Conjectural interval-family homomorphisms from dihedral type to type A

Let 1ba<n11\le b\le a<n-1 and a>1a>1. For the type-AA braid monoid, write w0[r,s]w_0^{[r,s]} for the longest element of the parabolic subgroup on the interval [r,s][r,s].

Interval-family homomorphism conjecture. The assignments

T^1Tw0[1,a],T^2Tw0[b,n1]\widehat{T}_1\mapsto T_{w_0^{[1,a]}},\qquad \widehat{T}_2\mapsto T_{w_0^{[b,n-1]}}

define a homomorphism Br+(I2(N))Brn+\operatorname{Br}^+(I_2(N))\to\operatorname{Br}^+_n if one of the following holds:

N=2nn+ba22Z>0;N=\frac{2n}{n+b-a-2}\in2\mathbb Z_{>0}; a+b=nandN=nb11+2Z>0;a+b=n\quad\text{and}\quad N=\frac{n}{b-1}\in1+2\mathbb Z_{>0}; a+1=2(b1),a+b<n,andN=6.a+1=2(b-1),\quad a+b<n,\quad\text{and}\quad N=6.

The paper presents these as a conjectural infinite family of non-disjoint standard homomorphisms and reports verification for n15n\le15.

Sources & referencesView supporting material

Primary source

Arkady Berenstein, Jacob Greenstein and Jian-Rong Li, “Artin monoids, their homomorphisms and twins”, arXiv:2606.26776 (2026).

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