Critical collapse for the Starobinsky R2 model

A bstract We study gravitational collapse for the Starobinsky R 2 model, a particular example of an f ( r ) theory, in spherically symmetric spacetime. add massless scalar field as matter content to work Einstein frame, where additional arises due conformal transformation. As general relativity, depending on initial data, we found that gravity and physical can collapse, forming black hole, which final solution is Schwarzschild metric. threshold hole formation through fine-tuning method studied critical near this regime.