As we embark on a week dedicated to the ETK, I will discuss the role of numerical relativity in gravitational wave astronomy. I hope to motivate future work in NR that is essential for achieving the science discoveries promised by current and future gravitational wave observatories.
This talk provides a broad overview of the Einstein Toolkit, its design, and history, as well as its main features.
One of the primary applications of numerical relativity is the generation of waveforms to be compared against gravitational-wave data. Such a comparison enables us to understand the systems emitting the gravitational waves. As gravitational-wave observatories improve, it's becoming increasingly important that our waveform templates are sufficiently accurate. There are many factors that go into...
In this tutorial, students will become familiar with how to download, compile, and run the Einstein Toolkit. If time allows, we may also discuss ways in which students can create their own thorns. The tutorial will be Jupyter notebook-based, so there is no need for students to prepare ahead of time by installing any prerequisites. The only thing students will need is a computer with a...
In this talk, I will present the latest developments of ongoing efforts at LSU to speed up simulations in the Einstein Toolkit under CarpetX. In particular, I will present our new results using Multi-Step Runge-Kutta time integrators which can speed up BBH evolutions by 30% with simple algorithmic changes. In order to do that, I will carefully review the stability theory of ODE solvers, which...
Adaptive Mesh Refinement (AMR) with subcycling in time enables different grid levels to advance using their own time steps, ensuring finer grids employ smaller steps for accuracy while coarser grids take larger steps to improve computational efficiency. We present the development, validation, and performance analysis of a subcycling in time algorithm implemented within the CarpetX driver in...
With the ongoing transition toward exascale computing to tackle a range of open questions via numerical simulations, the development of GPU-optimized codes has become essential. In this talk, I will highlight the key features of AsterX, a novel open-source, modular, GPU-accelerated general relativistic magnetohydrodynamic (GRMHD) code for fully dynamical spacetimes in 3D Cartesian coordinates....
In this talk, we will introduce EmitCactus, a development environment which provides users with the capability of generating complete, performant, GPU-ready CarpetX thorns from a high-level, symbolic Python-based DSL. We will discuss the modular design of EmitCactus which allows for the development of custom frontends (e.g., NRPy LaTeX) and backends (e.g., drivers besides CarpetX). We will...
In this talk, we will give a live demo instructing those of all experience levels in the use of EmitCactus. We will guide attendees through the process of writing a recipe in the EmitCactus DSL to generate a GPU-ready CarpetX thorn.
The advent of gravitational-wave (GW) astronomy has revolutionized our understanding of the universe and expanded the frontiers of multi-messenger astrophysics. Accurately interpreting these signals, particularly from phenomena such as binary neutron star mergers, requires detailed numerical simulations that solve the coupled Einstein and general relativistic magnetohydrodynamics (GRMHD)...
We give an introduction to the Nmesh code, which is intended to run efficiently on large supercomputers. The goal is to solve challenging relativistic astrophysics problems such as binary neutron star or black hole mergers. To treat matter (e.g. neutron stars) we have implemented the Valencia formulation of the evolution equations for general relativistic hydrodynamics. These can be coupled to...
Binary neutron star mergers (BNS) are extraordinary astrophysical events, acting as an important source for the production of a significant fraction of the universe's heavy r-process elements. Neutrinos drive the composition of the ejected matter and play a crucial role in cooling the massive hot remnant formed from the merger of neutron stars, necessitating their accurate modeling in BNS...
In this talk, I present the numerical relativity module developed within AthenaK, an open-source, performance-portable astrophysics code optimized for exascale computing. Driven by the demand for high-accuracy gravitational waveforms and the need to efficiently utilize emerging hardware architectures, AthenaK adopts the Z4c formulation to evolve the Einstein equations. We demonstrate the...
Accurate modeling of neutrino transport plays a crucial role in understanding astrophysical phenomena such as core-collapse supernovae and neutron star mergers. In this seminar we will review two popular methods for approximating the seven-dimensional Boltzmann equation: the truncated momentum formalism (M1 scheme) and Monte-Carlo (MC) algorithms. Then we present the Guided Moment (GM)...
As the numerical relativity community focuses on detailed microphysics in neutron star mergers, and as accelerator hardware becomes ubiquitous, GPU-resident simulations and neutrino transport are becoming routine. I discuss my experience with both performance portability and Monte Carlo neutrino transport for post-neutron star merger disk and kilonova modeling, with an emphasis on gotchas and...
We present BHaHAHA (BlackHoles@Home Apparent Horizon Algorithm), a new open-source apparent horizon (AH) finder that uses hyperbolic relaxation, reformulating the elliptic Marginally Outer Trapped Surface (MOTS) equation as a damped scalar wave equation on the 2-sphere via a reference-metric approach. As such, it exists as the first-ever hyperbolic flow method. Key techniques—such as...
I will describe SPHINCS-BSSN: a code that combines spacetime evolution on a grid with a Lagrangian treatment of the matter. That is, the matter is evolved using the method of Smoothed Particle Hydrodynamics (SPH). I will describe the advantages (and disadvantages) of using particle methods and will describe how we overcame the technical challenges of coupling the matter to the spacetime. I...
Neutrino-matter coupling via weak interactions is one of the most important physical mechanisms in the evolution of core-collapse supernovae (CCSN). The numerical modeling of these systems is an inherently multi-physics, multi-method and multi-scale problem. In this talk, we will give an introduction to neutrino radiation hydrodynamics and then describe the union of three codes to simulate...
Simulations to calculate a single gravitational waveform (GW) can take several weeks. Yet, thousands of such simulations are needed to detect and interpret gravitational waves. Future detectors will require even more accurate waveforms than those currently used. Here, we discuss the Dendro-GR framework, a large-scale, wavelet-driven octree-based adaptive mesh refinement with support for...
