Speaker
Description
In the context of perturbative quantum field theory, the addition of quadratic-curvature operators to the Einstein-Hilbert action makes it possible to achieve strict renormalizability in four dimensions. The additional terms are multiplied by dimensionless coefficients that are related to the masses of the extra gravitational degrees of freedom and to the interaction couplings. In this talk, we will study the limits in which those parameters tend to infinity and show that different types of decouplings can occur. Remarkably, these limits are found to be sensitive to a non-zero cosmological constant. In particular, we will show that the helicity-0 of the spin-2 massive ghost is the only one that survives when the coefficient of the Weyl-squared term tends to infinity in the presence of a cosmological constant, while other helicities decouple. We will discuss physical implications of our analysis in relation to the high-energy limit and the role of the cosmological constant in quantum gravity.
