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

TL;DR

This study tests the impact of hypothetical fifth forces on local distance measurements used to determine the Hubble constant, finding strong constraints that do not resolve the existing tension in its value.

Contribution

It introduces a model incorporating environmental screening of fifth forces into the local distance ladder calibration, providing new constraints on such theories.

Findings

Fifth force effects are strongly constrained and consistent with null results.

The inferred Hubble constant remains high at 73.1 km/s/Mpc, maintaining the Hubble tension.

Adding TRGB data does not significantly change the constraints or the tension.

Abstract

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 $\Phi$, 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 $>5 \, \sigma$. 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.