Quantum metrics on crossed products with groups of polynomial growth

Abstract: We show how to equip the crossed product between a group of polynomial growth and a compact quantum metric space with a compact quantum metric space structure. When the quantum metric on the base space arises from a spectral triple, which is compatible with the action of the group, we furthermore show that the crossed product becomes a spectral metric space. Lastly, we analyse the spectral triple at the crossed product level from the point of view of unbounded $KK$-theory and show that it arises as an internal Kasparov product of unbounded Kasparov modules.