An anisotropic bouncing universe in non-local gravity

Abstract

We show that it is possible to realize a cosmological bouncing solution in an anisotropic but homogeneous Bianchi-I background in a class of non-local, infinite derivative theories of gravity. We show that the anisotropic shear grows slower than in general relativity during the contraction phase, peaks to a finite value at the bounce point, and then decreases as the universe asymptotes towards isotropy and homogeneity, and ultimately to de Sitter. Along with a cosmological constant, the matter sector required to drive such a bounce is found to consist of three components - radiation, stiff matter and $k$-matter (whose energy density decays like the inverse square of the average scale factor). Generically, $k$-matter exerts anisotropic pressures. We will test the bouncing solution in local and non-local gravity and show that in the latter case it is possible to simultaneously satisfy positivity of energy density and, at least in the late time de Sitter phase, avoid the introduction of propagating ghost/tachyonic modes.

arXiv comment18 pages, 1 figure, 1 table. We dedicate this work to the memory of John D. Barrow. v2 matches the one published in JCAP

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• Non-local Lagrangian fields: Noether's theorem and Hamiltonian formalism
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• Anisotropic Cosmology in the Local Limit of Nonlocal Gravity
• Bouncing cosmology in the limiting curvature theory of gravity
• Gravitational Bounce from the Quantum Exclusion Principle
• Universe bouncing its way to inflation
• Smearing out contact terms in ghost-free infinite derivative quantum gravity
• The Star Universe Model -- Another FLRW Patch