PENR-Methods

In a new paper, my RIT graduate student Jacob Lange provides detailed demonstrations and descriptions of a new method to infer the properties of binary black holes: by direct comparison to solutions of Einstein’s equations. As part of the LIGO Scientific Collaboration, we used this method to infer the properties of the first detected binary black hole (GW150914).

Why does this matter? Observations of binary black holes can tell us about the lives and deaths of massive stars. But only if we can confidently infer the binary’s properties. For example, LIGO measurements could begin to differentiate between strongly precessing binaries (probably made in dynamical environments) from stellar siblings (born in isolated pairs). But inferring the properties of precessing binaries is hard.

Some of our earlier inferences have been made using approximations to solutions to Einstein’s equations. These approximations are well-known to be omitting a lot of physics present in real solutions, most particularly for precessing mergers. By contrast, numerical solutions of Einstein’s equations always include all available physics. So this method lets us make more precise inferences, without bias.

For experts: This methods paper describes the underpinnings and validation studies for the method used in our LVC-all paper comparing numerical solutions of Einstein’s equations to GW150914. We describe and validate our one-step extraction procedure, applied to most simulations by default. We show most sources of systematic error are under control. We demonstrate our method using a variety of sources.

For more information

* Lange et al [A Parameter Estimation Method that Directly Compares Gravitational Wave Observations to Numerical Relativity](https://arxiv.org/abs/1705.09833), submitted to PRD

• Abbott et al, Directly comparing GW150914 with numerical solutions of Einstein’s equations for binary black hole coalescence, available here (summary on this article here)