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arXiv · 2006.03581

Mapping Poincar\'{e} gauge cosmology to Horndeski theory for emergent dark energy

W. E. V. Barker·A. N. Lasenby·M. P. Hobson·W. J. Handley
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Abstract

The ten-parameter, quadratic Poincar\'e gauge theory of gravity is a plausible alternative to general relativity. We show that the rich background cosmology of the gauge theory is described by a non-canonical bi-scalar-tensor theory in the Jordan frame: the `metrical analogue'. This provides a unified framework for future investigation by the broader community. For many parameter choices, the non-canonical term reduces to a Cuscuton field of the form $\smash{\sqrt{|X^{\phi\phi}|}}$. The Einstein-Cartan-Kibble-Sciama theory maps to a pure quadratic Cuscuton, whereas the teleparallel theory maps to the Einstein-Hilbert Lagrangian. We apply the metrical analogue to novel unitary and power-counting-renormalisable cases of Poincar\'e gauge theory. These theories support the concordance $\Lambda$CDM background cosmology up to an optional, effective dark radiation component, we explain this behaviour in terms of a stalled Cuscuton. We also obtain two dark energy solutions from one of these cases: accelerated expansion from a negative bare cosmological constant whose magnitude is screened, and emergent dark energy to replace vanishing bare cosmological constant in $\Lambda$CDM.

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W. E. V. Barker, A. N. Lasenby, M. P. Hobson, W. J. Handley. 2020-06-05. Mapping Poincar\'{e} gauge cosmology to Horndeski theory for emergent dark energy. https://doi.org/10.1103/physrevd.102.084002

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