Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session C11: Numerical Analysis of Black Hole Binary Systems |
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Sponsoring Units: GGR DCOMP Chair: Wolfgang Tichy, Florida Atlantic University Room: Plaza Court 1 |
Saturday, May 2, 2009 1:30PM - 1:42PM |
C11.00001: Algebraic Classification of Numerical Spacetimes and Black-Hole-Binary Remnants Manuela Campanelli, Carlos Lousto, Yosef Zlochower In this paper we develop a technique for determining the algebraic classification of a numerical spacetime, possibly resulting from a generic black-hole-binary merger, using the Newman-Penrose Weyl scalars. We demonstrate these techniques for a test case involving a close binary with arbitrarily oriented spins and unequal masses. We find that, post merger, the spacetime quickly approaches Petrov type II, and only approaches type D on much longer timescales. These techniques allow us to begin to explore the validity of the ``no-hair theorem'' for generic merging-black-hole spacetimes [Preview Abstract] |
Saturday, May 2, 2009 1:42PM - 1:54PM |
C11.00002: Binary Black Hole simulations using multi-block domains Enrique Pazos, Manuel Tiglio, Larry Kidder, Oleg Korobkin, Matt Duez, Saul Teukolsky We present results from the simulation of equal mass binary black holes using a multiple block domain decomposition. Our scheme makes use of high-order finite difference operators, excision and the generalized harmonic formulation of Einstein's equations. We are able to compute wave-forms and compare them with numerical solutions obtained by pseudo-spectral methods. [Preview Abstract] |
Saturday, May 2, 2009 1:54PM - 2:06PM |
C11.00003: Binary Black Hole Evolutions of Approximate Puncture Initial Data Tanja Bode, Frank Herrmann, Ian Hinder, Pablo Laguna, Deirdre Shoemaker, Birjoo Vaishnav We present a study of numerical evolutions using an approximate, i.e. constraint-violating, non-spinning, equal-mass binary black hole initial data as proposed by Faye et al. (2004). Analysis of the waveforms from this approximate initial data and that of the constraint-satisfying initial data shows a match larger than 0.97 for an initial separation of 10M, well within the match required for signal detection. We also demonstrate the differences in the evolution are due to negative Hamiltonian constraint violations in the neighborhood of the punctures. We show these constraint violations behave as negative energy/matter clouds which lead to a decrease in the masses of the black holes, affecting the dynamics of the binary system. [Preview Abstract] |
Saturday, May 2, 2009 2:06PM - 2:18PM |
C11.00004: Evolving Black Holes with Wavy Initial Data Bernard Kelly, Wolfgang Tichy, Yosef Zlochower, Manuela Campanelli, Bernard Whiting In Kelly et al. [Phys. Rev. D v. 76, 024008 (2007)], we presented new binary black-hole initial data adapted to puncture evolutions in numerical relativity. This data satisfies the constraint equations to 2.5 post-Newtonian order, and contains a transverse-traceless ``wavy'' metric contribution, violating the standard assumption of conformal flatness. We report on progress in evolving this data with a modern moving-puncture implementation of the BSSN equations in several numerical codes. We will discuss the effect of the new metric terms on junk radiation and continuity of physical radiation extracted. [Preview Abstract] |
Saturday, May 2, 2009 2:18PM - 2:30PM |
C11.00005: BSSN revisited David Brown The puncture method for numerical evolution of black holes relies on the BSSN formulation of Einstein's equations and a standard set of gauge evolution equations. There are a number of issues that are not well understood. For example: (1) Some of the characteristics are incoming at the puncture. What boundary conditions does the puncture prescription effectively impose? (2) BSSN with the standard gauge is susceptible to gauge shocks. How are shocks avoided in practice? I will report on progress toward answering these and other questions. [Preview Abstract] |
Saturday, May 2, 2009 2:30PM - 2:42PM |
C11.00006: Blandfor-Znajeck in binary black holes systems Carlos Palenzuela, Matthew Anderson, Eric W. Hirschmann, Luis Lehner, Steve Liebling, David Neilsen We investigate the behavior of electromagnetic fields influenced by the dynamics of a binary black hole system. In particular, our studies are tied to understanding the interaction between magnetic fields produced at a circumbinary disk in the late stages of the supermassive black hole merger. [Preview Abstract] |
Saturday, May 2, 2009 2:42PM - 2:54PM |
C11.00007: Characteristic-Cauchy code patching for a binary-black hole evolution Maria Babiuc The methodology called Cauchy-Characteristic Extraction (CCE) utilizes Cauchy evolution within some prescribed timelike world-tube, but replaces the need for an outer boundary condition by matching to a characteristic evolution in the exterior of this world-tube. The Cauchy and the characteristic approaches have complementary strengths and weaknesses. Unification of the two methods seems to be a promising way of combining the strengths of both formalisms. At the boundary, since the coordinates of the Cauchy system are arbitrary while the coordinates of the characteristic system are based on the light-cone structure of space-time, a non-trivial coordinate transformation takes place when matching the characteristic and Cauchy evolution equations. The waveform extraction is carried out at some inner worldtube in order to avoid the errors introduced by the outer boundary treatment. This methodology has not yet been extended to the binary black hole problem, due to the errors introduced by the finite size and other geometrical properties of the extraction worldtube. This work investigates the steps involved in developing the algorithms and implementing it into a computational module that will perform the important task of patching a Characteristic code to a Cauchy evolution code, in the astrophysical realistic case of a binary black hole evolution, which have strong requirements for numerical accuracy and place greater demands on computational resources. [Preview Abstract] |
Saturday, May 2, 2009 2:54PM - 3:06PM |
C11.00008: Investigating Variational Integrators for Numerical Relativity Will Farr We report on numerical simulations of simple general relativistic systems using variational integrators. Our variational integrators apply the stationary action principle to discretized versions of the Plebanski action for gravity to derive discrete evolution equations. The discrete action has (discrete) diffeomorphism and local Lorentz transformation symmetries; these symmetries generate discrete constraints which are analogous to the constraints of the continuous system. Because they are derived from the discrete action, our discrete evolution equations are discrete-constraint-preserving. We demonstrate this remarkable property in our simple simulations and discuss the issues involved in using this technique in larger, astrophysically-interesting simulations. [Preview Abstract] |
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