  We explore the multi-black hole spacetimes from the perspective of the
ultra-high energy particle collisions. Such a discussion is limited to the
spacetimes containing a single black hole so far. We deal with the
Majumdar-Papapetrou solution representing a system consisting of two identical
black holes in the equilibrium. In order to identify the conditions suitable
for the process of high energy collisions, we consider particles confined to
move on the equatorial plane towards the axis of symmetry with the zero angular
momentum. We consider collision between the particles moving in opposite
directions at the location midway between the black holes on the axis. We show
that the center of mass energy of collision between the particles increases
with the decrease in the separation between the black holes and shows
divergence in the limit where the separation goes to zero. We estimate the size
of the region close to the central point on the equatorial plane where it would
be possible to have high energy collisions and show that this region has a
reasonably large spatial extent. We further explore the process of high energy
collisions with the general geodesics with arbitrary angular momentum on the
equatorial plane away from the central point. Although in this paper we deal
with theMajumdar-Papapetrou spacetime which serves as a toy example
representing multiple black holes, we speculate on the possibility that the
ultra-high energy collisions would also occur in the more general setting like
colliding black holes, when distance between the black holes is extremely
small, which can in principle be verified in the numerical relativity
simulations.
