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arXiv · 1809.03496

Gravity in mimetic scalar-tensor theories after GW170817

Alexander Ganz·Nicola Bartolo·Purnendu Karmakar·Sabino Matarrese
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Abstract

We derive the most general mimetic scalar-tensor theory assuming a healthy "seed" action and accounting for the constraints on the speed of gravitational-wave propagation arising from the GW170817 event. By analysing linear perturbations around a flat FLRW background in this model, we obtain a suitable form of the Poisson equation, which allows us to calculate the effective gravitational constant felt by "ordinary" matter. By restricting to a minimally coupled model, such an effective gravitational constant is equivalent to that obtained within General Relativity, with cold dark matter plus a perfect fluid dark energy component, with vanishing sound speed. Assuming, further, a $Λ$CDM background, the effective gravitational constant cannot be distinguished from that of the standard $Λ$CDM model, at linear order. For the full non-minimally coupled mimetic gravity model we obtain a non-vanishing gravitational slip and an effective gravitational constant which always differs from that of standard $Λ$CDM.

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Alexander Ganz, Nicola Bartolo, Purnendu Karmakar, Sabino Matarrese. 2018-09-10. Gravity in mimetic scalar-tensor theories after GW170817. https://doi.org/10.1088/1475-7516%2F2019%2F01%2F056

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