English

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

Algebraic Geometry 2026-03-09 v1

Abstract

We give an explicit example of a fibration f ⁣:XYf \colon X \to Y between smooth projective varieties whose "orbifold base" Δf\Delta_f in the sense of Campana has the property that the induced morphism X(Y,Δf)X \to (Y, \Delta_f) is not a morphism of C-pairs (i.e., it is not an "orbifold morphism"). We however also show that this cannot happen if ff is "neat" and (Y,Δf)(Y, \Delta_f) is sufficiently well-behaved. Finally, we discuss the implications of this statement towards conjectures of Campana aiming to give algebro-geometric characterizations of those varieties which either admit a dense entire curve or a potentially dense set of integral points.

Keywords

Cite

@article{arxiv.2603.06083,
  title  = {The map to the orbifold base need not be an orbifold map},
  author = {Finn Bartsch},
  journal= {arXiv preprint arXiv:2603.06083},
  year   = {2026}
}

Comments

13 pages, comments welcome!

R2 v1 2026-07-01T11:06:29.393Z