Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
Let α* be any basis of col(Π) and β* be any basis of col(Π′); we note col(α⊥) = col(α*⊥), col(β⊥) = col(β*⊥) so no distinction is made between α⊥ and α*⊥, β⊥ and β*⊥ in the following discussion.