The Nielsen Identities for the Two-Point Functions of QED and QCD

We consider the Nielsen identities for the two-point functions of full QCD and QED in the class of Lorentz gauges. For pedagogical reasons the identities are first derived in QED to demonstrate the gauge independence of the photon self-energy, and of the electron mass shell. In QCD we derive the general identity and hence the identities for the quark, gluon and ghost propagators. The explicit contributions to the gluon and ghost identities are calculated to one-loop order, and then we show that the quark identity requires that in on-shell schemes the quark mass renormalisation must be gauge independent. Furthermore, we obtain formal solutions for the gluon self-energy and ghost propagator in terms of the gauge dependence of other, independent Green functions.Comment: 25 pages, plain TeX, 4 figures available upon request, MZ-TH/94-0

Factors influencing soil macrofaunal communities in post-pastoral successions of western France

The soil macrofaunal communities (Lumbricidae, Formicidae, Coleoptera, Chilopoda, Diplopoda, Isopoda, Arachnida, Gastropoda) were studied in six plots representing different stages in theoretical post-pastoral succession chalk grassland. Macrofaunal biomass was high in all the plots (70.2-140.3 g/m2). The macroinvertebrate communities along successional gradients respond to two major environmental factors : the structure of the vegetation, which determines the diversity of microhabitats and life conditions for macroinvertebrates ; and the quality of above-ground litter production, which depends on the nature of vegetation and the presence of domestic herbivores. (Résumé d'auteur

Infra-Red Finite Charge Propagation

The Coulomb gauge has a long history and many uses. It is especially useful in bound state applications. An important feature of this gauge is that the matter fields have an infra-red finite propagator in an on-shell renormalisation scheme. This is, however, only the case if the renormalisation point is chosen to be the static point on the mass shell, p = (m, 0, 0, 0). In this letter we show how to extend this key property of the Coulomb gauge to an arbitrary relativistic renormalisation point. This is achieved through the introduction of a new class of gauges of which the Coulomb gauge is a limiting case. A physical explanation for this result is given.Comment: 8 pages, plain TeX, to appear in Modern Physics Letters

An Evaluation of Conventional Cephalometric Appraisals

Although lateral cephalographic diagnosis is central to craniofacial skeletal assessment, their classification (categorization) remains largely empiric. In this study, pre- and post-treatment lateral cephalographic dimensional arrays were subjected to the classic numerical taxonomic technique of cluster analysis. The resultant patient groupings (clusters) were not only inconsistent with respect to their Angle malocclusion categories, but also the composition of each cluster group varies depending upon the dimensional arrays analyzed. These findings demonstrate that lateral cephalometric categorization remains largely subjective.Bien que le diagnostic céphalométrique latéral soit essentiel pour l’évaluation du squelette craniofacial, les classifications (catégorisation) restent largement empiriques. Dans le présent travail, les mesures céphalométriques latérales prises avant et après traitement ont été soumises à la technique taxonomique numérique classique de l’analyse de groupe. Les groupes de patients obtenus n’étaient pas compatibles avec leur situation dans la classification des malocclusions d’Angle. De plus, la composition de chaque groupe variait en fonction de l’ordre des dimensions analysées, ces résultats prouvent que la catégorisation céphalométrique latérale reste tout à fait subjective

Population dynamics and adaptative strategies of Martiodrilus carimaguensis (Oligochaeta, Glossoscolecidae), a native species from the well-drained savannas of Colombia

#Martiodrilus carimaguensis (Oligochaeta, Glossoscolecidae) is a large, anecic native earthworm species which was found in natural and disturbed savannas in the Oxisols of the Colombian Llanos. Its population dynamics were studied in a native savanna, and in a 17 year old grazed grass-legume pasture where density and biomass were higher. Monthly cast deposition on the soil surface in the improved pasture was 38.4 x 10(exp 3) fresh casts/ha, eleven times more than in the native savanna. A strong relationship was found between numbers of #M. carimaguensis and numbers of fresh surface casts. Different patterns of adaptation to the dry season were observed for adults and juveniles. Adults are active for eight months whereas juveniles enter diapause 3-4 months earlier. The vertical distribution pattern of the earthworm population also shows marked seasonal changes. (Résumé d'auteur

The Structure of Screening in QED

The possibility of constructing charged particles in gauge theories has long been the subject of debate. In the context of QED we have shown how to construct operators which have a particle description. In this paper we further support this programme by showing how the screening interactions arise between these charges. Unexpectedly we see that there are two different gauge invariant contributions with opposite signs. Their difference gives the expected result.Comment: 8 pages, LaTe

Nonverbal Behavior During Face-to-face Social Interaction in Schizophrenia

Patients with a diagnosis of schizophrenia display social cognitive deficits. However, little is known about patients’ nonverbal communication during their social encounters with others. This review identified 17 studies investigating nonverbal communication in patients’ unscripted face-to-face interactions, addressing a) nonverbal differences between patients and others, b) nonverbal behavior of the patients’ partners, c) the association between nonverbal behavior and symptoms, and d) the association between nonverbal behavior and social outcomes. Patients displayed fewer nonverbal behaviors inviting interaction, with negative symptoms exacerbating this pattern. Positive symptoms were associated with heightened nonverbal behavior. Patients’ partners changed their own nonverbal behavior in response to the patient. Reduced prosocial behaviors, inviting interaction, were associated with poorer social outcomes. The evidence suggests that patients’ nonverbal behavior, during face-to-face interaction, is influenced by patients symptoms and impacts the success of their social interactions

A New Symmetry for QED

We demonstrate that QED exhibits a previously unobserved symmetry. Some consequences are discussed.Comment: 9 pages, MZ-TH/93-02, DIAS-STP-93-0

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

Is the ground state of Yang-Mills theory Coulombic?

We study trial states modelling the heavy quark-antiquark ground state in SU(2) Yang-Mills theory. A state describing the flux tube between quarks as a thin string of glue is found to be a poor description of the continuum ground state; the infinitesimal thickness of the string leads to UV artifacts which suppress the overlap with the ground state. Contrastingly, a state which surrounds the quarks with non-abelian Coulomb fields is found to have a good overlap with the ground state for all charge separations. In fact, the overlap increases as the lattice regulator is removed. This opens up the possibility that the Coulomb state is the true ground state in the continuum limit.Comment: 10 pages, 9 .eps figure