Algorithms for Dynamical Fermions

This is the write-up of three lectures on algorithms for dynamical fermions that were given at the ILFTN workshop ‘Perspectives in Lattice QCD’ in Nara during November 2005. The first lecture is on the fundamentals of Markov Chain Monte Carlo methods and introduces the Hybrid Monte Carlo (HMC) algorithm and symplectic integrators; the second lecture covers topics in approximation theory and thereby introduces the Rational Hybrid Monte Carlo (RHMC) algorithm and ways of evading integrator instabilities by means of multiple pseudofermion fields; the third lecture introduces on-shell chiral (Ginsparg–Wilson) lattice fermions and discusses five-dimensional formulations for computing fermion propagators for such fermions.