Primordial Gravitational Waves from Galaxy Intrinsic Alignments
  Galaxy shapes have been observed to align with external tidal fields
generated by the large-scale structures of the Universe. While the main source
for these tidal fields is provided by long-wavelength density perturbations,
tensor perturbations also contribute with a non-vanishing amplitude at linear
order. We show that parity-breaking gravitational waves produced during
inflation leave a distinctive imprint in the galaxy shape power spectrum which
is not hampered by any scalar-induced tidal field. We also show that a certain
class of tensor non-Gaussianities produced during inflation can leave a
signature in the density-weighted galaxy shape power spectrum. We estimate the
possibility of observing such imprints in future galaxy surveys.
