Track propagation for different detector and magnetic field setups in Acts

Track finding and fitting are amongst the most complex part of event reconstruction in high-energy physics, and dominates usually the computing time in high luminosity environment. A central part of track reconstruction is the transport of a given track parameterisation (i.e. the parameter estimation and associated covariances) through the detector, respecting the magnetic field setup and the traversed detector material. While a track propagation in a sparse environment (e.g. a tracking detector) can be sufficiently good approximated by considering discrete interactions at several positions, the propagation in a material dense environment (e.g. calorimeters) is better served by a continuous application of material effects. Recently, a common Tracking software project (Acts) born initially from the Common Tracking code of the ATLAS experiment has been developed in order to preserve the algorithmic concepts from the LHC start-up era and prepare them for the high luminosity era of the LHC and beyond. The software is designed in an abstract, detector independent way and prepared to allow highly parallelised execution of all involved software modules, including magnetic field access and alignment conditions. Therefore the propagation algorithm needs to be as flexible and adjustable which will be the main focus of this talk. The implemented solution for using a fourth order Runge-Kutta-Nyström integration and its extension with continuous material integration and eventual time propagation is presented, such as the navigation through different geometry setups involving different environments are shown.