Infinite-dimensionality conjecture for generalized Fomin–Kirillov algebras

Let nn be a positive integer, let αijk,βijk,γij,λijkl{1,1}\alpha_{ijk},\beta_{ijk},\gamma_{ij},\lambda_{ijkl}\in\{1,-1\}, and let A(α,β,γ,λ)A(\alpha,\beta,\gamma,\lambda) be the algebra generated by xijx_{ij} for iji\ne j and 1i,jn1\leq i,j\leq n, subject to

xij2=0,xij=γijxji,x_{ij}^2=0,\qquad x_{ij}=\gamma_{ij}x_{ji}, xijxjk+αijkxjkxki+βijkxkixij=0,x_{ij}x_{jk}+\alpha_{ijk}x_{jk}x_{ki}+\beta_{ijk}x_{ki}x_{ij}=0,

for 1i,j,kn1\leq i,j,k\leq n, and

xijxkl=λijklxklxijx_{ij}x_{kl}=\lambda_{ijkl}x_{kl}x_{ij}

for any distinct i,j,k,li,j,k,l. Infinite-dimensionality conjecture. The algebra A(α,β,γ,λ)A(\alpha,\beta,\gamma,\lambda) is infinite dimensional when n>4n>4. Furthermore, the Nichols algebra B(O(1 2),ρ)\mathfrak{B}(\mathcal O_{(1\ 2)},\rho) is infinite dimensional for n>6n>6 when ρ=sgnsgn\rho=\operatorname{sgn}\otimes\operatorname{sgn} or ρ=ϵsgn\rho=\epsilon\otimes\operatorname{sgn}. The claim concerns the generalized quadratic algebras extending the Fomin–Kirillov algebra and specific Nichols algebras over the symmetric group; the source gives no resolution or supporting evidence beyond this assertion.

Sources & referencesView supporting material

Primary source

Shouchuan Zhang, Weicai Wu, Zhengtang Tan and Yao-Zhong Zhang, “Nichols algebras over classical Weyl groups, Fomin-Kirillov algebras and Lyndon basis”, arXiv:1307.8227 (2017).

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