The conjectural description of real discrete series for affine Hecke algebras of type B

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Let H\mathcal{H} be the affine Hecke algebra with labels q2=q1mq_2=q_1^m obtained from the parameters qαˇq_{\check{\alpha}} as in the source, with q1>1q_1>1 and q21q_2\geq 1. Let W0rW_0r be the W0W_0-orbit of the center of a real residual coset of H\mathcal{H}. Write ΔW0r\Delta_{W_0r} for the corresponding set of modules, H0\mathcal{H}_0 for the finite Hecke algebra, R(M)R(M) for the W0W_0-module obtained from an H0\mathcal{H}_0-module MM in the limit qαˇ1/21q_{\check{\alpha}}^{1/2}\to1, and ama_m for the stated aa-function. Let W^0\hat{W}_0 denote the irreducible W0W_0-representations, let ϵ\epsilon be the sign representation, and let m\succ_m be an ordering on W^0\hat{W}_0 refining the preorder defined by ψχam(ψ)am(χ)\psi\succ\chi\Rightarrow a_m(\psi)\leq a_m(\chi), with similarity classes as intervals. Conjectural description. (i) ΔW0r\Delta_{W_0r} is indexed by Σm(W0r)\Sigma_m(W_0r). (ii) The modules in ΔW0r\Delta_{W_0r} are naturally graded for the action of H0\mathcal{H}_0; their top nonzero degree is am(Σm(W0r))a_m(\Sigma_m(W_0r)), and the H0\mathcal{H}_0-representations in that degree are irreducible, with corresponding W0W_0-representations Σm(W0r)ϵ\Sigma_m(W_0r)\otimes\epsilon. (iii) If MχM_\chi is the H\mathcal{H}-module labelled by χW^0\chi\in\hat{W}_0 using (ii) and the stated partition of W^0\hat{W}_0, so that R(Mχtop)χϵR(M_\chi^{\mathrm{top}})\cong\chi\otimes\epsilon, then the matrix (R(Mχ),ψ)ψ,χW^0(R(M_\chi),\psi)_{\psi,\chi\in\hat{W}_0} is block-lower triangular with blocks given by the similarity classes. (iv) The H0\mathcal{H}_0-structure of MχM_\chi can be computed using Shoji's generalized Green functions. The statement proposes a detailed parametrization and character-theoretic description of the real discrete-series modules for these affine Hecke algebras; the supplied text does not establish it or give resolution evidence, so its status remains open.

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Primary source

K. Slooten, “Reducibility of induced discrete series representations for affine Hecke algebras of type B”, arXiv:math/0511206 (2005).

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