Inflation in Extra-Dimensions with one or two branes
Abstract
In this paper, we study two inflationary models, namely, monomial inflation and the simplest α-attractor inflation, within extra-dimensional frameworks. We consider three extra-dimensional setups: Dark Dimension, which embeds one flat extra-dimension to explain the observed smallness of the 4D cosmological constant 4; and the two Randall-Sundrum scenarios with one warped extra-dimension, namely RS1 with two branes and RS2 with one brane. We derive the corresponding Friedmann equations, compute the slow-roll parameters in each case, and we fit the experimental data for (ns - 1, α, s2, r), using Planck, BICEP, and ACT data. We find that monomial inflation is strongly disfavored in all scenarios, while α-attractor inflation provides an excellent fit to current observations, with extra-dimensional setups offering additional flexibility compared to the standard 4D case.
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