https://doi.org/10.1140/epjp/s13360-020-00875-x
Regular Article
Exorcising ghosts in quantum gravity
1
Center of Mathematics, Federal University of ABC, Santo André, Brazil
2
Dipartimento di Fisica e Astronomia, Università di Bologna, Via Irnerio 46, 40126, Bologna, Italy
3
I.N.F.N., Sezione di Bologna, IS - FLAG, Via B. Pichat 6/2, 40127, Bologna, Italy
Received:
20
August
2020
Accepted:
20
October
2020
Published online:
27
October
2020
We remark that Ostrogradsky ghosts in higher-derivative gravity, with a finite number of derivatives, are fictitious as they result from an unjustified truncation performed in a complete theory containing infinitely many curvature invariants. The apparent ghosts can then be projected out of the quadratic gravity spectrum by redefining the boundary conditions of the theory in terms of an integration contour that does not enclose the ghost poles. This procedure does not alter the renormalizability of the theory. One can thus use quadratic gravity as a quantum field theory of gravity that is both renormalizable and unitary.
© The Author(s) 2020
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
