An Environmental Variation of Constants

Understand

Models of modified gravity, whereby local tests of gravity are evaded thanks to a screening mechanism of the chameleon or Damour-Polyakov types, lead to a spatial variation of the particle masses and the fine structure constant.

• This is triggered by the environmental dependence of the value of the scalar field whose presence modifies gravity.
• In dense media, the field settles at a density dependent value while in sparse environments it takes the background cosmological value.
• We estimate that the maximal deviation of constants from their present values is constrained by local tests of gravity, and must be less than $10^{-6}$.