New effective-one-body description of coalescing nonprecessing spinning black-hole binaries

We present a new, tunable effective-one-body (EOB) model of the motion and radiation of coalescing black-hole binaries with arbitrary mass ratio and aligned spins. The most novel feature of our formalism is the introduction, and systematic use, of the (gauge-invariant) concept of centrifugal radius r(c). In the spinning small mass-ratio limit, the main radial potential expressed in terms of r(c) differs very little (and only multiplicatively so) from the usual Schwarzschild potential 1-2M/r(c). This motivates a new, multiplicative way of blending finite-mass-ratio deformations with spin deformations. In the present exploratory work we consider a minimal version of our spinning EOB model (containing essentially only two adjustable parameters: one in the Hamiltonian and one in the waveform) and calibrate its (dominant mode) waveform against a sample of fifteen equal-mass, equal-spin waveforms produced by the SXS Collaboration, and covering the dimensionless spin range -0.95 <= chi <= +0.98. The numerical relativity/EOB phasing disagreement remains remarkably small (less than or similar to +/- 0.15 rad) over the entire spin range.