Gravitational Wave Data Science
The direct detection of gravitational radiation by the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) and Virgo has realized a long-awaited promise to open a new window on the Universe. Once a signal has been detected, the parameters (e.g. masses and spins) of the gravitational wave source, and their uncertainties, can be determined by comparing the signal to waveforms predicted by general relativity (GR) through methods such as Bayesian inference. To realize the full scientific potential of gravitational wave experiments, from single-source parameter inference and detection to tests of GR, we must (i) develop fast and accurate GW models for the expected incoming signal, (ii) design algorithms and codes that are tailored to the GW detection and inference problem, and (iii) leverage high-performance scientific computing resources and best practices for our data analysis efforts.
U2GRC researchers have been involved in all aspects of this scientific process, including building gravitational wave models, developing signal detection pipelines, carrying out parameter estimation studies and tests of GR, and designing novel algorithms using dimensionality and machine learning techniques. For more information about this research, please check out some of our key papers:
Black Hole Perturbation Theory
This project deals with estimating properties of the gravitational waves produced by the merger of two black holes, especially in the so-called extreme-mass-ratio limit (EMRI). This is of direct relevance to the various gravitational wave observatories that are being built world-wide (eg. LIGO, LISA). For more information: this link is a popular article about our work published by Nature Magazine. And here is another link that is a Discovery Magazine popular article of our recent work. Here are some movies and snapshots, showing the gravitational waves emerging from coalescence of two black holes using such techniques: movies, snapshot. For more information about this research, please check out some of our key papers:
Black Holes Singularities in Classical & Quantum Gravity
It is widely believed that the theory of quantum gravitation will resolve the issue of physical singularities (for example, the infinite density at the moment of the big bang and also in the center of black holes) that plague classical general relativity. This project attempts to study the nature of black hole singularities in the context of both, classical theory and also loop quantum gravity. For more information about this research, please check out some of our key papers:
Computational Relativity with Discontinuous Galerkin Methods
To handle a diverse class of astrophysical sources in an efficient, robust and accurate manner, the development of advanced and flexible methods is paramount. Discontinuous Galerkin (DG) methods have the potential to offer unique benefits for a wide class of problems. We have developed DG methods for the first-order and second-order BSSN system (a numerically well-suited formulation of the Einstein equation) which achieve spectral accuracy (i.e. exponential convergence of numerical errors) and long-time stability and have also applied DG method to fully relativistic fluid problems.
In the context of extreme mass ratio binary black hole inspiral systems (EMRIs) the solutions are forced by distributional (i.e. Dirac delta function) source terms. We developed a DG scheme to exactly represent such distributional solutions through a modification of the relevant numerical flux terms. Furthermore, it was demonstrated that the method maintains spectral accuracy even at the location of the Dirac delta distribution. Accurate numerical modeling is crucial for the incorporation of important physical effects neglected by linearization such as the gravitational self-force.
U2GRC researchers continue to develop and use DG methods for computational relativity. For more information about this research, please check out some of our key papers:
Stellar Astrophysics & Supernovae
Details available here: https://rfisher.sites.umassd.edu
Novel Approaches to Scientific Supercomputing
Details available here: task-based parallelism for PDE-solvers, video-gaming technologies for scientific supercomputing