Speaker
Description
Anti-ultralocality refers to the amplification of spatial gradients, inhomogeneities, and anisotropies during phases of decelerating expansion. The effect is driven by nonlinear general relativistic dynamics in the Einstein–scalar field system of equations. Previous numerical relativity studies have shown that, beginning with generic initial conditions following a big bang, this amplification prevents inflation from starting in models with power-law inflaton potentials. We present the effects of anti-ultralocality in models with plateau-like inflaton potentials which are thought to predict a much lower tensor-to-scalar ratio consistent with present observational upper limits. These predictions, however, assume homogeneity and isotropy are reached with 60 or more e-folds of inflation remaining. Using numerical relativity studies based on codes validated in earlier investigations and a rigorous protocol that tests whether initial conditions are generic and whether the final 60 e-folds satisfy observational constraints, we find that plateau models are especially vulnerable to anti-ultralocality effects due to both the substantial decelerating expansion period between the Planck energy density and the plateau energy density (12 orders of magnitude smaller) and the extreme flatness of the plateau itself. The resulting growth of gradients and shear either prevents 60 e-folds of inflation or drives the inflaton into self-reproduction, leading to multiverse outcomes inconsistent with current constraints on the tensor-to-scalar ratio.
| Other topic / keywords: | Numerical Relativity |
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