On rational injectivity of Kasparovs assembly map in dimension <=2
  The author presents a new proof of injectivity of the composition of the inverse of the rational Chern Character in homology applied to the classifying space BG of a (countable) discrete group G, restricted to dimensions less or equal than two, with the rationalized Assembly map of Kasparov into the (operator) K-Theory of the full group C^*-algebra C^*(G) (tensored with the rational numbers). 
Ulrich Haag
math.KT