A One-Parameter Family of Time-Symmetric Initial Data for the Radial Infall of a Particle into a Schwarzschild Black Hole

TL;DR

This paper introduces a one-parameter family of initial data for simulating a particle falling into a Schwarzschild black hole, analyzing how initial conditions affect gravitational waveforms and energy radiation.

Contribution

It constructs and evolves a new class of initial data within black-hole perturbation theory, revealing how initial gravitational radiation influences waveforms and energy emission.

Findings

Initial data significantly affect waveform shapes and spectra.

Conformally-flat initial data minimizes energy radiated at large separations.

Minimization of radiated energy by conformally-flat data does not hold at small separations.

Abstract

A one-parameter family of time-symmetric initial data for the radial infall of a particle into a Schwarzschild black hole is constructed within the framework of black-hole perturbation theory. The parameter measures the amount of gravitational radiation present on the initial spacelike surface. These initial data sets are then evolved by integrating the Zerilli-Moncrief wave equation in the presence of the particle. Numerical results for the gravitational waveforms and their power spectra are presented; we show that the choice of initial data strongly influences the waveforms, both in their shapes and their frequency content. We also calculate the total energy radiated by the particle-black-hole system, as a function of the initial separation between the particle and the black hole, and as a function of the choice of initial data. Our results confirm that for large initial separations, a conformally-flat initial three-geometry minimizes the initial gravitational-wave content, so that the total energy radiated is also minimized. For small initial separations, however, we show that the conformally-flat solution no longer minimizes the energy radiated.