Amos Ori

The last three minutes: Issues in gravitational-wave measurements of coalescing compact binaries

Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching cosmological, where the event rate may be many per year. Because the binary’s accumulated orbital phase can be measured to a fractional accuracy ≪10^-3 and relativistic effects are large, the wave forms will be far more complex and carry more information than has been expected. Improved wave form modeling is needed as a foundation for extracting the waves’ information, but is not necessary for wave detection.

Mode sum regularization approach for the self-force in black hole spacetime

We present a method for calculating the self-force (the “radiation reaction force”) acting on a charged particle moving in a strong field orbit in black hole spacetime. In this approach, one first calculates the contribution to the self-force due to each multipole mode of the particle’s field. Then, the sum over modes is evaluated, subject to a certain regularization procedure. Here we develop this regularization procedure for a scalar charge on a Schwarzschild background, and present the results of its implementation for radial trajectories (not necessarily geodesic).

Transition from inspiral to plunge for a compact body in a circular equatorial orbit around a massive, spinning black hole

There are three regimes of gravitational-radiation-reaction-induced inspiral for a compact body with mass μ, in a circular, equatorial orbit around a Kerr black hole with mass M≫μ: (i) the adiabatic inspiral regime, in which the body gradually descends through a sequence of circular, geodesic orbits; (ii) a transition regime, near the innermost stable circular orbit (isco); (iii) the plunge regime, in which the body travels on a geodesic from slightly below the isco into the hole’s horizon. This paper gives an analytic treatment of the transition regime and shows that, with some luck, gravitational waves from the transition might be measurable by the space-based LISA mission.

Late time decay of scalar perturbations outside rotating black holes

We present an analytic method for calculating the late-time tails of a linear scalar field outside a Kerr black hole. We give the asymptotic behavior at timelike infinity (for fixed r), at future null-infinity, and along the event horizon (EH). In all three asymptotic regions we find a power-law decay. We show that the power indices describing the decay of the various modes at fixed r differ from the corresponding Schwarzschild values. Also, the scalar field oscillates along the null generators of the EH (with advanced-time frequency proportional to the modes magnetic number m).

Formation of closed timelike curves in a composite vacuum/dust asymptotically flat spacetime

We present a new asymptotically flat time-machine model made solely of vacuum and dust. The spacetime evolves from a regular spacelike initial hypersurface S and subsequently develops closed timelike curves. The initial hypersurface S is asymptotically flat and topologically trivial. The chronology violation occurs in a compact manner; namely, the first closed causal curves form at the boundary of the future domain of dependence of a compact region in S (the core). This central core is empty, and so is the external asymptotically flat region. The intermediate region surrounding the core (the envelope) is made of dust with positive energy density. This model trivially satisfies the weak, dominant, and strong energy conditions. Furthermore, it is governed by a well-defined system of field equations which possesses a well-posed initial-value problem.

Gravitational Self-Force on a Particle Orbiting a Kerr Black Hole

We present a practical method for calculating the gravitational self-force, as well as the electromagnetic and scalar self-forces, for a particle in a generic orbit around a Kerr black hole. In particular, we provide the values of all the regularization parameters needed for implementing the (previously introduced) mode-sum regularization method. We also address the gauge-regularization problem, as well as a few other issues involved in the calculation of gravitational radiation reaction in Kerr spacetime.

Regularization parameters for the self-force in Schwarzschild spacetime. II. Gravitational and electromagnetic cases

We obtain all ‘‘regularization parameters’’ ~RPs! needed for calculating the gravitational and electromagnetic self-forces for an arbitrary geodesic orbit around a Schwarzschild black hole. These RP values are required for implementing the previously introduced mode-sum method, which allows a practical calculation of the selfforce by summing over contributions from individual multipole modes of the particle’s field. In the gravitational case, we provide here full details of the analytic method and results briefly reported in a recent Letter @Phys. Rev. Lett. 88, 091101 ~2002!#. In the electromagnetic case, the RPs are obtained here for the first time.

Gravitational self force and gauge transformations

We explore how the gravitational self-force ~or ‘‘radiation reaction’’ force !, acting on a pointlike test particle in curved spacetime, is modified in a gauge transformation. We derive the general transformation law, describing the change in the self-force in terms of the infinitesimal displacement vector associated with the gauge transformation. Based on this transformation law, we extend the regularization prescription by Mino et al. and Quinn and Wald ~originally formulated within the harmonic gauge! to an arbitrary gauge. Then we extend the method of mode-sum regularization ~which provides a practical means for calculating the regularized self-force and was recently applied to the harmonic-gauge gravitational self-force! to an arbitrary gauge. We find that the regularization parameters involved in this method are gauge-independent. We also explore the gauge transformation of the self-force from the harmonic gauge to the Regge-Wheeler gauge and to the radiation gauge, focusing attention on the regularity of these gauge transformations. We conclude that the transformation of the self-force to the Regge-Wheeler gauge in Schwarzschild spacetime is regular for radial orbits and irregular otherwise, whereas the transformation to the radiation gauge is irregular for all orbits.

Regularization parameters for the self-force in Schwarzschild spacetime: scalar case

We derive the explicit values of all regularization parameters ~RP! for a scalar particle in an arbitrary geodesic orbit around a Schwarzschild black hole. These RP are required within the previously introduced mode-sum method for calculating the local self-force acting on the particle. In this method, one first calculates the ~finite! contribution to the self-force due to each individual multipole mode of the particle’s field, and then applies a certain regularization procedure to the mode sum, involving the RP. The explicit values of the RP were presented in a recent paper @L. Barack et al., Phys. Rev. Lett. 88, 091101 ~2002!#. Here we give the full details of the RP derivation in the scalar case. The calculation of the RP in the electromagnetic and gravitational cases will be discussed in an accompanying paper.

Oscillatory Null Singularity inside Realistic Spinning Black Holes

We calculate the asymptotic behavior of the curvature scalar (Riemann