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Mergers of two carbon-oxygen white dwarfs have long been suspected to be progenitors of Type Ia Supernovae. Here we present our modifications to the cosmological smoothed particle hydrodynamics code Gadget to apply it to stellar physics…

High Energy Astrophysical Phenomena · Physics 2015-06-05 R. Pakmor , P. Edelmann , F. K. Roepke , W. Hillebrandt

We investigate the merger between a 16 solar mass star, on its way to becoming a red supergiant (RSG), and a 4 solar mass main-sequence companion. Our study employs three-dimensional hydrodynamic simulations using the state-of-the-art…

Solar and Stellar Astrophysics · Physics 2023-10-24 Sagiv Shiber , Emmanouil Chatzopoulos , Bradley Munson , Juhan Frank

GAMER, a parallel Graphic-processing-unit-accelerated Adaptive-MEsh-Refinement hydrodynamic code, has been extended to support magnetohydrodynamics (MHD) with both the corner-transport-upwind (CTU) and MUSCL-Hancock schemes and the…

Computational Physics · Physics 2018-06-22 Ui-Han Zhang , Hsi-Yu Schive , Tzihong Chiueh

We discuss the performance of direct summation codes used in the simulation of astrophysical stellar systems on highly distributed architectures. These codes compute the gravitational interaction among stars in an exact way and have an…

Astrophysics · Physics 2008-11-26 Alessia Gualandris , Simon Portegies Zwart , Alfredo Tirado-Ramos

To achieve scalability with today's heterogeneous HPC resources, we need a dramatic shift in our thinking; MPI+X is not enough. Asynchronous Many Task (AMT) runtime systems break down the global barriers imposed by the Bulk Synchronous…

Distributed, Parallel, and Cluster Computing · Computer Science 2024-01-09 Thomas Heller , Patrick Diehl , Zachary Byerly , John Biddiscombe , Hartmut Kaiser

Merging finetuned Large Language Models (LLMs) has become increasingly important for integrating diverse capabilities into a single unified model. However, prevailing model merging methods rely on linear arithmetic in Euclidean space, which…

Machine Learning · Computer Science 2026-02-06 Sihan Yang , Kexuan Shi , Weiyang Liu

We describe the Stagger Code for simulations of magneto-hydrodynamic (MHD) systems. This is a modular code with a variety of physics modules that will let the user run simulations of deep stellar atmospheres, sunspot formation, stellar…

Instrumentation and Methods for Astrophysics · Physics 2024-05-07 Robert F. Stein , Åke Nordlund , Remo Collet , Regner Trampedach

We apply a novel method with machine learning to calibrate sub-grid models within numerical simulation codes to achieve convergence with observations and between different codes. It utilizes active learning and neural density estimators.…

Astrophysics of Galaxies · Physics 2022-10-07 Boon Kiat Oh , Hongjun An , Eun-jin Shin , Ji-hoon Kim , Sungwook E. Hong

Numerical simulations have become one of the key tools used by theorists in all the fields of astrophysics and cosmology. The development of modern tools that target the largest existing computing systems and exploit state-of-the-art…

Sparse Tucker Decomposition (STD) algorithms learn a core tensor and a group of factor matrices to obtain an optimal low-rank representation feature for the \underline{H}igh-\underline{O}rder, \underline{H}igh-\underline{D}imension, and…

Distributed, Parallel, and Cluster Computing · Computer Science 2020-12-09 Hao Li , Zixuan Li , Kenli Li , Jan S. Rellermeyer , Lydia Y. Chen , Keqin Li

The tree method is a widely implemented algorithm for collisionless $N$-body simulations in astrophysics well suited for GPU(s). Adopting hierarchical time stepping can accelerate $N$-body simulations; however, it is infrequently…

Instrumentation and Methods for Astrophysics · Physics 2016-11-09 Yohei Miki , Masayuki Umemura

Numerical relativity is central to the investigation of astrophysical sources in the dynamical and strong-field gravity regime, such as binary black hole and neutron star coalescences. Current challenges set by gravitational-wave and…

General Relativity and Quantum Cosmology · Physics 2022-11-04 Boris Daszuta , Francesco Zappa , William Cook , David Radice , Sebastiano Bernuzzi , Viktoriya Morozova

We describe a new implementation of a parallel Tree-SPH code with the aim to simulate Galaxy Formation and Evolution. The code has been parallelized using SHMEM, a Cray proprietary library to handle communications between the 256 processors…

Astrophysics · Physics 2009-10-31 Cesario Lia , Giovanni Carraro

Hierarchical models of structure formation predict that dark matter halo assembly histories are characterised by episodic mergers and interactions with other haloes. An accurate description of this process will provide insights into the…

Astrophysics of Galaxies · Physics 2019-11-26 Rhys J. J. Poulton , Chris Power , Aaron S. G. Robotham , Pascal J. Elahi

Accurate $N$-body simulations of multiple systems such as binaries and triples are essential for understanding the formation and evolution of interacting binaries and binary mergers, including gravitational wave sources, blue stragglers and…

Instrumentation and Methods for Astrophysics · Physics 2024-12-04 Long Wang

An Eulerian TVD code and a Lagrangian SPH code are used to simulate the off-axis collision of equal-mass main sequence stars in order to address the question of whether stellar mergers can produce a remnant star where the interior has been…

Astrophysics · Physics 2008-11-26 Hy Trac , Alison Sills , Ue-Li Pen

Simulations in stellar astrophysics involve the coupling of hydrodynamics and nuclear reactions under a wide variety of conditions, from simmering convective flows to explosive nucleosynthesis. Numerical techniques such as operator…

Computational Physics · Physics 2020-01-08 M. Zingale , M. P. Katz , J. B. Bell , M. L. Minion , A. J. Nonaka , W. Zhang

Maximizing parallelism level in applications can be achieved by minimizing overheads due to load imbalances and waiting time due to memory latencies. Compiler optimization is one of the most effective solutions to tackle this problem. The…

Distributed, Parallel, and Cluster Computing · Computer Science 2017-03-29 Zahra Khatami , Hartmut Kaiser , J. Ramanujam

We present the first self-consistent, three dimensional study of hydrodynamic simulations of mass transfer in binary systems with bipolytropic (composite polytropic) components. In certain systems, such as contact binaries or during the…

Solar and Stellar Astrophysics · Physics 2018-09-26 Kundan Kadam , Patrick M. Motl , Dominic C. Marcello , Juhan Frank , Geoffrey C. Clayton