bc system ($bc$ system)

A bc system is the anticommuting counterpart of a beta-gamma system. For weights $h$ and $1-h$, its central charge is $-2(6h^2-6h+1)$.

The worldsheet ghost fields form a bc system with conformal weights $2$ and $-1$. Setting $J=2$ in $c=-2(6J^2-6J+1)$ gives central charge $-26$ in each chirality. The worldsheet Weyl anomaly of $D$ free embedding bosons cancels at $D=26$.

For reparameterization ghosts of weights two and minus one, the canonical anticommutators imply $b(z)c(w)\sim 1/(z-w)$. This operator-product expansion fixes the ghost contractions and the ghost stress tensor.