Turnaround radius in modified gravity

Understand

In an accelerating universe in General Relativity there is a maximum radius above which a shell of test particles cannot collapse, but is dispersed by the cosmic expansion.

• This radius could be used in conjunction with observations of large structures to constrain the equation of state of the universe.
• We extend the concept of turnaround radius to modified theories of gravity for which the gravitational slip is non-vanishing.