Ab initio structure factors for spin-dependent dark matter direct
  detection
  We present converged ab initio calculations of structure factors for elastic
spin-dependent WIMP scattering off all nuclei used in dark matter
direct-detection searches: $^{19}$F, $^{23}$Na, $^{27}$Al, $^{29}$Si,
$^{73}$Ge, $^{127}$I, and $^{129,131}$Xe. From a set of established two- and
three-nucleon interactions derived within chiral effective field theory, we
construct consistent WIMP-nucleon currents at the one-body level, including
effects from axial-vector two-body currents. We then apply the in-medium
similarity renormalization group to construct effective valence-space
Hamiltonians and consistently transformed operators of nuclear responses.
Combining the recent advances of natural orbitals with three-nucleon forces
expressed in large spaces, we obtain basis-space converged structure factors
even in heavy nuclei. Generally results are consistent with previous
calculations, but large uncertainties in $^{127}$I highlight the need for
further study.
