Constraining Fifth Forces using the Local Distance Ladder: Implications for the Hubble Tension

We revisit the local distance ladder measurement of the Hubble constant in models where gravity is modified by a fifth force, an additional long-range interaction. In many such theories the force is screened; suppressed in dense environments but potentially active in galaxies used for distance calibration. We model this environmental dependence using three quantities that characterize each galaxy’s large-scale gravitational environment: the external gravitational potential $Φ$, acceleration $a$, and curvature $K$. Our baseline analysis recalibrates the SH0ES-team’s Cepheid-supernova distance ladder, incorporating the fifth force via its impact on the Cepheid period-luminosity relation. Across models, a fifth force is strongly constrained, with posteriors concentrated around a null result. The inferred Hubble constant is $H_0 = 73.1 \pm 1.0 , \mathrm{km/s/Mpc}$, retaining the Hubble tension at $>5 , σ$. As an additional test, we incorporate four independent Tip of the Red Giant Branch (TRGB) distance datasets into a joint Cepheid-TRGB-supernova calibration. These combined analyses further constrain the magnitude of fifth-force effects. Taken together, our results show that, across the class of screened fifth-force models we analyze, the calibration of the local distance ladder remains essentially unchanged, leaving the Hubble tension intact.

💡 Research Summary

The authors revisit the local distance‑ladder determination of the Hubble constant in the context of screened fifth‑force theories, which introduce an additional long‑range interaction whose strength depends on the surrounding gravitational environment. To capture this environmental dependence they employ three proxy fields – the external gravitational potential Φ, the external acceleration a, and the external curvature K – computed from large‑scale structure reconstructions out to 200 Mpc (Ref.