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Does BICEP2's observation rules out ekpyrotic cosmological model ?

  1. Apr 4, 2014 #1
    Dear every specialists, I heard that BICEP2's observation r=A_t/A_s=0.2 n_t=0 indicate two things:

    1) n_t=0 excludes ekpyrotic cosmological model (ECM) definitely because ECM predicts n_t=2

    2) r=0.2 excludes almost all current string inflation model (SIM) such as KKLMMT because this observation requires inflaton field vary at leasts 10Mp while SIM do not allows such big range varyings

    Who can tell me more about this two point of view
  2. jcsd
  3. Apr 4, 2014 #2


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    The Tilt of Primordial Gravitational Waves Spectra from BICEP2
    Cheng Cheng, Qing-Guo Huang
    (Submitted on 21 Mar 2014)
    In this paper we constrain the tilt of the spectra of primordial gravitational waves from Background Imaging of Cosmic Extragalactic Polarization (BICEP2) data only. We find r=0.21+0.04−0.10 and nt=−0.06+0.25−0.23 (at 68% C.L.) which implies that a scale-invariant primordial gravitational waves spectra is consistent with BICEP2 nicely. Our results provide strong evidence for supporting inflation model, and the alternative models, for example the ekpyrotic model which predicts n_t=2, are ruled out at more than 5σ significance.
    Comments: 3 pages, 1 figure

    This might also interest you, although it does not precisely address your two points:
    Last edited: Apr 4, 2014
  4. Apr 7, 2014 #3

    Turok commented on this here:
    “It would conclusively refute the ekpyrotic and cyclic models we proposed a decade ago. However, more recent bouncing universe models based on the Higgs field might still be viable.”
  5. Apr 8, 2014 #4


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    Jim Carrey on ekpyrotic Universe (start at about 3:00):
    Last edited by a moderator: Sep 25, 2014
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