relativistic quantum gravity with the action where all possible terms quadratic in the curvature tensor are added to the Einstein-Hilbert term. This model was shown to be renormalizable in the work by K.S. Stelle. In this paper, we demonstrate that the
model is also unitary contrary to the statements made in the literature, in particular in the work by Stelle. New expressions for the
Lagrangian within dimensional regularization and the graviton propagator are derived. We demonstrate that the
model is a good candidate for the fundamental quantum theory of gravity.
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