Black holes resemble both liquids and solids

In a new twist to string theory, scientists are suggesting that black holes have properties that resemble the dynamics of both solids and liquids.

Niels Obers, a professor of theoretical particle physics and cosmology at the Niels Bohr Institute at the University of Copenhagen, says that a black hole can be looked at like a particle. A particle has in principle no dimensions. If you give it an extra dimension, it becomes a string; and adding another dimension turns it into a plane, known as a ‘brane’.

“In string theory, you can have different branes, including planes that behave like black holes, which we call black branes,” says Obers. “The black branes are thermal, that is to say, they have a temperature and are dynamical objects. When black branes are folded into multiple dimensions, they form a ‘blackfold’.”

Now, Obers and his team say they’ve made a new breakthrough in the description of the physics of black holes based on the theories of black branes and blackfolds.

“The black branes are hydro-dynamic objects, that is to say that they have the properties of a liquid,” says doctoral student Jay Armas. “We have now discovered that black branes also have properties, which can be explained in terms of solids. They can behave like elastic material when we bend them.”

When the black branes are bent and folded into a blackfold, he says, a piezoelectric effect is created – think of a slightly bent and charged black string with a greater concentration of electric charge on the innermost side. This produces two electrically charged poles on the black strings.

And because black holes are predicted by Einstein’s theory of gravity, this implies a surprising relationship between gravity and fluid mechanics and solid-state physics.

“With these new theories, we expect to be able to explain other black hole phenomena, and we expect to be able to better understand the physical properties of neutron stars,” says Obers.

“We also expect to gain a greater understanding of the so-called particle theories, which are, for example, relevant for understanding the quark-gluon-plasma in the primordial universe.”