The maximum sizes of large scale structures in alternative theories of gravity

Understand

The maximum size of a cosmic structure is given by the maximum turnaround radius -- the scale where the attraction due to its mass is balanced by the repulsion due to dark energy.

• We derive generic formulae for the estimation of the maximum turnaround radius in any theory of gravity obeying the Einstein equivalence principle, in two situations: on a spherically symmetric spacetime and on a perturbed Friedman-Robertson-Walker spacetime.
• We show that the two formulae agree.
• As an application of our formula, we calculate the maximum turnaround radius in the case of the Brans-Dicke theory of gravity.