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The COINCIDENCE PROBLEM in a PHANTOM CYCLIC MODEL of the UNIVERSE

The COINCIDENCE PROBLEM in a PHANTOM CYCLIC MODEL of the UNIVERSE. Hui-Yiing Chang. Outline. Composition of the universe and governing principles Phantom models Coincidence problem Phantom model with future singularity Phantom cyclic model Toy model Coincidental fraction

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The COINCIDENCE PROBLEM in a PHANTOM CYCLIC MODEL of the UNIVERSE

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  1. The COINCIDENCE PROBLEM in a PHANTOM CYCLIC MODEL of the UNIVERSE Hui-Yiing Chang

  2. Outline • Composition of the universe and governing principles • Phantom models • Coincidence problem • Phantom model with future singularity • Phantom cyclic model • Toy model • Coincidental fraction • Conclusion

  3. Equation of State • Energy density

  4. Composition of universe: • 30% non-relativistic matter • 70% dark energy • Equation of state for • is • evolves differently according to different models

  5. In phantom models, for , • Therefore, at epochs much earlier than the present, • while at epochs much later than the present, where according to current observations.

  6. Period of Coincidence , where is accepted to be 10.

  7. Phantom Dark Energy Model with future singularity • Finite lifetime • Possible to calculate coincidental fraction f • For , • for • for • for (Scherrer) • Coincidence problem significantly ameliorated

  8. Ilie et al.’s Phantom Cyclic Model

  9. Toy model • tracks • decreases to • behaves like phantom fluid, enters inflationary phase • increases to

  10. Friedmann equation in terms of and components: Assume is constant.

  11. The time the universe takes to complete one cycle: • The time the universe takes to expand from to :

  12. In each cycle, the fraction of time that the universe spends in a coincidental state: , which is also that of entire universe’s lifetime.

  13. This ameliorates the coincidence problem.

  14. Reference: Preprint: H.-Y. Chang and R.J. Scherrer, The Coincidence Problem in a Phantom Cyclic Model of the Universe. R.J. Scherrer, Phantom Dark Energy, Cosmic Doomsday, and the Coincidence Problem, Phys. Rev. D 71, 063519 (2005). C. Ilie, T. Biswas and K. Freese, Are we seeing the beginnings of inflation?, Phys. Rev. D 80, 103521 (2009).

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