AEI: No Universe Without Big Bang

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AEI: No Universe Without Big Bang

Post by bystander » Fri Jun 16, 2017 4:26 pm

No Universe without Big Bang
Albert Einstein Institute | Max Planck Institute for Gravitational Physics | 2017 Jun 15

Researchers from the Max Planck Institute for Gravitational Physics in Potsdam and the Perimeter Institute in Canada disprove the theory of the "smooth beginning"
[img3="No "smooth beginning": almost paradoxically, a smooth beginning causes large quantum fluctuations to grow (right), and thus prevents the development of a large universe as we know it (left). (Credit: J.-L. Lehners (AEI))"]http://www.aei.mpg.de/2062557/zoom-1496402320.jpg[/img3][hr][/hr]
According to Einstein’s theory of relativity, the curvature of spacetime was infinite at the big bang. In fact, at this point all mathematical tools fail, and the theory breaks down. However, there remained the notion that perhaps the beginning of the universe could be treated in a simpler manner, and that the infinities of the big bang might be avoided. This has indeed been the hope expressed since the 1980s by the well-known cosmologists James Hartle and Stephen Hawking with their “no-boundary proposal”, and by Alexander Vilenkin with his “tunnelling proposal”. Now scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam and at the Perimeter Institute in Canada have been able to use better mathematical methods to show that these ideas cannot work. The big bang, in its complicated glory, retains all its mystery.

One of the principal goals of cosmology is to understand the beginning of our universe. Data from the Planck satellite mission shows that 13.8 billion years ago the universe consisted of a hot and dense soup of particles. Since then the universe has been expanding. This is the main tenet of the hot big bang theory, but the theory fails to describe the very first stages themselves, as the conditions were too extreme. Indeed, as we approach the big bang, the energy density and the curvature grow until we reach the point where they become infinite.

As an alternative, the “no-boundary” and “tunneling” proposals assume that the tiny early universe arose by quantum tunnelling from nothing, and subsequently grew into the large universe that we see. The curvature of spacetime would have been large, but finite in this beginning stage, and the geometry would have been smooth - without boundary. This initial configuration would replace the standard big bang. ... As a result of Heisenberg’s uncertainty relation, these models do not only imply that smooth universes can tunnel out of nothing, but also irregular universes. In fact, the more irregular and crumpled they are, the more likely. “Hence the “no-boundary proposal” does not imply a large universe like the one we live in, but rather tiny curved universes that would collapse immediately”, says Jean-Luc Lehners ...

Lorentzian Quantum Cosmology - Job Feldbrugge, Jean-Luc Lehners, Neil Turok No Smooth Beginning for Spacetime - Job Feldbrugge, Jean-Luc Lehners, Neil Turok
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