Bouncing unitary cosmology I. Mini-superspace general solution

Sean Gryb, Karim Thebault

Research output: Contribution to journalArticle (Academic Journal)peer-review

13 Citations (Scopus)
101 Downloads (Pure)


We offer a new proposal for cosmic singularity resolution based upon a quantum cosmology with a unitary bounce. This proposal is illustrated via a novel quantization of a mini-superspace model in which there can be superpositions of the cosmological constant. This possibility leads to a finite, bouncing unitary cosmology. Whereas the usual Wheeler-DeWitt cosmology generically displays pathological behaviour in terms of non-finite expectation values and non-unitary dynamics, the finiteness and unitarity of our model are formally guaranteed. For classically singular models with a massless scalar field and cosmological constant, we show that well-behaved quantum observables can be constructed and generic solutions to the universal Schrödinger equation are singularity-free. Generic solutions of our model displays novel features including: (i) superpositions of values of the cosmological constant; (ii) universal effective physics due to non-trivial self-adjoint extensions of the Hamiltonian; and (iii) bound 'Efimov universe' states for negative cosmological constant. The last feature provides a new platform for quantum simulation of the early universe. A companion paper provides detailed interpretation and analysis of particular cosmological solutions that display a cosmic bounce due to quantum gravitational effects, a well-defined FLRW limit far from the bounce, and a semi-classical turnaround point in the dynamics of the scalar field which resembles an effective inflationary epoch.

Original languageEnglish
Article number035009
Number of pages21
JournalClassical and Quantum Gravity
Issue number3
Early online date18 Jan 2019
Publication statusPublished - 18 Jan 2019

Structured keywords

  • Centre for Science and Philosophy


  • bouncing cosmology
  • cosmological constant
  • problem of time
  • quantum cosmology
  • singularity resolution


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