Gravitational Radiation and Relativistic Astrophysics

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This is a research project on the physics and astrophysics of gravitational wave sources, partially in support of the Laser Interferometer Gravitational-wave Observatory (LIGO); it will be carried out by the Caltech Relativity Theory (CaRT) group, led by Yanbei Chen (PI), Christian Ott and Mark Scheel (Co-PIs). Through numerical simulations and analytical studies, this project will not only provide more accurate models for LIGO sources, but will also lead to a deeper understanding of the behavior of space-time geometry and matter under extreme conditions - near black holes, neutron stars, especially when these extreme objects collide with each other. These more accurate models and deeper theoretical insight will also be applied to the analysis of LIGO gravitational-wave data. This project will serve as a training ground for young physicists and astrophysicists, by teaching them a wide variety of research techniques. Members of the CaRT will also pursue a wide range of activities that reach out to the broader scientific community and the general public.More specifically, the project will consists of three directions: (A) By combining analytical techniques and numerical simulations (using the Spectral Einstein Code [SpEC]): (i) Increasingly accurate gravitational waveforms for binary black hole coalescence will be generated and used to produce numerical template banks for LIGO; (ii) The geometrodynamics of highly curved spacetimes will be visualized and explored. (B) SpEC will be applied to the study of gravitational wave (GW) sources with matter (neutron-star binaries, neutron-star/black-hole binaries), contributing to a deeper understanding of: (i) their GW, neutrino, and electromagnetic emissions, as well as (ii) their use in constraining the nuclear Equation of State (EOS). Newly developed higher-order hydrodynamics methods will be incorporated into SpEC. With these, ultra-long inspiral simulations will be carried out and compared to post-Newtonian theory. Recently discovered EOS-dependence of NSNS post-merger oscillations will also be investigated in full general relativity. (C) The CaRT group will contribute to the LIGO Scientific Collaboration's (LSC) efforts to detect GWs and extract information from detected signals. They will (i) lead the effort to infer physics from future GW observations of core-collapse supernovae; (ii) participate in searches for GWs from distant core-collapse supernovae; (iii) improve methods for the detection of GWs from continuous sources such as pulsars.