2 problems

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Choffrut's conjecture on the rank-four grammic congruence
Choffrut's conjecture. For $n=4$ , the grammic congruence is generated by the Knuth relations together with the pairs
Conjectureopencombinatorial-algebra grammic-monoids monoid-presentationsarXiv posted 2 days ago
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The positive surface braid monoid presentation conjecture
Let $\Sigma$ be an oriented marked surface and let $\Delta$ be a triangulation. Let $Br_\Delta^+$ be the submonoid of $Br_\Delta$ generated by the elements $T_{\gamma,\Delta}$ for…
Conjectureopenbraid-groups marked-surfaces monoid-presentationsarXiv posted 2 days ago

Choffrut's conjecture on the rank-four grammic congruence