The semisimplicity criterion for cyclotomic Hecke–Clifford superalgebras

Let K\mathbb{K} be the ground field, let qq be the parameter, let Q=(Q1,Q2,,Qm)(K)m\underline{Q}=(Q_1,Q_2,\ldots,Q_m)\in(\mathbb{K}^*)^m, and let f=fQ()f=f^{(\bullet)}_{\underline{Q}} with {0,s,ss}\bullet\in\{\mathtt{0},\mathtt{s},\mathtt{ss}\}. Write HΔf(n)\mathcal{H}^f_{\Delta}(n) for the corresponding cyclotomic Hecke–Clifford superalgebra, and call a module completely splittable when the elements X1,X2,,XnX_1,X_2,\ldots,X_n act semisimply on it. Let Pn(q2,Q)P^{\bullet}_{n}(q^2,\underline{Q}) be the associated parameter polynomial. Semisimplicity and complete splittability conjecture. The following are equivalent:

  1. The algebra HΔf(n)\mathcal{H}^f_{\Delta}(n) is semisimple.
  2. Every irreducible HΔf(n)\mathcal{H}^f_{\Delta}(n)-module is completely splittable.
  3. Pn(q2,Q)0P^{\bullet}_{n}(q^2,\underline{Q})\neq 0.

This would characterize semisimplicity through the complete splittability of irreducible modules and the nonvanishing of the parameter polynomial. The preceding results establish that the nonvanishing condition implies semisimplicity and that, under this condition, every irreducible module is completely splittable; the converse implications are stated here as a conjecture and are left for future work.

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Primary source

Lei Shi and Jinkui Wan, “On representation theory of cyclotomic Hecke-Clifford algebras”, arXiv:2501.06763 (2025).

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