The cosmos appears have a preference for things which can be round. Planets and stars are inclined to be spheres because gravity pulls clouds of gas and mud toward the middle of mass. The same is true for black holes – or more precisely, black hole event horizons – which, based on the speculation, should be spherical in a universe with three dimensions of space and one dimension of time.
But do the identical constraints apply if our universe has larger dimensions, as sometimes postulated—dimensions we cannot see but whose effects are still tangible? Are other shapes of black holes possible with these settings?
The answer to this last query, the maths tells us, is yes. Over the past twenty years, scientists have found occasional exceptions to the rule that constrains black holes to a spherical shape.
Now latest paper he goes much further, showing in an intensive mathematical proof that an infinite variety of shapes are possible within the fifth dimension and beyond. The article shows that Albert Einstein’s equations of general relativity can result in an enormous number of exotic-looking, multidimensional black holes.
The latest work is solely theoretical. It doesn’t tell us whether such black holes exist in nature. But if we by some means detected such oddly shaped black holes – perhaps as microscopic products of collisions in a particle collider – “this is able to robotically show that our universe is multi-dimensional,” he said. Marcus Khurigeometer at Stony Brook University and co-author of a latest paper with Jordan Rainone, a recent doctorate in mathematics from Stony Brook. “So now it’s only a matter of waiting to see if our experiments can detect them.”
A donut with a black hole
Like many black hole stories, this one begins with Stephen Hawking, specifically his 1972 proof that the surface of a black hole at any given time should be a two-dimensional sphere. (While a black hole is a three-dimensional object, its surface has only two spatial dimensions.)
Little thought was given to extending Hawking’s theorem until the Eighties and Nineties, when enthusiasm for string theory—an concept that required perhaps 10 or 11 dimensions—was growing. Physicists and mathematicians then began to noticeably consider what these extra dimensions might imply for the topology of black holes.
Black holes are one in all Einstein’s most difficult equation predictions – 10 combined non-linear differential equations which can be extremely difficult to cope with. In general, they will only be explicitly solved under highly symmetric and subsequently simplified circumstances.
In 2002, three a long time after Hawking’s result, physicists Robert Emparan AND Harvey Real— currently on the University of Barcelona and the University of Cambridge respectively — found a highly symmetric solution to Einstein’s equations in the shape of a black hole in five dimensions (4 in space plus one in time). Emparan and Reall named this object “black ring” – a three-dimensional surface with the overall contours of a donut.
It’s hard to assume a three-dimensional surface in five-dimensional space, so we could say an easy circle as an alternative. Any point on this circle could be replaced with a two-dimensional sphere. The results of this mixture of circle and spheres is a three-dimensional object that might be regarded as a solid lumpy donut.
In principle, such donut-like black holes could form in the event that they were spinning at the best speed. “If they’re spinning too fast, they’ll disintegrate, and if they are not spinning fast enough, they’ll turn into a ball again,” Rainone said. “Emparan and Reall found a pleased medium: their ring rotated fast enough to remain like a donut.”
