Finn Bartsch

collaborators

10 papers

math.AG2026

The theorem of Maehara-Severi for maps of general type

Finn Bartsch, Ariyan Javanpeykar, Erwan Rousseau

We prove a finiteness result for dominant rational maps whose orbifold base is of general type. Our finiteness result generalizes Maehara's theorem that a given variety dominates o…

math.AG2026

Weakly special varieties, Campana stacks, and Remarks on Orbifold Mordell

Finn Bartsch, Ariyan Javanpeykar

We construct the first weakly special surfaces that are not Campana-special, including the complement of the plane curve $x^{2} y^{3} = 1$ in $A^{2}$ . We prove that the set of $\…

math.AG2026

The map to the orbifold base need not be an orbifold map

Finn Bartsch

We give an explicit example of a fibration $f : X \to Y$ between smooth projective varieties whose "orbifold base" $I^_{f}$ in the sense of Campana has the property that the ind…

math.AG2026

The Weakly Special Conjecture contradicts orbifold Mordell, and hence the abc conjecture

Starting from an Enriques surface over $Q (t)$ considered by Lafon, we give the first examples of smooth projective weakly special threefolds which fibre over the projectiv…

math.AG2025

Symmetric products and puncturing Campana-special varieties

Finn Bartsch, Ariyan Javanpeykar, Aaron Levin

We give a counterexample to the Arithmetic Puncturing Conjecture and Geometric Puncturing Conjecture of Hassett-Tschinkel using symmetric powers of uniruled surfaces, and propose a…

math.AG2025

The theorem of Maehara-Severi for maps of general type

Weakly special varieties, Campana stacks, and Remarks on Orbifold Mordell

The map to the orbifold base need not be an orbifold map

The Weakly Special Conjecture contradicts orbifold Mordell, and hence the abc conjecture

Symmetric products and puncturing Campana-special varieties

More counterexamples to the Arithmetic Puncturing Problem