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TOPIC: Cyclic Universe

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 Hořava-Lif****z gravity Permalink Horava-Lif****z gravity (or Horava gravity) is a theory of quantum gravity proposed by Petr Horava in 2009. It solves the problem of different concepts of time in quantum field theory and general relativity by treating the quantum concept as the more fundamental so that space and time are not equivalent (anisotropic).Read more __________________

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 RE: Cyclic Universe Permalink Title: Oscillating Universe in Horava-Lif****z GravityAuthors: Kei-ichi Maeda, Yosuke Misonoh, Tsutomu KobayashiWe study the dynamics of isotropic and homogeneous universes in the generalised Horava-Lif****z gravity, and classify all possible evolutions of vacuum spacetime. In the case without the detailed balance condition, we find a variety of phase structures of vacuum spacetimes depending on the coupling constants as well as the spatial curvature K and a cosmological constant \Lambda. A bounce universe solution is obtained for \Lambda> 0, K= ±1 or \Lambda= 0, K=- 1, while an oscillation spacetime is found for \Lambda\geq 0, K=1, or \Lambda< 0, K= ±1. We also propose a quantum tunnelling scenario from an oscillating spacetime to an inflationary universe, resulting in a macroscopic cyclic universe. Read more (856kb, PDF) __________________

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 Permalink Title: Conformal formulation of cosmological futuresAuthors: Philipp A Hoehn, Susan M ScottWe summarise the new conformal framework of an Anisotropic Future Endless Universe and an Anisotropic Future Singularity. Both new definitions are motivated by, but not restricted to quiescent cosmology and the Weyl curvature hypothesis, which previously only possessed a framework for a classical initial state of the universe, namely the Isotropic Singularity. Some of the features of the framework are briefly discussed. Read more (14kb, PDF) __________________

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 Permalink Ed ~ thank you for your question. I don't believe in the classic cyclical scenarios.Also I believe that the final state of affairs is incorrect; due to the BH evaporation process and space-time expansion, that will lead to an essentially empty universe. Particles would become isolated in their own observable universe with the result that they lose their identity and space and time become meaningless. The universe would now posses conditions that would lead to another big-bang event(s).-- Edited by Blobrana on Sunday 20th of December 2009 04:31:56 PM __________________
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 Permalink Blobrana wrote:Title: The Phantom Bounce: A New Proposal for an Oscillating CosmologyAuthors: Katherine Freese, Matthew G. Brown, William H. Kinney The classic black hole overproduction of oscillating universes is resolved due to their destruction by the phantom energy. Read more (23kb, PDF)So don't you think, that under scenario proposed by Authors of article Planck mass BH would still accumulate with progress off new and new expansion phases and Big Rip phenomenons and as time pass we would end up with Universe which consist solely of Planck mass BHs, eg BH remnants?Such scenario is still implying some sort of final end of Universe because once it have happened, nothing materially new would be going on upon subsequent expansions/big rip phases where only space of vacuum and BH remnants are eternally "reprocessed" and nothing else can exist. So that is not truly cyclical scenario.Once only space and BH remnants exist, that's it. Final state of affairs have been reached and further oscillations are meaningless.Just other flavor of "Thermal Death" in philosophical sense at least.  __________________

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 Permalink Title: Emergence of a Cyclic Universe from the Hagedorn SoupAuthors: Tirthabir Biswas(Version v3)One of the challenges of constructing a successful cyclic universe scenario is to be able to incorporate the second law of thermodynamics which typically leads to Tolman's problem of ever shrinking cycles. In this paper we construct a non-singular toy model where as the cycles shrink in the past they also spend more and more time in the entropy conserving Hagedorn phase. Thus in such a scenario the entropy asymptotes to a finite non-zero constant in the infinite past. The universe emerges'' from a small (string size) geodesically complete quasi-periodic space-time. This paradigm also naturally addresses some of the classic puzzles of Big Bang cosmology, such as the largeness, horizon and flatness problems. Read more (9kb, PDF) __________________

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 RE: Bouncing universe Permalink (May 23, 2006)Bounce Preceded BangThe Big Bang may have been a Big Bounce, say theorists searching for what preceded the birth of our own universe.If their new mathematical simulations are correct, what came before the Big Bang was a previous universe a lot like our own. It collapsed on itself, then some weird physics caused it to inflate into the universe we have today.Read more __________________

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 Permalink Title: Bouncing universe and non-BPS branesAuthors: Philipp Höffer v. Loewenfeld, Jin U Kang, Nicolas Moeller, Ivo Sachs(Version v2)We describe string frame bouncing universe scenarios involving the creation and annihilation of a non-BPS D9-brane in type IIA superstring theory. We find several classes of solutions, in which the bounce is driven by the tachyon dynamics of the non-BPS brane. The metric and the dilaton are consistently described in terms of the lowest order effective action. The bounce solutions interpolate between contracting and expanding pre-big bang (or post-big bang) solutions. The singular behaviour of our bounce solutions is the same as that of the pre-big bang (or post-big bang) solution. Upon adding a simple dilaton potential the asymptotic curvature singularity is removed but the dilaton still grows without bound. Such a potential may result from \alpha' corrections in the open string sector. Read more  (1025kb, PDF) __________________

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Posts: 131433
Date:
 Permalink Title: Bouncing universe and non-BPS branesAuthors: Philipp Höffer v. Loewenfeld, Jin U Kang, Nicolas Moeller, Ivo SachsWe describe string frame bouncing universe scenarios involving the creation and annihilation of a non-BPS D9-brane in type IIA superstring theory. We find several classes of solutions, in which the bounce is driven by the tachyon dynamics of the non-BPS brane. The metric and the dilaton are consistently described in terms of the lowest order effective action. The bounce solutions interpolate between contracting and expanding pre-big bang (or post-big bang) solutions. The singular behaviour of our bounce solutions is the same as that of the pre-big bang (or post-big bang) solution. Upon adding a simple dilaton potential the asymptotic curvature singularity is removed but the dilaton still grows without bound. Such a potential may result from \alpha' corrections in the open string sector. Read more  (1025kb, PDF) __________________
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