Cosmological extra dimensions can mimic dark energy

Abstract

We present a simple model of a higher dimensional spacetime in which the 4d submanifold is a FLRW metric, while the extra dimensions are compactified to a hypersphere. We calculate the Friedmann equations of this model finding that the extra dimensions interact in a non-trivial way with the 4d submanifold evolution. We prove that what is observed as Dark Energy could be explained only as an effect due to the Gaussian curvature and the expansion rate of the extra dimensions. We calculate the luminosity distance in this model and derive the acceleration parameter q. We find that Ωm and q are in some sense dressed by terms coming from the extra dimensions, thus a Universe filled only with matter (both luminous and dark) and with extra dimensions can explain the observational data. We find that the extra dimensions do not affect the CMB spectrum, but this is not a solution to the Hubble tension. We fit our model to SNe data and find evidence for the presence of 3-4 extra dimensions which are presently contracting.