9328 1806.03605 10.1007/JHEP11(2018)021 21 21 Quantum gravity, fakeons and microcausality Regular Article - Theoretical Physics 1 20 2018 11 6 2018 8 1 2018 10 28 2018 11 6 The Author(s) 2018 13130 2018 2018 11 11 Damiano Anselmi damiano.anselmi@unipi.it Marco Piva marco.piva@df.unipi.it 0000 0004 1757 3729 grid.5395.a Dipartimento di Fisica “Enrico Fermi” Università di Pisa Largo B. Pontecorvo 3 56127 Pisa Italy grid.470216.6 INFN, Sezione di Pisa Largo B. Pontecorvo 3 56127 Pisa Italy Abstract We investigate the properties of fakeons in quantum gravity at one loop. The theory is described by a graviton multiplet, which contains the fluctuation h μν of the metric, a massive scalar ϕ and the spin-2 fakeon χ μν . The fields ϕ and χ μν are introduced explicitly at the level of the Lagrangian by means of standard procedures. We consider two options, where ϕ is quantized as a physical particle or a fakeon, and compute the absorptive part of the self-energy of the graviton multiplet. The width of χ μν , which is negative, shows that the theory predicts the violation of causality at energies larger than the fakeon mass. We address this issue and compare the results with those of the Stelle theory, where χ μν is a ghost instead of a fakeon. Keywords Beyond Standard Model Models of Quantum Gravity Renormalization Regularization and Renormalons ArXiv ePrint: 1806.03605