Topological charge renormalization: A test case for 3-loop vacuum   calculations using overlap fermions and Symanzik improved gluons
  We calculate perturbative renormalization properties of the topological charge, using the standard lattice discretization given by a product of twisted plaquettes. We use the overlap and clover action for fermions, and the Symanzik improved gluon action for 4- and 6-link loops.   We compute the multiplicative renormalization of the topological charge density to one loop; this involves only the gluon part of the action. The power divergent additive renormalization of the topological susceptibility is calculated to 3 loops. 
A. Skouroupathis and H. Panagopoulos (Department of Physics,   University of Cyprus, Nicosia)