In Liouville theory, primary fields are usually parametrized by their momentum rather than their conformal dimension, and denoted V α α ( z ) . Both fields V α α ( z ) and V Q − − α α ( z ) correspond to the primary state of the representation V Δ Δ ⊗ ⊗ V ¯ ¯ Δ Δ , and are related by the reflection relation