Solving the Standard Model Problems in Softened Gravity

Understand

The Higgs naturalness problem is solved if the growth of Einstein's gravitational interaction is softened at an energy $ \lesssim 10^{11}\,$GeV (softened gravity).

• We work here within an explicit realization where the Einstein-Hilbert Lagrangian is extended to include terms quadratic in the curvature and a non-minimal coupling with the Higgs.
• We show that this solution is preserved by adding three right-handed neutrinos with masses below the electroweak scale, accounting for neutrino oscillations, dark matter and the baryon asymmetry.
• The smallness of the right-handed neutrino masses (compared to the Planck scale) and the QCD $\theta$-term are also shown to be natural.