English

More counterexamples to the Arithmetic Puncturing Problem

Algebraic Geometry 2025-12-08 v1 Complex Variables Number Theory

Abstract

We construct examples of threefolds with terminal singularities (resp. surfaces with canonical singularities) which are special in the sense of Campana, have a potentially dense set of integral points, admit a dense entire curve, have vanishing Kobayashi pseudometric, and are geometrically special in the sense of Javanpeykar-Rousseau but whose regular locus fails to have any of these properties. This improves on earlier work by Cadorel-Campana-Rousseau and joint work by the author with Javanpeykar-Levin, where such fourfolds with canonical singularities were constructed, and gives refined answers to questions due to Hassett-Tschinkel and Kamenova-Lehn. Lastly, we show that some of our examples satisfy the weak approximation property and briefly discuss a question on puncturing varieties satisfying strong approximation raised by Wittenberg.

Keywords

Cite

@article{arxiv.2512.05345,
  title  = {More counterexamples to the Arithmetic Puncturing Problem},
  author = {Finn Bartsch},
  journal= {arXiv preprint arXiv:2512.05345},
  year   = {2025}
}

Comments

9 pages, comments welcome!

R2 v1 2026-07-01T08:10:32.230Z