Topcolor-like dynamics and new matter generations
  We explore a scenarios where topcolor-like dynamics operates in the presence of fourth generation matter fields. Using the Minimal Walking Technicolor as a concrete basis for model building, we construct explicit models and confront them with phenomenology. We show that if a new QCD generations exist, both the top-bottom mass splitting as well as the splitting between bottom quark mass and the masses of the fourth generation quarks can be naturally explained within topcolor-like dynamics. On the other hand, the much studied Minimal Walking Technicolor model where only a fourth generation of leptons arise, also leads to a viable model. 
Hidenori S. Fukano and Kimmo Tuominen
hep-ph