Abstract to be announced. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Heger will be available for meetings by arrangement with his hosts, Friedrich Roepke (friedrich.roepke@h-its.org) and Andreas Sander (andreas.sander@uni-heidelberg.de)