Screened fifth forces lower the TRGB-calibrated Hubble constant too

Understand

The local distance ladder measurement of the Hubble constant requires a connection between geometric distances at low redshift and Type Ia supernovae in the Hubble flow, which may be achieved through either the Cepheid period--luminosity relation or the luminosity of the Tip of the Red Giant Branch (TRGB) feature of the Hertzsprung--Russell diagram.

• Any potential solution to the Hubble tension that works by altering the distance ladder must produce consistency of both the Cepheid and TRGB $H_0$ calibrations with the CMB.
• In this paper we extend our models of screened fifth forces (Desmond et al 2019) to cover the TRGB framework.
• A fifth force lowers TRGB luminosity, so a reduction in inferred $H_0$ requires that the stars that calibrate the luminosity---currently in the LMC---are on average less screened than those that calibrate the supernova magnitude.