... THEORY OF P1577fixed points of A1⊂ P1. By definition, the Hurwitz number Cg(µ) countspossibly disconnected covers with weights, where the weight of a cover is thereciprocal of the order of ... coefficients of the expansion of the operator A(z,uz)in powers of z:A(z,uz)=k∈ZAkzk.(2.24)As observed in the proof of Proposition 7, the operator Akfor k = −1 involvesonly terms of energy ... directions.Hence, for general values of µi, the matrix element on the right side of (2.17)is not a priori well-defined. By expansion of the definition of A(µi,uµi), theAnnals of Mathematics The...