Dilaton

The dilaton is a hypothetical particle of the scalar field. It appears in theories with extra dimensions when the volume of the compactified dimensions varies. 

The dilaton made its first appearance in Kaluza-Klein theory. It also appears in string theory. Roman Jackiw proposed Jackiw-Teitelboim gravity, a model that includes one dimension of space and one of time that included a dilaton field. This model is used to describe some near extremal black holes.