Quantum transport of atomic matterwaves in anisotropic 2D and 3D disorder

The macroscopic transport properties in a disordered potential, namely diffusion and weak/strong localization, closely depend on the microscopic and statistical properties of the disorder itself. This dependence is rich of counter-intuitive consequences. It can be particularly exploited in matter wave experiments, where the disordered potential can be tailored and controlled, and anisotropies are naturally present. In this work, we apply a perturbative microscopic transport theory and the self-consistent theory of Anderson localization to study the transport properties of ultracold atoms in anisotropic 2D and 3D speckle potentials. In particular, we discuss the anisotropy of single-scattering, diffusion and localization. We also calculate a disorder-induced shift of the energy states and propose a method to include it, which amounts to renormalize energies in the standard on-shell approximation. We show that the renormalization of energies strongly affects the prediction for the 3D localization threshold (mobility edge). We illustrate the theoretical findings with examples which are revelant for current matter wave experiments, where the disorder is created with a laser speckle. This paper provides a guideline for future experiments aiming at the precise location of the 3D mobility edge and study of anisotropic diffusion and localization effects in 2D and 3D

Anderson Localization of Matter Waves in 3D Anisotropic Disordered Potentials

Using a cutoff-free formulation of the coherent transport theory, we show that the interference terms at the origin of localization strongly affect the transport anisotropy. In contrast to the common hypothesis, we then find that the anisotropies of incoherent and coherent diffusion are significantly different, in particular at criticality. There, we show that the coherent transport anisotropy is mainly determined by the properties of the disorder-averaged effective scattering medium while the incoherent transport contributions become irrelevant

Un palais épiscopal à Bosra

In Bosra, the capital of the province of Arabia in proto-Byzantine period, a big palace so-called "palace of Trajan", is located near the largest church of the city. The latter could serve as a Cathedral and the Palace of Trajan, as a palace for the metropolitan bishop.A Bosra, capitale de la province d'Arabie à l'époque proto-byzantine, une vaste demeure palatiale appelée "palais de Trajan", est située à proximité d'une grande église à plan centré. Cette dernière aurait pu faire office de cathédrale et le Palais de Trajan, de palais pour l'évêque métropolitain

Les bains du Palais de Trajan

Rapport préliminaire.Rapport de mission présentant les premiers résultats des dégagements et fouilles réalisés sur les petits bains privés du "Palais de Trajan" à Bosra. Epoque byzantine et omayyade

Strongly interacting bosons on a three-leg ladder in the presence of a homogeneous flux

We perform a density-matrix renormalization-group study of strongly interacting bosons on a three-leg ladder in the presence of a homogeneous flux. Focusing on one-third filling, we explore the phase diagram in dependence of the magnetic flux and the inter-leg tunneling strength. We find several phases including a Meissner phase, vortex liquids, a vortex lattice, as well as a staggered-current phase. Moreover, there are regions where the chiral current reverses its direction, both in the Meissner and in the staggered-current phase. While the reversal in the latter case can be ascribed to spontaneous breaking of translational invariance, in the first it stems from an effective flux increase in the rung direction. Interactions are a necessary ingredient to realize either type of chiral-current reversal

Vortex and Meissner phases of strongly-interacting bosons on a two-leg ladder

We establish the phase diagram of the strongly-interacting Bose-Hubbard model defined on a two-leg ladder geometry in the presence of a homogeneous flux. Our work is motivated by a recent experiment [Atala et al., Nature Phys. 10, 588 (2014)], which studied the same system, in the complementary regime of weak interactions. Based on extensive density matrix renormalization group simulations and a bosonization analysis, we fully explore the parameter space spanned by filling, inter-leg tunneling, and flux. As a main result, we demonstrate the existence of gapless and gapped Meissner and vortex phases, with the gapped states emerging in Mott-insulating regimes. We calculate experimentally accessible observables such as chiral currents and vortex patterns.Comment: 4 pages + Supplementary Materia

Spontaneous increase of magnetic flux and chiral-current reversal in bosonic ladders: Swimming against the tide

The interplay between spontaneous symmetry breaking in many-body systems, the wavelike nature of quantum particles and lattice effects produces an extraordinary behavior of the chiral current of bosonic particles in the presence of a uniform magnetic flux defined on a two-leg ladder. While non-interacting as well as strongly interacting particles, stirred by the magnetic field, circulate along the system's boundary in the counterclockwise direction in the ground state, interactions stabilize vortex lattices. These states break translational symmetry, which can lead to a reversal of the circulation direction. Our predictions could readily be accessed in quantum gas experiments with existing setups or in arrays of Josephson junctions.Comment: 5 pages + 5 pages of supplementary materia

Dynamics of apparent horizons in quantum gravitational collapse

We study the gravitational collapse of a massless scalar field within the effective scenario of loop quantum gravity. Classical singularity is avoided and replaced by a quantum bounce in this model. It is shown that, quantum gravity effects predict a threshold scale below which no horizon can form as the collapse evolves towards the bounce.Comment: Contribution to the Spanish Relativity Meeting in Portugal 2012 (ERE2012), Guimaraes, Portuga

La grande église à plan centré du quartier est de Bosra

Les fouilles menées par la mission archéologique franco-syrienne en Syrie du Sud entre 1985 et 2000 ont permis de découvrir et dégager une grande église à plan centré dans le quartier oriental de la ville antique de Bosra. Entièrement bâtie en basalte, elle présente un vaste espace central de presque 30 m de diamètre délimité par une colonnade circulaire et un déambulatoire inscrits dans un bâtiment de plan carré dont les quatre angles contiennent de larges exèdres. Sur les quatre côtés du bâtiment, des constructions largement saillantes prennent appui. L'église est fondée sur un remblai massif recouvrant deux monuments d'époques protobyzantine et nabatéenne à vocation peut-être cultuelle. Plusieurs de leurs éléments ont été remployés dans la construction de l'église élevée à la fin du Ve ou au début du VIe siècle et manifestement abandonnée à la fin du VIIIe siècle. Le réexamen des vestiges de cet ouvrage majeur pour la ville et pour l'architecture religieuse d'époque byzantine en Syrie permet de formuler des hypothèses sur sa restitution volumétrique et sur les modes de couvertures adoptés pour ses différents composants. Deux modes de couverture sont fréquemment mis en œuvre en Syrie du Sud : la couverture en dalles de basalte jointives et les voûtes en opus caementicum, agglomérat de mortier et de scories basaltiques légères. Les vestiges en place nous fournissent fort peu d'indices et nous privilégions ces deux types de couverture pour les pièces annexes qui composent cette vaste église. En revanche, la coupole de l'espace central et la couverture du déambulatoire sont plus problématiques en raison de leur grande portée et il serait tentant d'envisager, à cet endroit, une solution utilisant le bois, coupole à deux coques imbriquées pour l'une et charpente en demi ferme couverte de tuiles pour l'autre