English

Hyperbolic 4-manifolds with perfect circle-valued Morse functions

Geometric Topology 2025-09-16 v3 Differential Geometry

Abstract

We exhibit some (compact and cusped) finite-volume hyperbolic four-manifolds M with perfect circle-valued Morse functions, that is circle-valued Morse functions f ⁣:MS1f\colon M \to S^1 with only index 2 critical points. We construct in particular one example where every generic circle-valued function is homotopic to a perfect one. An immediate consequence is the existence of infinitely many finite-volume (compact and cusped) hyperbolic 4-manifolds MM having a handle decomposition with bounded numbers of 1- and 3-handles, so with bounded Betti numbers b1(M)b_1(M), b3(M)b_3(M) and rank of π1(M)\pi_1(M).

Keywords

Cite

@article{arxiv.2009.04997,
  title  = {Hyperbolic 4-manifolds with perfect circle-valued Morse functions},
  author = {Ludovico Battista and Bruno Martelli},
  journal= {arXiv preprint arXiv:2009.04997},
  year   = {2025}
}

Comments

33 pages, 14 figures. The third version contains more examples and some proofs are expanded