Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 11, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1475-7516/2020/11/032
Keywords
dark energy theory; modified gravity
Funding
- JSPS [19K03854, 17K14297]
- MEXT KAKENHI [15H05890]
- Grants-in-Aid for Scientific Research [19K03854] Funding Source: KAKEN
Ask authors/readers for more resources
For a scalar field phi coupled to cold dark matter (CDM), we provide a general framework for studying the background and perturbation dynamics on the isotropic cosmological background. The dark energy sector is described by a Horndeski Lagrangian with the speed of gravitational waves equivalent to that of light, whereas CDM is dealt as a perfect fluid characterized by the number density n(c) and four-velocity u(c)(mu). For a very general interacting Lagrangian f (n(c), phi, X, Z), where f depends on n(c), phi, X = -partial derivative(mu)phi partial derivative(mu)phi/2, and Z = u(c)(mu)partial derivative(mu)phi, we derive the full linear perturbation equations of motion without fixing any gauge conditions. To realize a vanishing CDM sound speed for the successful structure formation, the interacting function needs to be of the form f = -f(1)(phi, X, Z)n(c) + f(2)(phi, X, Z). Employing a quasi-static approximation for the modes deep inside the sound horizon, we obtain analytic formulas for the effective gravitational couplings of CDM and baryon density perturbations as well as gravitational and weak lensing potentials. We apply our general formulas to several interacting theories and show that, in many cases, the CDM gravitational coupling around the quasi de-Sitter background can be smaller than the Newton constant G due to a momentum transfer induced by the Z-dependence in f(2).
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available