h⁰ of the ideal sheaf I on a Dedekind curve, defined as the k-dimension
of I viewed as a submodule.
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h¹ of the ideal sheaf I, defined via Serre duality as the k-dimension
of Hom_A(I, Ω_{A/k}).
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Serre duality definition for ideal sheaves: h¹(I) = dim_k Hom_A(I, Ω_{A/k}).
For the unit ideal I = ⊤, the Serre-dual definition h¹(I) agrees
with h¹(O_X) defined as dim_k Ω_{A/k}.
Serre duality consistency check: h¹(O_X) = dim_k Ω_{A/k},
combining the ideal-sheaf duality with the Hom(⊤, Ω) ≃ Ω equivalence.
h¹ of the unit ideal sheaf equals dim_k Ω_{A/k}, the geometric genus.
Euler characteristic of an ideal sheaf on a Dedekind curve:
χ(I) = h⁰(I) − h¹(I).
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Serre duality on ℙ¹ (nonneg case): for n ≥ 0,
dim H¹(O(n)) = dim H⁰(O(-2 - n)).
Serre duality on ℙ¹ (negative case): for n < 0,
dim H¹(O(n)) = dim H⁰(O(-2 - n)).
Serre duality on ℙ¹ for all n: dim H¹(O(n)) = dim H⁰(O(-2 - n)).
Alternative name for h¹ of an ideal sheaf, emphasizing the sheaf perspective.
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Sheaf-theoretic Serre duality: h¹(I) = dim_k Hom_A(I, Ω_{A/k}).