n_generations_eq
plain-language theorem explainer
The number of Standard Model fermion generations equals 3 by definitional equality with the face-pair count on the 3-cube. Anyone assembling the high-T relativistic DOF tally g_* cites this to pin the generation factor. The proof is a one-line reflexivity check that face_pairs(3) reduces to 3.
Claim. The generation count equals three: $\mathrm{face\_pairs}(3) = 3$.
background
This module performs exact rational bookkeeping for the high-temperature Standard Model effective relativistic degrees of freedom $g_\star = g_b + (7/8)g_f = 106.75$, valid only for $T \gtrsim T_{\mathrm{EW}}$. The module status is honest bookkeeping over adopted SM content, not a novel RS prediction.
RS supplies three inputs proved upstream: the gauge group $\mathrm{SU}(3)\times\mathrm{SU}(2)\times\mathrm{U}(1)$ from $Q_3$ automorphisms, the generation count $3 = \mathrm{face_pairs}(3)$ from spatial dimension $D = 3$ (ParticleGenerations), and the Fermi/Bose sign from the eight-tick spin-statistics theorem. The local definition of the generation count is $\mathrm{face_pairs},3$, matching the Cosmology and Unification aliases that hard-code the value 3.
Face-pairs on the 3-cube count opposite-face pairings; with $D = 3$ forced by the T8 step of the unified forcing chain, that count is three, which is identified with the three SM generations.
proof idea
One-line term proof by rfl. The local definition sets the generation count equal to face_pairs 3, and that expression is definitionally equal to the natural number 3, so reflexivity closes the goal with no further lemmas.
why it matters
Feeds the certificate gStarCert, which packages the full $g_\star$ assembly: bosonic and fermionic DOF equalities, generation and color counts, and the gluon count. Without pinning generations to 3, the fermionic contribution $(7/8)\cdot 90$ cannot be certified.
In the Recognition framework this is the bookkeeping face of the T8 / ParticleGenerations result that $D = 3$ forces three generations via face-pairs on the cube. The module doc lists it among the RS-derived inputs to $g_\star$, alongside GaugeFromCube and the spin-statistics sign. It does not invent the generation count; it records the already-forced value so the rational arithmetic $28 + (7/8)\cdot 90 = 427/4$ typechecks.
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