MULTI-BLACK-HOLES IN 3D AND 4D ANTI-DE SITTER SPACETIMES

The (single) black hole solutions of Banados, Teitelboim and Zanelli ( BTZ) in 2+1 dimensional anti-de Sitter space are generalized to an arb itrary number n of such black holes. The resulting multi-black-hole (M BH) spacetime is locally isometric to anti-de Sitter space, and global ly it is obtained from the latter as a quotient space by means of suit able identifications. The MBH spacetime has n asymptotically anti-de S itter exterior regions, each of which has the geometry of a single BTZ black hole. These exterior regions are separated by n horizons from a common interior region. This interior region can be described as a '' closed'' universe containing n black holes. Similar configurations in 3+1 dimensions, with horizons of toroidal and higher genus topologies, are also presented.