Topological susceptibility from the overlap

The chiral symmetry at finite lattice spacing of Ginsparg-Wilson fermionicactions constrains the renormalization of the lattice operators; in particular,the topological susceptibility does not require any renormalization, when usinga fermionic estimator to define the topological charge. Therefore, the overlapformalism appears as an appealing candidate to study the continuum limit of thetopological susceptibility while keeping the systematic errors undertheoretical control. We present results for the SU(3) pure gauge theory usingthe index of the overlap Dirac operator to study the topology of the gaugeconfigurations. The topological charge is obtained from the zero modes of theoverlap and using a new algorithm for the spectral flow analysis. A detailedcomparison with cooling techniques is presented. Particular care is taken inassessing the systematic errors. Relatively high statistics (500 to 1000independent configurations) yield an extrapolated continuum limit with errorsthat are comparable with other methods. Our current value from the overlap is$\chi^{1/4} = 188 \pm 12 \pm 5 \MeV$.Comment: 18 pages, 7 figure