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

Abstract

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.

17 pages plus references; v2: conclusions unchanged; mainly involves new numerics avoiding obscure SciPy bug that occurred in v1, and updates Alcock-Paczynski methodology

References in corpus (21)

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• Cosmological Constraints from the SDSS Luminous Red Galaxies
• Beyond the Cosmological Standard Model
• Covariant Galileon
• Baryon Acoustic Oscillations in the Lyα forest of BOSS DR11 quasars
• Generalized Galileons: All scalar models whose curved background extensions maintain second-order field equations and stress tensors
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• Galileon Cosmology
• Galileon inflation
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• Linear perturbations in Galileon gravity models
• Effective Theory of Dark Energy at Redshift Survey Scales
• Fast and accurate mock catalogue generation for low-mass galaxies
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• Unscreening Modified Gravity in the Matter Power Spectrum
• Accuracy of the growth index in the presence of dark energy perturbations
• Unitarity and the Vainshtein Mechanism
• Initial conditions for cosmological N-body simulations of the scalar sector of theories of Newtonian, Relativistic and Modified Gravity
• Disformal transformations on the CMB
• Nonlinear stochastic growth rates and redshift space distortions

Cited by in corpus (14)

• Gravity in the Era of Equality: Towards solutions to the Hubble problem without fine-tuned initial conditions
• Effective Theory of Dark Energy at Redshift Survey Scales
• Galileon inflation evades the no-go for PBH formation in the single-field framework
• Void Lensing as a Test of Gravity
• Primordial non-Gaussianity from ultra slow-roll Galileon inflation
• The matter power spectrum in redshift space using effective field theory
• Scalar induced gravity waves from ultra slow-roll Galileon inflation
• Realisation of the ultra-slow roll phase in Galileon inflation and PBH overproduction
• Large fluctuations and Primordial Black Holes
• Positivity bounds from multiple vacua and their cosmological consequences
• Mass accretion rates of clusters of galaxies: CIRS and HeCS
• Initial conditions for cosmological N-body simulations of the scalar sector of theories of Newtonian, Relativistic and Modified Gravity
• The Shape Dependence of Vainshtein Screening in the Cosmic Matter Bispectrum
• Disformal transformations on the CMB