Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session D14: Numerical Relativity: Black Hole Binaries |
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Sponsoring Units: DGRAV Chair: Carlos Lousto, Rochester Institute of Technology Room: A226 |
Saturday, April 14, 2018 3:30PM - 3:42PM |
D14.00001: An update on the SXS waveform catalog for binary black holes Catherine Woodford \newline Numerical solutions of binary black holes yield arguably the most accurate gravitational waveforms for the coalescence of two black holes. Such ``numerical waveforms'' are the basis for numerous inspiral-merger-ringdown waveform models used to detect gravitational waves from coalescing black holes, to estimate the properties of the coalescing binaries, and to test general relativity with the observed gravitational waves. ``Numerical waveforms'' are also used to study systematic errors of parameter estimation.~ Catalogs of numerical waveforms enable all these applications. Over the past years, the Simulating Extreme Spacetimes collaboration (SXS) has computed an increasingly comprehensive catalog of numerical waveforms, increasing greatly the original SXS catalog from 2013.~ This talk summarises the current status of this catalog, including its parameter space coverage and an assessment of the uncertainties in the numerical waveforms in the catalog. [Preview Abstract] |
Saturday, April 14, 2018 3:42PM - 3:54PM |
D14.00002: Comparison of Binary Black Hole Initial Data Sets Mark Scheel, Vijay Varma We present improvements to construction of binary black hole initial data used in SpEC (Spectral Einstein Code). We introduce new boundary conditions for the elliptic equations that enforce the excision surfaces to be slightly inside rather than on the apparent horizons, thus avoiding extrapolation into the black holes at the last stage of initial data construction. We find that this improves initial data constraint violations near and inside the apparent horizons by about 3 orders of magnitude. We construct several initial data sets including initial data in the harmonic and damped harmonic gauges and compare them by evolving them. We show that the gravitational waveform extracted during the evolution of these different initial data sets agree very well, after excluding the spurious transients known as "junk radiation". Among the cases considered, harmonic initial data leads to significantly lower junk radiation, smaller temporal variation in black hole spins and masses during the junk radiation stage, smaller constraint violations, and better computational efficiency. [Preview Abstract] |
Saturday, April 14, 2018 3:54PM - 4:06PM |
D14.00003: Binary black hole spacetimes in harmonic coordinates Prayush Kumar, Harald Pfeiffer Harmonic coordinates are often used in analytical relativity calculations targeted at binary black hole spacetimes, as they provide for the simplification of Einstein equations to a set of quasilinear wave equations. In this talk, I will discuss the existence and characteristics of simple harmonic coordinates in highly dynamical (numerical) spacetimes of merging black holes. I will also describe a method of tracking black hole trajectories in pure harmonic coordinates. This method has the potential to enable gauge-dependent comparisons of two-body kinematics between Numerical Relativity and post-Newtonian theory results, allowing for better calibration of general relativistic models for binary black hole dynamics. [Preview Abstract] |
Saturday, April 14, 2018 4:06PM - 4:18PM |
D14.00004: Transitional precession in binary black hole systems Serguei Ossokine, Lawrence Kidder, Harald Pfeiffer Binary black holes continue to represent some of the best sources of gravitational waves. For precessing systems, it has long been predicted by post-Newtonian theory that transitional precession can take place. Transitional precession occurs when the spin, orbital and total angular momentum vectors drastically change direction during the evolution, in sharp contrast to the more standard scenario where these vectors precess in a cone. The rich dynamics of transitional precession is in turn imprinted on the gravitational waveform. We present numerical relativity simulations of transitional precession and compare the results to predictions from state-of-the-art waveform models. [Preview Abstract] |
Saturday, April 14, 2018 4:18PM - 4:30PM |
D14.00005: Massively Parallel Simulations of Binary Black Hole Intermediate-Mass-Ratio Inspirals David Neilsen, Milinda Fernando, Hari Sundar, Eric Hirschmann, Hyun Lim Intermediate Mass Ratio Inspirals (IMRIs) are binary black hole systems with mass ratios between $q=1/10^2$ and $q=1/10^4$. These binaries may be formed in globular clusters, and their gravitational waves will be important sources for LISA, as well as aLIGO and third-generation detectors. IMRI binaries are very difficult to simulate in numerical relativity, where mass ratios are typically larger than $q=1/10$, because the disparate length scales of the black holes requires significant computational resources. We are developing a new relativistic code to solve the Einstein equations for black hole systems with $q< 1/10$. This code is based on the Dendro platform for parallel octrees, which scales to $10^5$ cores. The computational grid is dynamically generated using the Adaptive Multiresolution Wavelet Method. This resulting computational grid is sparse and adapted to the geometry of the spacetime, leading to high computational efficiency. We will discuss the computational performance of our code and present preliminary results of binary mergers. [Preview Abstract] |
Saturday, April 14, 2018 4:30PM - 4:42PM |
D14.00006: Inside the Final Black Hole Bhavesh Khamesra, Deborah Ferguson, Christopher Evans, Pablo Laguna, Deirdre Shoemaker In numerical relativity simulations of binary black holes, the appearance of a common apparent horizon signals the merger of the black holes and thus the formation of the final black hole. At this stage, the final black hole is fully dynamical and highly distorted, emitting gravitational radiation as it settles into a single rotating black hole of the Kerr type. When the common apparent horizon appears, the apparent horizons of the merging black holes do not disappear, although they are no longer outermost marginally trapped surfaces. We present results of the dynamics of the marginally trapped surfaces inside the final black hole that before the merger were the apparent horizons of the colliding black holes. The results provide insights on the formation of the common apparent horizon, as well as the internal structure and the dynamical horizon of the final black hole. [Preview Abstract] |
Saturday, April 14, 2018 4:42PM - 4:54PM |
D14.00007: On choosing the start time of binary black hole ringdown I: Theory Maria Okounkova, Swetha Bhagwat, Stephan Ballmer, Duncan Brown, Matthew Giesler, Mark Scheel, Saul Teukolsky The final stage of a binary black hole (BBH) merger is ringdown, in which the system is described by a Kerr BH with quasinormal mode (QNM) perturbations. It is far from straightforward to identify the time at which the ringdown begins. Yet determining this time is important for precision tests of the general theory of relativity that compare an observed signal with QNM descriptions of the ringdown, such as tests of the no-hair theorem. We present an algorithmic method to analyze the choice of ringdown start time in the observed waveform. This talk will outine the theoretical framework used in this analysis, and the following talk, ``On choosing the start time of binary black hole ringdown II: Results'', will discuss the results. This method is based on determining how close the strong field is to a Kerr BH (Kerrness). Using numerical relativity simulations, we characterize the Kerrness of the strong-field region close to the BH using a set of local, gauge-invariant geometric and algebraic conditions that measure local isometry to Kerr. We produce a map that associates each time in the gravitational waveform with a value of each of these Kerrness measures; this map is produced by following outgoing null characteristics from the strong and near-field regions to the wave zone. [Preview Abstract] |
Saturday, April 14, 2018 4:54PM - 5:06PM |
D14.00008: On choosing the start time of binary black hole ringdown II: Results swetha bhagwat, Maria Okounkova, Stefan Ballmer, Duncan Brown, Matthew Giesler, Mark Scheel, Saul Teukolsky The final stage of a binary black hole merger is ringdown, in which the system is described by a Kerr black hole with quasinormal mode perturbations. It is far from straightforward to identify the time at which the ringdown begins. Yet determining this time is important for precision tests of the general theory of relativity that compare an observed signal with quasinormal mode descriptions of the ringdown, such as tests of the no-hair theorem. We present an algorithmic method to analyze the choice of ringdown start time in the observed waveform. This talk will discuss the results of applying the framework outlined in the previous talk, ``On choosing the start time of binary black hole ringdown I: Theory'' on a numerical relativity simulation with parameters consistent with GW150914 - the first gravitational wave detection. We find that the choice of ringdown start time of $3\,\mathrm{ms}$ after merger used in the GW150914 study to test general relativity corresponds to a high dimensionless perturbation amplitude of $ \sim 7.5 \times 10^{-3}$ in the strong-field region. This suggests that in higher signal-to-noise detections, one would need to start analyzing the signal at a later time for studies that depend on the validity of black hole perturbation theory. [Preview Abstract] |
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