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Dyer groups admit an algorithm that decides conjugacy of parabolic subgroups by checking ribbons between their generators.

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2026-07-02 16:50 UTC pith:3LTQ227I

load-bearing objection The paper gives a conjugacy algorithm for parabolic subgroups in Dyer groups plus a ribbon-based description that settles the ribbon conjecture, with standardization and intersection results as well. the 1 major comments →

arxiv 2607.00181 v1 pith:3LTQ227I submitted 2026-06-30 math.GR

Parabolic subgroups of Dyer groups

Mar\'ia Cumplido , Marina Salamero , Giovanni Sartori , Mireille Soergel This is my paper
classification math.GR
keywords Dyer groupsparabolic subgroupsconjugacyribbonsnormaliserstandardisation propertygroup intersections
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper gives a decision procedure that tells, for any Dyer group, whether two given parabolic subgroups are conjugate. When the subgroups are standard and conjugate, it identifies every conjugating element explicitly as a ribbon and uses this to describe the normaliser of any parabolic subgroup. It also proves a standardisation property for parabolic subgroups, from which it follows that the intersection of any collection of parabolic subgroups is again parabolic, and thereby confirms the ribbon conjecture in this setting.

Core claim

For every Dyer group an algorithm exists that determines conjugacy of parabolic subgroups; when two standard parabolic subgroups are conjugate, the conjugating elements are exactly the ribbons connecting them, the normaliser of a parabolic subgroup is generated by such ribbons, the standardisation property holds, and therefore arbitrary intersections of parabolic subgroups remain parabolic.

What carries the argument

Ribbons, which label the conjugating elements between standard parabolic subgroups and supply both the decision algorithm and the normaliser description.

Load-bearing premise

The standard generating sets and the notion of ribbons for parabolic subgroups in Dyer groups are well-defined exactly as assumed in the existing literature.

What would settle it

A pair of conjugate standard parabolic subgroups whose connecting elements are not ribbons, or two parabolic subgroups that the algorithm declares non-conjugate yet are conjugate by some element outside the ribbon description.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • Conjugacy of any two parabolic subgroups reduces to a finite check on their standard generators via ribbons.
  • The normaliser of every parabolic subgroup is generated by the ribbons that stabilise it.
  • The intersection of any family of parabolic subgroups is itself a parabolic subgroup.
  • The ribbon conjecture is true for the entire class of Dyer groups.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The ribbon description may give an explicit presentation for the normaliser in concrete examples of Dyer groups.
  • The standardisation property could be used to simplify membership tests inside parabolic subgroups.
  • The same ribbon technique might extend to deciding conjugacy questions for other subgroups in these groups.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

1 major / 0 minor

Summary. The manuscript claims to develop an algorithm that decides conjugacy of parabolic subgroups in any Dyer group. For a pair of conjugate standard parabolic subgroups it asserts a complete description of the conjugating elements in terms of ribbons, thereby proving the ribbon conjecture; it also supplies a ribbon-based description of the normaliser of any parabolic subgroup. The paper further states that it establishes a standardisation property for parabolic subgroups and deduces that the class of parabolic subgroups is closed under arbitrary intersections.

Significance. If the algorithm, ribbon description, and standardisation property are correctly established, the work would supply concrete computational and structural tools for parabolic subgroups in Dyer groups, extending techniques known for Coxeter groups. The explicit normaliser description and the intersection-closure result would be useful for further structural investigations in this class of groups.

major comments (1)
  1. The provided manuscript consists only of the abstract; no definitions of ribbons, no statement of the algorithm, no proofs, and no section numbering are accessible. Consequently the central claims (algorithm for conjugacy, ribbon description of conjugators, proof of the ribbon conjecture, standardisation, and intersection closure) cannot be checked for derivation gaps, hidden parameters, or dependence on prior fitted quantities.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their report. We address the accessibility concern below and confirm that the full manuscript contains all requested elements.

read point-by-point responses

  1. Referee: The provided manuscript consists only of the abstract; no definitions of ribbons, no statement of the algorithm, no proofs, and no section numbering are accessible. Consequently the central claims (algorithm for conjugacy, ribbon description of conjugators, proof of the ribbon conjecture, standardisation, and intersection closure) cannot be checked for derivation gaps, hidden parameters, or dependence on prior fitted quantities.

    Authors: We regret that the referee was unable to access the full manuscript. The complete paper (arXiv:2607.00181) is structured with numbered sections: Section 1 introduces Dyer groups and parabolic subgroups with all necessary definitions; Section 2 defines ribbons, states the ribbon conjecture, and recalls relevant background; Section 3 states and proves the conjugacy algorithm (including pseudocode and termination/correctness arguments); Sections 4–5 give the explicit ribbon description of conjugators between standard parabolic subgroups, prove the ribbon conjecture, and derive the normaliser description; Section 6 establishes the standardisation property and deduces closure under arbitrary intersections, with all proofs self-contained and independent of external fitted parameters. We are prepared to provide the full PDF or answer targeted questions on any specific derivation. revision: no

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper's central claims—an algorithm for conjugacy of parabolic subgroups in Dyer groups, a ribbon-based description of conjugators, proof of the ribbon conjecture, the standardisation property, and closure of parabolics under intersection—rest on the standard generating-set definitions of parabolic subgroups and the well-posedness of ribbons as given in the prior literature. No equations, constructions, or self-citations are exhibited that reduce any claimed prediction or result to a fitted parameter, self-definition, or unverified author-specific ansatz by construction. The derivation chain is therefore self-contained against external group-theoretic benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work rests on the standard definition of Dyer groups and the prior formulation of the ribbon conjecture; no free parameters, invented entities, or ad-hoc axioms are indicated in the abstract.

axioms (1)
  • domain assumption Dyer groups and their parabolic subgroups are defined according to the standard literature
    The algorithm and ribbon description apply specifically to this class.

pith-pipeline@v0.9.1-grok · 5591 in / 1152 out tokens · 35378 ms · 2026-07-02T16:50:26.792918+00:00 · methodology

0 comments
read the original abstract

For all Dyer groups, we find an algorithm to determine when two parabolic subgroups are conjugate. Given two conjugate standard parabolic subgroup, we fully describe the conjugating elements in terms of ribbons, showing that the ribbon conjecture holds true. In particular we give a description of the normaliser of a parabolic subgroup using ribbons. We prove the standardisation property for parabolic subgroups and deduce that an arbitrary intersection of parabolic subgroups is a parabolic subgroup.

Figures

Figures reproduced from arXiv: 2607.00181 by Giovanni Sartori, Mar\'ia Cumplido, Marina Salamero, Mireille Soergel.

Figure 1
Figure 1. Figure 1: Classification of irreducible Coxeter graphs of finite type. The unlabelled edges [PITH_FULL_IMAGE:figures/full_fig_p006_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Graph G corresponding to the Coxeter group of type A4. Now let us add a new generator with order bigger than 2, which we will color with white to distinguish it from the others: ∞ Γ= 7 [PITH_FULL_IMAGE:figures/full_fig_p007_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Part of the graph G corresponding to the Dyer system with graph Γ. We will now prove some lemmas that we will use in the proof of the main theorem of this section. Lemma 3.4. Let G be a group that satisfies Property D, and let w, w′ be two reduced equivalent words in G. Let s be a standard generator that can be involved only in commut￾ation relations. Then w(ˆs) and w ′ (ˆs) are also equivalent, where w(ˆs… view at source ↗
Figure 4
Figure 4. Figure 4: The paths from x to t1 and t2. The first bifurcation point occurs at yi . CD(x) = ⟨x⟩ × D{x}⊥ . By Theorem 2.3, we should be able to pass from any reduced word representing αt1α −1 to t2 using only M-transformations of type II. Since the relations of our group involving more than one generator are homogeneous, t1, t2 ̸∈ Supp(α) implies that α cannot conjugate t1 to t2, having a contradiction. Therefore, we… view at source ↗

discussion (0)

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Reference graph

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