Quasi-isotropic cycles and non-singular bounces in a Mixmaster cosmology

Chandrima Ganguly, Marco Bruni

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A Bianchi IX Mixmaster spacetime is the most general spatially homogeneous solution of Einstein's equations and it can represent the space-averaged Universe. We introduce two novel mechanisms resulting in a Mixmaster Universe with non-singular bounces which are quasi-isotropic. A fluid with a non-linear equation of state allows non-singular bounces. Using negative anisotropic stresses successfully isotropises this Universe and mitigates the well known Mixmaster chaotic behaviour. Thus the Universe can be an eternal Mixmaster, going through an infinite series of different cycles separated by bounces, with a sizable fraction of cycles isotropic enough to be well approximated by a standard Friedmann-Lema\^itre-Robertson-Walker model from the radiation era onward.
Original languageEnglish
Article number201301
Number of pages6
JournalPhysical Review Letters
Issue number20
Publication statusPublished - 12 Nov 2019


  • gr-qc
  • astro-ph.CO
  • RCUK
  • STFC
  • ST/N000668/1


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