RUI: Studies in Numerical Relativity

Bowdoin College, Brunswick ME

Investigators

Abstract

Einstein’s theory of general relativity describes all gravitational interactions in the universe, ranging from the force that pulls a falling apple to the Earth, to the expansion of the Universe itself. In particular, this theory describes black holes and neutron stars — so-called "compact objects" that have extremely strong gravitational fields. The goal of this award is to study what happens when such an object collides with a larger star: would such a collision be observable, would the remnant of the collision form a new type of star, or would it collapse to form another black hole, possibly in an unusual mass range? Answers to these questions will help shed light on the abundance of compact objects, including very small black holes that may have formed in the early Universe and that may contribute to its dark-matter content, and will help understand recent observations by the LIGO gravitational wave detectors of black holes with unusual masses. Finding these answers requires the tools of numerical relativity, i.e. computer programs that can find solutions to Einstein’s equations of general relativity numerically. Undergraduate students will participate in these activities, providing them with a “hands-on” research experience, and generating a research-enriched learning environment at Bowdoin College. The scientific goals of these research efforts include the development and implementation of numerical algorithms for the solution of Einstein's equations of general relativity, as well as their application in the numerical modeling of relativistic objects, in particular neutron stars and black holes. In the next funding period these activities will focus on so-called "Thorne-Zytkow-like-Objects", i.e. larger "host" stars that harbor smaller compact objects as "parasites". Examples include neutron stars that harbor small black holes, possibly of primordial origin, white dwarfs that harbor neutron stars, and main sequence stars that harbor black holes or neutron stars. Specific research activities will explore processes by which these objects may form, including capture and/or binary merger, and will determine whether or not they are dynamically stable, whether their co-evolution and ultimate collapse results in observable gravitational-wave or electromagnetic signals, and whether these scenarios provide viable evolutionary pathways to black holes outside the mass ranges resulting from standard stellar evolution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.