Chameleon dark energy can resolve the Hubble tension

Values of the Hubble constant between the direct measurements from various independent local observations and that inferred from the cosmic microwave background with the $\mathrm{\Lambda }$-cold-dark-matter model are in tension with persistent significance. We propose a late-time inhomogeneous resolution suggesting that a chameleon field coupled to a local overdensity of matter could be trapped at a higher potential energy density as an effective cosmological constant driving the local expansion rate faster than that of the background with lower matter density. We illustrate this mechanism in a toy model in which a region with only 20% overdensity of matter is sufficient to resolve the Hubble tension, and the Hubble constant measured by the local distance ladders could be accommodated by the chameleon coupled to the observed overdensities from the large-scale structure surveys.

Figure 1

Left panel: effective potential (blue curve) of the chameleon field receives larger contributions (red curve) to the original chameleon potential (green curve) from overdensity (solid curves) than underdensity (dashed curves). Right panel: overdensity of a region with respect to a local Hubble constant for chameleon potentials (3) of different $n$ confronted with the local distance ladder measurement (blue shaded area) and Planck 2018 measurement (red shaded area).

Figure 2

Left panel: local profile of the matter density fraction from BOSS DR12 $\mathrm{LOWZ}+\mathrm{CMASS}$ NGC (blue) and SGC (red) samples. Inset: galaxy bias borrowed from [109]. Right panel: inferred value of the Hubble constant from the BOSS DR12 $\mathrm{LOWZ}+\mathrm{CMASS}$ NGC (blue) and SGC (red) samples with respect to the various measurements, as indicated.

Figure 3

The Mollweide view of the SNe (black triangles), SBF (green squares), masers (blue diamonds), lensing events (purple crosses) from the TDCOSMO sample, and the host galaxy NGC4993 of GW170817 (red point) in the equatorial coordinate system. The galaxy survey regions covered by BOSS DR12 are shown as shaded regions, where the central part is in SGC while the rest of the shaded regions are in the NGC.