Defocusing of null rays in infinite derivative gravity

Conroy, Aindriú and Koshelev, Alexey S. and Mazumdar, Anupam (2017) Defocusing of null rays in infinite derivative gravity. Journal of Cosmology and Astroparticle Physics, 2017 (1). ISSN 1475-7516

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Einstein's General theory of relativity permits spacetime singularities, where null geodesic congruences focus in the presence of matter, which satisfies an appropriate energy condition. In this paper, we provide a minimal defocusing condition for null congruences without assuming any Ansatz-dependent background solution. The two important criteria are: (1) an additional scalar degree of freedom, besides the massless graviton must be introduced into the spacetime; and (2) an infinite derivative theory of gravity is required in order to avoid tachyons or ghosts in the graviton propagator. In this regard, our analysis strengthens earlier arguments for constructing non-singular bouncing cosmologies within an infinite derivative theory of gravity, without assuming any Ansatz to solve the full equations of motion.

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Journal Article
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Journal of Cosmology and Astroparticle Physics
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This is an author-created, un-copyedited version of an article accepted for publication/published in Journal of Cosmology and Astroparticle Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi:10.1088/1475-7516/2017/01/017
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16 Feb 2017 09:00
Last Modified:
16 Sep 2023 01:29