charm

The module implements the standard instantaneous-threshold model of $g_*(T)$, the effective relativistic degrees of freedom as a function of temperature. Each species contributes its full DOF count while $T$ exceeds its mass threshold and drops out below it; the QCD crossover at $T_{\mathrm{QCD}}\approx 0.15,\mathrm{GeV}$ switches the strong sector from QGP to hadronic content.

A thermal species is a four-field record: a name string, a rational mass threshold in GeV (only order relative to $T$ matters), a natural number of internal degrees of freedom, and a Boolean flag for fermionic versus bosonic statistics. Masses are imported PDG-rounded rationals; the $\varphi$-ladder mass modules predict them independently and are not re-derived here.

Charm sits in the electroweak-sector table alongside top, Higgs, $Z$, $W$, bottom, tau, muon, and electron. The 12 DOF count is the usual SM bookkeeping for a colored Dirac quark ($2\times 2\times 3$).

Pure definition: a structure literal packing the four Species fields. No tactics, no lemmas, no proof term beyond the constructor application $\langle\texttt{"charm"},,127/100,,12,,\mathsf{true}\rangle$.

Feeds the electroweak species list used to evaluate the step-function $g_(T)$ as temperature falls through the charm threshold. Downstream mass-verification code also indexes the charm fermion for charge, rung, sector, and positivity of the predicted mass on the $\varphi$-ladder. The entry is imported SM content (ordering threshold only), not an RS derivation of the charm mass; RS mass modules supply that prediction separately. Closes part of the external-review gap that the repository lacked a temperature-dependent $g_(T)$.