Towards viable cosmological models of disformal theories of gravity

Jeremy Sakstein
Phys. Rev. D 91, 024036 – Published 26 January 2015

Abstract

The late-time cosmological dynamics of disformal gravity are investigated using dynamical systems methods. It is shown that in the general case there are no stable attractors that screen fifth forces locally and simultaneously describe a dark energy dominated universe. Viable scenarios have late-time properties that are independent of the disformal parameters and are identical to the equivalent conformal quintessence model. Our analysis reveals that configurations where the Jordan frame metric becomes singular are only reached in the infinite future, thus explaining the natural pathology resistance observed numerically by several previous works. The viability of models where this can happen is discussed in terms of both the cosmological dynamics and local phenomena. We identify a special parameter tuning such that there is a new fixed point that can match the presently observed dark energy density and equation of state. This model is unviable when the scalar couples to the visible sector but may provide a good candidate model for theories where only dark matter is disformally coupled.

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  • Received 29 September 2014

DOI:https://doi.org/10.1103/PhysRevD.91.024036

© 2015 American Physical Society

Authors & Affiliations

Jeremy Sakstein

  • Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, Cambridge CB3 0WA, United Kingdom; Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, United Kingdom; and Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 6B9, Canada

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Vol. 91, Iss. 2 — 15 January 2015

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