Graviballs and Dark Matter
  We investigate the possible existence of graviballs, a system of bound
gravitons, and show that two gravitons can be bound together by their
gravitational interaction. This idea connects to black hole formation by a
high-energy $2\to N$ scattering and to the gravitational geon studied by Brill
and Hartle. Our calculations rely on the formalism and techniques of quantum
field theory, specifically on low-energy quantum gravity. By solving
numerically the relativistic equations of motion, we have access to the
space-time dynamics of the (2-gravitons) graviball formation. We argue that the
graviball is a viable dark matter candidate and we compute the associated
gravitational lensing.
