9 research outputs found
Faradejevi talasi u ultrahladnim dipolnim Boze gasovima
Nakon pionirskih eksperimenata sa sistemima ultrahladnih atoma u kojima je realizovana Boze-Ajnčtajn kondenzacija sa slabom kontaktnom interakcijom, bila je potrebna čitava decenija...After pioneering experiments that realized Bose-Einstein condensates in systems of
ultracold atoms with weak contact interactions, it took a decade for experimental
techniques to advance and enable measurement of effects of the dipole-dipole interaction
that exist between atoms or molecules with a permanent or induced electric
or magnetic dipole moment..
Fortran and C programs for the time-dependent dipolar Gross-Pitaevskii equation in an anisotropic trap
Many of the static and dynamic properties of an atomic Bose-Einstein
condensate (BEC) are usually studied by solving the mean-field Gross-Pitaevskii
(GP) equation, which is a nonlinear partial differential equation for
short-range atomic interaction. More recently, BEC of atoms with long-range
dipolar atomic interaction are used in theoretical and experimental studies.
For dipolar atomic interaction, the GP equation is a partial
integro-differential equation, requiring complex algorithm for its numerical
solution. Here we present numerical algorithms for both stationary and
non-stationary solutions of the full three-dimensional (3D) GP equation for a
dipolar BEC, including the contact interaction. We also consider the simplified
one- (1D) and two-dimensional (2D) GP equations satisfied by cigar- and
disk-shaped dipolar BECs. We employ the split-step Crank-Nicolson method with
real- and imaginary-time propagations, respectively, for the numerical solution
of the GP equation for dynamic and static properties of a dipolar BEC. The
atoms are considered to be polarized along the z axis and we consider ten
different cases, e.g., stationary and non-stationary solutions of the GP
equation for a dipolar BEC in 1D (along x and z axes), 2D (in x-y and x-z
planes), and 3D, and we provide working codes in Fortran 90/95 and C for these
ten cases (twenty programs in all). We present numerical results for energy,
chemical potential, root-mean-square sizes and density of the dipolar BECs and,
where available, compare them with results of other authors and of variational
and Thomas-Fermi approximations.Comment: To download the programs click other and download sourc
SPEEDUP Code for Calculation of Transition Amplitudes via the Effective Action Approach
We present Path Integral Monte Carlo C code for calculation of quantum
mechanical transition amplitudes for 1D models. The SPEEDUP C code is based on
the use of higher-order short-time effective actions and implemented to the
maximal order =18 in the time of propagation (Monte Carlo time step), which
substantially improves the convergence of discretized amplitudes to their exact
continuum values. Symbolic derivation of higher-order effective actions is
implemented in SPEEDUP Mathematica codes, using the recursive Schroedinger
equation approach. In addition to the general 1D quantum theory, developed
Mathematica codes are capable of calculating effective actions for specific
models, for general 2D and 3D potentials, as well as for a general many-body
theory in arbitrary number of spatial dimensions.Comment: 17 pages, 3 figures, uses cicp.cl
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
Development of Grid e-Infrastructure in South-Eastern Europe
Over the period of 6 years and three phases, the SEE-GRID programme has
established a strong regional human network in the area of distributed
scientific computing and has set up a powerful regional Grid infrastructure. It
attracted a number of user communities and applications from diverse fields
from countries throughout the South-Eastern Europe. From the infrastructure
point view, the first project phase has established a pilot Grid infrastructure
with more than 20 resource centers in 11 countries. During the subsequent two
phases of the project, the infrastructure has grown to currently 55 resource
centers with more than 6600 CPUs and 750 TBs of disk storage, distributed in 16
participating countries. Inclusion of new resource centers to the existing
infrastructure, as well as a support to new user communities, has demanded
setup of regionally distributed core services, development of new monitoring
and operational tools, and close collaboration of all partner institution in
managing such a complex infrastructure. In this paper we give an overview of
the development and current status of SEE-GRID regional infrastructure and
describe its transition to the NGI-based Grid model in EGI, with the strong SEE
regional collaboration.Comment: 22 pages, 12 figures, 4 table
Discovering, Indexing and Interlinking Information Resources [version 2; referees: 1 approved, 2 approved with reservations]
The social media revolution is having a dramatic effect on the world of scientific publication. Scientists now publish their research interests, theories and outcomes across numerous channels, including personal blogs and other thematic web spaces where ideas, activities and partial results are discussed. Accordingly, information systems that facilitate access to scientific literature must learn to cope with this valuable and varied data, evolving to make this research easily discoverable and available to end users. In this paper we describe the incremental process of discovering web resources in the domain of agricultural science and technology. Making use of Linked Open Data methodologies, we interlink a wide array of custom-crawled resources with the AGRIS bibliographic database in order to enrich the user experience of the AGRIS website. We also discuss the SemaGrow Stack, a query federation and data integration infrastructure used to estimate the semantic distance between crawled web resources and AGRIS
NI4OS-Europe Second report on provider and repository integration and horizontal service delivery
"Second report on provider and repository integration and horizontal service delivery" presents the resource and provider on-boarding status. The deliverable gives details on the updated on-boarding procedure and presents integrated repositories, thematic and generic services, as well as services from the pre-production environment and relevant statistics