The Effects of Gravitational Slip on the Higher-Order Moments of the
  Matter Distribution
  Cosmological departures from general relativity offer a possible explanation
for the cosmic acceleration. To linear order, these departures (quantified by
the model-independent parameter $\varpi$, referred to as a `gravitational
slip') amplify or suppress the growth of structure in the universe relative to
what we would expect to see from a general relativistic universe lately
dominated by a cosmological constant. As structures collapse and become more
dense, linear perturbation theory is an inadequate descriptor of their
behavior, and one must extend calculations to non-linear order. If the effects
of gravitational slip extend to these higher orders, we might expect to see a
signature of $\varpi$ in the bispectrum of galaxies distributed on the sky. We
solve the equations of motion for non-linear perturbations in the presence of
gravitational slip and find that, while there is an effect on the bispectrum,
it is too weak to be detected with present galaxy surveys. We also develop a
formalism for incorporating scale dependence into our description of
gravitational slip.
