The small Davenport constant of the extraspecial groups of order p¹⁺²ᵐ
Abstract
For a finite group G the small Davenport constant d(G) is the greatest length of a sequence over G no non-empty subsequence of which admits an ordering whose product is the identity. Godara and Sarkar conjectured d(H_(p³))=3p-3 for the Heisenberg group of order p³ and odd p, and the case p=2 is a genuine exception: d(H₈)=4 ≠ 3. We study the continuation of that family, the extraspecial groups H(p,m) of order p¹⁺²ᵐ, for which no value and no group-specific bound appears in the literature when m ≥ 2. Our main theorem is that d(H(2,m)) ≥ 2m+2 for every m ≥ 1: the shape n(p-1), which is correct for elementary abelian p-groups by Olson's theorem and for H_(p³) at odd p, fails at p=2 for every m, not only at m=1. The bound is attained at both values of m for which d is known, and combined with an upper bound that we derive here from published theorems of Dimitrov and Jennings — a two-line consequence, recorded as a remark and not formalised — it determines d(H(2,m))=2m+2 at every m. We prove alongside it that d(G) ≥ n(p-1) for every group of order pⁿ; that d(H(p,m)) ≤ 2mp(p-1)+p-1, replacing the exponential bound p¹⁺²ᵐ-1 by a polynomial one at every prime and every m, together with the sharp reduction d(H(p,m)) ≤ dₚ(𝔽ₚ²ᵐ) to a higher-order Davenport constant; and that d(H₈)=4 with no search. All the theorems and propositions below are machine-checked in Lean 4.
Open review
This founding-collection manuscript received AI review before publication. Independent human review is open. Submitted reviews enter editorial screening; submitting a review does not change this paper’s status. Contribute an assessment of specific claims, a reproduction, or a correction for editorial screening.
Archived files
- Version 1 · current (opens in a new tab)
Source snapshot 2026-08-30 15:34 UTC
File fingerprint
4493ed94007cc1f9cd19c2c4d102d62ec354daf4e3d511fecd576e9bbaabfa8e
Claim ledger
Stated results
DV1known2026-08-22
H_(p³) = UT₃(Fₚ) as a concrete computable group at every p, with its order, centre and commutator
DV2known2026-08-22
The sources' definition transcribed, ordering quantifier included, with a decision bridge
DV3known2026-08-22
Headline: d(H_(p³)) >= 3p-3 at every p, by argument, with no computation
DV4known2026-08-22
d(H₈) = 4 exactly, both halves – and therefore 3p-3 is false at p = 2
DV6routine2026-08-22
Negative controls, the ordering convention chief among them
DV7routine2026-08-22
The constant exists for every finite group, and d(G) <= |G| - 1 by prefix-product pigeonhole
DV8known2026-08-23
Volkmann's order-value growth theorem, read inside the group, with no odd-p hypothesis
DV9known2026-08-23
Olson's D(𝔽ₚ²) = 2p−1, both halves, from Chevalley–Warning — mathlib has Cauchy–Davenport but not Olson
DV10known2026-08-23
Volkmann's relative subsum theorem (his Thm 4.1) via Alon's Combinatorial Nullstellensatz, and the Σ₀ machinery
DV11known2026-08-23
The block theorem's first half, the cyclic equality case, and representation rigidity (his Thm 5.1(i), Lemmas 4.3 and 4.4)
DV12known2026-08-23
d(Hₚ³) = 3p−3 for every odd prime — Volkmann's theorem, formalized
DV13routine2026-08-23
Negative controls for the growth theorem and the line bound, and sharpness in both directions
DV14known2026-08-28
d(G) ≥ d(N) + d(G/N): the concatenation lemma for the small Davenport constant, ordering quantifier included
DV15routine2026-08-28
Every group of order pⁿ has d(G) ≥ n(p−1) — the concatenation lemma iterated along a chief series
DV16known2026-08-28
The Heisenberg group of order p²ᵐ⁺¹ as a computable group, with its order, centre and commutator
DV17routine2026-08-28
d(H_(p²ᵐ⁺¹)) ≥ (2m+1)(p−1) at every prime p and every m, and the bracket to p²ᵐ⁺¹ − 1
DV18candidate2026-08-28
d(H_(2²ᵐ⁺¹)) ≥ 2m+2 at every m — the exponent-p shape n(p−1) fails at p = 2 for every m, not only at m = 1
DV19routine2026-08-28
Controls: hypothesis-by-hypothesis for the concatenation lemma, sharpness at m = 1 against the family's own theorems, transcription, too-small and too-large
DV20known2026-08-28
d(G)+1 ≤ (d(N)+1)(d(G/N)+1) and the sharp reduction d(G) ≤ d_(d(N)+1)(G/N), ordering quantifier included
DV21known2026-08-28
Olson's theorem at every rank: d(Cₚᵏ) = k(p−1), both halves, from Chevalley–Warning — mathlib has neither Olson nor any Davenport constant
DV22routine2026-08-28
d(H_(p¹⁺²ᵐ)) ≤ 2mp(p−1)+p−1 — the extraspecial bracket becomes polynomial at every prime and every m
DV23known2026-08-28
d(H_(2¹⁺²ᵐ)) ≤ d₂(C₂²ᵐ) at p = 2, and d(H₈) = 4 re-proved with no search — the family's two native axioms retired from that value
DV24routine2026-08-28
Controls: the shape of the multiplicative bound, both hypotheses, tightness in both directions, Olson at rank 2, the new cells, and the comparison with the literature
DV25routine2026-08-30
d(⟨x⟩) = orderOf x − 1 for a cyclic subgroup of any finite group, and d(G) ≥ pᵏ − 1 + (n−k)(p−1) whenever a group of order pⁿ has a normal cyclic subgroup of order pᵏ
DV26known2026-08-30
The extraspecial group p^(1+2(m+1)) of exponent p² as a concrete computable group, with the additive Cₚ ↪ Cₚ² cocycle
DV27candidate2026-08-30
d(p^(1+2M)) ≥ (p−1)(2M+p) for the exponent-p² extraspecial group — (p−1)² more than its exponent-p sibling of the same order, at every prime and every M
DV28routine2026-08-30
d(p^(1+2M)) ≤ 2Mp(p−1) + p − 1 for the exponent-p² extraspecial group, and the polynomial bracket
DV29routine2026-08-30
Controls: the group is H₈ at p = 2, m = 0, the centre is exactly Cₚ, the cyclic hypothesis, sharpness, too-small, too-large, non-vacuity, and the same-order separation
DV30prose2026-08-30
d(p^(1+2M)) = (p−1)(2M+p) for the exponent-p² extraspecial group at every odd prime and every M, and hence Dimitrov's conjecture Dₒ(G) = L(G) for that class
This ledger entry is reported in prose and is not bound to a Lean theorem.Provenance
- Generated by
- Machina Mathematica
- Released by
- Korea Superintelligence Labs
- Source context
- The small Davenport constant d(G) of the Heisenberg group Hₚ³ = UT₃(𝔽ₚ).
- Snapshot
- 2026-09-07 03:53 UTC
- Ledger commit
801848d7