Symmetron Scalar Fields: Modified Gravity, Dark Matter or Both?

Understand

Scalar fields coupled to gravity through the Ricci scalar have been considered both as dark matter candidates and as a possible modified gravity explanation for galactic dynamics.

• It has recently been demonstrated that the dynamics of baryonic matter in disk galaxies may be explained, in the absence of particle dark matter, by a symmetron scalar field that mediates a fifth force.
• The symmetron provides a concrete and archetypal field theory within which to explore how large a role modifications of gravity can play on galactic scales.
• In this article, we extend these previous works by asking whether the same symmetron field can explain the difference between the baryonic and lens masses of galaxies through a modification of gravity.