One of the most awe-inspiring properties of black holes is their
absolute simplicity, or as John Wheeler famously put it, “black holes
have no hair”. As their progenitor collapses, its memory is forever
lost, and all that remains is a quiescient, almost featureless, black
hole. In a new article to appear in Physical Review Letters, our group
questions whether this conclusion applies to realistic, astrophysical
black holes
Isolated, “clean” black holes are almost xeroxed copies of one
another, differing at most in mass and rotation. These objects are
described by a solution discovered by Roy Kerr in 1963. Remarkably, Kerr
black holes are ubiquitous in almost any other theory of gravity, to
the extend that the “Kerr hypothesis” is the current paradigm in
astrophysics.
We have shown that in simple, well-motivated extensions of
Einstein’s theory known as scalar-tensor theories, black holes may not
be described by the Kerr metric, as was previously thought. The crucial
ingredient is the matter surrounding astrophysical black holes,
typically in the form of accretion disks. The presence of matter in such
“dirty” black holes forces the hairless Kerr black hole to develop a
new charge — new “hair” — anchoring it to the surrounding matter and
possibly to the entire galaxy”.
This hair growth is accompanied by a peculiar emission of
gravitational waves, potentially detectable by upcoming laser
interferometers, which may test the Kerr hypothesis and probe the very
foundations of gravity.
See the media blurb on our article, in New Scientist, Huffington Post, and Público .
|