Analytical Black-Hole Binary Merger Waveforms.

We present a highly accurate, fully analytical model for the late inspiral, merger, and ringdown of black-hole binaries with arbitrary mass ratios and spin vectors and the associated gravitational radiation, including the contributions of harmonics beyond the fundamental mode. This model assumes only that nonlinear effects remain small throughout the entire coalescence and is developed based on a physical understanding of the dynamics of late stage binary evolution, in particular, on the tendency of the dynamical binary spacetime to behave like a linear perturbation of the stationary merger-remnant spacetime, even at times before the merger has occurred. We demonstrate that our model agrees with the most accurate numerical relativity results to within their own uncertainties throughout the merger-ringdown phase, and it does so for example cases spanning the full range of binary parameter space that is currently testable with numerical relativity.

Black holes are neither particle accelerators nor dark matter probes.

It has been suggested that maximally spinning black holes can serve as particle accelerators, reaching arbitrarily high center-of-mass energies. Despite several objections regarding the practical achievability of such high energies, and demonstrations past and present that such large energies could never reach a distant observer, interest in this problem has remained substantial. We show that, unfortunately, a maximally spinning black hole can never serve as a probe of high energy collisions, even in principle and despite the correctness of the original diverging energy calculation.

Constraining the braneworld with gravitational wave observations.

Some braneworld models may have observable consequences that, if detected, would validate a requisite element of string theory. In the infinite Randall-Sundrum model (RS2), the AdS radius of curvature, l, of the extra dimension supports a single bound state of the massless graviton on the brane, thereby reproducing Newtonian gravity in the weak-field limit. However, using the AdS/CFT correspondence, it has been suggested that one possible consequence of RS2 is an enormous increase in Hawking radiation emitted by black holes.

Consistency of post-Newtonian waveforms with numerical relativity.

General relativity predicts the gravitational wave signatures of coalescing binary black holes. Explicit waveform predictions for such systems, required for optimal analysis of observational data, have so far been achieved primarily using the post-Newtonian (PN) approximation. The quality of this treatment is unclear, however, for the important late-inspiral portion.