https://doi.org/10.1140/epjp/s13360-023-04486-0
Review
Higher-derivative quantum gravity with purely virtual particles: renormalizability and unitarity
Faculty of Physics, University of Warsaw, Pasteura 5, 02-093, Warsaw, Poland
Received:
2
June
2023
Accepted:
8
September
2023
Published online:
2
October
2023
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.
© The Author(s) 2023
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