Strengthened Fourier-type nn-operator Clarkson inequality conjecture

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Let H\mathscr{H} be a Hilbert space, let Bp(H)\mathbb{B}_p(\mathscr{H}) denote the Schatten pp-class, and define ωj=ejiπ/n\omega_j=e^{ji\pi/n}. Let A1,…,An∈Bp(H)A_1,\ldots,A_n\in\mathbb{B}_p(\mathscr{H}). The strengthened Fourier-type conjecture. For p≥2p\ge2,

n2−p/2(∑j=1n∥Aj∥p2)p/2≤∑k=1n∥∑j=1nωj−1k−1Aj∥pp.n^{2-p/2}\left(\sum_{j=1}^n\|A_j\|_p^2\right)^{p/2}\le\sum_{k=1}^n\left\|\sum_{j=1}^n\omega_{j-1}^{k-1}A_j\right\|_p^p.

For 0<p≤20<p\le2, the inequality is reversed. The source introduces this as a replacement conjecture after reporting that the preceding Fourier-type conjecture is false; no resolution of the strengthened assertion is supplied.

References

Primary source

Teng Zhang, “Clarkson–McCarthy type inequalities, part I: _p–_p and _q–_p Schatten p-estimates”, arXiv:2410.21961 (2026).

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