Appleby–Flammia–McConnell–Yard ray class field conjecture for SICs

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Let d≥4d\geq 4, set Δd=(d+1)(d−3)\Delta_d=(d+1)(d-3), and let Kd=\Q(Δd)K_d=\Q(\sqrt{\Delta_d}). For a Weyl–Heisenberg line-SIC SS in dimension dd, let \fieldvecS\fieldvec{S} denote its SIC field, and let Hd′∞1∞2H_{d'\infty_1\infty_2} be the ray class field of KdK_d with modulus d′∞1∞2d'\infty_1\infty_2, where d′=dd'=d for odd dd and d′=2dd'=2d for even dd. Appleby, Flammia, McConnell, and Yard's conjecture. At least one Weyl–Heisenberg line-SIC has \fieldvecS=Hd′∞1∞2\fieldvec{S}=H_{d'\infty_1\infty_2}, and every such line-SIC has \fieldvecS\fieldvec{S} a finite Galois extension of \Q\Q containing Hd′∞1∞2H_{d'\infty_1\infty_2}. The two assertions were verified in the cited dimensions and for all currently known SICs there, but remain conjectural in general.

References

Primary source

Gene S. Kopp and Jeffrey C. Lagarias, “SIC-POVMs and orders of real quadratic fields”, arXiv:2407.08048 (2026).

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