Evidence for a Phase Transition in 2D Causal Set Quantum Gravity

Abstract: We present evidence for a phase transition in a theory of 2D causal set quantum gravity which contains a dimensionless non-locality parameter $\epsilon \in (0,1]$. The transition is between a continuum phase and a crystalline phase, characterised by a set of covariant observables. For a fixed size of the causal set the transition temperature $\beta_c^{-1}$ decreases monotonotically with $\epsilon$. The line of phase transitions in the $\beta_c^2$ v/s $\epsilon$ plane asymptotes to the infinite temperature axis, suggesting that the continuum phase survives the analytic continuation.