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  Spinor driven cosmic bounces and their cosmological perturbations

Farnsworth, S., Lehners, J.-L., & Qiu, T. (2017). Spinor driven cosmic bounces and their cosmological perturbations. Physical Review D, 96: 083530. doi:10.1103/PhysRevD.96.083530.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0000-637E-4 Version Permalink: http://hdl.handle.net/21.11116/0000-0002-EA11-3
Genre: Journal Article

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 Creators:
Farnsworth, Shane1, Author              
Lehners, Jean-Luc2, Author              
Qiu, Taotao, Author
Affiliations:
1Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society, ou_24014              
2String Cosmology, AEI-Golm, MPI for Gravitational Physics, Max Planck Society, ou_1753351              

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Free keywords: General Relativity and Quantum Cosmology, gr-qc,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO,High Energy Physics - Theory, hep-th
 Abstract: When coupling fermions to gravity, torsion is naturally induced. We consider the possibility that fermion bilinears can act as a source for torsion, altering the dynamics of the early universe such that the big bang gets replaced with a classical non-singular bounce. We extend previous studies in several ways: we allow more general fermion couplings, consider both commuting and anti-commuting spinors, and demonstrate that with an appropriate choice of potential one can easily obtain essentially arbitrary equations of state, including violations of the null energy condition, as required for a bounce. As an example, we construct a model of ekpyrotic contraction followed by a non-singular bounce into an expanding phase. We analyze cosmological fluctuations in these models, and show that the perturbations can be rewritten in real fluid form. We find indications that spinor bounces are stable, and exhibit several solutions for the perturbations. Interestingly, spinor models do not admit a scalar-vector-tensor decomposition, and consequently some types of scalar fluctuations can act as a source for gravitational waves already at linear order. We also find that the first order dynamics are directionally dependent, an effect which might lead to distinguished observational signatures.

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 Dates: 2017-09-102017
 Publication Status: Published in print
 Pages: 43 pages, 10 figures
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 Table of Contents: -
 Rev. Method: -
 Identifiers: arXiv: 1709.03171
DOI: 10.1103/PhysRevD.96.083530
URI: http://arxiv.org/abs/1709.03171
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Title: Physical Review D
  Other : Phys. Rev. D.
Source Genre: Journal
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Publ. Info: Lancaster, Pa. : American Physical Society
Pages: - Volume / Issue: 96 Sequence Number: 083530 Start / End Page: - Identifier: ISSN: 0556-2821
CoNE: /journals/resource/111088197762258