Turtles all the way down: multiscale simulations connecting star and planet formation

The formation of stars and planets happens over multiple scales, which can interact. In particular, planet formation happens in the dense, complex environment of star forming regions. This thesis primarily explores the effects of high stellar density and presence of nearby massive stars (or a low density and absence of massive stars) on the evolution of protoplanetary disks, and their consequences for planet formation. Additionally, the dynamics of stellar feedback-driven shells is explored, and a novel operator splitting algorithm is introduced that allows for flexible coupling of a large number of physical models.