Energy extraction from boosted black holes: Penrose process, jets, and the membrane at infinity

TL;DR

This paper develops a theoretical framework for energy extraction from boosted black holes, deriving analogues of the Penrose process and Blandford-Znajek mechanism, and introduces a membrane paradigm at infinity to interpret jet power.

Contribution

It introduces a novel theory for jets from boosted black holes, including a new membrane paradigm at infinity and a formula for jet power based on black hole velocity and magnetic flux.

Findings

Jet power scales with the square of black hole velocity and magnetic flux.

Energy extraction from boosted black holes is similar to that from spinning black holes but with key differences.

The membrane paradigm at infinity aids in interpreting jet phenomena from boosted black holes.

Abstract

Numerical simulations indicate that black holes carrying linear momentum and/or orbital momentum can power jets. The jets extract the kinetic energy stored in the black hole's motion. This could provide an important electromagnetic counterpart to gravitational wave searches. We develop the theory underlying these jets. In particular, we derive the analogues of the Penrose process and the Blandford-Znajek jet power prediction for boosted black holes. The jet power we find is $(v/2M)^2 \Phi^2/(4\pi)$, where $v$ is the hole's velocity, $M$ is its mass, and $\Phi$ is the magnetic flux. We show that energy extraction from boosted black holes is conceptually similar to energy extraction from spinning black holes. However, we highlight two key technical differences: in the boosted case, jet power is no longer defined with respect to a Killing vector, and the relevant notion of black hole mass is observer dependent. We derive a new version of the membrane paradigm in which the membrane lives at infinity rather than the horizon and we show that this is useful for interpreting jets from boosted black holes. Our jet power prediction and the assumptions behind it can be tested with future numerical simulations.