The cosmological constant has been a problem in physics since Einstein, but new research may show why it takes the value that it does despite quantum fluctuations that should make its value practically infinite.
PROVIDENCE, R.I. [Brown University] - The cosmological constant is the mathematical description of the energy that drives the ever-accelerating expansion of the cosmos. It's also the source of one of the most enduring and confounding problems in modern physics.
The constant's observed value is fundamentally at odds with quantum field theory (QFT), the leading theory describing the elementary particles and forces that make up the universe. QFT predicts that quantum fluctuations in the vacuum of space should make the value of the constant enormous - practically infinite. But its observed value is a tiny fraction of that prediction.
Researchers at Brown University have proposed a provocative new answer for why that is.
The scientists show that math underlying the simplest formulation of quantum gravity bears a striking resemblance to the math describing the quantum Hall effect, an exotic state of matter in which electricity flows with uncanny precision. In the quantum Hall state, electrical conductance is held steady, regardless of any imperfections in the conducting material, by the system's topology - the mathematical "shape" of the quantum state. The researchers show that there's an analogous topology in what's known as the Chern-Simons-Kodama state, a proposed ground state of quantum gravity.
"What we've shown is that if space-time has this non-trivial topology, then it resolves one of the deadliest problems of the cosmological constant," said study co-author Stephon Alexander, a professor of physics at Brown. "All the quantum perturbations that should blow up the value of the cosmological constant are rendered inert by this topology, which keeps the constant's value stable."
The research, which Alexander co-authored with Brown Theoretical Physics Center colleagues Aaron Hui and Heliudson Bernardo, is published in Physical Review Letters.
