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Article
Report number	arXiv:2306.13714 ; CERN-TH-2023-116 ; LMU-ASC 21/23 ; MPP-2023-134
Title	On the Ghost Problem of Conformal Gravity
Author(s)	Hell, Anamaria (Munich U., ASC) ; Lust, Dieter (Munich U., ASC ; Munich, Max Planck Inst.) ; Zoupanos, George (CERN ; Heidelberg U.)
Publication	2023-08-24
Imprint	2023-06-23
Number of pages	24
Note	24 pages
In:	JHEP 2308 (2023) 168
DOI	10.1007/JHEP08(2023)168
Subject category	gr-qc ; General Relativity and Cosmology ; hep-th ; Particle Physics - Theory
Abstract	We study the metric perturbations around the de Sitter and Minkowski backgrounds in Conformal Gravity. We confirm the presence of ghosts in both cases. In the de Sitter case, by applying the Maldacena boundary conditions - the Neumann boundary condition and the positive-frequency mode condition - to the metric, we show that one cannot recover a general solution for the perturbations. In turn, alongside the Neumann boundary condition, we derive an additional condition with which the perturbations of conformal gravity and dS perturbations of Einstein gravity with cosmological constant coincide. We further show that the Neumann boundary condition does not lead to a general solution in Minkowski space. Conversely, we derive the alternative boundary conditions, with which we attain an agreement between the perturbations of conformal and Einstein gravity in full generality, thus removing the ghost of conformal gravity.
Copyright/License	preprint: (License: arXiv nonexclusive-distrib 1.0) publication: © 2023-2025 The Authors (License: CC-BY-4.0), sponsored by SCOAP³

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