Asymptotic existence of nodal curve components with expected moduli

For integers r,d,g,tr,d,g,t with 0tg0\le t\le g, let E(r,d,g,t)E'(r,d,g,t) be the locus of integral, non-degenerate degree-dd curves in Pr\mathbb{P}^r of arithmetic genus gg having exactly tt ordinary nodes as their only singularities and satisfying h1(C,OC(2))=0h^1(C,\mathcal{O}_C(2))=0. An irreducible component Γ\Gamma of this locus has expected dimension when its Hilbert-scheme dimension is (r+1)d(r3)(g1)(r+1)d-(r-3)(g-1), and has the expected number of moduli when

dim(ur,d,g,t(Γ))=min{3g3t,3g3+ρ(d,g,r)t}.\dim\bigl(u_{r,d,g,t}(\Gamma)\bigr)=\min\{3g-3-t,3g-3+\rho(d,g,r)-t\}.

Asymptotic existence conjecture. Fix an integer r3r\geq 3. There is a function Or:NN\mathbb{O}_r:\mathbb{N}\to\mathbb{N} such that limg+Or(g)/g=0\lim_{g\to+\infty}\mathbb{O}_r(g)/g=0 and an integer g0g_0 such that, for all integers g,t,dg,t,d with gg0g\geq g_0, 0tg0\leq t\leq g, and ρ(g,r,d)+t2gOr(g)-\rho(g,r,d)+t\leq 2g-\mathbb{O}_r(g), the locus E(r,d,g,t)E'(r,d,g,t) has an irreducible component with expected dimension and the expected number of moduli.

This predicts asymptotic existence of components of the Hilbert scheme of curves in projective space having both unobstructed deformation theory and the smallest dimension permitted by the moduli map. The statement concerns all sufficiently large genera in the specified numerical range; no resolution status is supplied in the source.

Sources & referencesView supporting material

Primary source

Edoardo Ballico, “Nodal curves and components of the Hilbert scheme of curves in P^r with the expected number of moduli”, arXiv:1304.5840 (2013).

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