Unitarity bounds on low scale quantum gravity

Understand

We study the unitarity of models with low scale quantum gravity both in four dimensions and in models with a large extra-dimensional volume.

• We find that models with low scale quantum gravity have problems with unitarity below the scale at which gravity becomes strong.
• An important consequence of our work is that their first signal at the Large Hadron Collider would not be of a gravitational nature such as graviton emission or small black holes, but rather linked to the mechanism which fixes the unitarity problem.
• We also study models with scalar fields with non minimal couplings to the Ricci scalar.