The Stephani universe is an inhomogeneous alternative to ΛCDM. We show that the exotic fluid driving the Stephani exact solution of Einstein’s equations is an unusual form of k-essence that is linear in “velocity”. Much as the Stephani universe can be embedded into (a section of) flat 5-d Minkowski space-time, we show that the k-essence obtains through dimensional reduction of a 5-d strongly coupled non-linear “electrodynamics” that, in the empty Stephani universe, corresponds to space filling magnetic branes in string/M-theory.
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