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Beyond the growth rate of cosmic structure: Testing modified gravity models with an extra degree of freedom

Burrage, Clare; Parkinson, David; Seery, David

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Authors

David Parkinson

David Seery



Abstract

© 2017 American Physical Society. In "modified" gravity the observed acceleration of the universe is explained by changing the gravitational force law or the number of degrees of freedom in the gravitational sector. Both possibilities can be tested by measurements of cosmological structure formation. In this paper we elaborate the details of such tests using the Galileon model as a case study. We pay attention to the possibility that each new degree of freedom may have stochastically independent initial conditions, generating different types of potential well in the early universe and breaking complete correlation between density and velocity power spectra. This "stochastic bias" can confuse schemes to parametrize the predictions of modified gravity models, such as the use of the growth parameter f alone. Using data from the WiggleZ Dark Energy Survey we show that it will be possible to obtain constraints using information about the cosmological-scale force law embedded in the multipole power spectra of redshift-space distortions. As an example, we obtain an upper limit on the strength of the conformal coupling to matter in the cubic Galileon model, giving |1/M|200/MP. This allows the fifth-force to be stronger than gravity, but is consistent with zero coupling.

Citation

Burrage, C., Parkinson, D., & Seery, D. (2017). Beyond the growth rate of cosmic structure: Testing modified gravity models with an extra degree of freedom. Physical Review D, 96(4), Article 043509. https://doi.org/10.1103/PhysRevD.96.043509

Journal Article Type Article
Acceptance Date Mar 1, 2017
Online Publication Date Aug 11, 2017
Publication Date Aug 15, 2017
Deposit Date Oct 17, 2017
Publicly Available Date Oct 17, 2017
Journal Physical Review D
Print ISSN 2470-0010
Electronic ISSN 2470-0029
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 96
Issue 4
Article Number 043509
DOI https://doi.org/10.1103/PhysRevD.96.043509
Public URL https://nottingham-repository.worktribe.com/output/877929
Publisher URL https://journals.aps.org/prd/abstract/10.1103/PhysRevD.96.043509
Additional Information Burrage, Clare, Parkinson, David and Seery, David. Beyond the growth rate of cosmic structure: Testing modified gravity models with an extra degree of freedom
Phys. Rev. D 96, 043509.

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