Inroads into Ghost-free Euclidean and Lorentzian Quantum Gravity

Higher-curvature theories can improve gravity's high-energy behaviour but may introduce modes that conflict with unitarity. This seminar studies renormalization flows in Einstein cubic gravity and Lorentzian calculations of graviton spectral functions. It examines constraints from causality and gauge symmetry, and how coupled spectral representations can produce effective-action information compatible with those requirements.