When black holes meet Kaluza-Klein bubbles

We explore the physical consequences of a recently discovered class of exact solutions to the five dimensional Kaluza-Klein theory. We find a number of surprising features including the following: (1) In the presence of a Kaluza-Klein bubble, there are arbitrarily large black holes with topology S³. (2) In the presence of a black hole or a black string, there are expanding bubbles (with de Sitter geometry) which never reach null infinity. (3) A bubble can hold two black holes of arbitrary size in static equilibrium. In particular, two large black holes can be close together without merging to form a single black hole.