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NEC violation in mimetic cosmology revisited

Author(s): Ijjas, Anna; Ripley, Justin; Steinhardt, Paul J.

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dc.contributor.authorIjjas, Anna-
dc.contributor.authorRipley, Justin-
dc.contributor.authorSteinhardt, Paul J.-
dc.date.accessioned2019-03-27T18:26:57Z-
dc.date.available2019-03-27T18:26:57Z-
dc.date.issued2016-09-10en_US
dc.identifier.citationIjjas, Anna, Ripley, Justin, Steinhardt, Paul J. (2016). NEC violation in mimetic cosmology revisited. PHYSICS LETTERS B, 760 (132 - 138). doi:10.1016/j.physletb.2016.06.052en_US
dc.identifier.issn0370-2693-
dc.identifier.urihttp://arks.princeton.edu/ark:/88435/pr1497d-
dc.description.abstractIn the context of Einstein gravity, if the null energy condition (NEC) is satisfied, the energy density in expanding space-times always decreases while in contracting space-times the energy density grows and the universe eventually collapses into a singularity. In particular, no non-singular bounce is possible. It is, though, an open question if this energy condition can be violated in a controlled way, i.e., without introducing pathologies, such as unstable negative-energy states or an imaginary speed of sound. In this letter, we will re-examine the claim that the recently proposed mimetic scenario can violate the NEC without pathologies. We show that mimetic cosmology is prone to gradient instabilities even in cases when the NEC is satisfied (except for trivial examples). Most interestingly, the source of the instability is always the Einstein-Hilbert term in the action. The matter stress-energy component does not contribute spatial gradient terms but instead makes the problematic curvature modes dynamical. We also show that mimetic cosmology can be understood as a singular limit of known, well-behaved theories involving higher-derivative kinetic terms and discuss ways of removing the instability. (C) 2016 The Authors. Published by Elsevier B.V.en_US
dc.format.extent132 - 138en_US
dc.language.isoen_USen_US
dc.relation.ispartofPHYSICS LETTERS Ben_US
dc.rightsFinal published version. This is an open access article.en_US
dc.titleNEC violation in mimetic cosmology revisiteden_US
dc.typeJournal Articleen_US
dc.identifier.doidoi:10.1016/j.physletb.2016.06.052-
dc.date.eissued2016-06-28en_US
dc.identifier.eissn1873-2445-
pu.type.symplectichttp://www.symplectic.co.uk/publications/atom-terms/1.0/journal-articleen_US

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