The final theory from the late Stephen Hawking about the multiverse has just been published. The celebrated English theoretical physicist and cosmologist passed away on March 14 at the age of 76.

The New Theory

The new theory explains that the universe is less complicated than previous multiverse theories. Hawking collaborated with KU Leuven professor Thomas Hertog on this theory.

In July 2017, Hertog first proposed the new theory at a conference at the University of Cambridge. It was formerly published in the Journal of High Energy Physics on May 2.

In the new paper, Hawking and Hertog try to change the theory of eternal inflation, which states that there are many bubble universes nucleating and increasing within a background multiverse that is also expanding.

"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 previously said. "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."

Eternal Inflation

Hawking and Hertog debunked the current theory of eternal inflation, which was first introduced in 1979. After the Big Bang, the theory of eternal inflation states that some bubbles of space ceased inflation, which resulted in an obstruction. Simultaneously, other bubbles in space continued inflation.

"The problem with the usual account of eternal inflation is that it assumes an existing background universe that evolves according to [Albert] Einstein's theory of general relativity, and treats the quantum effects as small fluctuations around this," said Hertog.

The new theory by Hawking and Hertog states that eternal inflation is limited within a contiguous area and is timeless.

String Theory

To reach their new conclusion, Hawking and Hertog based their findings on string theory, which reconciles general relativity with quantum physics, by categorizing all objects as either filaments or membranes. They created a variation of the string theory's concept of holography, which states that objects in 3D space can relate on a mathematical level to 2D objects on surfaces.

This approach allows them to explain the new theory of eternal inflation without having to use Einstein's theory on the subject.

There will have to be more research into the new theory to explain how significant this can be for the universe.

"We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes," said Hawking.