Revisiting event horizon finders
Abstract
Event horizons are the defining physical features of black hole spacetimes, and are of considerable interest in studying black hole dynamics. Here, we reconsider three techniques to find event horizons in numerical spacetimes: integrating geodesics, integrating a surface, and integrating a level-set of surfaces over a volume. We implement the first two techniques and find that straightforward integration of geodesics backward in time is most robust. We find that the exponential rate of approach of a null surface towards the event horizon of a spinning black hole equals the surface gravity of the black hole. In head-on mergers we are able to track quasi-normal ringing of the merged black hole through seven oscillations, covering a dynamic range of about 10^5. Both at late times (when the final black hole has settled down) and at early times (before the merger), the apparent horizon is found to be an excellent approximation of the event horizon. In the head-on binary black hole merger, only some of the future null generators of the horizon are found to start from past null infinity; the others approach the event horizons of the individual black holes at times far before merger.
Additional Information
© 2009 IOP Publishing Limited 2009. Print publication: Issue 3 (7 February 2009); received 16 September 2008, in final form 10 November 2008; published 13 January 2009. We gratefully acknowledge useful discussions with Lee Lindblom, Peter Diener, Saul Teukolsky and Kip Thorne. We particularly thank Kip Thorne for pointing out the relationship between the surface gravity and the rate of divergence of geodesics from the EH. This work was supported by grants from the Sherman Fairchild Foundation and the Brinson Foundation, and by NSF grants PHY-0601459, PHY-0652995, DMS-0553302 and NASA grant NNG05GG52G.Additional details
- Eprint ID
- 14639
- Resolver ID
- CaltechAUTHORS:20090722-142406238
- Sherman Fairchild Foundation
- Brinson Foundation
- PHY-0601459
- NSF
- PHY-0652995
- NSF
- DMS-0553302
- NSF
- NNG05GG52G
- NASA
- Created
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2009-08-08Created from EPrint's datestamp field
- Updated
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2022-07-12Created from EPrint's last_modified field
- Caltech groups
- TAPIR