Dynamical Rearrangement of Theta Parameter in Presence of Mixed   Chern-Simons Term
  We study the five-dimensional SU(3)_c x U(1)_C gauge theory on the orbifold S^1/Z_2 with a mixed Chern-Simons term. We particularly pay attention to the realization of the dynamical rearrangement of the theta parameter for SU(3)_c. It is shown that the physics remains invariant under a large gauge transformation which even changes the action, completely removing the theta parameter, because of the Hosotani mechanism for the U(1)_C gauge interactions. In other words, we show that the theta parameter can be regarded as a boundary condition for the orbifolding in light of the dynamical rearrangement. 
Naoyuki Haba, Yoshiharu Kawamura, and Kin-ya Oda