The first interior shell of the Bougard-Joret extremal problem

Version 0.02 proves the entire admissible first interior shell: for every integer k at least 3 and every independence number a from 2 through k+1, the minimum size of a k-connected graph of order a+k+1 and independence number a is ceiling(k(a+k+1)/2). The construction combines classical Harary graphs, complement matchings and injective missing-neighbor pairs, with a self-contained connectivity proof for all parity cases. All extremizers at a=2 are complements of disjoint cycles of lengths at least five. The complete nonstar-tree characterization at a=k-1 from version 0.01 is retained. Exact finite controls cover 75 graphs and include an independent NetworkX audit. The original disproof remains credited to Das and Gupta; classical and previously published parameter overlaps are identified. This settles a restricted infinite shell, not the general revised first regime or second regime. Preprint, not peer reviewed.

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Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-09-05
DOI
https://doi.org/10.5281/zenodo.22341644
Citations
2
Primary Topic
Advanced Graph Theory Research
Type
preprint
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preprint

The first interior shell of the Bougard-Joret extremal problem

Felipe Santibañez-Leal
2 citations
Zenodo (CERN European Organization for Nuclear Research)
Advanced Graph Theory Research
preprint

The first interior shell of the Bougard-Joret extremal problem

Felipe Santibañez-Leal
preprint en
2 citations

Abstract

Version 0.02 proves the entire admissible first interior shell: for every integer k at least 3 and every independence number a from 2 through k+1, the minimum size of a k-connected graph of order a+k+1 and independence number a is ceiling(k(a+k+1)/2). The construction combines classical Harary graphs, complement matchings and injective missing-neighbor pairs, with a self-contained connectivity proof for all parity cases. All extremizers at a=2 are complements of disjoint cycles of lengths at least five. The complete nonstar-tree characterization at a=k-1 from version 0.01 is retained. Exact finite controls cover 75 graphs and include an independent NetworkX audit. The original disproof remains credited to Das and Gupta; classical and previously published parameter overlaps are identified. This settles a restricted infinite shell, not the general revised first regime or second regime. Preprint, not peer reviewed.

Zenodo (CERN European Organization for Nuclear Research)
Eos Neuroscience (United States) (US)
Advanced Graph Theory Research
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