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arXiv · 1204.6329

Coincidence Problem in Cyclic Phantom Models of the Universe

Hui-Yiing Chang·Robert J. Scherrer
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Abstract

We examine cyclic phantom models for the universe, in which the universe is dominated sequentially by radiation, matter, and a phantom dark energy field, followed by a standard inflationary phase. Since this cycle repeats endlessly, the Universe spends a substantial portion of its lifetime in a state for which the matter and dark energy densities have comparable magnitudes, thus ameliorating the coincidence problem. We calculate the fraction of time that the universe spends in such a coincidental state and find that it is nearly the same as in the case of a phantom model with a future big rip. In the limit where the dark energy equation of state parameter, w, is close to -1, we show that the fraction of time, f, for which the ratio of the dark energy density to the matter density lies between r_1 and r_2, is f = -(1+w) ln [(\sqrt{r_2} + \sqrt{1+r_2})/(\sqrt{r_1} + \sqrt{1+r_1})].

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Hui-Yiing Chang, Robert J. Scherrer. 2012-07-17. Coincidence Problem in Cyclic Phantom Models of the Universe. https://doi.org/10.1103/physrevd.86.027303

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