Instability in the molecular dynamics step of a hybrid Monte Carlo algorithm in dynamical fermion lattice QCD simulations - art. no. 114501

We investigate instability and reversibility within hybrid Monte Carlo simu lations using a nonperturbatively improved Wilson action. We demonstrate th e onset of instability as tolerance parameters and molecular dynamics step sizes are varied. We compare these findings with theoretical expectations a nd present limits on simulation parameters within which a stable and revers ible algorithm is obtained for physically relevant simulations. Results of optimization experiments with respect to tolerance parameters are also pres ented.