Inhomogeneous initial conditions for inflation: A wibbly-wobbly timey-wimey path to salvation

Abstract

We use the 3+1 formalism of numerical relativity to investigate the robustness of Starobinsky and Higgs inflation to inhomogeneous initial conditions, in the form of either field gradient or kinetic energy density. Sub-Hubble and Hubble-sized fluctuations generically lead to inflation after an oscillatory phase between gradient and kinetic energies. Hubble-sized inhomogeneities also produce contracting regions that may end up forming primordial black holes, subsequently diluted by inflation. We analyse the dynamics of the preinflation era and the generation of vector and tensor fluctuations. Our analysis further supports the robustness of inflation to any size of inhomogeneity, in the field, velocity or equation of state. At large field values, the preinflation dynamics only marginally depends on the field potential and it is expected that such behaviour is universal and applies to any inflation potential of plateau-type, favoured by CMB observations after Planck.

17 pages, 9 figures. Improved discussions, references added

References in corpus (6)

• The Standard Model Higgs boson as the inflaton
• Evolution to a smooth universe in an ekpyrotic contracting phase with w > 1
• Robustness of slow contraction to cosmic initial conditions
• Inflating an Inhomogeneous Universe
• Fully relativistic nonlinear cosmological evolution in spherical symmetry using the BSSN formalism
• Cosmological initial data for numerical relativity

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