Research output: Contribution to journal › Article

**Bouncing unitary cosmology I. Mini-superspace general solution.** / Gryb, Sean; Thebault, Karim.

Research output: Contribution to journal › Article

Gryb, S & Thebault, K 2019, 'Bouncing unitary cosmology I. Mini-superspace general solution', *Classical and Quantum Gravity*, vol. 36, no. 3, 035009. https://doi.org/10.1088/1361-6382/aaf823

Gryb, S., & Thebault, K. (2019). Bouncing unitary cosmology I. Mini-superspace general solution. *Classical and Quantum Gravity*, *36*(3), [035009]. https://doi.org/10.1088/1361-6382/aaf823

Gryb S, Thebault K. Bouncing unitary cosmology I. Mini-superspace general solution. Classical and Quantum Gravity. 2019 Jan 18;36(3). 035009. https://doi.org/10.1088/1361-6382/aaf823

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title = "Bouncing unitary cosmology I. Mini-superspace general solution",

abstract = "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 Schr{\"o}dinger 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.",

keywords = "bouncing cosmology, cosmological constant, problem of time, quantum cosmology, singularity resolution",

author = "Sean Gryb and Karim Thebault",

year = "2019",

month = "1",

day = "18",

doi = "10.1088/1361-6382/aaf823",

language = "English",

volume = "36",

journal = "Classical and Quantum Gravity",

issn = "0264-9381",

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number = "3",

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AU - Gryb, Sean

AU - Thebault, Karim

PY - 2019/1/18

Y1 - 2019/1/18

N2 - 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.

AB - 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.

KW - bouncing cosmology

KW - cosmological constant

KW - problem of time

KW - quantum cosmology

KW - singularity resolution

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