Cusp singularities in f(R) gravity: pros and cons

Understand

We investigate cusp singularities in f(R) gravity, especially for Starobinsky and Hu-Sawicki dark energy models.

• We illustrate that, by using double-null numerical simulations, a cusp singularity can be triggered by gravitational collapses.
• This singularity can be cured by adding a quadratic term, but this causes a Ricci scalar bump that can be observed by an observer outside the event horizon.
• Comparing with cosmological parameters, it seems that it would be difficult to see super-Planckian effects by astrophysical experiments.