Search results for "Computational Science"
showing 10 items of 124 documents
Concurrent molecular dynamics simulation of spinodal phase transition on transputer arrays
1990
Abstract We describe a concurrent implementation on cost-effective transputer arrays of a molecular dynamics program to efficiently simulate physical systems consisting of thousands of mobile particles with an interaction range much shorter than the system dimensions. This program, which uses a geometric decomposition strategy and includes a distributed dynamic load balancer, has been extensively tested by simulating the two-dimensional spinodal phase separation of a large Lennard-Jones system.
A Monte-Carlo based model of the AX-PET demonstrator and its experimental validation
2013
AX-PET is a novel PET detector based on axially oriented crystals and orthogonal wavelength shifter (WLS) strips, both individually read out by silicon photo-multipliers. Its design decouples sensitivity and spatial resolution, by reducing the parallax error due to the layered arrangement of the crystals. Additionally the granularity of AX-PET enhances the capability to track photons within the detector yielding a large fraction of inter-crystal scatter events. These events, if properly processed, can be included in the reconstruction stage further increasing the sensitivity. Its unique features require dedicated Monte-Carlo simulations, enabling the development of the device, interpreting …
Effect of low mass dark matter particles on the Sun
2010
We study the effect of dark matter (DM) particles in the Sun, focusing in particular on the possible reduction of the solar neutrinos flux due to the energy carried away by DM particles from the innermost regions of the Sun, and to the consequent reduction of the temperature of the solar core. We find that in the very low-mass range between 4 and 10 GeV, recently advocated to explain the findings of the DAMA and CoGent experiments, the effects on neutrino fluxes are detectable only for DM models with very small, or vanishing, self-annihilation cross section, such as the so-called asymmetric DM models, and we study the combination of DM masses and Spin Dependent cross sections which can be e…
A weakly random Universe?
2010
The cosmic microwave background (CMB) radiation is characterized by well-established scales, the 2.7 K temperature of the Planckian spectrum and the $10^{-5}$ amplitude of the temperature anisotropy. These features were instrumental in indicating the hot and equilibrium phases of the early history of the Universe and its large scale isotropy, respectively. We now reveal one more intrinsic scale in CMB properties. We introduce a method developed originally by Kolmogorov, that quantifies a degree of randomness (chaos) in a set of numbers, such as measurements of the CMB temperature in some region. Considering CMB as a composition of random and regular signals, we solve the inverse problem of …
Accelerated fluctuation analysis by graphic cards and complex pattern formation in financial markets
2009
The compute unified device architecture is an almost conventional programming approach for managing computations on a graphics processing unit (GPU) as a data-parallel computing device. With a maximum number of 240 cores in combination with a high memory bandwidth, a recent GPU offers resources for computational physics. We apply this technology to methods of fluctuation analysis, which includes determination of the scaling behavior of a stochastic process and the equilibrium autocorrelation function. Additionally, the recently introduced pattern formation conformity (Preis T et al 2008 Europhys. Lett. 82 68005), which quantifies pattern-based complex short-time correlations of a time serie…
Calculation of the two-loop heavy-flavor contribution to Bhabha scattering
2008
We describe in detail the calculation of the two-loop corrections to the QED Bhabha scattering cross section due to the vacuum polarization by heavy fermions. Our approach eliminates one mass scale from the most challenging part of the calculation and allows us to obtain the corrections in a closed analytical form. The result is valid for arbitrary values of the heavy fermion mass and the Mandelstam invariants, as long as s,t,u >> m_e^2.
“RecPack” a reconstruction toolkit
2004
We present a C++ toolkit to do tracking and vertex reconstruction. The toolkit incorporates common fitting methods, as the Kalman Filter, a framework to define a detector setup, a general navigation and a simple simulation. Furthermore, the toolkit provides a collection of interfaces which facilitates the addition of new fitting methods, trajectory models, geometrical objects, pattern recognition logic, etc. Although the toolkit was originally developed to be used in High Energy Physics, it could be applied to other fields.
top data system ( TDS) software for infrared spectrum simulation of asymmetric molecules: some improvements to the TDS packages
2005
Abstract The spherical top data system (STDS) program suite developed in Dijon has been extended with the aim of studying any rovibrational band or polyad of XY 2 Z 2 ( C 2 v ) asymmetric top molecules. We work in the O ( 3 ) ⊃ T d ⊃ C 2 v chain because these species result from the substitution of two ligands of a corresponding “parent” spherical top and thus are relatively close to tetrahedral symmetry. The choice of this group chain has consequences on the method used to specify the input parameters of the programs for Hamiltonian and transition moment model calculations. One example concerning the ground state of the SO2F2 quasi-spherical molecule is presented. As before, this suite con…
Online Data Reduction using Track and Vertex Reconstruction on GPUs for the Mu3e Experiment
2017
The Mu3e experiment searches for the lepton flavour violating decay μ + → e + e − e + , aiming to achieve a sensitivity of 2 · 10 −15 in its first phase and ultimately aspiring to a final sensitivity of 10 −16 . During the first phase of the experiment, a muon rate of ∼ 10 8 μ /s will be available, resulting in a data rate of ∼ 80 Gbit/s. The trigger-less readout system is based on optical links and switching FPGAs sending the complete detector data for a time slice to one node of the filter farm. A full online reconstruction is necessary to reduce the data rate to a manageable amount to be written to disk. Graphics processing units (GPUs) are used to fit tracks with a non-iterative 3D trac…
The Two Loop Crossed Ladder Vertex Diagram with Two Massive Exchanges
2008
We compute the (three) master integrals for the crossed ladder diagram with two exchanged quanta of equal mass. The differential equations obeyed by the master integrals are used to generate power series expansions centered around all the singular (plus some regular) points, which are then matched numerically with high accuracy. The expansions allow a fast and precise numerical calculation of the three master integrals (better than 15 digits with less than 30 terms in the whole real axis). A conspicuous relation with the equal-mass sunrise in two dimensions is found. Comparison with a previous large momentum expansion is made finding complete agreement.