Dimensional Dependence of Black Hole Formation in Self-Similar Collapse of Scalar Field

We study classical and quantum self-similar collapses of a massless scalar field in higher dimensions, and examine how the increase in the number of dimensions affects gravitational collapse and black hole formation. Higher dimensions seem to favor formation of black hole rather than other final states, in that the initial data space for black hole formation enlarges as dimension increases. On the other hand, the quantum gravity effect on the collapse lessens as dimension increases. We also discuss the gravitational collapse in a brane world with large but compact extra dimensions.