  This extended abstract briefly summarizes ongoing research activity on the
evaluation and experimental validation of physics methods for photon and
electron transport. The analysis includes physics models currently implemented
in Geant4 as well as modeling methods used in other Monte Carlo codes, or not
yet considered in general purpose Monte Carlo simulation systems. The
validation of simulation models is performed with the support of rigorous
statistical methods, which involve goodness-of-fit tests followed by
categorical analysis. All results are quantitative, and are fully documented.
