Faraday waves in binary non-miscible Bose-Einstein condensates

We show by extensive numerical simulations and analytical variational calculations that elongated binary non-miscible Bose-Einstein condensates subject to periodic modulations of the radial confinement exhibit a Faraday instability similar to that seen in one-component condensates. Considering the hyperfine states of $^{87}$Rb condensates, we show that there are two experimentally relevant stationary state configurations: the one in which the components form a dark-bright symbiotic pair (the ground state of the system), and the one in which the components are segregated (first excited state). For each of these two configurations, we show numerically that far from resonances the Faraday waves excited in the two components are of similar periods, emerge simultaneously, and do not impact the dynamics of the bulk of the condensate. We derive analytically the period of the Faraday waves using a variational treatment of the coupled Gross-Pitaevskii equations combined with a Mathieu-type analysis for the selection mechanism of the excited waves. Finally, we show that for a modulation frequency close to twice that of the radial trapping, the emergent surface waves fade out in favor of a forceful collective mode that turns the two condensate components miscible.Comment: 13 pages, 10 figure

Thermal conductance of the Fermi-Pasta-Ulam chains: Atomic to mesoscopic transition

We demonstrate that in the atomic-scale limit the thermal conductance $\mathcal K$ of the FPU model and its variants strongly deviates from the mesoscopic behavior due to the relevance of contact resistance. As a result, atomic chains follow $\log \mathcal K = \nu \log T$, where the power law coefficient $\nu$ is exactly two times larger than the mesoscopic value. We smoothly interconnect the atomic and mesoscopic limits, and demonstrate that this turnover behavior takes place in other nonlinear FPU-like models. Our results are significant for nanoscale applications, manifesting an atomic thermal conductance with temperature scaling superior to the mesoscopic limit

C programs for solving the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap

We present C programming language versions of earlier published Fortran programs (Muruganandam and Adhikari, Comput. Phys. Commun. 180 (2009) 1888) for calculating both stationary and non-stationary solutions of the time-dependent Gross-Pitaevskii (GP) equation. The GP equation describes the properties of dilute Bose-Einstein condensates at ultra-cold temperatures. C versions of programs use the same algorithms as the Fortran ones, involving real- and imaginary-time propagation based on a split-step Crank-Nicolson method. In a one-space-variable form of the GP equation, we consider the one-dimensional, two-dimensional, circularly-symmetric, and the three-dimensional spherically-symmetric harmonic-oscillator traps. In the two-space-variable form, we consider the GP equation in two-dimensional anisotropic and three-dimensional axially-symmetric traps. The fully-anisotropic three-dimensional GP equation is also considered. In addition to these twelve programs, for six algorithms that involve two and three space variables, we have also developed threaded (OpenMP parallelized) programs, which allow numerical simulations to use all available CPU cores on a computer. All 18 programs are optimized and accompanied by makefiles for several popular C compilers. We present typical results for scalability of threaded codes and demonstrate almost linear speedup obtained with the new programs, allowing a decrease in execution times by an order of magnitude on modern multi-core computers.Comment: 8 pages, 1 figure; 18 C programs included (to download, click other and download the source

Le tableur et l'option informatique : vers la programmation par objets

Des difficultés décelées auprès de plusieurs groupes d'élèves dans l'enseignement optionnel de l'informatique en classe de seconde m'ont amené à élaborer puis à affiner par étapes successives une approche particulière du programme. Cette communication présente l'état d'avancement de ma réflexion à ce sujet au cours de l'année scolaire 1987/88. Dans la première partie de l'année scolaire les élèves apprennent à identifier dans un problème les objets significatifs, à reconnaître a priori le type de données informatiques qui permettra le codage de ces objets (valeurs logiques, chaînes de caractères, nombres, objets composés) et la nature de la définition de ces objets (définition simple, définition conditionnelle, définition itérative). La découverte de ces notions s'effectue progressivement, les objets à définition itérative qui constituent l'introduction à l'algorithmique séquentielle classique ne sont abordés que lorsque la notion d'objet est maîtrisée par un nombre suffisant d'élèves. Cette démarche englobe à la fois le cours théorique, les exercices et les travaux pratiques sur ordinateurs. Son originalité principale est de s'appuyer pour les travaux pratiques sur le tableur Multiplan, utilisé dans un contexte de résolution de problème, de simulation et d'aide à la décision au cours de la première moitié de l'année scolaire. La force du tableur par opposition à un langage traditionnel résulte : - de la visualisation permanente de l'état des données (des objets), - de la possibilité de repousser les difficultés liées à la notion de séquence tout en préparant son introduction et son étude systématique, - de la facilité de la prise en main. Les résultats obtenus par des élèves lors d'un exercice d'analyse et lors de deux travaux pratiques sont commentés à titre d'illustration et servent de base à des comparaisons entre le tableur d'une part, et d'autre part les langages impératifs, les langages applicatifs et les langages à objets

PENGARUH STRUKTUR CORPORATE GOVERNANCE, AUDIT TENURE, DAN SPESIALISASI INDUSTRI AUDITOR TERHADAP INTEGRITAS LAPORAN KEUANGAN (Studi pada Perusahaan Manufaktur yang Terdaftar di BEI Tahun 2008-2011)

This research aims to analyze the effects of corporate governance structure, audit tenure and auditor industry specialization on integrity of financial statement of manufacturing sector in Indonesia’s companies. Integrity of financial statement define as how far a financial statement disclosure shows truth and honest information. Independent variables used in this study were structure corporate governance was analyzed by (independent commissioner, ownership of managerial , ownership of institutional, audit committee), audit tenure and auditor industry specialization to integrity of financial statement. Dependent variable used in this study is integrity of financial statement was analyzed by conservatism, year observation from 2008 until 2011. The sample in this study were manufacturing sector companies listed in Indonesian Stock Exchange (IDX) in the periode 2008-2011. The number of sample used were 46 companies listed were taken by purposive sampling. The analysis method of this research used multiple linear regression analysis. The result of this research showed that independent commisioners and audit committee had positive and significat influence to integrity of financial statement; meanwhile ownership of managerial, ownership of institutional, audit tenure and auditor industry specialization had not significant effect to integrity of financial statemen