Comparison of measured and calculated dynamic aperture

Dynamic aperture experiments at the Fermilab Main Ring, the Tevatron, the SPS and HERA are reviewed and compared with simulations. The agreement between experiments with additional strong nonlinearities and corresponding simulations is fairly good, if the relevant parameters are sufficiently well known and included in the model. Direct comparison is more problematic if machines under normal operating conditions with relatively weak non-linear fields are considered. Nevertheless, the agreement is reasonable and discrepancies can be accounted for by known imperfections of the model