Asymptotic existence of nodal curve components with bounded numbers of nodes

For integers r,d,g,xr,d,g,x with 0xg0\le x\le g, let E(r,d,g,x)E'(r,d,g,x) be the locus of integral, non-degenerate degree-dd curves in Pr\mathbb{P}^r of arithmetic genus gg having exactly xx 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,x(Γ))=min{3g3x,3g3+ρ(d,g,r)x}.\dim\bigl(u_{r,d,g,x}(\Gamma)\bigr)=\min\{3g-3-x,3g-3+\rho(d,g,r)-x\}.

Bounded-nodes existence conjecture. Fix integers r3r\geq 3 and t0t\geq 0. There is a function Or,t:NN\mathbb{O}_{r,t}:\mathbb{N}\to\mathbb{N} such that limg+Or,t(g)/g=0\lim_{g\to+\infty}\mathbb{O}_{r,t}(g)/g=0 and an integer g0tg_0\geq t such that, for all integers g,x,dg,x,d with gg0g\geq g_0, 0xt0\leq x\leq t, and ρ(g,r,d)+x3gOr,t(g)-\rho(g,r,d)+x\leq 3g-\mathbb{O}_{r,t}(g), the locus E(r,d,g,x)E'(r,d,g,x) has an irreducible component with expected dimension and the expected number of moduli.

This is a stronger asymptotic assertion in the bounded-node regime, allowing every number of nodes up to a fixed tt while retaining the expected-dimensional and expected-moduli conclusions. The source supplies no evidence that the conjecture has been resolved.

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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