Cyclical universe

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The cyclic universe is a cosmological non-standard model of the origin and evolution of the universe in which the collisions of the worlds take place repeatedly. It represents an extension of the ekpyrotic model , which in turn is an alternative to inflation , which in turn supplements the classic big bang model .

development

The physicists Paul Steinhardt and Neil Turok apply the formalism of string theories , but this is not mandatory. A four-dimensional field theory would also make the calculations possible. They postulate that our universe emerged from the clash of two universes, a brane collision , so that the Big Bang phenomenon can be explained for the first time in cosmological models .

construction

The space-time within the string cosmology on which the collision is supposed to occur is five-dimensional (5D). In technical jargon , this 5D structure is also called bulk . Now there are two limiting four-dimensional (4D) “walls” of this 5D space-time, which are called branes (one time and three space dimensions: 3-brane). Each of these walls represents a universe. One is the precursor universe of our present-day universe, the other is a parallel universe. It is now conceivable that the two universes would only be separated from each other on the Planck scale , but they would be separated by a further, higher spatial dimension , an extra dimension. Only gravity can mediate between the universes and get through five-dimensional space-time. In this way, dark matter from the neighboring universe can make itself felt in ours. Matter and radiation remained restricted to their respective universe.

The speculative radion field

The cause of the collision of the worlds ( ekpyrosis ) is seen in the dark energy , which seems to play a decisive role in the cosmos anyway. This form of energy is predominant in the observed late universe, as measurements ( BOOMERANG , MAXIMA, COBE , WMAP , etc.) suggest. It even trumps the familiar visible, baryonic matter plus hot and cold dark matter by a factor of 2. Paul Steinhardt postulates a force field that he calls the radion field . It manifests as time-varying dark energy, i.e. a new form of quintessence . The radion field exists in all areas of the 5D space-time between the two 3-branes. Since the radion field fluctuates , it induces changes in the distance of the bounding universes. The branes are dynamic, and the special potential form of the field creates a cycle of approach, collision and distance. This cyclical process is identified with the concept of the cyclical model. With every big bang, which signifies the beginning of a universe, a preceding "final bang" is associated with it, which extinguishes a previously existing universe. The singularity of curvature in the Big Bang is therefore associated with a vanishing distance between the universes in the fifth dimension, with space only collapsing in one extra dimension.

This is a very important consequence of the cyclical model and a decisive difference to the previous view of the Big Bang, where space collapses in all dimensions. Because that means for the essential physical parameters temperature and density that they remained finite and did not diverge. In the collapse, a temperature of 10 23  Kelvin was derived. After the collision, the branes diverge again in the fifth dimension. Steinhardt and Turok found a so-called attractor solution that enables the cycles to be repeated as often as desired.

What is attractive about it is that it models the situation before the Big Bang. A dynamic bulk branen system could therefore answer the question of what was before the Big Bang. Similar to the quintessences, the radion field as a dynamic form of dark energy allows the solution of the question why the cosmological constant is so small, but not zero.

The model is speculative, however, because the extra dimensions, which are absolutely necessary in the cyclical model, have not yet been proven experimentally. Apart from that, the question arises as to how this model could ever be tested, even if the existence of the extra dimensions were ever proven. Because for an experimental test, information from the precursor state would have to get into our current universe. According to the cyclical model, the only possible transmitter would be gravity.

In addition to Paul Steinhardt and Neil Turok , Roger Penrose is also a representative of this theory .

See also

Individual evidence

  1. ^ A b Paul J. Steinhardt, Neil Turok: The Cyclic Universe: An Informal Introduction. In: Nuclear Physics B - Proceedings Supplements. Volume 124, July 2003, pp. 38-49, arXiv.org, doi: 10.1016 / S0920-5632 (03) 02075-9 .
  2. ↑ P. Brenner: Branenwelten in string cosmology as a multi-verse . In: Z. f. Cosmology . tape 17 , 2007, p. 101-123 .
  3. ↑ Tetsuya Shiromizu, Kei-ichi Maeda, Misao Sasaki: The Einstein Equations on the 3-Brane World. In: Physical Review D. Volume 62, arxiv.org, doi: 10.1103 / PhysRevD.62.024012 .
  4. ^ Paul J. Steinhardt, Neil Turok: Is Vacuum Decay Significant in Ekpyrotic and Cyclic Models? In: Physical Review D. Volume 66, arxiv.org, doi: 10.1103 / PhysRevD.66.101302 .
  5. ^ Andrew H. Jaffe, Matthew Abroe, Julian Borrill et al .: Recent Results from the MAXIMA Experiment. In: New Astronomy Reviews. Volume 34, pp. 727-732, arXiv.org, doi: 10.1016 / j.newar.2003.07.020 .
  6. ^ The Cyclic Universe: Paul Steinhardt. In: edge.org. November 19, 2002, accessed March 19, 2019 .
  7. ↑ Justin Khoury, Burt A. Ovrut, Paul J. Steinhardt, Neil Turok: The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang. In: Physical Review D. Volume 62, arXiv.org, , doi: 10.1103 / PhysRevD.64.123522 .
  8. ^ Paul J. Steinhardt, Neil Turok: A Cyclic Model of the Universe. In: Science. Volume 296, arXiv.org, doi: 10.1126 / science.1070462 .
  9. ^ Paul J. Steinhardt, Neil Turok: Why the Cosmological Constant Is Small and Positive. In: Science. Volume 312, arXiv.org, doi: 10.1126 / science.1126231 .
  10. ↑ Joel K. Erickson, Steven Gratton, Paul J. Steinhardt, Neil Turok: Cosmic Perturbations Through the Cyclic Ages. In: Physical Review D. Volume 75, arXiv.org, doi: 10.1103 / PhysRevD.75.123507 .
  11. ↑ Andreas Müller: Cyclical Universe. In: Spektrum.de. 2007, accessed March 19, 2019 .