OWR-734-007 · Complete counterexample

Algebraic Shifting Can Destroy Every Polynomial HVC Bound

Manuscript 27 October 2026 · Online 27 October 2026

math.COmath.ATmath.ACUnrefereed preprint

Abstract

Kalai asked whether algebraic shifting preserves homological VC dimension, a uniform polynomial bound on total Betti numbers in a family closed under induced subcomplexes and links. We give a full negative answer to the unrestricted assertion in Oberwolfach Report 32/2004, p1730, Conjecture 3, recorded as OWR-734-007 in UnsolvedMath v1.6.0. A strongly hereditary family of minimum polynomial HVC exponent exactly 1, with constant 3, has after either exterior or symmetric algebraic shifting over the rationals a strongly hereditary closure with no finite polynomial HVC exponent. For a shift of the r-dimensional cross-polytope boundary, the link of the first s vertices has 2r-s vertices and top reduced Betti number binom(r,s); central links therefore grow exponentially. The proof uses established shifting properties and the classical shifted facet interpretation of h-vectors, which are credited. The example has unbounded simplicial dimension and does not resolve a fixed-dimensional modification or neighboring fractional-Helly and nerve conjectures. This four-page English preprint includes a standard-library checker with 4,317 exact checks. Developed with AI assistance and self-audited, it is unrefereed, without independent review, proof-assistant verification or absolute-priority certification.

Record

Affiliation
Mercury Software GmbH
Result
Complete counterexample
Categories
math.CO · math.AT · math.AC
Manuscript
27 October 2026
Online release
27 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, “Algebraic Shifting Can Destroy Every Polynomial HVC Bound,” EulerSolve Research Papers, OWR-734-007, 2026. https://doi.org/10.5281/zenodo.23697440.

BibTeX
@misc{ferudun2026hvcshifting,
  author = {Ferudun, Alper},
  title = {Algebraic Shifting Can Destroy Every Polynomial HVC Bound},
  year = {2026},
  howpublished = {EulerSolve Research Papers},
  url = {https://eulersolve.org/papers/owr-734-007/},
  doi = {10.5281/zenodo.23697440},
  note = {OWR-734-007; unrefereed preprint}
}

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