adjoint_dim
plain-language theorem explainer
The adjoint representation of SU(n) has dimension n² − 1. Standard-model bookkeeping cites this when counting gluons (n=3) and weak bosons (n=2) in the high-T g_★ tally. The body is a one-line arithmetic definition, not a derived theorem.
Claim. For each natural number $n$, the dimension of the adjoint representation of $SU(n)$ is $n^2 - 1$.
background
This module performs exact rational bookkeeping for the high-temperature Standard Model effective relativistic degrees of freedom
$$g_\star = g_b + \tfrac78 g_f = 28 + \tfrac78\cdot 90 = 106.75,$$
valid only for $T \gtrsim T_{\mathrm{EW}}$. Recognition Science supplies the gauge factor $SU(3)\times SU(2)\times U(1)$ (from $Q_3$ automorphisms) and the generation count 3 (from $D=3$); the matter representations and the $7/8$ thermal weight are imported textbook inputs.
In Lie theory the adjoint of $SU(n)$ is the real vector space of traceless Hermitian $n\times n$ matrices, whose real dimension is $n^2-1$. That integer multiplies the two transverse polarizations of each massless gauge boson above the electroweak scale, giving the bosonic contributions that enter $g_b$.
proof idea
Pure definition: the body is the arithmetic expression $n^2-1$. No tactics, lemmas, or hypotheses. Downstream equalities such as su3_adjoint and su2_adjoint discharge the concrete cases $n=3$ and $n=2$ by native_decide.
why it matters
Local glue for the bosonic half of $g_\star$. Downstream, gluon_dof is adjoint_dim 3 * 2 (8 gluons × 2 polarizations), weak_boson_dof_symmetric is adjoint_dim 2 * 2 + 1 * 2 (W triplet plus B, each with 2 polarizations), and the theorems su3_adjoint / su2_adjoint pin the integers 8 and 3. The parent theorem bosonic_traces_to_Q3 packages these into the claim that every bosonic DOF traces to $Q_3$ structure and that bosonic_dof = 28. In the RS forcing chain the gauge group itself is upstream (GaugeFromCube); this definition only converts that group data into the textbook adjoint dimensions used by the thermal count. Status remains bookkeeping over adopted SM content, not a novel RS prediction.
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