Empirical validation of general relativity III: Gravity and cosmology
Why is gravity so important in cosmology?
Newtonian vs GR cosmology
Cosmological observable sensitive to the nature of gravity
Lensing
In GR
\[\text{d}s^2 \simeq -(1+\psi)\text{d}t^2 + a^2(t)(1-2\phi)\text{d}\vec{l}^2\] \[\psi = \phi\] \[- \int \text{d}s \vec{\nabla}_{\perp}(\psi + \phi)\] \[\delta \alpha = \frac{2 GM}{r}\]In modified gravity:
\[\psi \neq \phi\]