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Machine learning applied to simulations of collisions between rotating, differentiated planets Comput. Astrophys. Cosmol. Pub Date : 2020-12-02 Miles L. Timpe, Maria Han Veiga, Mischa Knabenhans, Joachim Stadel, Stefano Marelli
In the late stages of terrestrial planet formation, pairwise collisions between planetary-sized bodies act as the fundamental agent of planet growth. These collisions can lead to either growth or disruption of the bodies involved and are largely responsible for shaping the final characteristics of the planets. Despite their critical role in planet formation, an accurate treatment of collisions has
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Technologies for supporting high-order geodesic mesh frameworks for computational astrophysics and space sciences. Comput. Astrophys. Cosmol. Pub Date : 2020-03-27 Vladimir Florinski,Dinshaw S Balsara,Sudip Garain,Katharine F Gurski
Many important problems in astrophysics, space physics, and geophysics involve flows of (possibly ionized) gases in the vicinity of a spherical object, such as a star or planet. The geometry of such a system naturally favors numerical schemes based on a spherical mesh. Despite its orthogonality property, the polar (latitude-longitude) mesh is ill suited for computation because of the singularity on
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Cosmological N-body simulations: a challenge for scalable generative models Comput. Astrophys. Cosmol. Pub Date : 2019-12-19 Nathanaël Perraudin, Ankit Srivastava, Aurelien Lucchi, Tomasz Kacprzak, Thomas Hofmann, Alexandre Réfrégier
Deep generative models, such as Generative Adversarial Networks (GANs) or Variational Autoencoders (VAs) have been demonstrated to produce images of high visual quality. However, the existing hardware on which these models are trained severely limits the size of the images that can be generated. The rapid growth of high dimensional data in many fields of science therefore poses a significant challenge
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A detection metric designed for O’Connell effect eclipsing binaries Comput. Astrophys. Cosmol. Pub Date : 2019-11-08 Kyle B. Johnston, Rana Haber, Saida M. Caballero-Nieves, Adrian M. Peter, Véronique Petit, Matt Knote
We present the construction of a novel time-domain signature extraction methodology and the development of a supporting supervised pattern detection algorithm. We focus on the targeted identification of eclipsing binaries that demonstrate a feature known as the O’Connell effect. Our proposed methodology maps stellar variable observations to a new representation known as distribution fields (DFs). Given
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DESTINY: Database for the Effects of STellar encounters on dIsks and plaNetary sYstems Comput. Astrophys. Cosmol. Pub Date : 2019-09-09 Asmita Bhandare, Susanne Pfalzner
Most stars form as part of a stellar group. These young stars are mostly surrounded by a disk from which potentially a planetary system might form. Both, the disk and later on the planetary system, may be affected by the cluster environment due to close fly-bys. The here presented database can be used to determine the gravitational effect of such fly-bys on non-viscous disks and planetary systems.
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The IllustrisTNG simulations: public data release Comput. Astrophys. Cosmol. Pub Date : 2019-05-14 Dylan Nelson, Volker Springel, Annalisa Pillepich, Vicente Rodriguez-Gomez, Paul Torrey, Shy Genel, Mark Vogelsberger, Ruediger Pakmor, Federico Marinacci, Rainer Weinberger, Luke Kelley, Mark Lovell, Benedikt Diemer, Lars Hernquist
We present the full public release of all data from the TNG100 and TNG300 simulations of the IllustrisTNG project. IllustrisTNG is a suite of large volume, cosmological, gravo-magnetohydrodynamical simulations run with the moving-mesh code Arepo. TNG includes a comprehensive model for galaxy formation physics, and each TNG simulation self-consistently solves for the coupled evolution of dark matter
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CosmoGAN: creating high-fidelity weak lensing convergence maps using Generative Adversarial Networks Comput. Astrophys. Cosmol. Pub Date : 2019-05-06 Mustafa Mustafa, Deborah Bard, Wahid Bhimji, Zarija Lukić, Rami Al-Rfou, Jan M. Kratochvil
Inferring model parameters from experimental data is a grand challenge in many sciences, including cosmology. This often relies critically on high fidelity numerical simulations, which are prohibitively computationally expensive. The application of deep learning techniques to generative modeling is renewing interest in using high dimensional density estimators as computationally inexpensive emulators
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A new hybrid technique for modeling dense star clusters Comput. Astrophys. Cosmol. Pub Date : 2018-11-28 Carl L. Rodriguez, Bharath Pattabiraman, Sourav Chatterjee, Alok Choudhary, Wei-keng Liao, Meagan Morscher, Frederic A. Rasio
The “gravitational million-body problem,” to model the dynamical evolution of a self-gravitating, collisional N-body system with ∼106 particles over many relaxation times, remains a major challenge in computational astrophysics. Unfortunately, current techniques to model such systems suffer from severe limitations. A direct N-body simulation with more than 105 particles can require months or even years
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Fast cosmic web simulations with generative adversarial networks Comput. Astrophys. Cosmol. Pub Date : 2018-11-23 Andres C. Rodríguez, Tomasz Kacprzak, Aurelien Lucchi, Adam Amara, Raphaël Sgier, Janis Fluri, Thomas Hofmann, Alexandre Réfrégier
Dark matter in the universe evolves through gravity to form a complex network of halos, filaments, sheets and voids, that is known as the cosmic web. Computational models of the underlying physical processes, such as classical N-body simulations, are extremely resource intensive, as they track the action of gravity in an expanding universe using billions of particles as tracers of the cosmic matter
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Observing supermassive black holes in virtual reality Comput. Astrophys. Cosmol. Pub Date : 2018-11-19 Jordy Davelaar, Thomas Bronzwaer, Daniel Kok, Ziri Younsi, Monika Mościbrodzka, Heino Falcke
We present a 360∘ (i.e., 4π steradian) general-relativistic ray-tracing and radiative transfer calculations of accreting supermassive black holes. We perform state-of-the-art three-dimensional general-relativistic magnetohydrodynamical simulations using the BHAC code, subsequently post-processing this data with the radiative transfer code RAPTOR. All relativistic and general-relativistic effects, such
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On the parallelization of stellar evolution codes Comput. Astrophys. Cosmol. Pub Date : 2018-11-16 David Martin, Jordi José, Richard Longland
Multidimensional nucleosynthesis studies with hundreds of nuclei linked through thousands of nuclear processes are still computationally prohibitive. To date, most nucleosynthesis studies rely either on hydrostatic/hydrodynamic simulations in spherical symmetry, or on post-processing simulations using temperature and density versus time profiles directly linked to huge nuclear reaction networks. Parallel
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A MODEST review Comput. Astrophys. Cosmol. Pub Date : 2018-11-06 Anna Lisa Varri, Maxwell Xu Cai, Francisca Concha-Ramírez, František Dinnbier, Nora Lützgendorf, Václav Pavlík, Sara Rastello, Antonio Sollima, Long Wang, Alice Zocchi
We present an account of the state of the art in the fields explored by the research community invested in “Modeling and Observing DEnse STellar systems”. For this purpose, we take as a basis the activities of the MODEST-17 conference, which was held at Charles University, Prague, in September 2017. Reviewed topics include recent advances in fundamental stellar dynamics, numerical methods for the solution
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Entropy-limited hydrodynamics: a novel approach to relativistic hydrodynamics Comput. Astrophys. Cosmol. Pub Date : 2017-07-04 Federico Guercilena, David Radice, Luciano Rezzolla
We present entropy-limited hydrodynamics (ELH): a new approach for the computation of numerical fluxes arising in the discretization of hyperbolic equations in conservation form. ELH is based on the hybridisation of an unfiltered high-order scheme with the first-order Lax-Friedrichs method. The activation of the low-order part of the scheme is driven by a measure of the locally generated entropy inspired
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PKDGRAV3: beyond trillion particle cosmological simulations for the next era of galaxy surveys Comput. Astrophys. Cosmol. Pub Date : 2017-05-18 Douglas Potter, Joachim Stadel, Romain Teyssier
We report on the successful completion of a 2 trillion particle cosmological simulation to $z=0$ run on the Piz Daint supercomputer (CSCS, Switzerland), using 4000+ GPU nodes for a little less than 80 h of wall-clock time or 350,000 node hours. Using multiple benchmarks and performance measurements on the US Oak Ridge National Laboratory Titan supercomputer, we demonstrate that our code PKDGRAV3, delivers
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The black hole accretion code Comput. Astrophys. Cosmol. Pub Date : 2017-05-03 Oliver Porth, Hector Olivares, Yosuke Mizuno, Ziri Younsi, Luciano Rezzolla, Monika Moscibrodzka, Heino Falcke, Michael Kramer
We present the black hole accretion code (BHAC), a new multidimensional general-relativistic magnetohydrodynamics module for the MPI-AMRVAC framework. BHAC has been designed to solve the equations of ideal general-relativistic magnetohydrodynamics in arbitrary spacetimes and exploits adaptive mesh refinement techniques with an efficient block-based approach. Several spacetimes have already been implemented
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The evolution of hierarchical triple star-systems Comput. Astrophys. Cosmol. Pub Date : 2016-12-23 Silvia Toonen, Adrian Hamers, Simon Portegies Zwart
Field stars are frequently formed in pairs, and many of these binaries are part of triples or even higher-order systems. Even though, the principles of single stellar evolution and binary evolution, have been accepted for a long time, the long-term evolution of stellar triples is poorly understood. The presence of a third star in an orbit around a binary system can significantly alter the evolution
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Riemann solvers and Alfven waves in black hole magnetospheres. Comput. Astrophys. Cosmol. Pub Date : 2016-09-13 Brian Punsly,Dinshaw Balsara,Jinho Kim,Sudip Garain
In the magnetosphere of a rotating black hole, an inner Alfven critical surface (IACS) must be crossed by inflowing plasma. Inside the IACS, Alfven waves are inward directed toward the black hole. The majority of the proper volume of the active region of spacetime (the ergosphere) is inside of the IACS. The charge and the totally transverse momentum flux (the momentum flux transverse to both the wave
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In situ and in-transit analysis of cosmological simulations. Comput. Astrophys. Cosmol. Pub Date : 2016-08-24 Brian Friesen,Ann Almgren,Zarija Lukić,Gunther Weber,Dmitriy Morozov,Vincent Beckner,Marcus Day
Modern cosmological simulations have reached the trillion-element scale, rendering data storage and subsequent analysis formidable tasks. To address this circumstance, we present a new MPI-parallel approach for analysis of simulation data while the simulation runs, as an alternative to the traditional workflow consisting of periodically saving large data sets to disk for subsequent ‘offline’ analysis
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Achieving convergence in galaxy formation models by augmenting N-body merger trees Comput. Astrophys. Cosmol. Pub Date : 2016-08-22 Andrew J Benson, Chris Cannella, Shaun Cole
Accurate modeling of galaxy formation in a hierarchical, cold dark matter universe requires the use of sufficiently high-resolution merger trees to obtain convergence in the predicted properties of galaxies. When semi-analytic galaxy formation models are applied to cosmological N-body simulation merger trees, it is often the case that those trees have insufficient resolution to give converged galaxy
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Simulations of stripped core-collapse supernovae in close binaries Comput. Astrophys. Cosmol. Pub Date : 2016-03-01 Alex Rimoldi, Simon Portegies Zwart, Elena Maria Rossi
We perform smoothed-particle hydrodynamical simulations of the explosion of a helium star in a close binary system, and study the effects of the explosion on the companion star as well as the effect of the presence of the companion on the supernova remnant. By simulating the mechanism of the supernova from just after core bounce until the remnant shell passes the stellar companion, we are able to separate
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Efficient conservative ADER schemes based on WENO reconstruction and space-time predictor in primitive variables. Comput. Astrophys. Cosmol. Pub Date : 2016-01-13 Olindo Zanotti,Michael Dumbser
We present a new version of conservative ADER-WENO finite volume schemes, in which both the high order spatial reconstruction as well as the time evolution of the reconstruction polynomials in the local space-time predictor stage are performed in primitive variables, rather than in conserved ones. To obtain a conservative method, the underlying finite volume scheme is still written in terms of the