Bergelson's Theorem for weakly mixing C*-dynamical systems
  We study a nonconventional ergodic average for asymptotically abelian weakly mixing C*-dynamical systems, related to a second iteration of Khintchine's recurrence theorem obtained by Bergelson in the measure theoretic case. A noncommutative recurrence theorem for such systems is obtained as a corollary. 
Rocco Duvenhage