Synopsis: Turbulence around a Black Hole

A black hole perturbed by a collision or other encounter may take longer to relax if turbulence develops in the gravity field around it.
Synopsis figure
S. R. Green et al., Phys. Rev. X (2014)

Researchers have used a relationship between general relativity and hydrodynamics (the so-called gravity-fluid correspondence) to study how black holes might behave when perturbed by, for example, a collision with another object. As described in Physical Review X, the effects of turbulence could make certain vibrations on the black hole spacetime last longer—and display a qualitatively different behavior—than expected.

The gravity-fluid correspondence is based on the realization that, under certain circumstances, Einstein’s general relativity equations resemble the Navier-Stokes equations for fluid dynamics. Typically, scientists have fiddled with the gravity side in order to gain insight into some hard problem on the fluid side. For example, recent work has tried to describe the turbulent motion of fluid particles by mapping it onto a curved geometry of spacetime.

Stephen Green of the University of Guelph, Canada, and his colleagues have investigated the gravity-fluid correspondence in the other direction, by trying to understand black hole perturbations through a study of fluid turbulence. They consider a two-dimensional fluid, whose velocity fluctuations correspond to ringing vibrations on the black hole surface. The fluid’s viscosity characterizes energy loss into the black hole, which causes the perturbations to decay, or “ring down.” As opposed to previous work, the team looked at the long-term consequences of turbulence in gravity and found that, in certain cases, a black hole can develop turbulent signatures such as rotating gravitational wave vortices. This black hole turbulence prolongs the perturbation, as short wavelength vibrations cascade into long wavelength vibrations that decay more slowly. Ongoing work may tell us whether black hole turbulence is observable through, for example, “jitter” in the emission lines from accreting gas. – Michael Schirber


Features

More Features »

Announcements

More Announcements »

Subject Areas

GravitationFluid Dynamics

Previous Synopsis

Next Synopsis

Related Articles

Synopsis: Transition to Superlubricity in 2D
Fluid Dynamics

Synopsis: Transition to Superlubricity in 2D

Studying particles sliding over a 2D potential lattice, researchers have observed a phase transition between a frictional regime and a frictionless, “superlubric” regime Read More »

Synopsis: Neutron Test for Newton’s Gravity
Gravitation

Synopsis: Neutron Test for Newton’s Gravity

Experiments with neutrons search for violations of gravity’s inverse square law at subnanometer distances. Read More »

Viewpoint: Polymers Reduce Drag More than Expected
Fluid Dynamics

Viewpoint: Polymers Reduce Drag More than Expected

Adding polymer to a liquid was thought to reduce drag only up to a point, but new experiments have found exceptions to the usual limit. Read More »

More Articles