  We compute the two-loop heavy quark jet-function in the heavy quark limit.
This is one of the key ingredients in next-to-next-to-leading order (NNLO) and
next-to-next-to-leading-log order (NNLL) computations of the invariant mass
distribution of top-jets at a future e+e- collider. The shape of the top
invariant mass distribution is affected by large logs which we compute at NNLL
order. Exploiting the non-abelian exponentiation theorem, a definition of the
top jet-mass is given which is transitive and whose renormalization group
evolution is determined by the cusp-anomalous dimension to all orders in
perturbation theory. Relations of the jet-mass to the pole, MSbar, and 1S
masses are presented at two-loop order.
