ar X iv : h ep - l at / 0 20 90 41 v 2 1 5 Se p 20 02 Composite reweighting with Imaginary Chemical Potentials in SU ( 3 )

We review the overlap pathology of the Glasgow reweighting method for finite density QCD, and discuss the sampling bias that effects the determination of the ensemble-averaged fugacity polynomial expansion coefficients that form the Grand Canonical Partition function. The expectation of the difference in free energies between canonical partition functions generated with different measures is presented as an indicator of a systematic quark number dependent biasing in the reweighting approach. The advantages of building up an unbiased polynomial expansion for the Grand Canonical Partition function through a series of parallel ensembles generated by reweighting with imaginary chemical potentials are then contrasted with those of addressing the overlap pathology through a secondary reweighting.