A 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 {\it 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 $-0.95\leq \chi \leq +0.98$. The numerical relativity / EOB phasing disagreement remains remarkably small ($\lesssim \pm 0.15$ rad) over the entire spin range. 
Thibault Damour and Alessandro Nagar
gr-qc