File photo of Stephen Hawking. Stephen Hawking has died at the age of 76, his family has said. The British theoretical physicist was known for his groundbreaking work with black holes and relativity, and was the author of several popular science books including A Brief History of Time. (Photo:/Agencies)
Renowned British scientist Professor Stephen Hawking's final theory on the origin of the universe has been published in the Journal of High Energy Physics, the University of Cambridge said on Wednesday.
The paper, co-authored by Hawking and Professor Thomas Hertog from KU Leuven, was submitted for publication before Hawking's death earlier this year, according to the University of Cambridge.
Modern theories of the big bang predict that our local universe came into existence with a brief burst of inflation.
It is widely believed, however, that once inflation starts, there are regions where it never stops. It is thought that quantum effects can keep inflation going forever in some regions of the universe so that globally, inflation is eternal.
The observable part of our universe would then be just a hospitable pocket universe, a region in which inflation has ended and stars and galaxies formed.
"The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean," Hawking was quoted as saying in a press release from Cambridge.
"The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse. But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite the theory can't be tested."
In their new paper, Hawking and Hertog say this account of eternal inflation as a theory of the big bang is wrong.
"The problem with the usual account of eternal inflation is that it assumes an existing background universe that evolves according to Einstein's theory of general relativity and treats the quantum effects as small fluctuations around this," said Hertog.
"However, the dynamics of eternal inflation wipes out the separation between classical and quantum physics. As a consequence, Einstein's theory breaks down in eternal inflation."
"We predict that our universe, on the largest scales, is reasonably smooth and globally finite. So it is not a fractal structure," said Hawking.
Their results, if confirmed by further work, would have far-reaching implications for the multiverse paradigm. Hertog now plans to study the implications of the new theory on smaller scales that are within reach of our space telescopes.
