Populations réfugiées : de l'exil au retour

Depuis les années 1970, la population cambodgienne a été contrainte à des déplacements de diverses natures. Ainsi, plusieurs centaines de milliers de Cambodgiens, fuyant a posteriori le régime totalitaire khmer rouge, l'occupation vietnamienne et les combats entre factions politiques, trouvèrent un refuge provisoire au sein des camps frontaliers de Thaïlande. La réinstallation au Cambodge de ces réfugiés est remise en cause par le manque de terres car la plupart d'entre elles ont été dévastées par les combats, sont encore minées ou sont tombées aux mains de militaires en cours de démobilisation, qui forcent les civils à travailler pour leur compte ou bien les expulsent de leurs terres. (Résumé d'auteur

Gravitational Self Force in a Schwarzschild Background and the Effective One Body Formalism

We discuss various ways in which the computation of conservative Gravitational Self Force (GSF) effects on a point mass moving in a Schwarzschild background can inform us about the basic building blocks of the Effective One-Body (EOB) Hamiltonian. We display the information which can be extracted from the recently published GSF calculation of the first-GSF-order shift of the orbital frequency of the last stable circular orbit, and we combine this information with the one recently obtained by comparing the EOB formalism to high-accuracy numerical relativity (NR) data on coalescing binary black holes. The information coming from GSF data helps to break the degeneracy (among some EOB parameters) which was left after using comparable-mass NR data to constrain the EOB formalism. We suggest various ways of obtaining more information from GSF computations: either by studying eccentric orbits, or by focussing on a special zero-binding zoom-whirl orbit. We show that logarithmic terms start entering the post-Newtonian expansions of various (EOB and GSF) functions at the fourth post-Newtonian (4PN) level, and we analytically compute the first logarithm entering a certain, gauge-invariant "redshift" GSF function (defined along the sequence of circular orbits).Comment: 44 page

Projets de territoires et observation des agglomérations : réflexion à partir des cas de Tours et d'Orléans

Orléans et Tours, qui sont les deux agglomérations principales de la région Centre, comptent parmi les aires urbaines françaises qui ont connu, au cours des années 1990, un fort accroissement de leur population. D'Orléans à Nantes, la vallée de la Loire présente le double avantage d'être proche d'une des régions européennes les plus dynamiques - l'Ile de France - et d'être bien équipée en infrastructures autoroutières et ferrées. Les agglomérations d'Orléans et de Tours font donc partie des espaces français attractifs pour les activités économiques et les ménages en quête de localisation. Pourtant, comparées à d'autres villes françaises ou étrangères, Orléans et Tours ne sont absolument pas des métropoles. Après avoir rappelé les éléments principaux qui caractérisent la région Centre et tout particulièrement son espace ligérien, nous verrons à la lumière de l'examen d'un ensemble de diagnostics urbains, liés à quelques exercices récents de planification, que les conditions de l'émergence d'un processus de métropolisation sont loin d'être réunie

Symmetries,Singularities and the De-Emergence of Space

Recent work has revealed intriguing connections between a Belinsky-Khalatnikov-Lifshitz-type analysis of spacelike singularities in General Relativity and certain infinite dimensional Lie algebras, and in particular the `maximally extended' hyperbolic Kac--Moody algebra E10. In this essay we argue that these results may lead to an entirely new understanding of the (quantum) nature of space(-time) at the Planck scale, and hence -- via an effective `de-emergence' of space near a singularity -- to a novel mechanism for achieving background independence in quantum gravity.Comment: 10 page

Cooperative scattering measurement of coherence in a spatially modulated Bose gas

Correlations of a Bose gas released from an optical lattice are measured using superradiant scattering. Conditions are chosen so that after initial incident light pumping at the Bragg angle for diffraction, due to matter wave amplification and mode competition, superradiant scattering into the Bragg diffracted mode is preponderant. A temporal analysis of the superradiant scattering gain reveals periodical oscillations and damping due to the initial lack of coherence between lattice sites. Such damping is used for characterizing first order spatial correlations in our system with a precision of one lattice period.Comment: 4pages, 3figures, to appear in Phys. Rev.

Accurate mass measurements of 26^{26}Ne, 26−30^{26-30}Na, 29−33^{29-33}Mg performed with the {\sc Mistral} spectrometer

The minuteness of the nuclear binding energy requires that mass measurements be highly precise and accurate. Here we report on new measurements $^{29-33}$Mg and $^{26}$Na performed with the {\sc Mistral} mass spectrometer at {\sc Cern}'s {\sc Isolde} facility. Since mass measurements are prone to systematic errors, considerable effort has been devoted to their evaluation and elimination in order to achieve accuracy and not only precision. We have therefore conducted a campaign of measurements for calibration and error evaluation. As a result, we now have a satisfactory description of the {\sc Mistral} calibration laws and error budget. We have applied our new understanding to previous measurements of $^{26}$Ne, $^{26-30}$Na and $^{29,32}$Mg for which re-evaluated values are reported.Comment: submitted to Nuclear Physics