Yang-Mills Flow and Uniformization Theorems

We consider a parabolic-like systems of differential equations involving geometrical quantities to examine uniformization theorems for two- and three-dimensional closed orientable manifolds. We find that in the two-dimensional case there is a simple gauge theoretic flow for a connection built from a Riemannian structure, and that the convergence of the flow to the fixed points is consistent with the Poincare Uniformization Theorem. We construct a similar system for the three-dimensional case. Here the connection is built from a Riemannian geometry, an SO(3) connection and two other 1-form fields which take their values in the SO(3) algebra. The flat connections include the eight homogeneous geometries relevant to the three-dimensional uniformization theorem conjectured by W. Thurston. The fixed points of the flow include, besides the flat connections (and their local deformations), non-flat solutions of the Yang-Mills equations. These latter "instanton" configurations may be relevant to the fact that generic 3-manifolds do not admit one of the homogeneous geometries, but may be decomposed into "simple 3-manifolds" which do.Comment: 21 pages, Latex, 5 Postscript figures, uses epsf.st

A Kucha\v{r} Hypertime Formalism For Cylindrically Symmetric Spacetimes With Interacting Scalar Fields

The Kucha\v{r} canonical transformation for vacuum geometrodynamics in the presence of cylindrical symmetry is applied to a general non-vacuum case. The resulting constraints are highly non-linear and non-local in the momenta conjugate to the Kucha\v{r} embedding variables. However, it is demonstrated that the constraints can be solved for these momenta and thus the dynamics of cylindrically symmetric models can be cast in a form suitable for the construction of a hypertime functional Schr\"odinger equation.Comment: 5 pages, LaTeX, UBCTP-93-02

Le champ filonien à Zn-(Pb, Cu, As, Hg) du district minier de Fedj Hassène (Nord Ouest de la Tunisie): Minéralogie, Eléments en traces, Isotopes du Soufre et Inclusions Fluides

Le district minier de Fedj Hassène est situé à proximité de la frontière algéro-tunisienne, à 10 Km au sud de la ville de Ghardimaou. Il regroupe plusieurs filons à Pb-Zn, localement accompagnés par des sulfures de Cu, d'As et d'Hg. Les réserves sont estimées à 370.000 t à 10% de Zn et 0,2% de Pb. Les minéralisations remplissent des fractures subparallèles à la faille d'Ain Kohla de direction ESEWNW et des fentes d'extension qui recoupent les calcaires marneux du Turonien moyen. Le filon principal est formé par de la sphalérite massive brune et accessoirement par de la galène et de la barytine. Le minerai peut se présenter sous forme massive ou sous la forme de ciment de brèche. L'association minérale est composée par de la sphalérite, galène, chalcopyrite, pyrite et orpiment. La gangue est formée par de la calcite massive et localement par de la barytine et du quartz. L'analyse des éléments en trace dans la sphalérite révèle des teneurs en poids de 0,84% Fe, 0,14% Cd et 0,02% Mn. L'étude des inclusions fluides dans la calcite et la sphalérite montre l'existence d'un fluide caractérisé par une salinité de l'ordre de 23% poids équiv. NaCl à température décroissante lors de la mise en place des minéralisations (194 °C lors du dépôt de la calcite et 133 °C lors du dépôt de la sphalérite). Ce fluide est caractérisé par une densité comprise entre 1,00 g/cm3 et 1,11 g/cm3 avec une pression de piégeage estimée de 200 bars. La précipitation des sulfures parait être contrôlée par une chute de la température. Les mesures des isotopes du soufre dans la sphalérite donnent des valeurs de δ34S toutes positives et variant dans une gamme très restreinte comprise entre + 4,6‰ et 6,4‰ VCDT (moyenne=5,6‰). Ces valeurs indiquent une origine commune du soufre réduit qui est formé par les processus de ré duction thermique de sulfates. La source des sulfates admet les évaporites triasiques de la région comme reservoir potentiel. Les études géologiques et minéralogiques couplées à la microthermométrie des inclusions fluides et la géochimie des éléments en traces et des isotopes du soufre permettent de classer le gisement filonien de Fedj Hassène dans le groupe des gisements polymétalliques (Pb-Zn-As, Hg) typiques de la zone des nappes de la Tunisie du Nord et de l'Algérie nord-orientale

Surface Subsidence Over Deep Solution Mined Storage Cavern Field

Ten years observation by GDF on Tersanne solution-mined gas storage field, offers the opportunity for a mechanical interpretation of the surface subsidence. According to the geological context, the rockmass was modellised by a two-layered medium with highly contrasted mechanical behavior: a soft elastic clay cover, and a viscous salt mass. Given the field uncertainties, mostly related to the cover layer, and the three- dimensional nature of the problem, indirect methods were used to obtain bounds for the surface subsidence evolution and a parametric study was performed. Comparison with data of the field allows to determine likely rock mass parameters, put forward some typical mechanical response, and give some insight on the trends of the subsidence phenomena

Investigation of plastic deformation heterogeneities in duplex steel by EBSD

An EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail.International audienceAn EBSD analysis of a duplex steel (austeno-ferritic) deformed in tension up to fracture is presented. The main purpose of the paper is to describe, qualitatively and quantitatively, the differences in the behavior of the two phases during plastic deformation. In order to do so, several topological maps are measured on the deformed state using the electron backscatter diffraction technique. Distributions of grain size, misorientation, image quality factor and texture are then analyzed in detail

Somewhere in Europe (1947): locating Hungary within a shifting geopolitical landscape

Somewhere in Europe/Valahol Európában (Radványi, 1947) was one of the first films made in Hungary after 1945. Financed by the Hungarian Communist Party (MKP), it loudly proclaimed a broad European pertinence in an effort to privilege the universal narrative of childhoods disrupted by the war over narrowly national political concerns. The film’s story of a gang of half-starved children battling for survival in a bombed-out Central European landscape places it squarely within a transnational post-war film-making tradition. Similarities with both Italian neorealism and Soviet socialist realist cinema indicate a shared European experience of the war, but is also attributable to the international training and experience of the film’s personnel. The director Radványi had worked in the Italian industry, while the scriptwriter was the well-known film theorist Béla Balázs, who had worked in Weimar Germany and Soviet Russia. This article argues that in spite of its ostensible commitment to a communist and humanist ideology, the film gives an insight into the Hungarian national obsession with territorial integrity. Hungary’s participation in World War II on the side of the Axis, and its position as a defeated nation under Allied occupation, are seen to complicate the film text. This article contends that in spite its transnational flavour, the film’s focus on lost children wandering a borderless Europe suggests a preoccupation with the country’s uncertain position within a shifting geopolitical landscape. In turn, the film’s official reading by Nemeskürty shows an eagerness to accept the film’s representation of Hungary as a blameless victim of the war, and gives evidence of a need to insert a (false) break between the country’s wartime past as a member of the Axis, and the country’s 1968 present as a member of the Communist world order

To the North Coast of Devon: Collaborative Navigation While Exploring Unfamiliar Terrain

Navigation-knowing where one is and finding a safe route-is a fundamental aspect of all exploration. In unfamiliar terrain, one may use maps and instruments such as a compass or binoculars to assist, and people often collaborate in finding their way. This paper analyzes a group of people driving a humvee from a base camp to the north coast of Devon Island in the High Canadian Arctic. A complete audio recording and video during most stops allows a quantitative and semantic analysis of the conversations when the team stopped to take bearings and replan a route. Over a period of 2 hours, the humvee stopped 20 times, with an average duration of 3.15 min/pause and 3.85 min moving forward. The team failed to reach its goal due to difficult terrain causing mechanical problems. The analysis attempts to explain these facts by considering a variety of complicating factors, especially the navigation problem of relating maps and the world to locate the humvee and to plan a route. The analysis reveals patterns in topic structure and turn-taking, supporting the view that the collaboration was efficient, but the tools and information were inadequate for the task. This work is relevant for planning and training for planetary surface missions, as well as developing computer systems that could aid navigation

Deformation heterogeneity study of a 6061-T6 aluminum alloy processed by equal channel angular pressing

Among the severe plastic deformation techniques, the equal channel angular pressing (ECAP) has drastically improved the mechanical properties of the processed alloys. However, information regarding friction phenomenon, which modifies the deformation at the surface and the heterogeneity microstrain state produced by the process itself, is still scarce. In the present work, the deformation heterogeneity and the friction effect, at the surface in the bulk material of the 6061-T6 aluminum alloy processed by ECAP, is presented and discussed. The residual stress (RS) measurements were performed by means of X-Ray diffraction. By means of synchrotron diffraction, volumetric sections of the ECAPed samples were characterized. Finite element analysis showed a good agreement with the experimentally obtained residual stress and microhardness mapping results. The study also showed that the highest deformation zones were located at the outer parts of the deformed samples (top and bottom), while the inner zone showed strain oscillations of up to 49±2 MPa.Peer ReviewedPostprint (author's final draft

Using 3D Stringy Gravity to Understand the Thurston Conjecture

We present a string inspired 3D Euclidean field theory as the starting point for a modified Ricci flow analysis of the Thurston conjecture. In addition to the metric, the theory contains a dilaton, an antisymmetric tensor field and a Maxwell-Chern Simons field. For constant dilaton, the theory appears to obey a Birkhoff theorem which allows only nine possible classes of solutions, depending on the signs of the parameters in the action. Eight of these correspond to the eight Thurston geometries, while the ninth describes the metric of a squashed three sphere. It therefore appears that one can construct modified Ricci flow equations in which the topology of the geometry is encoded in the parameters of an underlying field theory.Comment: 17 pages, Late