We address the cosmological constant problem in the context of two-dimensional dilaton-Maxwell gravity, coupled to an arbitrary number of scalar matter fields. We are able to quantize the model non-perturbatively; we determine that the realization of the classical symmetries at the quantum level provides a mechanism that fixes the value of the cosmological constant.
Zonetti, S., & Govaerts, J. (2013). Two-dimensional quantum dilaton gravity and the quantum cosmological constant. Journal of Physics Conference Series, 410(1), 12134. https://doi.org/10.1088/1742-6596/410/1/012134 (Original work published 2013)