Conjectural type-A standard homomorphisms with a generator times the longest element

Fix nn and i∈[2,n−2]i\in[2,n-2]. Let TiT_i be the standard generator and let w0[1,n−1]w_0^{[1,n-1]} be the longest element of the parabolic subgroup on [1,n−1][1,n-1] in type AnA_n.

Type-A twelve-period homomorphism conjecture. Define

T^1↦TiTn,T^2↦Tw0[1,n−1].\widehat{T}_1\mapsto T_iT_n,\qquad \widehat{T}_2\mapsto T_{w_0^{[1,n-1]}}.

Then these assignments define a standard homomorphism

Br⁡+(I2(12/d))→Br⁡n+1+,\operatorname{Br}^+(I_2(12/d))\to\operatorname{Br}^+_{n+1},

where

d=1+δ2i,n+δ2i,n−1+δ2i,n+1.d=1+\delta_{2i,n}+\delta_{2i,n-1}+\delta_{2i,n+1}.

This is listed as another conjectural family of non-disjoint standard homomorphisms; the paper states that the families in this section were verified for n≤15n\le15.

References

Primary source

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

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