TY  - JOUR
AU  - Beltran Jimenez, J.
AU  - Delhom, A.
PY  - 2020
DA  - 2020//
TI  - Instabilities in metric-affine theories of gravity with higher order curvature terms
T2  - Eur. Phys. J. C
JO  - European Physical Journal C
SP  - 585 - 27pp
VL  - 80
IS  - 6
PB  - Springer
AB  - We discuss the presence of ghostly instabilities for metric-affine theories constructed with higher order curvature terms. We mainly focus on theories containing only the Ricci tensor and show the crucial role played by the projective symmetry. The pathological modes arise from the absence of a pure kinetic term for the projective mode and the non-minimal coupling of a 2-form field contained in the connection, and which can be related to the antisymmetric part of the metric in non-symmetric gravity theories. The couplings to matter are considered at length and cannot be used to render the theories stable. We discuss different procedures to avoid the ghosts by adding additional constraints. We finally argue how these pathologies are expected to be present in general metric-affine theories unless much care is taken in their construction.
SN  - 1434-6044
UR  - https://arxiv.org/abs/2004.11357
UR  - https://doi.org/10.1140/epjc/s10052-020-8143-z
DO  - 10.1140/epjc/s10052-020-8143-z
LA  - English
N1  - WOS:000546247100009
ID  - BeltranJimenez+Delhom2020
ER  -