Viability of quadratic gravity as a realistic quantum gravity framework

Determine whether quadratic gravity, defined by a renormalizable curvature-squared action with R^2 and R^{\mu\nu}R_{\mu\nu} terms (agravity), constitutes a viable and realistic framework for quantum gravity, and ascertain its consistency as a quantum theory across relevant energy scales.

Background

The paper reviews quadratic (curvature-squared) gravity, which improves ultraviolet behavior and renders the theory perturbatively renormalizable, but may introduce ghostlike degrees of freedom and potential unitarity issues. While some works argue for acceptable behavior of scattering amplitudes at ultra-Planckian energies, the overall consistency and realism of quadratic gravity remain debated.

In this context, the authors emphasize that the broader question of the viability of quadratic gravity as a practical and consistent quantum gravity framework is not settled and requires further investigation.