December 12, 2012
Researchers Shed Light On Remarkable Properties Of Black Holes
April Flowers for redOrbit.com - Your Universe Online
Many mysteries surround black holes, but new research led by the Niels Bohr Institute has come up with groundbreaking new theories that might explain several of their more mysterious properties. The new study reveals that black holes have properties that resemble the dynamics of both solids and liquids.
Black holes are extremely compact, so compact in fact that they generate an incredibly strong gravitational pull. Everything that comes near them is swallowed up, even light is unable to escape. Light that hits a black hole will not be reflected and is instead entirely absorbed, making the black hole basically invisible.
"But black holes are not completely black, because we know that they emit radiation and there are indications that the radiation is thermal, i.e. it has a temperature," explains Niels Obers, a professor of theoretical particle physics and cosmology at the Niels Bohr Institute at the University of Copenhagen.
Though researchers understand the compact nature of black holes, they do not know their quantum properties yet. To understand the physics of black holes, Obers works with theoretical modeling. He compares black holes to a particle, which, in principle, has no dimensions. A particle is simply a point. If you give a point a dimension, it becomes a string. Add an extra dimension to a string and it becomes a plane. These planes are called "branes" — related to membrane from the biological world.
"In string theory, you can have different branes, including planes that behave like black holes, which we call black branes. 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'," explains Niels Obers. Obers worked out this new way of looking at black branes with Troels Harmark, associate professor in theoretical physics at the Niels Bohr Institute, in 2009.
Obers and current research team have made a new breakthrough in describing 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. 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," explains Jay Armas, a doctoral student in Obers laboratory.
When black branes are bent and folded into a blackfold, explains Armas, a piezoelectric effect is created. Piezoelectricity is created from compression, or pressure, providing a transducer effect, which can be understood as a slightly bent and charged black string. The string has a greater concentration of electric charge on the inner side relative to the outer side, producing two electrically charged poles on the black strings. Einstein's theory of gravity predicted black holes, meaning that there is a surprising relationship between gravity, 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. 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," explains Niels Obers.
The results of this study were recently published in the journal Physical Review Letters.
Image 2 (below): In theoretical physics you can have different planes that behave like black holes and they are called black branes. When black branes are folded into multiple dimensions they form a 'blackfold', which new research shows has a relationship between gravity and fluid mechanics and solid-state physics. Credit: Artist impression by Merete Rasmussen