Latest in physics.comp-ph

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Uncertainty Quantification for Geometry Deformations of Superconducting Cavities using Eigenvalue TrackingFeb 08 2018The electromagnetic field distribution as well as the resonating frequency of various modes in superconducting cavities are sensitive to small geometry deformations. The occurring variations are motivated by measurements of an available set of resonators ... More
A simple descriptor for energetics at fcc-bcc metal interfacesFeb 08 2018We develop a new and user-friendly method for calculating interface energies from first-principles. Our approach avoids problems that derive from the numerical differences between bulk and slab calculations, such as the number of k-points along the direction ... More
Neural-network Kohn-Sham exchange-correlation potential and its out-of-training transferabilityFeb 08 2018We incorporate in the Kohn-Sham self consistent equation a trained neural-network projection from the charge density distribution to the Hartree-exchange-correlation potential $n \rightarrow V_{\rm Hxc}$ for possible numerical approach to the exact Kohn-Sham ... More
A discrete unified gas-kinetic scheme for immiscible two-phase flowsFeb 08 2018In this work, we extend the discrete unified gas-kinetic scheme (DUGKS) [Guo et al., Phys. Rev. E 88, 033305 (2013)] to continue two-phase flows. In the framework of DUGKS, two kinetic model equations are used to solve the quasi-incompressible phase-field ... More
A local parallel communication algorithm for polydisperse rigid body dynamicsFeb 08 2018The simulation of large ensembles of particles is usually parallelized by partitioning the domain spatially and using message passing to communicate between the processes handling neighboring subdomains. The particles are represented as individual geometric ... More
Relativistic coupled-cluster theory analysis of energies, hyperfine structure constants, and dipole polarizabilities of Cd$^{+}$Feb 08 2018Roles of electron correlation effects in the determination of attachment energies, magnetic dipole hyperfine structure constants and electric dipole (E1) matrix elements of the low-lying states in the singly charged cadmium ion (Cd$^+$) have been analyzed. ... More
A fast C++ implementation of thermal functionsFeb 08 2018We provide a small C++ library with Mathematica and Python interfaces for computing thermal functions, defined $$ J_\text{B/F}(y^2) \equiv \Re \int_0^\infty x^2 \log\left[1 \mp e^{-\sqrt{x^2 + y^2}} \right] \,\text{d}x, $$ which appear in finite-temperature ... More
Fourier Analysis and Evaluation of DG, FD and Compact Difference Methods for Conservation LawsFeb 08 2018Large eddy simulation (LES) has been increasingly used to tackle vortex-dominated turbulent flows. In LES, the quality of the simulation results hinges upon the quality of the numerical discretizations in both space and time. It is in this context we ... More
Efficient collective swimming by harnessing vortices through deep reinforcement learningFeb 07 2018Fish in schooling formations navigate complex flow-fields replete with mechanical energy in the vortex wakes of their companions. Their schooling behaviour has been associated with evolutionary advantages including collective energy savings. How fish ... More
Comment on 'Simulation of ultra-relativistic electrons and positrons channeling in crystals with MBN Explorer'Feb 07 2018The snapshot model of crystal atoms has been implemented in the Monte Carlo code ChaS (Channeling Simulator) and is being successfully used for simulation of ultrarelativistic particle channeling. The model has been criticized by Sushko et al. (J. Comp. ... More
A general tool for LTE thermochemistry for adiabatic nondiffusive fluid dynamics: applications to 2D planar discontinuity flows in SPHFeb 07 2018Chemical reactions in fluid dynamics deeply modify the flow physical conditions through both the contribution of the energy of reactions and the variation of the mean molecular weight and of the ratio of specific heats. This occurs typically on time scales ... More
Eigenmode computations of frequency-dispersive photonic open structures: A non-linear eigenvalue problemFeb 07 2018In this paper, we propose and compare different ways to address the numerical computation of the electromagnetic modes of frequency-dispersive scattering structures. A classical finite element formulation is derived for each proposed solution, which leads ... More
A computational framework for microstructural modelling of polycrystalline materials with damage and failureFeb 06 2018In the present thesis, a computational framework for the analysis of the deformation and damage phenomena occurring at the micro-scale of polycrystalline materials is presented. Micro-mechanics studies are commonly performed using the Finite Element Method ... More
Wannier-function-based constrained DFT with nonorthogonality-correcting Pulay forces in application to the reorganization effects in graphene-adsorbed pentaceneFeb 05 2018Pulay terms arise in the Hellman-Feynman forces in electronic structure calculations when one employs a basis set made of localized orbitals that move with their host atoms. If the total energy of the system depends on a subspace population, defined in ... More
Efficiency of high-performance discontinuous Galerkin spectral element methods for under-resolved turbulent incompressible flowsFeb 05 2018The present paper addresses the numerical solution of turbulent flows with high-order discontinuous Galerkin methods for discretizing the incompressible Navier-Stokes equations. The efficiency of high-order methods when applied to under-resolved problems ... More
Interaction of phonons with discrete breather in strained grapheneFeb 05 2018We numerically analyze the interaction of small-amplitude phonon waves with standing gap discrete breather (DB) in strained graphene. To make the system support gap DB, strain is applied to create a gap in the phonon spectrum. We only focus on the in-plane ... More
Semimetal behavior of bilayer staneneFeb 05 2018Stanene is a two-dimensional (2D) buckled honeycomb structure which has been studied recently owing to its promising electronic properties for potential electronic and spintronic applications in nanodevices. In this article, we present a first-principles ... More
Corner transport upwind lattice Boltzmann model for bubble cavitationFeb 05 2018Aiming to study the bubble cavitation problem in quiescent and sheared liquids, a third-order isothermal lattice Boltzmann (LB) model that describes a two-dimensional ($2D$) fluid obeying the van der Waals equation of state, is introduced. The evolution ... More
The Discontinuous Asymptotic Telegraphers Equation ($P_1$) ApproximationFeb 04 2018Modeling the propagation of radiative heat-waves in optically thick material using a diffusive approximation is a well-known problem. In an optically thin material, classic methods, such as classic diffusion or classic $P_1$ yield the wrong heat wave ... More
Positivity-preserving scheme for two-dimensional advection-diffusion equations including mixed derivativesFeb 03 2018In this work, we propose a positivity-preserving scheme for solving two-dimensional advection-diffusion equations including mixed derivative terms, in order to improve the accuracy of lower-order methods. The solution to these equations, in the absence ... More
Hot carrier dynamics in plasmonic transition metal nitridesFeb 02 2018Extraction of non-equilibrium hot carriers generated by plasmon decay in metallic nanostructures is an increasingly exciting prospect for utilizing plasmonic losses, but the search for optimum plasmonic materials with long-lived carriers is ongoing. Transition ... More
The spectrum of non-centrosymmetrically layered spherical cavity resonator. I.The mode decomposition methodJan 31 2018We develop a theoretical method for solving Maxwell's equations to obtain the frequency spectra of inhomogeneous and asymmetric cavity resonators using a couple of effective Debye-type potentials. The structure we study specifically is the layered spherical ... More
Hyperfine interaction with the $^{229}$Th nucleus and its low lying isomeric stateJan 31 2018The thorium nucleus with mass number $A=229$ has attracted much interest because its extremely low lying first excited isomeric state at about $8$eV opens the possibility for the development of a nuclear clock. However, neither the exact energy of this ... More
Landau-Ginzburg theory of cortex dynamics: Scale-free avalanches emerge at the edge of synchronizationJan 31 2018Understanding the origin, nature, and functional significance of complex patterns of neural activity, as recorded by diverse electrophysiological and neuroimaging techniques, is a central challenge in neuroscience. Such patterns include collective oscillations ... More
w2dynamics: Local one- and two-particle quantities from dynamical mean field theoryJan 30 2018We describe the hybridization-expansion continuous-time quantum Monte Carlo code package "w2dynamics", developed in Wien and W\"urzburg. We discuss the main features of this multi-orbital quantum impurity solver for the Anderson impurity model, dynamical ... More
Efficient mesoscale hydrodynamics: multiparticle collision dynamics with massively parallel GPU accelerationJan 30 2018We present an efficient open-source implementation of the multiparticle collision dynamics (MPCD) algorithm that scales to run on hundreds of graphics processing units (GPUs). We especially focus on optimizations for modern GPU architectures and communication ... More
An Analysis of the Convergence of Stochastic Lagrangian/Eulerian Spray SimulationsJan 30 2018This work derives how the convergence of stochastic Lagrangian/Eulerian simulations depends on the number of computational parcels, particularly for the case of spray modeling. A new, simple, formula is derived that can be used for managing the numerical ... More
The MAPLE package TDDS for computing Thomas decompositions of systems of nonlinear PDEsJan 30 2018We present the Maple package TDDS (Thomas Decomposition of Differential Systems) for decomposition of polynomially nonlinear differential systems, which in addition to equations may contain inequations, into a finite set of differentially triangular and ... More
Theory of AC quantum transport with fully electrodynamic couplingJan 29 2018With the continued scaling of microelectronic devices along with the growing demand of high-speed wireless telecommunications technologies, there is increasing need for high-frequency device modeling techniques that accurately capture the quantum mechanical ... More
Density-Wavefunction Mapping in Degenerate Current-Density-Functional TheoryJan 29 2018We show that the particle density, $\rho(\mathbf{r})$, and the paramagnetic current density, $\mathbf{j}^{p}(\mathbf{r})$, are not sufficient to determine the set of degenerate ground-state wave functions. This is a general feature of degenerate systems ... More
Orbital-enriched Flat-top Partition of Unity Method for the Schrödinger EigenproblemJan 29 2018Quantum mechanical calculations require the repeated solution of a Schr\"odinger equation for the wavefunctions of the system. Recent work has shown that enriched finite element methods significantly reduce the degrees of freedom required to obtain accurate ... More
Trefftz Approximations in Complex Media: Accuracy and ApplicationsJan 29 2018Approximations by Trefftz functions are rapidly gaining popularity in the numerical solution of boundary value problems of mathematical physics. By definition, these functions satisfy locally, in weak form, the underlying differential equations of the ... More
An Energy Stable One-Field Fictitious Domain Method for Fluid-Structure InteractionsJan 28 2018In this article, the energy stability of a one-field fictitious domain method is proved and validated by numerical tests in two and three dimensions. The distinguishing feature of this method is that it only solves for one velocity field for the whole ... More
Domain decomposition for quasi-periodic scattering by layered media via robust boundary-integral equations at all frequenciesJan 27 2018We develop a non-overlapping domain decomposition method (DDM) for the solution of quasi-periodic scalar transmission problems in layered media. Our approach relies on robust boundary-integral equation formulations of Robin-to-Robin (RtR) maps throughout ... More
Nitrogen concentration effect on Ce doped SiOxNy emission: towards optimized Ce3+ for DEL applicationsJan 26 2018Ce-doped SiO x N y films are deposited by magnetron reactive sputtering from a CeO 2 target under nitrogen reactive gas atmosphere. Visible photoluminescence measurements regarding the nitrogen gas flow reveal a large emission band centered at 450 nm ... More
Antimargination of microparticles and platelets in the vicinity of branching vesselsJan 26 2018We investigate the margination of microparticles/platelets in blood flow through complex geometries typical for in vivo vessel networks: a vessel confluence and a bifurcation. Using 3D Lattice-Boltzmann simulations, we find that behind the confluence ... More
Translocation Mobilities of Proteins in Nanopores: A Coarse-Grained Molecular Dynamics StudyJan 26 2018We investigate the translocation of a protein through model nanopores using coarse-grained (CG) non-equilibrium molecular dynamics (NEMD) simulations and compare the results with a continuum model. We considered the effects of nanopore confinement and ... More
Task-based Parallel Computation of the Density Matrix in Quantum-based Molecular Dynamics using Graph PartitioningJan 26 2018Quantum-based molecular dynamics (QMD) is a highly accurate and transferable method for material science simulations. However, the time scales and system sizes accessible to QMD are typically limited to picoseconds and a few hundred atoms. These constraints ... More
Algebraic multigrid preconditioners for two-phase flow in porous media with phase transitionsJan 25 2018Multiphase flow is a critical process in a wide range of applications, including oil and gas recovery, carbon sequestration, and contaminant remediation. Numerical simulation of multiphase flow requires solving of a large, sparse linear system resulting ... More
Strain-induced Weyl and Dirac states and direct-indirect gap transitions in group-V materialsJan 24 2018We perform comprehensive density-functional theory calculations on strained two-dimensional phosphorus (P), arsenic (As) and antimony (Sb) in the monolayer, bilayer, and bulk $\alpha$-phase, from which we compute the key mechanical and electronic properties ... More
Electronic Branched Flow in Graphene with Random Potential: Theory and Machine Learning PredictionJan 24 2018We investigate the ultra-relativistic electronic flow in a two-dimensional random potential relevant to charge carrier dynamics in Dirac solids. As an example, the random potential in graphene, the prototypical Dirac solid, arises from inhomogeneous charge ... More
Convenient Interface to Inverse Ising (ConIII): A Python package for solving maximum entropy modelsJan 24 2018ConIII (pronounced CON-ee) is an open-source Python project providing a simple interface to solving maximum entropy models, with a focus on the Ising model. We describe the maximum entropy problem and give an overview of the algorithms that are implemented ... More
Perspectives on Reproducibility and Sustainability of Open-Source Scientific Software from Seven Years of the Dedalus ProjectJan 24 2018As the Science Mission Directorate contemplates establishing an open code policy, we consider it timely to share our experiences as the developers of the open-source partial differential equation solver Dedalus. Dedalus is a flexible framework for solving ... More
Why does hydronium diffuse faster than hydroxide in liquid water?Jan 24 2018Proton transfer via hydronium and hydroxide ions in water is ubiquitous. It underlies acid-base chemistry, certain enzyme reactions, and even infection by the flu. Despite two-centuries of investigation, the mechanism underlying why hydronium diffuses ... More
A Generalized Muon Trajectory Estimation Algorithm with Energy Loss for Application to Muon TomographyJan 23 2018This work presents a generalized muon trajectory estimation (GMTE) algorithm to estimate the path of a muon in either uniform or nonuniform media. The use of cosmic ray muons in nuclear nonproliferation and safeguards verification applications has recently ... More
Machine Learning and Finite Element Method for Physical Systems ModelingJan 22 2018Modeling of physical systems includes extensive use of software packages that implement the accurate finite element method for solving differential equations considered along with the appropriate initial and boundary conditions. When the problem size ... More
Degenerate Variational Integrators for Magnetic Field Line Flow and Guiding Center TrajectoriesJan 22 2018Symplectic integrators offer many advantages for the numerical solution of Hamiltonian differential equations, including bounded energy error and the preservation of invariant sets. Two of the central Hamiltonian systems encountered in plasma physics ... More
Adaptive parallelism with RMI: Idle high-performance computing resources can be completely avoidedJan 22 2018In practice, standard scheduling of parallel computing jobs almost always leaves significant portions of the available hardware unused, even with many jobs still waiting in the queue. The simple reason is that the resource requests of these waiting jobs ... More
Nanophotonic Light Management for Perovskite-Silicon Tandem Solar CellsJan 22 2018Perovskite-silicon tandem solar cells are currently one of the most investigated concepts to overcome the theoretical limit for the power conversion efficiency of silicon solar cells. For monolithic tandem solar cells the available light must be distributed ... More
Relativistic Normal Coupled-Cluster Theory for Accurate Determination of Electric Dipole Moments of Atoms: First application to $^{199}$Hg atomJan 22 2018Recent relativistic coupled-cluster (RCC) calculations of electric dipole moments (EDMs) of diamagnetic atoms due to parity and time-reversal violating (P,T-odd) interactions, that are essential ingredients for probing new physics beyond the standard ... More
A Laser-Plasma Positron Accelerator using Particle-Shower Plasma-Wave interactionsJan 19 2018An all-optical laser-plasma positron accelerator is introduced and modeled using the interaction of laser-driven particle-showers with laser-driven electron plasma-waves. The principle uncovered here shows the trapping and acceleration of positrons that ... More
A pseudospectral method for solution of the radiative transport equationJan 19 2018The Boltzmann transport equation accurately describes a number of physical phenomena, though analytic solutions are known only for simple geometries. We present a pseudospectral technique to efficiently compute numerical solutions to the time-domain transport ... More
Molecular Dynamics Simulations of Turbostratic Dry and Hydrated Montmorillonite with Intercalated Carbon DioxideJan 19 2018Molecular dynamics simulations using classical force fields were carried out to study energetic and structural properties of rotationally disordered clay mineral-water-CO2 systems at pressure and temperature relevant to geological carbon storage. The ... More
A network partition method for solving large-scale complex nonlinear processesJan 18 2018A numerical framework based on network partition and operator splitting is developed to solve nonlinear differential equations of large-scale dynamic processes encountered in physics, chemistry and biology. Under the assumption that those dynamic processes ... More
Wave-packet numerical investigation of thermal diffuse scattering: A time-dependent quantum approach to the Debye methodJan 17 2018The effects of thermal diffuse scattering on the transmission and eventual diffraction of highly accelerated electrons are investigated with a method that incorporates the frozen phonon approximation to the exact numerical solution of the time-dependent ... More
A multiscale method for simulating fluid interfaces covered with large molecules such as asphaltenesJan 17 2018(Abbreviated) In this paper we report on the development of a multiscale method for simulating complex liquid-liquid systems such as water in contact with oil containing asphaltenes. We consider simulations where water drops covered with asphaltenes are ... More
A unified framework for heat and mass transport at the atomic scaleJan 17 2018Feb 07 2018We present a unified framework to simulate heat and mass transport in systems of particles. The proposed framework is based on kinematic mean field theory and uses a phenomenological master equation to compute effective transport rates between particles ... More
Molecular Dynamics Simulations of Ballistic Penetration of Pentagraphene SheetsJan 16 2018The superior mechanical properties and low density of carbon nanostructures make them promising ballistic protection materials, stimulating investigations on their high-strain-rate behavior. Recent experiments and simulations revealed graphene possesses ... More
Adaptive Kinetic-Fluid Models for Expanding PlasmasJan 15 2018We describe gas dynamic and plasma effects for transient plasma jets under different conditions. Our Unified Flow Solver (UFS) is evaluated for simulations of mixed continuum-rarefied flows, transient gas expansion dynamics and collisionless plasma expansion. ... More
Self-Consistent Description of Local Density Dynamics in Simple Liquids. The Case of Molten LithiumJan 15 2018The dynamic structure factor is the quantity, which can be measured by means of Brillouin light-scattering as well as by means of inelastic scattering of neutrons and X-rays. The spectral (or frequency) moments of the dynamic structure factor define directly ... More
Learning about random media from near-surface backscattering: using machine learning to measure particle size and concentrationJan 13 2018We ask what can be measured from a random media by using backscattered waves, emitted from and received at one source. We show that in 2D both the particle radius and concentration can be accurately measured for particles with Dirichlet boundary conditions. ... More
Enforcing the Courant-Friedrichs-Lewy Condition in Explicitly Conservative Local Time Stepping SchemesJan 09 2018An optimally efficient explicit numerical scheme for solving fluid dynamics equations, or any other parabolic or hyperbolic system of partial differential equations, should allow local regions to advance in time with their own, locally constrained time ... More
Numerical Analysis of Automodel Solutions for Superdiffusive TransportJan 09 2018The distributed computing analysis of the accuracy of automodel solutions for the Green's function of a wide class of superdiffusive transport of perturbation on a uniform background is carried out. The approximate automodel solutions have been suggested ... More
Warp-X: a new exascale computing platform for beam-plasma simulationsJan 08 2018Turning the current experimental plasma accelerator state-of-the-art from a promising technology into mainstream scientific tools depends critically on high-performance, high-fidelity modeling of complex processes that develop over a wide range of space ... More
Weighted Delta-Tracking with ScatteringJan 02 2018In this work, we expand the weighted delta-tracking routine to include a treatment for scattering. The weighted delta-tracking routine adds survival biasing to normal delta-tracking, improving overall problem figure of merit. In the original formulation ... More
Moment Approximations and Model Cascades for Shallow FlowDec 29 2017Shallow flow models are used for a large number of applications including weather forecasting, open channel hydraulics and simulation-based natural hazard assessment. In these applications the shallowness of the process motivates depth-averaging. While ... More
Coupling of Magneto-Thermal and Mechanical Superconducting Magnet Models by Means of Mesh-Based InterpolationDec 29 2017In this paper we present an algorithm for the coupling of magneto-thermal and mechanical finite element models representing superconducting accelerator magnets. The mechanical models are used during the design of the mechanical structure as well as the ... More
Laser Driving Highly Collimated $γ$-ray Pulses for the Generation of $μ^-μ^+$ and $e^-e^+$ Pairs in $γ-γ$ ColliderDec 24 2017A scheme to generate highly collimated $\gamma$-ray pulse is proposed for the production of muon and electron pairs in $\gamma-\gamma$ collider. The $\gamma$-ray pulse, with high conversion efficiency, can be produced as the result of electron phase-locked ... More
Analysis and Monte Carlo Modelling of Multiple Scattering of a Beam of Neutrons or Photons off of the Two Surfaces of a Broad Material Target as a Function of its ThicknessDec 22 2017We consider the scattering of neutrons and photons on solid volume rectangular targets. It is common to treat this problem using the Maxwell Boltzmann Transport Equation and to use underlying symmetries to simplify the calculation. For isotropic scattering ... More
User's guide to Monte Carlo methods for evaluating path integralsDec 22 2017We give an introduction to the calculation of path integrals on a lattice, with the quantum harmonic oscillator as an example. In addition to providing an explicit computational setup and corresponding pseudocode, we pay particular attention to the existence ... More
Direct S-matrix calculation for diffractive structures and metasurfacesDec 22 2017Jan 24 2018The paper presents a derivation of analytical components of S-matrices for arbitrary planar diffractive structures in the Fourier domain. Attained general formulas for S-matrix components can be applied within both formulations in the Cartesian and curvilinear ... More
MSM/RD: Coupling Markov state models of molecular kinetics with reaction-diffusion simulationsDec 21 2017Molecular dynamics (MD) simulations can model the interactions between macromolecules with high spatiotemporal resolution but at a high computational cost. By combining high-throughput MD with Markov state models (MSMs), it is now possible to obtain statistically ... More
Chiral scatterers designed by Bayesian optimizationDec 19 2017The helicity or chirality of scattered light is strongly linked to the dual symmetry of the scatterer. The latter depends on chiral materials or on scatterers which are not superimposable with their mirror image. This inherently yields asymmetric structures ... More
Direct simulation of liquid-gas-solid flow with a free surface lattice Boltzmann methodDec 19 2017Direct numerical simulation of liquid-gas-solid flows is uncommon due to the considerable computational cost. As the grid spacing is determined by the smallest involved length scale, large grid sizes become necessary -- in particular if the bubble-particle ... More
A Roadmap for HEP Software and Computing R&D for the 2020sDec 18 2017Dec 20 2017Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires ... More
A Roadmap for HEP Software and Computing R&D for the 2020sDec 18 2017Feb 11 2018Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires ... More
A Hybridizable Discontinuous Galerkin solver for the Grad-Shafranov equationDec 12 2017In axisymmetric fusion reactors, the equilibrium magnetic configuration can be expressed in terms of the solution to a semi-linear elliptic equation known as the Grad-Shafranov equation, the solution of which determines the poloidal component of the magnetic ... More
Perpendicular relativistic shocks in magnetized pair plasmaDec 07 2017Perpendicular relativistic ($\gamma_0=10$) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the ... More
An adaptive multiphysics model coupling vertical equilibrium and full multidimensions for multiphase flow in porous mediaNov 27 2017Efficient multiphysics models that can adapt to the varying complexity of physical processes in space and time are desirable for modeling fluid migration in the subsurface. Vertical equilibrium (VE) models are simplified mathematical models that are computationally ... More
Machine Learning by Two-Dimensional Hierarchical Tensor Networks: A Quantum Information Theoretic Perspective on Deep ArchitecturesOct 13 2017The resemblance between the methods used in studying quantum-many body physics and in machine learning has drawn considerable attention. In particular, tensor networks (TNs) and deep learning architectures bear striking similarities to the extent that ... More
A complete equation of state for non-ideal condensed phase explosivesOct 10 2017Dec 15 2017The objective of this work is to improve the robustness and accuracy of numerical simulations of both ideal and non-ideal explosives by introducing temperature dependence in mechanical equations of state for reactants and products. To this end, we modify ... More
Multi-dimensional Tensor Network Simulation of Open Quantum Dynamics in Singlet FissionOct 03 2017We develop a powerful tree tensor network states method that is capable of simulating exciton-phonon quantum dynamics of larger molecular complexes and open quantum systems with multiple bosonic environments. We interface this method with ab initio density ... More
A 2-D Finite-Element Model for Electro-Thermal Transients in Accelerator MagnetsOct 03 2017Dec 05 2017Superconducting accelerator magnets require sophisticated monitoring and means of protection due to the large energy stored in the magnetic field. Numerical simulations play a crucial role in understanding transient phenomena occurring within the magnet, ... More
Non-standard FDTD implementation of the Schrödinger equationSep 28 2017In this work, we apply the Cole's non-standard form of the FDTD to solve the time dependent Schr\"odinger equation. We deduce the equations for the non-standard FDTD considering an electronic wave function in the presence of potentials which can be higher ... More
Effects and limitations of a nucleobase-driven backmapping procedure for nucleic acids using steered Molecular DynamicsSep 25 2017Dec 14 2017Coarse-grained models can be of great help to address the problem of structure prediction in nucleic acids. On one hand they can make the prediction more efficient, while on the other hand, they can also help to identify the essential degrees of freedom ... More
Hyperbolic Relaxation Method for Elliptic EquationsAug 24 2017Nov 14 2017We show how the basic idea of parabolic Jacobi relaxation can be modified to obtain a new class of hyperbolic relaxation schemes that are suitable for the solution of elliptic equations. Some of the analytic and numerical properties of hyperbolic relaxation ... More
A fast finite-difference algorithm for topology optimization of permanent magnetsJul 31 2017We present a finite-difference method for the topology optimization of permanent magnets that is based on the FFT accelerated computation of the stray-field. The presented method employs the density approach for topology optimization and uses an adjoint ... More
Benchmarking Data Analysis and Machine Learning Applications on the Intel KNL Many-Core ProcessorJul 12 2017Knights Landing (KNL) is the code name for the second-generation Intel Xeon Phi product family. KNL has generated significant interest in the data analysis and machine learning communities because its new many-core architecture targets both of these workloads. ... More
Computing Singularly Perturbed Differential EquationsJul 06 2017Nov 21 2017A computational tool for coarse-graining nonlinear systems of ordinary differential equations in time is discussed. Three illustrative model examples are worked out that demonstrate the range of capability of the method. This includes the averaging of ... More
AC noise reduction based on exchange coupled grains for heat-assisted-magnetic recording: The effect of an FeRh interlayerJun 07 2017High storage density and high data rate are two of the most desired properties of modern hard disk drives. Heat-assisted magnetic recording (HAMR) is believed to achieve both. Recording media, consisting of exchange coupled grains with a high and a low ... More
Metastable Clusters and Channels Formed by Active Particles with Aligning InteractionsJun 05 2017We introduce a novel model for active particles with short-range aligning interactions and study their behaviour in crowded environments using numerical simulations. When only active particles are present, we observe a transition from a gaseous state ... More
Impact of cyclostationarity on fan broadband noise predictionJun 01 2017One of the dominant noise sources of modern Ultra High Bypass Ratio (UHBR) engines is the interaction of the rotor wakes with the leading edges of the stator vanes in the fan stage. While the tonal components of this noise generation mechanism are fairly ... More
Maximum entropy formalism for the analytic continuation of matrix-valued Green's functionsMay 24 2017Nov 06 2017We present a generalization of the maximum entropy method to the analytic continuation of matrix-valued Green's functions. To treat off-diagonal elements correctly based on Bayesian probability theory, the entropy term has to be extended for spectral ... More
Adaptive coarse-graining for large-scale DEM simulationsMay 10 2017The large time and length scales and, not least, the vast number of particles involved in industrial-scale simulations inflate the computational costs of the Discrete Element Method (DEM) excessively. Coarse grain models can help to lower the computational ... More
Contact forces distribution for a granular material from a Monte Carlo study on a single grainMay 04 2017The force network ensemble is one of the most promising statistical descriptions of granular media, with an entropy accounting for all force configurations at mechanical equilibrium consistent with some external stress. It is possible to define a temperature-like ... More
MULTIBAT: Unified workflow for fast electrochemical 3D simulations of lithium-ion cells combining virtual stochastic microstructures, electrochemical degradation models and model order reductionApr 13 2017We present a simulation workflow for efficient investigations of the interplay between 3D lithium-ion electrode microstructures and electrochemical performance, with emphasis on lithium plating. Our approach addresses several challenges. First, the 3D ... More
The ALF (Algorithms for Lattice Fermions) project release 1.0. Documentation for the auxiliary field quantum Monte Carlo codeApr 01 2017Jun 23 2017The Algorithms for Lattice Fermions package provides a general code for the finite temperature auxiliary field quantum Monte Carlo algorithm. The code is engineered to be able to simulate any model that can be written in terms of sums of single-body operators, ... More
Transition Jitter in Heat Assisted Magnetic Recording by Micromagnetic SimulationMar 10 2017Jun 27 2017In this paper we apply an extended Landau-Lifschitz equation, as introduced by Ba\v{n}as et al. for the simulation of heat-assisted magnetic recording. This equation has similarities with the Landau-Lifshitz-Bloch equation. The Ba\v{n}as equation is supposed ... More
Pomelo, a tool for computing Generic Set Voronoi Diagrams of Aspherical Particles of Arbitrary ShapeMar 10 2017We describe the development of a new software tool, called "Pomelo", for the calculation of Set Voronoi diagrams. Voronoi diagrams are a spatial partition of the space around the particles into separate Voronoi cells, e.g. applicable to granular materials. ... More
Efficiently reducing transition curvature in heat-assisted magnetic recording with state-of-the-art write headsMar 02 2017The curvature of bit transitions on granular media is a serious problem for the read-back process. We address this fundamental issue and propose a possibility to efficiently reduce transition curvatures with state-of-the-art heat-assisted magnetic recording ... More