<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>H</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>S</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math> tensions necessitate early and late time changes to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Λ</mml:mi><mml:mi>CDM</mml:mi></mml:math>
Steven J. Clark, Kyriakos Vattis, JiJi Fan, Savvas M. Koushiappas
Abstract
An only early or only late time alteration to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ has been inadequate at resolving both the ${H}_{0}$ and ${S}_{8}$ tensions simultaneously; however, a combination of early and late time alterations to $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ can provide a solution to both tensions. As an illustration, we examine a combined early dark energy, decaying dark matter model. While early dark energy has the ability to resolve the ${H}_{0}$ tension, it leads to a discrepancy in ${S}_{8}$ measurements. We show that the addition of decaying dark matter helps resolve the ${S}_{8}$ discrepancy that would otherwise be enhanced in an early dark energy model, while the latter is able to relieve the ${H}_{0}$ disagreement to within the 95th percentile interval. Our results show a preference for the combined model over $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ with $\mathrm{\ensuremath{\Delta}}\mathrm{AIC}=\ensuremath{-}6.72$, hinting that both early and late Universe modifications may be necessary to address the cosmological tensions.