  There is a major mismatch between the charged pion yields in Au+Au collisions
at low energies calculated by various transport models and the experimental
measured values from the Hades collaboration. In this work, reasonable
improvements on the equation of state, in-medium modification of cross
sections, and the influence of the nuclear potential for Delta resonances will
be investigated in the framework of the GiBUU transport model. As a result, we
demonstrate that theoretical calculations can indeed describe the charged pion
yields measured by Hades for Au+Au collisions rather well, but that a mismatch
then remains between calculations and data for the yields of neutral pions
extracted from dileptons within the same experiment.
