Zhang's quasisymmetric modulus conjecture

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For Z∈MdZ\in\mathbb{M}_d, let ∣Z∣qsym|Z|_{\mathrm{qsym}} denote the quasisymmetric modulus used in Zhang's conjecture. For A,B∈MdA,B\in\mathbb{M}_d, there are unitaries U,V∈MdU,V\in\mathbb{M}_d. Zhang's quasisymmetric modulus conjecture.

∣A+B∣qsym≤2(U∣A∣qsymU∗+V∣B∣qsymV∗).|A+B|_{\mathrm{qsym}}\le\sqrt{2}\left(U|A|_{\mathrm{qsym}}U^*+V|B|_{\mathrm{qsym}}V^*\right).

This is described as a related strong conjecture proposed by Zhang; the supplied text gives no resolution status.

References

Primary source

Jean-Christophe Bourin and Eun-Young Lee, “Averages over matrix unitary orbits and spectral order”, arXiv:2606.15624 (2026).

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