Black holes may define the perfect fluid, suggests a study of black holes that only exist in a theoretical 10-dimensional space. The finding may have spawned a new universal law in physics, which puts constraints on the way fluids behave in the real world.
Dam Thanh Son from the University of Washington, US, and his colleagues used string theory to model a 10-dimensional black hole as a liquid. String theory tries to explain fundamental properties of the universe by predicting that seven dimensions exist on top of the known three spatial dimensions. While the concept is currently unproven as a cosmological model, the tools of string theory can sometimes provide answers to real quantum problems.
That means that while the "black holes" modelled by Son are not astrophysical black holes, but mathematical objects that exist in string theory, their findings may have relevance to the real world.
The fluid has two properties that relate to the black hole's surface area: viscosity, which describes how thick the liquid is, and entropy density, which is a measure of the internal disorder. Son's team found that the ratio of these two properties is a constant which can be expressed as a mixture of fundamental constants from the quantum world.
Super-cooled atoms
They suggest this constant acts as a universal lower limit for the ratio of the viscosity to entropy in real fluids. This backs an argument based on Heisenberg's famed uncertainty principle suggesting that such a limit should exist.
"That is what we hypothesise. We couldn't prove that it's the case, but we couldn't find anything that is less viscous," says Son. For example, the value of this ratio for water is 400 times greater than for black hole fluid. Even liquid helium is nine times more viscous.
Fluids that could approach the limit include super-cooled clouds of atoms, or the plasmas created in particle colliders, suggests Son.
Physicists have already drawn comparisons between the fireball produced at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, New York, US, and string-theory black holes. "I've started taking it seriously," says Peter Steinberg from Brookhaven National Laboratory, who works with one of the teams collecting data at the RHIC.
Although RHIC have not yet measured the viscosity of their fireball, this would allow an experimental test of Son's prediction. "The final word will come from the experimentalists," Son says.
Journal reference: Physical Review Letters (vol 94, p111601)
Courtsey : Newscientist.com
Dam Thanh Son from the University of Washington, US, and his colleagues used string theory to model a 10-dimensional black hole as a liquid. String theory tries to explain fundamental properties of the universe by predicting that seven dimensions exist on top of the known three spatial dimensions. While the concept is currently unproven as a cosmological model, the tools of string theory can sometimes provide answers to real quantum problems.
That means that while the "black holes" modelled by Son are not astrophysical black holes, but mathematical objects that exist in string theory, their findings may have relevance to the real world.
The fluid has two properties that relate to the black hole's surface area: viscosity, which describes how thick the liquid is, and entropy density, which is a measure of the internal disorder. Son's team found that the ratio of these two properties is a constant which can be expressed as a mixture of fundamental constants from the quantum world.
Super-cooled atoms
They suggest this constant acts as a universal lower limit for the ratio of the viscosity to entropy in real fluids. This backs an argument based on Heisenberg's famed uncertainty principle suggesting that such a limit should exist.
"That is what we hypothesise. We couldn't prove that it's the case, but we couldn't find anything that is less viscous," says Son. For example, the value of this ratio for water is 400 times greater than for black hole fluid. Even liquid helium is nine times more viscous.
Fluids that could approach the limit include super-cooled clouds of atoms, or the plasmas created in particle colliders, suggests Son.
Physicists have already drawn comparisons between the fireball produced at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in Upton, New York, US, and string-theory black holes. "I've started taking it seriously," says Peter Steinberg from Brookhaven National Laboratory, who works with one of the teams collecting data at the RHIC.
Although RHIC have not yet measured the viscosity of their fireball, this would allow an experimental test of Son's prediction. "The final word will come from the experimentalists," Son says.
Journal reference: Physical Review Letters (vol 94, p111601)
Courtsey : Newscientist.com
