Regular Black Hole from gravitational collapse of dust and radiation

A black hole is the end state of the gravitational collapse of massive stars. However, a typical black hole contains a singularity and to avoid singularity formation we have to violate a strong energy condition that states that gravity must attract. The nature of the matter that prevents the singularity formation is still unknown. In this paper, we offer a simple model of gravitational collapse of dust and radiation. In the simplest case, such a model leads to a singular black hole. However, if we assume an energy exchange between dust and radiation, which increases towards the center of the collapsing cloud, then it becomes possible to construct a model of a regular black hole. We identify the conditions under which a regular center is possible and also give an explicit example of how such an interaction leads to a regular center.