Robustness of inflation to inhomogeneous initial conditions

Abstract

We consider the effects of inhomogeneous initial conditions in both the\nscalar field profile and the extrinsic curvature on different inflationary\nmodels. In particular, we compare the robustness of small field inflation to\nthat of large field inflation, using numerical simulations with Einstein\ngravity in 3+1 dimensions. We find that small field inflation can fail in the\npresence of subdominant gradient energies, suggesting that it is much less\nrobust to inhomogeneities than large field inflation, which withstands dominant\ngradient energies. However, we also show that small field inflation can be\nsuccessful even if some regions of spacetime start out in the region of the\npotential that does not support inflation. In the large field case, we confirm\nprevious results that inflation is robust if the inflaton occupies the\ninflationary part of the potential. Furthermore, we show that increasing\ninitial scalar gradients will not form sufficiently massive inflation-ending\nblack holes if the initial hypersurface is approximately flat. Finally, we\nconsider the large field case with a varying extrinsic curvature K, such that\nsome regions are initially collapsing. We find that this may again lead to\nlocal black holes, but overall the spacetime remains inflationary if the\nspacetime is open, which confirms previous theoretical studies.\n