The Power of Cosmic Flexion in Testing Modified Matter and Gravity
  Flexion is the weak lensing effect responsible for the weakly skewed and
arc-like appearance of lensed galaxies. The flexion signal-to-noise ratio can
be an order of magnitude larger than that of shear. For the first time, we show
how this makes flexion an invaluable tool for discriminating among alternative
cosmological models. We analyse a scalar field model of unified dark matter and
dark energy, a brane-world cosmology and two f(R) modified-action theories. We
show that these models can be distinguished from LCDM at several standard
deviations by measuring the power spectrum of cosmic flexion.
