Determination of constant lattice spacing trajectories in lattice QCD
  We argue that lattice simulations of full QCD with varying quark mass are best conducted at fixed lattice spacing rather than at fixed $\beta$. We present techniques which enable this to be carried out effectively, namely the tuning in bare parameter space and efficient stochastic estimation of the fermion determinant. Results and tests of the method are presented. We discuss other applications of such techniques. 
Alan C. Irving (University of Liverpool), UKQCD Collaboration