Algebraic Shifting Can Destroy Every Polynomial HVC Bound

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.

Authors

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-10-27
DOI
https://doi.org/10.5281/zenodo.23697439
Primary Topic
Advanced Combinatorial Mathematics
Type
preprint
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preprint

Algebraic Shifting Can Destroy Every Polynomial HVC Bound

Alper Ferudun
Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
preprint

Algebraic Shifting Can Destroy Every Polynomial HVC Bound

Alper Ferudun
preprint en

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.

Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
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Algebraic Shifting Can Destroy Every Polynomial HVC Bound — Alper Ferudun · Zenodo (CERN European Organization for Nuclear Research) (2026) | TGRS Research Map | TGRS