# Über-Gravity and the Cosmological Constant Problem [CL]

Recently, the idea of taking ensemble average over gravity models has been introduced. Based on this idea, we study the ensemble average over (effectively) all the gravity models dubbing the name \”ubergravity. The \”ubergravity has interesting universal properties, independent from the choice of basis: $i)$ it mimics Einstein-Hilbert gravity for high-curvature regime, $ii)$ it predicts stronger gravitational force for an intermediate-curvature regime, $iii)$ surprisingly, for low-curvature regime, i.e. $R<R_0$ where $R$ is Ricci scalar and $R_0$ is a given scale, the Lagrangian vanishes automatically and $iiii)$ there is a sharp transition between low- and intermediate-curvature regimes at $R=R_0$. We show that the \”ubergravity response is robust to any value of the vacuum energy, $\rho_{vac}$. This means the response to any non-vanishing value of $\rho_{vac}$ gives an exact deSitter solution where $R_0$ plays the role of the cosmological constant. Consequently, $R_0$ should be fixed by the observations and there is no need to fine-tune the cosmological constant.

N. Khosravi
Wed, 8 Mar 17
21/60