Double Spin-Long

As binary black holes (BBHs) spiral inward towards merger, both spin angular momenta precess, according to equations first solved analytically by my collaborators and I in 2014. In a followup to our breakthrough solution, we use our solution to understand how binary black holes precess and inspiral. We can efficiently predict and explain how spin orientations at infinity evolve into other spin configurations just prior to merger, an ingredient essential to many astrophysical processes (e.g., the evolution of supermassive black holes).

For experts In this work, we introduce a new way to describe precessing binaries that better respects the natural hierarchy of timescales of the problem; explain how these hierarchical coordinates evolve with time; and develop an extraordinarily efficient precession-averaged mechanism for evolving an ensemble of precessing binaries forward in time, treating the specific precession phase as a random variable. This exceptionally efficient approach can evolve precessing binaries from astrophysical seperations to the strong-field regime.

+/-(ξ)

• binaries with J&ltJ-(ξ) librate around one resonance

• binaries with J&gtJ+(ξ) librate around another resonance

• and binaries with J-&lt J &lt J+ circulate between them.

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For more information, see ``Solving double-spin evolution” below, and

• Gerosa et al 2015 A multi-timescale analysis of phase transitions in precessing black-hole binaries, submitted to PRD, and lead author Davide Gerosa’s animations Kesden et al 2015: Effective potentials and morphological transitions for binary black-hole spin precession (PRL 114 1103;arxiv:1411.0674)