Longitudinal diffeomorphisms obstruct the protection of vacuum energy

Understand

To guarantee the stability of the cosmological constant sector against radiative corrections coming from quantum matter fields, one of the most natural ingredients to invoke is the symmetry under scale transformations of the gravitational field.

• Previous attempts to follow this path have nevertheless failed in providing a consistent picture.
• Here we point out that this failure is intimately tied up to an assumption which is typically embedded in modern studies of the gravitational interaction: invariance under the full group of diffeomorphisms.
• We base the discussion on the gravitational theory known as Weyl transverse gravity.