Cyclic model: Difference between revisions
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One new cyclic model is a [[brane cosmology]] model of the [[Big Bang|creation of the universe]], derived from the earlier [[ekpyrotic]] model. It was proposed in 2001 by [[Paul Steinhardt]] of [[Princeton University]] and [[Neil Turok]] of [[Cambridge University]]. The theory describes a universe exploding into existence not just once, but repeatedly over time. |
One new cyclic model is a [[brane cosmology]] model of the [[Big Bang|creation of the universe]], derived from the earlier [[ekpyrotic]] model. It was proposed in 2001 by [[Paul Steinhardt]] of [[Princeton University]] and [[Neil Turok]] of [[Cambridge University]]. The theory describes a universe exploding into existence not just once, but repeatedly over time.{{Fact|date=March 2009}} |
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==The Steinhardt–Turok model == |
==The Steinhardt–Turok model == |
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Revision as of 09:01, 29 March 2009
 | This article needs attention from an expert in Physics. Please add a reason or a talk parameter to this template to explain the issue with the article. (November 2008) |
Cyclic model refers to several cosmological models in which the universe follows infinite, self-sustaining cycles (for example: an eternity of Big Bang-Big crunches).
Overview
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One new cyclic model is a brane cosmology model of the creation of the universe, derived from the earlier ekpyrotic model. It was proposed in 2001 by Paul Steinhardt of Princeton University and Neil Turok of Cambridge University. The theory describes a universe exploding into existence not just once, but repeatedly over time.[citation needed]
The Steinhardt–Turok model
As Richard C. Tolman showed, the earlier cyclic model failed because the universe would undergo inevitable thermodynamic heat death. However, the newer cyclic model evades this by having a net expansion each cycle, preventing entropy from building up. However, there are major problems with the model. Foremost among them is that colliding branes are not understood by string theorists, and nobody knows if the scale invariant spectrum will be destroyed by the big crunch, or even what happens when two branes collide. Moreover, like cosmic inflation, while the general character of the forces (in the ekpyrotic scenario, a force between branes) required to create the vacuum fluctuations is known, there is no candidate from particle physics. Moreover, the scenario uses some essential ideas from string theory, principally extra dimensions, branes and orbifolds.[citation needed] String theory itself is a controversial idea in physics.[1]
Lynds Cyclic Time model
Peter Lynds has proposed a model in which time is cyclic, and the universe repeats exactly an infinite number of times. Because it is the exact same cycle that repeats, however, it can also be interpreted as taking place just once. Lynds argues that his model addresses a number of problems in cosmology that other models are unable to, including the question of the origin of the universe. A key feature of Lynds' model is his treatment of thermodynamic time reversal. Rather than the second law of thermodynamics possibly be violated and entropy decrease, the order of events reverse so that entropy can continue to increase. As the laws of physics are time reversible (with the exception of the second law of thermodynamics), Lynds argues that this causes no problems, while also avoiding some.[2][3]
See also
Notes
- ^ Woit, Peter (2006). Not Even Wrong. London: Random House. ISBN 97800994488644.
{{cite book}}: Check|isbn=value: length (help) - ^ Bang/Crunch/Bang. http://www.fqxi.org/community/forum/topic/111
- ^ It all began with an end: New theory on origin and future of the universe. http://www.peterlynds.net.nz/plcs.pdf
Further reading
- Steinhardt, Paul J., Turok, Neil (2007). Endless Universe. New York: Doubleday. ISBN 978-0-385-50964-0.
{{cite book}}: CS1 maint: multiple names: authors list (link) - Tolman, R.C. (1934). Relativity, Thermodynamics, and Cosmology. Oxford: Clarendon Press. LCCN 340-32023. Reissued (1987) New York: Dover ISBN
0-486-65383-8.
- Lauris Baum and Paul H. Frampton, Phys. Rev. Lett. 98, 071301 (2007).
External links
- Paul J. Steinhardt, Department of Physics, Princeton University
- Paul H. Frampton, Department of Physics and Astronomy, The University of North Carolina at Chapel Hill
- Cyclic universe on arxiv.org
- Simplified Overview Comparing Standard and Ekpyrotic Models of the Universe
- "The Cyclic Universe": A Talk with Neil Turok