The reflection deletion conjecture for Coxeter groups

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Let WW be a Coxeter group, let w∈Ww\in W, and let t∈Wt\in W be a reflection. Write ℓ\ell for the Coxeter length function.

Reflection deletion conjecture. If

ℓ(wt)<ℓ(w)−1,\ell(wt)<\ell(w)-1,

then there exists a reduced expression

w=si1⋯siℓ−1siℓsiℓ+1⋯sirw=s_{i_1}\dotsm s_{i_{\ell-1}}s_{i_\ell}s_{i_{\ell+1}}\dotsm s_{i_r}

with iℓ−1=iℓ+1=ii_{\ell-1}=i_{\ell+1}=i such that

wt=si1⋯sis^iℓsi⋯sir,wt=s_{i_1}\dotsm s_i\hat{s}_{i_\ell}s_i\dotsm s_{i_r},

where the factor siℓs_{i_\ell} has been removed. The conjecture is a Coxeter-group reformulation of the preceding root-order conjecture and remains open in the supplied source.

References

Primary source

Changzheng Li, Konstanze Rietsch and Mingzhi Yang, “An anticanonical perspective on G/P Schubert varieties”, arXiv:2506.18388 (2025).

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