English

Non-complex cobordisms between quasipositive knots

Geometric Topology 2025-12-25 v3

Abstract

We show that for every genus g0g \geq 0, there exist quasipositive knots K0gK_0^g and K1gK_1^g such that there is a cobordism of genus g=g4(K1g)g4(K0g)g=|g_4(K_1^g)-g_4(K_0^g)| between K0gK_0^g and K1gK_1^g, but there is no ribbon cobordism of genus gg in either direction and thus no complex cobordism between these two knots. This gives a negative answer to a question posed by Feller in 2016.

Keywords

Cite

@article{arxiv.2504.04894,
  title  = {Non-complex cobordisms between quasipositive knots},
  author = {Maciej Borodzik and Paula Truöl},
  journal= {arXiv preprint arXiv:2504.04894},
  year   = {2025}
}

Comments

13 pages, 5 figures, 1 table. Comments welcome! v3: More details and improved exposition following the referee's comments. Section 5 added, along with 5 figures. Corresponds to version accepted for publication in J. Math. Pures Appl

R2 v1 2026-06-28T22:49:10.043Z