2023/05/21 by Marco Piva, Piva, Marco · 1 citation
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Physics - Theory (hep-th) #Noncommutative and Quantum Gravity Theories
paper · pdf · doi:10.48550/arxiv.2305.12549
openalex publication_date 2023/05/21 · openalex created_date 2023/05/24 · openalex updated_date 2026/07/28
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.