A research and development (R&D) project related to the extension of the
Geant4 toolkit has been recently launched to address fundamental methods in
radiation transport simulation. The project focuses on simulation at different
scales in the same experimental environment; this problem requires new methods
across the current boundaries of condensed-random-walk and discrete transport
schemes. The new developments have been motivated by experimental requirements
in various domains, including nanodosimetry, astronomy and detector
developments for high energy physics applications.Comment: To be published in the Proceedings of the CHEP (Computing in High
Energy Physics) 2009 conferenc