The typical scalar field theory has a cosmological constant problem. We propose a generic mechanism by which this problem is avoided at tree level by embedding the theory into a larger theory. The metric and the scalar field coupling constants in the original theory do not need to be fine-tuned, while the extra scalar field parameters and the metric associated with the extended theory are fine-tuned dynamically. Hence, no fine-tuning of parameters in the full Lagrangian is needed for the vacuum energy in the new physical system to vanish at tree level. The cosmological constant problem can be solved if the method can be extended to quantum loops.
Buniy, Roman V., and Thomas W. Kephart. "Toward solving the cosmological constant problem by embedding." Physical Review D 86.2 (2012): 023501. doi: 10.1103/PhysRevD.86.023501
American Physical Society