  Lattice Monte Carlo studies in SU(3) gauge theory have shown that the
topological charge distribution in the vacuum is dominated by thin coherent
membranes of codimension one arranged in a layered, alternating-sign sandwich.
A similar lamination of topological charge occurs in the 2D $CP^{N-1}$ model.
In holographic QCD, the observed topological charge sheets are naturally
interpreted as $D6$ branes wrapped around an $S_4$.. With this interpretation,
the laminated array of topological charge membranes observed on the lattice can
be identified as a "tachyonic crystal", a regular, alternating-sign array of
$D6$ and $\bar{D6}$ branes that arises as the final state of the decay of a
non-BPS $D7$ brane via the tachyonic mode of the attached string. In the gauge
theory, the homogeneous, space-filling $D7$ brane represents the perturbative
gauge vacuum, which is unstable toward lamination associated with a marginal
tachyonic boundary perturbation $\propto \cos(X/\sqrt{2\alpha'})$. For the
$CP^{N-1}$ model, the cutoff field theory can be cast as the low energy limit
of an open string theory in background gauge and tachyon fields $A_{\mu}(x)$
and $\lambda(x)$. This allows a detailed comparison with large $N$ field theory
results and provides strong support for the tachyonic crystal interpretation of
the gauge theory vacuum.
