Lee-Wick models and quantum gravity
4-3-006 - TH Conference Room
In general, higher-derivative theories are plagued by nonlocal divergences when they are defined directly in Minkowski spacetime. Wick rotating their Euclidean versions presents novel features and provides a new formulation of the Lee-Wick models, overcoming the need of external ad hoc prescriptions. Only the physical degrees of freedom propagate through the cuts of the cutting equations, which makes the S matrix perturbatively unitary. I discuss the main unitary and renormalizable models of quantum gravity that emerge from this approach. The Lee-Wick-inspired ones, which are superrenormalizable, are infinitely many. However, a new quantization prescription, which turns physical and/or ghost degrees of freedom into fake degrees of freedom by turning them into Lee-Wick pairs, is able to make sense of the unique theory of higher-derivative gravity that has a dimensionless gauge coupling.