AMR-010-0302 · Complete counterexample (universal bound)

No Uniform Hanna Neumann Bound for Convex-Core Volume

Manuscript 25 October 2026 · Online 25 October 2026

math.GTmath.GRUnrefereed preprint

Abstract

There is no universal constant K such that V(A intersection B) <= K V(A)V(B) for torsion-free convex-cocompact Kleinian groups, where V is three-dimensional convex-core volume. An explicit rank-two classical Schottky deformation has positive core volume tending to zero and constant systole arcosh(31). Independent parity kernels are distinct proper index-two subgroups of rank three, with rank-five intersection of index four; their volume ratio is exactly 1/V(G). Fixed ranks, fixed indices and a fixed positive systole therefore do not restore a uniform bound. We also give the exact finite-cover double-coset identity and prove a neighborhood-volume inequality by counting lifts. This is a complete counterexample to the universal-constant interpretation of Swarup's Question 3.2 in Bestvina's list, recorded as AMR-010-0302. It does not settle arbitrary ambient-dependent bounds for all infinite-index subgroups of one fixed G, so the broad source record is not claimed wholly resolved. Classical Schottky theory, Bonahon's volume regularity and covering theory are credited. AI-assisted, self-audited and unrefereed; no independent review, formal verification or absolute priority certification is claimed.

Record

Affiliation
Mercury Software GmbH
Result
Complete counterexample (universal bound)
Categories
math.GT · math.GR
Manuscript
25 October 2026
Online release
25 October 2026
Version
1.0
License
Creative Commons Attribution 4.0 International

Files and verification

The PDF is the canonical reading copy. The source archive contains the LaTeX manuscript, bibliography, reproducibility material, and audit documents without build artefacts.

Citation

Alper Ferudun, “No Uniform Hanna Neumann Bound for Convex-Core Volume,” EulerSolve Research Papers, AMR-010-0302, 2026. https://doi.org/10.5281/zenodo.23636651.

BibTeX
@misc{ferudun2026convexcore,
  author = {Ferudun, Alper},
  title = {No Uniform Hanna Neumann Bound for Convex-Core Volume},
  year = {2026},
  howpublished = {EulerSolve Research Papers},
  url = {https://eulersolve.org/papers/amr-010-0302/},
  doi = {10.5281/zenodo.23636651},
  note = {AMR-010-0302; unrefereed preprint}
}

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