You cannot press out the black hole

Abstract

It is shown that a ball-shaped black hole region homeomorphic with D n cannot be pressed out, along whichever axis penetrating the black hole region, into a black ring with a doughnutshaped black hole region homeomorphic with S 1 × D n-1. A more general prohibition law for the change of the topology of black holes, including a version of no-bifurcation theorems for black holes, is given.