We apply our previous work on cluster characters for Hom-infinite cluster
categories to the theory of cluster algebras. We give a new proof of
Conjectures 5.4, 6.13, 7.2, 7.10 and 7.12 of Fomin and Zelevinsky's Cluster
algebras IV for skew-symmetric cluster algebras. We also construct an explicit
bijection sending certain objects of the cluster category to the decorated
representations of Derksen, Weyman and Zelevinsky, and show that it is
compatible with mutations in both settings.
We prove the existence of cluster characters for Hom-infinite cluster
categories. For this purpose, we introduce a suitable mutation-invariant
subcategory of the cluster category. We sketch how to apply our results in
order to categorify any skew-symmetric cluster algebra. More applications and a
comparison to Derksen-Weyman-Zelevinsky's results will be given in a future
paper.