| PHY-01 |
3-D Radiation Magnetohydrodynamic Simulations of the Near Surface Layers of the Sun, Flavio Calvo (University of Geneva, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-01
3-D Radiation Magnetohydrodynamic Simulations of the Near Surface Layers of the Sun, Flavio Calvo (University of Geneva, Switzerland)
Co-authors: Oskar Steiner (Kiepenheuer-Institut für Sonnenphysik, Germany); Bernd Freytag (Uppsala University, Sweden)
We carry out numerical radiation magnetohydrodynamics simulations of the near surface layers of the Sun using the facilities at CSCS. The simulations reproduce the well known granular structure of the solar surface with excellent fidelity. Simulations with magnetic fields also reproduce magnetic bright points in the intergranular space as is observed on the Sun. Simulations without magnetic fields show tinier non-magnetic bright points, which have not been observationally detected so far but our simulations predict their existence and basic physical properties of them. The simulated model atmospheres also serve for the computation of synthetic polarimetric intensity maps.
| PHY-02 |
A Bucketsort Algorithm on GPUs for the Particle-In-Cell (PIC) Method, Andreas Jocksch (CSCS / ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-02
A Bucketsort Algorithm on GPUs for the Particle-In-Cell (PIC) Method, Andreas Jocksch (CSCS / ETH Zurich, Switzerland)
Co-authors: Farah Hariri (EPFL, Switzerland); Trach-Minh Tran (EPFL, Switzerland); Stefan Brunner (EPFL, Switzerland); Claudio Gheller (CSCS / ETH Zurich, Switzerland); Laurent Villard (EPFL, Switzerland)
The Particle-In-Cell (PIC) method is effectively used in many scientific simulation codes. We present variants of an in place bucketsort algorithm for the PIC method targeting GPUs. In order to optimise performance data locality is required. This relies on efficient sorting algorithms. We discuss the different datastructures that are used where particles are distributed to buckets or stored contiguously. Finally, we show that the performance increases with the amount of storage provided and with the orderliness of the particles. The overall PIC algorithm performs at its best if the sorting is applied.
| PHY-03 |
Ab Initio Atomic Heat Transport Via Green-Kubo Formalism, Aris Marcolongo (EPFL, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-03
Ab Initio Atomic Heat Transport Via Green-Kubo Formalism, Aris Marcolongo (EPFL, Switzerland)
Co-authors: Baroni Stefano (International School for Advanced Studies, Italy); Umari Paolo (Padua University, Italy)
Green Kubo formulas have never been used in combination to a fully ab initio framework in order to compute the thermal conductivity of liquids. We derive here an expliticit expression for the adiabatic energy current, the key quantity in the Green-Kubo formalism, within density-functional theory and ready to be implemented in ab initio plane-wave based codes. The resulting methodology is demonstrated, as a proof of principle, by comparing ab initio and classical molecular simulations of a model liquid-Argon system, for which accurate inter-atomic potentials are derived by the force-matching method. A first application to liquid water is also presented.
| PHY-04 |
Adopting CERN SixTrack Fortran Legacy Modeling Code to Perform Ensemble Simulations on GPU, Dmitry Mikushin (Università della Svizzera italiana, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-04
Adopting CERN SixTrack Fortran Legacy Modeling Code to Perform Ensemble Simulations on GPU, Dmitry Mikushin (Università della Svizzera italiana, Switzerland)
Co-authors: Alexey Ivakhnenko (Applied Parallel Computing LLC); Igor Zacharov (EPFL / Eurotech, Switzerland); Eric McIntosh (CERN, Switzerland)
In our talk we will present a reusable approach for poting 200K line Fortran codebase onto GPU: SixTrack model - the LHC Accelerator Beam Dynamics, a part of BOINC Distributed Volunteer Computing project at CERN. The model has been adapted to compile both with host compiler and CUDA Fortran. The problem of insufficient resource of parallelism is solved by performing ensemble simulations. GPU version executes most of the code on device, one block per simulation. Kernel intermixes single-threaded and parallel code portions implemented by postprocessing CUDA code at LLVM IR level. CPU and GPU performances are compared on standard SixDesk test set.
| PHY-05 |
Chaos in Terrestrial Planet Formation, Volker Hoffmann (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-05
Chaos in Terrestrial Planet Formation, Volker Hoffmann (University of Zurich, Switzerland)
Co-authors: Simon Grimm (University of Zurich, Switzerland); Ben Moore (University of Zurich, Switzerland); Joachim Stadel (University of Zurich, Switzerland)
The formation and evolution of planetary systems involves a variety of physical processes acting over a range of timescales. Here, we focus on simulations of terrestrial planet formation. We give an overview of formation models, relevant physics, and how simulations on HPC platforms drive the research. We then describe how these simulations are highly chaotic, such that identical initial conditions can rapidly diverge due to variations in the ordering of compute operations. This has implications for the predictive power of individual runs and suggests that a statistical approach is required.
| PHY-06 |
DIAPHANE: Building a Library for Radiation and Neutrino Transport in Hydrodynamic Simulations, Darren Reed (University of Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-06
DIAPHANE: Building a Library for Radiation and Neutrino Transport in Hydrodynamic Simulations, Darren Reed (University of Zurich, Switzerland)
Co-authors: Lucio Mayer (University of Zurich, Switzerland); Cladio Gheller (ETH Zurich / CSCS, Switzerland); Ruben Cabezon (University of Basel, Switzerland); Ali Rahmati (University of Zurich, Switzerland)
A central task of the 'DIAPHANE' PASC project is to develop a
library of radiation and neutrino transport routines for astrophysical and cosmological simulations. Applications span a wide range: supernovae, the formation of planets, black holes, stars, and galaxies, and many other problems where progress has been limited by the importance of efficient modeling of radiation or neutrino transport. The library includes algorithms for both optically thick and optically thin gas allowing for 'adaptive' radiative transfer modelling. I demonstrate its current functionality and discuss some of the challenges and strategies in making the library portable enough for multiple codes.
| PHY-07 |
High-Temperature Series Expansions for Quantum Lattice Models, Andreas Hehn (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-07
High-Temperature Series Expansions for Quantum Lattice Models, Andreas Hehn (ETH Zurich, Switzerland)
Co-authors: Matthias Troyer (ETH Zurich, Switzerland)
We present a framework to calculate high-order series expansions for quantum lattice models which allows to exploit the many levels of parallelism offered by today's supercomputers. Using this framework, we performed high-order high-temperature series expansions for frustrated spin-1/2 Heisenberg and Bose-Hubbard models on various lattice geometries.
| PHY-08 |
Polarizable Coarse-Grained Water and Protein Models for Dissipative Particle Dynamics, Emanuel Karl Peter (Università della Svizzera italiana, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-08
Polarizable Coarse-Grained Water and Protein Models for Dissipative Particle Dynamics, Emanuel Karl Peter (Università della Svizzera italiana, Switzerland)
Co-authors: Kirill Lykov (Università della Svizzera italiana, Switzerland); Igor V. Pivkin (Università della Svizzera italiana, Switzerland)
Polarizability effects play a major role in many biological processes from effects at lipid bilayers to protein folding. We developed a new method for modeling of polarizability effects in Dissipative Particle Dynamics (DPD). Based on a Drude oscillator model, we first implemented a new coarse-grained water model and applied it to simulations of water-membrane systems. Following that, we developed a model for simulations of proteins, which is based on the polarization of the protein backbone and a simplified representation of the sidechains. We believe that the new models can significantly expand the application range of DPD into the field of computational biophysics.
| PHY-09 |
Polarized Radiative Transfer in Discontinuous Media, Oskar Steiner (Istituto Ricerche Solari Locarno, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-09
Polarized Radiative Transfer in Discontinuous Media, Oskar Steiner (Istituto Ricerche Solari Locarno, Switzerland)
Co-authors: Francesco Züger (Istituto Ricerche Solari Locarno, Switzerland); Luca Belluzzi (Istituto Ricerche Solari Locarno, Switzerland)
Astrophysical numerical radiation hydrodynamic simulations often show shock fronts, contact discontinues, or steep gradients across which radiative transfer needs to be computed. In view of applications to the solar atmosphere, we here propose a new method for performing radiative transfer of polarized light through a discontinuous atmosphere using methods of shock capturing hydrodynamics. We use slope-limiter methods for the reconstruction of the source function.
| PHY-10 |
The Bulk Monopolization in Diagonal Magnetoelectrics, Florian Thöle (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-10
The Bulk Monopolization in Diagonal Magnetoelectrics, Florian Thöle (ETH Zurich, Switzerland)
Co-authors: Michael Fechner (ETH Zurich, Switzerland); Nicola Spaldin (ETH Zurich, Switzerland)
The magnetoelectric monopole - a term appearing in the expansion of the interaction energy of the magnetic field H with the magnetization density - is formally allowed to exist in materials with broken time-reversal and inversion symmetry and is related to the response of diagonal magnetoelectrics. By exploiting similarities to the modern theory of polarization, we develop a theory of bulk monopolization and implement a Wannier function-based calculation in first-principles simulations. We compare the values obtained in the bulk picture to values obtained in a local moment picture and point out the relevance of each description.
| PHY-11 |
Topological Quantum Computation and Fractional Quantum Hall: Phase Diagram of the 5/2 State, Kiryl Pakrouski (ETH Zurich, Switzerland) Abstract |
Poster Session, Monday, June 1, 2015
17:30 - 20:00
PHY-11
Topological Quantum Computation and Fractional Quantum Hall: Phase Diagram of the 5/2 State, Kiryl Pakrouski (ETH Zurich, Switzerland)
Co-authors: Matthias Troyer (ETH Zurich, Switzerland); Michael R. Peterson (California State University Long Beach, USA); Thierry Jolicoeur (CNRS, France / University Paris-Sud, France); Vito W. Scarola (Virginia Tech, USA); Chetan Nayak (University of California, USA / Microsoft Research, USA);
Interesting non-Abelian states, e.g., the Moore-Read Pfaffian and the anti-Pfaffian, offer candidate descriptions of the nu= 5/2 fractional quantum Hall state. To study the phase diagram of the nu= 5/2 state we numerically diagonalize a comprehensive effective Hamiltonian describing the fractional quantum Hall effect of electrons under realistic conditions in GaAs semiconductors. We conclude that the ground state is in the universality class of the Moore-Read Pfaffian state, rather than the anti-Pfaffian for small Landau level mixing strength. Our findings have important implications for the identification of non-Abelian fractional quantum Hall states.
