Compact Objects and Gravitational Radiation

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

The General Theory of Relativity discovered by Einstein tells us that the familiar, everyday force of gravity is a manifestation of something much stranger: the bending of the geometry of space-time by matter. Among the key predictions of the theory is the existence of gravitational waves (GW): ripples moving at the speed of light in the geometry of space-time caused by the fast motion of large masses. Although well tested in terms of their indirect effects on binary systems of compact stars, the direct detection of gravitational waves incident on Earth poses an outstanding challenge. The scientific rewards from achieving this ability would be enormous - ranging from probing the extreme dynamics of exploding stars to gleaning information about the state of the Universe almost at the moment of the Big Bang itself. The effort to enable this new window on the universe has occupied several decades of experimental and technological developments that have pushed the boundaries across diverse fields in the physical sciences. When the Advanced Laser Interferometric Gravitational Wave Observatory (aLIGO) reaches designed sensitivity as scheduled, the burst of radiation that may become the first detection of gravitational waves is already closer to the Earth than the closest star, Alfa Centauri. The gravitational waves in this first detection, and others following soon after, were very likely produced during the merger of binary systems involving black holes and/or neutron stars. There is realistic optimism that, at the turn of the decade, enough of these and other sources will be observed to state with confidence that proper observational gravitational wave physics has arrived. This will of course depend on having in place exquisite interferometric engineering, clever analysis of extremely noisy data, and state of the art source modeling. Regarding the latter, it is imperative to continue exploiting the tools of numerical relativity to model not only as many gravitational wave source scenarios as possible, but also to improve the physics content captured by the simulations. The science in this project supports directly this enterprise, namely numerical relativity modeling to enhance our understanding of sources of gravitational radiation and of gravitational phenomena driving electromagnetic signatures. The proposed research will have an impact beyond the confines of gravitational wave physics and numerical relativity. Achieving success in the multi-messenger, computing, and data-analytics projects in this project necessitates an interdisciplinary environment reaching across astrophysics, computing science and even engineering. The Center for Relativistic Astrophysics at Georgia Tech will be capable of providing such an environment since its mission is to foster research and education linking high-energy astrophysics, astro-particle physics, cosmology and gravitational wave physics. This award supports research focused on the computational modeling of black holes and neutron stars as sources of gravitational radiation. The proposal considers several projects that involve astrophysics with a common denominator -- the crucial role played by dynamical gravity and the curvature of space-time. The astrophysical phenomena in these projects arise from a marriage between general relativistic gravitation and complex multi-physics involving fluid flows, electromagnetic fields, radiation transport and realistic equations of state. The effort also aims at enhancing our comprehensive understanding of astrophysical phenomena beyond what gravitational waves alone will be able to tell, in other words, electromagnetic and gravitational wave phenomena leading to multi-messenger observations. The research is organized into two areas: 1) Compact object binaries and a sandbox of simulation data; and 2) Tidal stellar disruptions by massive black holes. The proposed work will give postdocs and students the opportunity to interact with researchers in computing science and engineering, to develop and implement numerical algorithms for magneto-hydrodynamics, work with large data sets and to participate in a variety of outreach activities. The experience gained in high performance computing, optimization, data analytics, and software engineering will further the careers of young researchers participating in the effort, acquiring valuable skills that are in demand in a broad range of professions.