  The mystery of dark energy suggests that there is new gravitational physics
on long length scales. Yet light degrees of freedom in gravity are strictly
limited by Solar System observations. We can resolve this apparent
contradiction by adding a Galilean-invariant scalar field to gravity. Called
Galileons, these scalars have strong self-interactions near overdensities, like
the Solar System, that suppress their dynamical effect. These nonlinearities
are weak on cosmological scales, permitting new physics to operate. In this
Letter, we point out that a massive gravity inspired coupling of Galileons to
stress energy gravity can have a surprising consequence: enhanced gravitational
lensing. Because the enhancement appears at a fixed scaled location for a wide
range of dark matter halo masses, stacked cluster analysis of weak lensing data
should be able to detect or constrain this effect.
