Environment Dependent Electron Mass and the H$_0$-Tension

Understand

A difference in the electron mass at recombination from the measured value today has been shown to relieve the Hubble tension.

• In this article we propose a simple mechanism that would allow for such a mass difference.
• Similar in form to the Higgs field, we consider a Yukawa coupling between the symmetron scalar field and the electron.
• However, the symmetron vacuum expectation value depends on the matter density of its environment which, in principle, would allow its contribution towards the electron mass to differ between recombination and today.