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What we heard about numerical relativity

What we heard about numerical relativity. Patrick Sutton California Institute of Technology and LIGO Scientific Collaboration. Things I think I* understood (an outsider’s view). * And some of my data analysis friends, who are not to be blamed for anything I say. Waveforms!.

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What we heard about numerical relativity

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  1. What we heard about numerical relativity Patrick Sutton California Institute of Technology and LIGO Scientific Collaboration

  2. Things I think I* understood(an outsider’s view) * And some of my data analysis friends, who are not to be blamed for anything I say.

  3. Waveforms! • Disappointed - had hoped we (LIGO) would be the first to publish waveforms from BH mergers ... • Comparison of waveforms for the equal-mass non-spinning case is really impressive. • Different groups, algorithms, initial data, boundary conditions, etc. Results appear really robust. • Husa: uncertainties in the NR waveforms are much smaller than the ~5% uncertainties in LIGO calibrations • Saw many plots with matches of 97% + • Also impressed with ability to model the NR waveforms with analytics (PN theory + QNMs), studies of eccentricity, etc. • Implies not only do we have trustworthy results but we’re also starting to understand them. 3

  4. Questions … • Why do the various groups get such good agreement when using different techniques? • Brady: Merger dynamics occur on short scales, therefore robust against boundary conditions … ? • What will happen when integrating for more orbits (dynamic timescale -> radiation reaction timescale)? • Convergence discussion & Mark Miller’s talk: While everyone’s equal-mass, non-spinning waveforms agree with good precision, do we know that they are accurate? • The spinning, arbitrary mass ratio waveforms will be ready when? 4

  5. Collaboration! • Pleased to see interest on NR community’s part in delivering data useful for the GW detection community • Husa: “I can give you 40 waveforms tomorrow” - Sutton: “Sounds good!” • Waveforms, yes … • … but also error estimates and robustness “guarantees” • Also saw increasing collaboration within NR community • Lots of work comparing waveforms, NR and PN, etc., establishing priorities for future work (NSF session last night). 5

  6. Collaboration! • Definitions of terms like “convergence” has to be settled, but the discussion has started. • Really important and highly non-trivial. Will require lots of discussion between data people and num-rels. • We (data analysts) have to figure out exactly what we require from the NR community, communicate that. • How accurate is “good enough” for detection? for parameter estimation? (with real detectors). • Integrated phase error vs. mismatch. 6

  7. Matter matters • Yuk Tung Liu & Josh Faber (UIUC) showed great slides possible evolutions of NS-NS and NS-BH binaries, which could produce both GWs and lead to short hard GRBs. • Significant impact on science from GW detections (e.g. burst searches based on GRBs). • Yunes, Husa, and others: • Recoil velocities have impact for, e.g., rate estimates. • Lots of other great presentations … 7

  8. Final Suggestions / Questions • Get these great talks and slides on the web! • When do we meet again? 8

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