Cosmological constant in spinfoam cosmology
  We consider a simple modification of the amplitude defining the dynamics of loop quantum gravity, corresponding to the introduction of the cosmological constant, and possibly related to the SL(2,C)q extension of the theory recently considered by Fairbairn-Meusburger and Han. We show that in the context of spinfoam cosmology, this modification yields the de Sitter cosmological solution. 
Eugenio Bianchi, Thomas Krajewski, Carlo Rovelli, Francesca Vidotto
gr-qc