Axion Misalignment Driven to the Hilltop
  The QCD axion serves as a well-motivated dark matter candidate and the
misalignment mechanism is known to reproduce the observed abundance with a
decay constant $f_a \simeq \mathcal{O}(10^{12})$ GeV for a misalignment angle
$\theta_{\rm mis} \simeq \mathcal{O}(1)$. While $f_a \ll 10^{12}$ GeV is of
great experimental interest, the misalignment mechanism requires the axion to
be very close to the hilltop, i.e. $\theta_{\rm mis} \simeq \pi$. This
particular choice of $\theta_{\rm mis}$ has been understood as fine-tuning the
initial condition. We offer a dynamical explanation for $\theta_{\rm mis}
\simeq \pi$ in a class of models. The axion dynamically relaxes to the minimum
of the potential by virtue of an enhanced mass in the early universe. This
minimum is subsequently converted to a hilltop because the CP phase of the
theory shifts by $\pi$ when one contribution becomes subdominant to another
with an opposite sign. We demonstrate explicit and viable examples in
supersymmetric models where the higher dimensional Higgs coupling with the
inflaton naturally achieves both criteria. Associated phenomenology includes a
strikingly sharp prediction of $3 \times 10^9$ GeV $\lesssim f_a \lesssim
10^{10}$ GeV and the absence of isocurvature perturbation.
