Resummation of Cactus Diagrams in Lattice QCD
  We show how to perform a resummation, to all orders in perturbation theory, of a certain class of gauge invariant diagrams in Lattice QCD. These diagrams are often largely responsible for lattice artifacts. Our resummation leads to an improved perturbative expansion. Applied to a number of cases of interest, this expansion yields results remarkably close to corresponding nonperturbative estimates. 
H. Panagopoulos (1) and E. Vicari (2) ((1) Univ. of Cyprus (2) Univ.   of Pisa)