Modified Gravity and the Radiation Dominated Epoch
arXiv:1210.2168 · doi:10.1103/PhysRevD.87.044004
Abstract
In this paper we consider scalar-tensor theories, allowing for both conformal and disformal couplings to a fluid with a generic equation of state. We derive the effective coupling for both background cosmology and for perturbations in that fluid. As an application we consider the scalar degree of freedom to be coupled to baryons and study the dynamics of the tightly coupled photon-baryon fluid in the early universe. We derive an expression for the effective speed of sound, which differs from its value in General Relativity. We apply our findings to the μ-distortion of the cosmic microwave background radiation, which depends on the effective sound-speed of the photon-baryon fluid, and show that the predictions differ from General Relativity. Thus, the μ-distortion provides further information about gravity in the very early universe well before decoupling.
10 pages, 7 figures
References in corpus (2)
Cited by in corpus (26)
- Transforming gravity: from derivative couplings to matter to second-order scalar-tensor theories beyond the Horndeski Lagrangian
- Disformal invariance of second order tensor-scalar theories: framing the Horndeski action
- DBI Galileons in the Einstein Frame: Local Gravity and Cosmology
- Effective Theory of Interacting Dark Energy
- Finite-time Cosmological Singularities and the Possible Fate of the Universe
- Disformal couplings and the dark sector of the universe
- Disformal Theories of Gravity: From the Solar System to Cosmology
- Effective Theory of Dark Energy at Redshift Survey Scales
- Disformal Gravity Theories: A Jordan Frame Analysis
- Constraints on Disformal Couplings from the Properties of the Cosmic Microwave Background Radiation
- Disformal transformation of cosmological perturbations
- Towards Viable Cosmological Models of Disformal Theories of Gravity
- Dark D-brane Cosmology
- Probing the imprints of generalized interacting dark energy on the growth of perturbations
- Solar System Constraints on Disformal Gravity Theories
- Spin-orbit effects for compact binaries in scalar-tensor gravity
- Scalar Fields Near Compact Objects: Resummation versus UV Completion
- Early Modified Gravity: Implications for Cosmology
- Disformally Coupled Quintessence
- Matters on a moving brane
- Non-Gaussianity in multi-sound-speed disformally coupled inflation
- Novel Screening with Two Bodies: Summing the ladder in disformal scalar-tensor theories
- Spin precession as a new window into disformal scalar fields
- More about scalar gravity
- Potential-driven Inflation with Disformal Coupling to Gravity
- Constraining disformal couplings with Redshift Space Distortion