ΛCDM and the principle of equivalence

Abstract

There is growing evidence that the net acceleration of the Universe over its entire history is essentially zero. This finding is critical in light of a recent examination of the Friedmann–Lemaître–Robertson–Walker (FLRW) metric using the local flatness theorem (LFT) in general relativity, which argues that FLRW is consistent with the principle of equivalence only if the total energy density ρ and pressure p satisfy the zero active mass condition, ρ + 3p = 0. This equation-of-state produces zero acceleration, and significantly mitigates the growing tension between lambda cold dark matter (ΛCDM) and the ever-improving observations. This article takes an alternative approach to this critical issue and directly tests the expansion rate predicted by the standard model against the requirements of the LFT. It demonstrates that ΛCDM simply does not satisfy the principle of equivalence. Some of the many important consequences of this outcome are discussed in the conclusions. © 2023 De Gruyter. All rights reserved.