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Halo modelling in chameleon theories

Lombriser, L.; Koyama, K.; Li, B.

Authors

L. Lombriser

K. Koyama



Abstract

We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations.

Journal Article Type Article
Publication Date Mar 13, 2014
Deposit Date Jan 13, 2014
Publicly Available Date May 8, 2014
Journal Journal of Cosmology and Astroparticle Physics
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 2014
Issue 03
Article Number 021
DOI https://doi.org/10.1088/1475-7516/2014/03/021
Keywords Modified gravity, Power spectrum.
Public URL https://durham-repository.worktribe.com/output/1473149

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