energy. We also indicate a line of thought that might be useful to improve the results of the Random Phase Approximation.Comment: 66 pages, REVTeX4, uses amsfonts and package longtabl

Earthworm management in tropical agroecosystems

Data of 145 and 69 earthworm communities from managed and natural ecosystems, respectively, of four continents and 15 tropical countries were analysed. The aim of the study was to separate the influence of phylogenetic, environmental and agricultural factors on the structure of earthworm communities in agroecosystems, and to evaluate their relative importance in the whole soil macrofauna community. Earthworms comprise 40-90% of macrofaunal biomass in most ecosystems except for annually cropped systems. Three major conclusions were drawn from the analysis of community structure (regional analysis) : (i) crops were, independently of region, characterized by a loss of native species and by the dominance of exotic endogeics ; (ii) pastures were highly heterogenous in terms of native or exotic species dominance ; (iii) native species survived better in management ecosystems of India and Africa than in Mexico-Central America. Local analysis in selected countries indicated that, as a general rule, the intensity of agricultural practices is negatively correlated with the amount of native species and the total abundance and biomass of earthworms ; the only exception was found in the conversion of savannas to pastures, in Colombian llanos. (Résumé d'auteur

Consistent OPE Description of Gluon Two- and Three-point Green Function?

We perform an OPE analysis of the flavorless non-perturbative gluon propagator and the symmetric three-gluon vertex in the Landau gauge. The first subdominant operator is $A_\mu A^\mu$ which can condensate in the Landau gauge ``vacuum'' although being a non-gauge invariant operator. We neglect all higher dimension operators. Then the gluon propagator and the symmetric three gluon vertex only depend on one common unknown condensate. We propose a consistency check from lattice data. At two loops for the leading coefficient and with $1/p^2$ corrections at tree-level order the two fitted values for the condensate do not agree. At three loops we argue that the today unknown $\beta_2^{\rm MOM}$ should be equal to $1.5(3)\times \beta_2^{\widetilde{\rm MOM}}=7400(1500)$ to fulfill the OPE relation. Inclusion of the power corrections' anomalous dimensions should improve further the agreement. We show that these techniques cannot be applied to the asymmetric three gluon vertex with one vanishing momentum.Comment: latex-file,10 figs.,13 pg