Physicists Show Gravity Can 'Break and Reconnect' Like a Solar Flare, Releasing Energy Into Matter
Columbia and Chilean researchers rewrote Einstein's equations in plasma-style variables and found gravitational field 'sheets' that can reconnect.
More than a century after Einstein wrote down the equations of gravity, physicists are still finding new ways to read them. Luca Comisso of Columbia University and Felipe Asenjo of Universidad Adolfo Ibáñez in Chile report that gravitational fields can break and reconnect, much like the magnetic fields behind solar flares.
In a plasma, magnetic field lines are dragged, stretched and twisted. Sometimes the stress becomes too great. "Magnetic reconnection is when these field lines, in some specific configuration, break and reattach in a different configuration," Comisso said. When they do, they release energy, which is the process that powers solar flares and is one of the most important energy-release mechanisms in astrophysics.
The new paper in Physical Review D argues gravity can do something similar, with a twist. Because space-time is four-dimensional, gravity involves field "sheets" rather than lines. "Adding one dimension to a line gives you a plane," Comisso explained. The sheets are mathematical structures, not physical objects, but when they reconnect, energy moves out of the gravitational field and into matter. The authors call this gravitational reconnection.
The idea came from an unconventional rewriting of the equations. Over the past few years, physicists have developed a formulation of Einstein's equations that is mathematically equivalent to the original but uses different variables. In that form, gravity begins to look a great deal like the equations that govern plasmas, the gases that make up the sun and fill much of the space between stars. Comisso has spent his career on plasmas and applied those methods to gravity.
The paper builds on earlier work in Physical Review Letters with Maricarmen Winkler that identified previously unrecognized rules limiting how space-time can bend, stretch and evolve. "Einstein's equations contain constraints on how space-time can evolve that are not immediately apparent," Asenjo said. The new paper shows how the connections in a gravitational field can change when the ideal conditions that preserve them break down.
The payoff would be in extreme settings. When astrophysicists want to know what happens as two black holes collide, they run enormous supercomputer simulations, then use the results to predict the gravitational-wave signals that detectors such as LIGO measure. In those environments space-time is so distorted that its behavior is extraordinarily hard to calculate. Rules that hold regardless of the details could offer insight that simulations alone may not.
For now, gravitational reconnection is a theoretical result with no experimental confirmation. The next step, the authors say, is to study how the process might unfold in specific astrophysical settings such as merging black holes, and whether it leaves measurable effects. Comisso hopes the approach will eventually help researchers predict how much energy such events release and what signatures they leave in gravitational waves.
The paper, "Reconnection of gravitational fields," carries the DOI 10.1103/lmqy-pf9k.
