Before professor Stephen Hawking passed away on March 14, he was working on a theory with his colleague, professor Thomas Hertog, regarding what happened after the Big Bang. The concept was initially presented during Hawking’s 75th birthday celebration last year. Now, their new theory has been published in the Journal of High Energy Physics.
Hawking and Hertog’s theory focuses largely on the concept of eternal inflation, the idea that, after the accelerated expansion, or cosmic inflation, following the Big Bang, the majority of the universe continued to experience inflation, barring certain exceptions, like the visible universe.
Hawking and Hertog disagreed with the common view on eternal inflation.
“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, according to a report by IFL Science.
“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.”
Under the eternal inflation concept, the Big Bang created a multiverse, with areas where cosmic inflation stopped becoming pocket universes with fractal volume. This is another point where Hawking and Hertog disagreed with the convention.
“We predict that our universe, on the largest scales, is reasonably smooth and globally finite. So, it is not a fractal structure,” said Professor Hawking in an interview prior to his death. “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.”
“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.”
Using string theory, a method for potentially reconciling relativity and quantum physics as well as the holographic principle, Hawking and Hertog approached eternal inflation from a new angle.
The result allowed eternal inflation to become a timeless state and with the potential to create a small range of potential universes, eliminating the fractal multiverse portion of the concept.
Based on how it is constructed, Hawking and Hertog’s theory may be testable.