Dimca–Sticlaru conjecture on branches of singularities of free and nearly free curves

Let CP2C\subset\mathbb{P}^2 be an irreducible plane curve. Using the Jacobian algebra and the quotient N(f)=If/JfN(f)=I_f/J_f associated with a homogeneous defining equation ff, call CC free when N(f)=0N(f)=0 and nearly free when N(f)0N(f)\ne 0 and dimN(f)k1\dim N(f)_k\leq 1 for every kk. A singularity has at most rr branches if its local reduced germ has no more than rr irreducible local components.

Dimca–Sticlaru's branch conjecture. (i) Any free irreducible plane curve CC has only singularities with at most two branches. (ii) Any nearly free irreducible plane curve CC has only singularities with at most three branches.

The conjecture gives local restrictions on singularities of irreducible free and nearly free plane curves. The cited passage does not report a resolution, so both assertions are recorded as open.

Sources & referencesView supporting material

Primary source

Enrique Artal Bartolo, Leire Gorrochategui, Ignacio Luengo and Alejandro Melle-Hernández, “On some conjectures about free and nearly free divisors”, arXiv:1511.09254 (2015).

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