To Evolution

Taming The Final Theory Of The Multiverse Stephen Hawking On The Big Bang

    Abdulaziz Sobh
    By Abdulaziz Sobh

    Categories: Science


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    Professor Stephen Hawking's final theory of the origin of the universe, in which he worked in collaboration with Professor Thomas Hertog of KU Leuven, was published today in the Journal of High Energy Physics.The theory, which was submitted for publication before Hawking's death earlier this year, is based on string theory and predicts that the universe is finite and much simpler than many current theories about the big bang say.Professor Hertog, whose work was supported by the European Research Council, first announced the new theory at a conference at Cambridge University in July last year, organized on the occasion of Professor Hawking's 75th birthday.Modern theories of the big bang predict that our local universe came into existence with a brief explosion of inflation - in other words, a fraction of a second after the Big Bang itself, the universe expanded at an exponential rate. It is believed, however, that once inflation begins, there are regions where it never stops. It is believed that quantum effects can keep inflation forever in some regions of the universe, so globally inflation is eternal. The observable part of our universe would then be just a hospitable universe of pocket, a region in which inflation 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 inflatable ocean," Hawking said in an interview last fall. "The local laws of physics and chemistry may differ from one pocket universe to another, which together would form a multiverse." But I have never been a fan of the multiverse. be tested. "In their new article, Hawking and Hertog say that this account of eternal inflation as a big bang theory 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 quantum effects as small fluctuations around that," said Hertog. "However, the dynamics of eternal inflation eliminate the separation of classical physics from quantum physics. As a consequence, Einstein's theory decomposes into eternal inflation." "We predict that our universe at the largest scales is reasonably smooth and globally finite, so it's not a fractal structure," Hawking said.The theory of eternal inflation proposed by Hawking and Hertog is based on string theory: a branch of theoretical physics that attempts to reconcile gravity and general relativity with quantum physics, in part by describing the fundamental components of the universe as small strings vibratory His approach uses the holographic concept of string theory, which postulates that the universe is a large and complex hologram: physical reality in certain three-dimensional spaces can be reduced mathematically to two-dimensional projections on a surface.Hawking and Hertog developed a variation of this concept of holography to project the dimension of time into eternal inflation. This allowed them to describe eternal inflation without having to rely on Einstein's theory. In the new theory, eternal inflation is reduced to a timeless state defined on a spatial surface at the beginning of time."When we trace the evolution of our universe backward in time, at some point we reach the threshold of eternal inflation, where our familiar notion of time ceases to have any meaning," Hertog said.The previous "theory of non-frontiers" by Hawking predicted that if you go back in time to the beginning of the universe, the universe shrinks and closes like a sphere, but this new theory represents a step beyond the previous work. "We are now saying that there is a limit to our past," Hertog said.Hertog and Hawking used their new theory to derive more reliable predictions about the global structure of the universe. They predicted that the universe that emerges from eternal inflation at the limit of the past is finite and much simpler than the infinite fractal structure predicted by the old theory of eternal inflation.Their results, if confirmed by later work, would have far-reaching implications for the multiverse paradigm. "We are not in a single universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes," Hawking said.This makes the theory more predictive and verifiable.Hertog now plans to study the implications of the new theory on smaller scales that are within the reach of our space telescopes. He believes that the primordial gravitational waves (waves in spacetime) generated at the exit of eternal inflation constitute the most promising "smoking gun" to test the model. The expansion of our universe from the beginning means that such gravitational waves would have very long wavelengths, outside the range of current LIGO detectors. But they could be heard by the planned gravitational wave observatory based on the European space, LISA, or seen in future experiments measuring the cosmic microwave background.