Uber-gravity and the cosmological constant problem

作者：Khosravi Nima^*

来源：Physics of the Dark Universe, 2018, 21: 21-26.

DOI：10.1016/j.dark.2018.05.003

• Modified gravity
• Dark energy
• Cosmological constant problem

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 (constructed from Ricci scalar) dubbing the name uber-gravity which is a fixed point in the model space. The uber-gravity has interesting universal properties, independent from the choice of basis: (Wi) 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 intermediatecurvature regimes at R = R-0. We show that the uber-gravity response is robust to all values of vacuum energy, rho(vac) when there is no other matter. So as a toy model, uber-gravity, gives a way to think about the hierarchy problems e.g. the cosmological constant problem. Due to the transition at R = R-0 there is a chance for uber-gravity to bypass Weinberg's no-go theorem. The cosmology of this model is also promising because of its non-trivial predictions for small curvature scales in comparison to Lambda CDM model.

• 出版日期2018-9