  The use of APE smearing or other blocking techniques in fermion actions can
provide many advantages. There are many variants of these fat link actions in
lattice QCD currently, such as FLIC fermions. The FLIC fermion formalism makes
use of the APE blocking technique in combination with a projection of the
blocked links back into the special unitary group. This reunitarisation is
often performed using an iterative maximisation of a gauge invariant measure.
This technique is not differentiable with respect to the gauge field and thus
prevents the use of standard Hybrid Monte Carlo simulation algorithms. The use
of an alternative projection technique circumvents this difficulty and allows
the simulation of dynamical fat link fermions with standard HMC and its
variants.
