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Entropy of Contracting Universe in Cyclic Cosmology

Lauris Baum·Paul H. Frampton
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Abstract

Following up a recent proposal \cite{BF} for a cyclic model based on phantom dark energy, we examine the content of the contracting universe (cu) and its entropy $S_{cu}$. We find that beyond dark energy the universe contains on average zero or at most a single photon which if present immediately after turnaround has infinitesimally energy which subsequently blue shifts to produce $e^+e^-$ pairs. These statements are independent of the equation of state $ω= p/ρ$ of dark energy provided $ω< -1$. Thus $S_{cu} = 0$ and if observations confirm $ω< -1$ the entropy problem is solved. We discuss the absence of a theoretical lower bound on $ϕ= |ω+ 1|$, then describe an anthropic fine tuning argument that renders unlikely extremely small $ϕ$. The present bound $ϕ\lesssim 0.1$ already implies a time until turnaround of $(t_T - t_0) \gtrsim 100$ Gy.

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Lauris Baum, Paul H. Frampton. 2007-03-18. Entropy of Contracting Universe in Cyclic Cosmology. https://doi.org/10.1142/s0217732308026170

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