Entropy, black holes, and the new cyclic universe

Anna Ijjas, Paul J. Steinhardt

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We track the evolution of entropy and black holes in a cyclic universe that undergoes repeated intervals of expansion followed by slow contraction and a smooth (non-singular) bounce. In this kind of cyclic scenario, there is no big crunch and no chaotic mixmaster behavior. We explain why the entropy following each bounce is naturally partitioned into near-maximal entropy in the matter-radiation sector and near-minimal in the gravitational sector, satisfying the Weyl curvature conditions conjectured to be essential for a cosmology consistent with observations. As a result, this kind of cyclic universe can undergo an unbounded number of cycles in the past and/or the future.

Original languageEnglish (US)
Article number136823
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - Jan 10 2022

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


  • Black hole
  • Bouncing cosmology
  • Cosmological bounce
  • Cyclic universe
  • Slow contraction


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