Superfluid-insulator transition of two-dimensional disordered Bose gases

We study the two-dimensional weakly repulsive Bose gas at zero temperature in the presence of correlated disorder. Using large-scale simulations, we show that the low-energy Bogoliubov cumulative density of states remains quadratic up to a critical disorder strength, beyond which a power law with disorder-dependent exponent $\beta<2$ sets in. We associate this threshold behavior with the transition from superfluid to Bose glass, and compare the resulting mean-field phase diagram with scaling laws and the Thomas-Fermi percolation threshold of the mean-field density profile.Comment: Published version, 5 pages, 4 figure

Anderson localization of Bogoliubov excitations on quasi-1D strips

Anderson localization of Bogoliubov excitations is studied for disordered lattice Bose gases in planar quasi-one-dimensional geometries. The inverse localization length is computed as function of energy by a numerical transfer-matrix scheme, for strips of different widths. These results are described accurately by analytical formulas based on a weak-disorder expansion of backscattering mean free paths.Comment: 4 pages, 2 figure

Anderson Localization of Expanding Bose-Einstein Condensates in Random Potentials

We show that the expansion of an initially confined interacting 1D Bose-Einstein condensate can exhibit Anderson localization in a weak random potential with correlation length \sigma_R. For speckle potentials the Fourier transform of the correlation function vanishes for momenta k > 2/\sigma_R so that the Lyapunov exponent vanishes in the Born approximation for k > 1/\sigma_R. Then, for the initial healing length of the condensate \xi > \sigma_R the localization is exponential, and for \xi < \sigma_R it changes to algebraic.Comment: published versioon (no significant change compared to last version

Extracting partial decay rates of helium from complex rotation: autoionizing resonances of the one-dimensional configurations

Partial autoionization rates of doubly excited one-dimensional helium in the collinear Zee and eZe configuration are obtained by means of the complex rotation method. The approach presented here relies on a projection of back-rotated resonance wave functions onto singly ionized $\textrm{He}^{+}$ channel wave functions and the computation of the corresponding particle fluxes. In spite of the long-range nature of the Coulomb potential between the electrons and the nucleus, an asymptotic region where the fluxes are stationary is clearly observed. Low-lying doubly excited states are found to decay predomintantly into the nearest single-ionization continuum. This approach paves the way for a systematic analysis of the decay rates observed in higher-dimensional models, and of the role of electronic correlations and atomic structure in recent photoionization experiments

Topological nematic spin liquid on the square kagome lattice

International audienceThe ground state of the spin-1/2 kagome antiferromagnet remains uncertain despite decades of active research. Here we step aside from this debated question to address the ground-state nature of a related, and potentially just as rich, system made of corner-sharing triangles: the square kagome lattice (SKL). Our work is motivated by the recent synthesis of a distorted SKL compound mentioned by Morita and Tohyama [J. Phys. Soc. Jpn. 87, 043704 (2018)]. We have studied its spin-1/2 J1−J2 phase diagram with an unrestricted Schwinger boson mean-field theory (SBMFT). Our results agree with previous observations of a plaquette phase (J2≪J1) and a ferrimagnet (J1≪J2). In addition, three original phases appear: two incommensurate orders and a topological quantum spin liquid with weak nematicity. The topological order is characterized by fluxes on specific gauge-invariant quantities and the phase is stable under anisotropic perturbations relevant for experiments. Finally, we provide dynamical structure factors of the reported phases that could be observed in inelastic neutron scattering

Détection axiale de turbulences de sillage par LIDAR Doppler dans un volume fluide simulé et reconstruction d'images 2,5 D

Les turbulences de sillage, causées par le déplacement dans l'atmosphère des ailes d'un avion, sont potentiellement extrêmement dangereuses pour un avion suivant l'avion générateur. Celles-ci peuvent être détectées par LIDAR Doppler; toutefois, l'utilisation (par exemple dans le cas d'un senseur embarqué) d'une configuration d'analyse coaxiale aux vortex rend cette détection plus délicate. Cet article présente une méthode de génération d'images 2,5 D par triangulation de Delaunay à partir d'une simulation simplifiée de tirs LIDAR Doppler balayant suivant un motif sinusoïdal bruité des turbulences de sillage simulées. Nous validons ainsi la viabilité d'un balayage axial des turbulences de sillage et par suite la faisabilité d'un dispositif de détection et d'avertissement embarqué dans un avion

Schwinger boson theory of the J1,J2=J3 kagome antiferromagnet

We study the kagome antiferromagnet for quantum spin-1/2 with first J1, second J2 and third J3 neighbour exchanges, along the J2 = J3 = J line. We use Schwinger-boson mean-field theory for the precise determination of the phase diagram, and two different rewritings of the Hamiltonian to build an intuition about the origin of the transitions. The spin liquid obtained at J = 0 remains essentially stable over a large window, up to J = 1/3, because it is only weakly frustrated by the J term. Then at J = 1/2, the intermediate Z2 spin liquid condenses into a long-range chiral order because of the change of nature of local magnetic fluctuations. As a side benefit, our Hamiltonian rewriting offers an exact solution for the ground state of our model on a Husimi cactus.Comment: Last version before publication in PR

Digital transformation e Robotic Process Automation in un Istituto Bancario

Nel prossimo futuro, la crescita del fenomeno del digital labor e il sempre maggiore utilizzo delle nuove tecnologie di Intelligent Automation avranno importanti impatti sulle aziende, sia dal punto di vista organizzativo, sia per quanto concerne il tema della gestione delle risorse umane. Numerose imprese hanno già avviato programmi ed iniziative per automatizzare alcune attività aziendali, ma spesso in un contesto di sistemi informativi molto frammentati ed ancora non definiti. In molti casi persiste una generalizzata incertezza nel definire gli ambiti applicativi di queste iniziative, quando avviarle e, soprattutto, come e quanto investire. Tra tutte le tecnologie di Intelligent Automation, oggi quella di maggiore interesse è la Robotic Process Automation. I benefici della RPA sono diversi: dalla riduzione dei costi, alla maggiore velocità dei tempi di esecuzione delle attività, dalla migliore qualità dei dati, fino al miglioramento delle condizioni di lavoro, con operatori più soddisfatti grazie a carichi di lavori più leggeri. Come spesso accade per gli elementi che portano una forte disruption all’in- terno delle organizzazioni, oltre a numerosi benefici esistono sfide importanti da affrontare. I progetti di RPA non sono complessi da sviluppare dal punto di vista tecnologico, ma devono essere accompagnati da importanti valutazioni. Spesso, sull’onda dell’entusiasmo, le aziende avviano progetti di RPA individuando una serie di attività ripetitive che possono essere automatizzate, senza interrogarsi sulla reale fattibilità del progetto. È necessario capire, prima di tutto, quali sono gli obiettivi di queste progettualità e, in secondo luogo, valutare l’applicabilità dell’automazione alle diverse attività individuate. Questo percorso non è solamente una mera scelta di attività e processi, bensì uno studio che deve essere affrontato seriamente con metodologie ed un approccio replicabile e robusto, accompagnato da analisi di processi in ottica di digitalizzazione