Ginsparg-Wilson operators and a no-go theorem
  If one uses a general class of Ginsparg-Wilson operators, it is known that CP symmetry is spoiled in chiral gauge theory for a finite lattice spacing and the Majorana fermion is not defined in the presence of chiral symmetric Yukawa couplings. We summarize these properties in the form of a theorem for the general Ginsparg-Wilson relation. 
Kazuo Fujikawa, Masato Ishibashi, Hiroshi Suzuki