Third generation seesaw mixing with new vectorlike weak-doublet quarks

We present a class of models with a third generation seesaw mixing with new vectorlike weak-doublet quarks. We analyze a low-energy phenomenology and present several strong dynamics, high-energy realizations of these models. In the top-color-type scenario, named top-bottom color, we obtain an effective, composite two Higgs doublet model where the third generation isospin splitting is introduced via tilting interactions related to the broken non-Abelian gauge groups [i.e., without strong, triviality-sensitive U(1) groups]. In addition, we discuss tt̅ production at the Next Linear Collider and suggest how one can experimentally observe and distinguish between the weak-doublet and the weak-singlet types of seesaw mixing.