
The Selection-Stitch Model (SSM) [2, 3] proposes that the physical vacuum is a Face-Centered
Cubic (FCC) crystallization of spacetime, with baryonic matter identied as a single K=4 node
trapped in the tetrahedral interstitial void of the K=12 FCC bulk. The framework derives the
proton-to-electron mass ratio
m
p
m
e
= (K + 1)K
2
− c
skew
K = 13 ×144 − 3 × 12 = 1836
(2)
from purely structural counts of the trapped tetrahedral-void defect [2]. An equivalent derivation
via a
[[192, 130, 3]]
CSS code on the FCC lattice [3] reaches the same number through a fault-
tolerant verication cost
E
s
× C
s
= 36 × 51 = 1836
.
The unifying picture is
incomplete crystallization
. In the SSM the vacuum crystallizes into
the FCC lattice, and every node in the perfect bulk reaches full coordination
K = 12
. Matter
is where this crystallization fails to complete: a node trapped below bulk coordination at an
interstitial site, unable to stitch into the surrounding lattice. The companion paper [2] develops
this for the tetrahedral void, where a
K = 4
remnant becomes the proton, and shows how its
incomplete bonding generates fractional charge, color connement, and the proton mass. The
present paper applies the same picture to the lattice's other interstitial site: the octahedral void
admits a
K = 6
remnant, a second form of incomplete crystallization at a more symmetric
site, which we identify as a dark matter candidate. The two particles are then not independent
constructions but the two ways the FCC crystal can fail to close around an interstitial node
the tetrahedral remnant giving visible matter, the octahedral remnant giving dark matter.
The FCC unit cell contains two distinct interstitial void types: 8 tetrahedral voids (each
bounded by 4 FCC vertices) and 4 octahedral voids (each bounded by 6 FCC vertices), with
all bounding edges at the nearest-neighbor distance
L
(Section 2). The framework that traps a
defect in the tetrahedral void simultaneously admits an analogous defect in the octahedral void
the same K=4 to K=12 phase transition, the same kinematic operators, the same geometric
mechanism, applied to the second interstitial site that the FCC lattice provides. The natural
question is what physics this companion defect predicts.
This paper develops the case that the octahedral-void defect is a viable candidate for dark
matter. The case is built in two pieces. First, four qualitative properties of the defect fol-
low within the SSM structural-symmetry rules from the bonding graph
K
2,2,2
and bound-
ing polyhedron (the regular octahedron with
O
h
symmetry): absence of rst-order electro-
magnetic coupling, absence of the baryonic SU(3) color-generating mechanism, self-conjugate
(Majorana-type) character, and suppressed rst-order radiative cooling. These match the stan-
dard requirements for cold dark matter without invoking any free parameters. Second, the
structural-counting framework of Ref. [2] that yields the proton's verication cost
C
p
= 1836
extends to the octahedral defect by inclusion-exclusion on the
K
2,2,2
bonding graph, termi-
nating exactly at third order because the octahedron's six vertices forbid any 4-matching:
C
DM
= 25 ×144 −30 ×10 + 8 ×8 = 3364
. The three terms are the inclusion-exclusion structure
made explicit: a base verication cost, minus the pairwise overlaps where two ux channels
double-count, plus the triple overlaps restored where three channels coincide. Each coecient
is a xed structural count, not a tted value:
25
is the number of disrupting nodes (6 bounding
vertices
×
4 bonds, plus the trapped center),
144 = K
2
the second-shell footprint at bulk coor-
dination
K = 12
,
30
the skew-edge pairs of
K
2,2,2
and
10
their pairwise rst-shell overlap, and
the two
8
s the perfect matchings of the octahedron and their triple overlap; Section 4 derives
all six by direct enumeration. The framework therefore predicts the dark matter mass directly:
m
DM
=
C
DM
C
p
× m
p
=
3364
1836
× 938.272
MeV
= 1.719
GeV
,
(3)
using only the proton mass [9] as a calibration input. A
∼ 1.5
1.6
GeV gamma-ray line re-
cently reported in three active galactic nuclei [4] sits near this mass; the annihilation channel
2