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weight -- weight of a semigroup

Synopsis

Description

If S is the Weierstrass semigroup S of a point p on a Riemann surface C, then the vanishing sequence (v_0,\dots, v_(g-1)) of the canonical series at p is the list of orders of vanishing of differential forms at p, and the ramification sequence at p is (v_0 - 0, v_1 - 1, .. ,v_(g-1) - (g-1)). The weight of the Weierstrass point p is the sum of the ramification sequence at p.

The vanishing sequence can be computed from the set G of gaps in S as v_i = G_i - 1, so the weight is sum(G_i - 1 - i) or as the number of pairs (a,b) such that a is in S, b is a gap, and a < b.

i1 : weight {5,7}

o1 = 36
i2 : semigroup{5,7}

o2 = {0, 5, 7, 10, 12, 14, 15, 17, 19, 20, 21, 22, 24, 25, 26, 27, 28}

o2 : List
i3 : gaps{5,7}

o3 = {1, 2, 3, 4, 6, 8, 9, 11, 13, 16, 18, 23}

o3 : List

The effective weight ewt is the number of such pairs where a is a minimal generator of S; this may be a better measure.

i4 : mingens{5,7}

o4 = {5, 7}

o4 : List
i5 : ewt {5,7}

o5 = 15

See also

Ways to use weight:

For the programmer

The object weight is a method function.