Relative ultragraph algebras and infinite interval maps

In this paper, we introduce the notion of relative ultragraph algebras and extend classical injectivity criteria for representations, particularly those arising from branching systems,to this relative setting. This new concept is closely connected to, and indeed motivated by, the dynamics of certain interval maps that we call infinite Markov maps. The central point is that these algebras provide the natural framework in which representations induced by such maps are defined.