Flat space cosmologies in two dimensions - Phase transitions and   asymptotic mass-domination
  We study flat space cosmologies in two dimensions by taking the flat space limit of the Achucarro-Ortiz model. We unravel a phase transition between hot flat space and flat space cosmologies, and derive a new dilaton-dependent counterterm required for the consistency of the Euclidean partition function. Our results generalize to asymptotically mass-dominated 2-dimensional dilaton gravity models, whose thermodynamical properties we discuss. The novel case of asymptotic mass-domination is neither covered by the comprehensive discussion of hep-th/0703230 nor by the more recent generalization to dilaton gravity with confining U(1) charges in 1406.7007. 
Arjun Bagchi, Daniel Grumiller, Jakob Salzer, Sourav Sarkar and   Friedrich Sch\"oller
hep-th gr-qc