Locality properties of Neuberger's lattice Dirac operator

The gauge covariant lattice Dirac operator D which has recently been propos ed by Neuberger satisfies the Ginsparg-Wilson relation and thus preserves c hiral symmetry. The operator also avoids a doubling of fermion species, but its locality properties are not obvious. We now prove that D is local (wit h exponentially decaying tails) if the gauge field is sufficiently smooth a t the scale of the cutoff. Further analytic and numerical studies moreover suggest that the locality of the operator is in fact guaranteed under far m ore general conditions. (C) 1999 Elsevier Science B.V. All rights reserved.