Abstract: | We present a new spectral-method-based algorithm for finding apparent horizons in three-dimensional space-like hypersurfaces without symmetries. While there are already a wide variety of algorithms for finding apparent horizons, our new algorithm does not suffer from the same weakness as previous spectral apparent horizon finders: namely the monopolar coefficient (? = 0 in terms of the spherical harmonics decomposition) needed to be determined by a root-finding procedure. Hence, this leads to a much faster and more robust spectral apparent horizon finder. The finder is tested with the Kerr–Schild and Brill–Lindquist data. Our finder is accurate and as efficient as the currently fastest methods recently developed by Schnetter (2003 Class. Quantum Grav. 20 4719) and Thornburg (2004 Class. Quantum Grav. 21 743). At typical resolutions it takes only 0.5 s to find the apparent horizon of a Kerr–Schild black hole with a = 0.9M to the accuracy ~10?5 for the fractional error in the horizon's location on a 2 GHz processor. |