Higher-derivative quantum gravity with purely virtual particles: renormalizability and unitarity
Marco Piva
Abstract
Abstract We review the formulation of quantum field theories with purely virtual particles, a new type of degrees of freedom that can mediate interactions without ever appear as external on-shell states. This property allows to solve the problem of ghosts in higher-derivative quantum gravity, leading to a renormalizable and unitary theory. The main steps for the BRST quantization of gravity are recalled and renormalizability is discussed. Then, we introduce purely virtual particles in a general quantum field theory and show the derivation of the so-called spectral identities, which are a key ingredient to prove unitarity. Finally, phenomenological consequences and predictions in inflationary cosmology are presented.
Topics & Concepts
UnitarityQuantum gravityPhysicsTheoretical physicsGravitationQuantization (signal processing)Unitary stateQuantumQuantum field theoryQuantum cosmologyRenormalizationSpin foamClassical mechanicsMathematical physicsQuantum mechanicsLoop quantum gravityMathematicsPolitical scienceLawAlgorithmCosmology and Gravitation TheoriesBlack Holes and Theoretical PhysicsNoncommutative and Quantum Gravity Theories