Comparing theR algorithm and RHMC for staggered fermions

Abstract TheR algorithm is widely used for simulating two flavours of dynamical staggered fermions. We give a simple proof that the algorithm converges to the desired probability distribution to withinO(δπ2) errors, but show that the relevant expansion parameter is (δτ/m)2,m being the quark mass. The Rational Hybrid Monte Carlo (RHMC) algorithm provides an exact (i.e., has no step size errors) alternative for simulating the square root of the staggered Dirac operator. We propose using it to test the validity of theR algorithm for simulations carried out withδτ ≈ m.