Hanner inequality for Schatten norms of operator tuples

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Let A0,A1,…,An−1A_0,A_1,\ldots,A_{n-1} be operators on a separable Hilbert space, and let p,qp,q satisfy 1/p+1/q=11/p+1/q=1. Operator Hanner-type conjecture. For 2≤p<∞2\leq p<\infty,

n(∑j=0n−1∥Aj∥pp)q/p≤∥∑j=0n−1Aj∥pq+∑0≤j<k≤n−1∥Aj−Ak∥pq,n\left(\sum_{j=0}^{n-1}\lVert A_j\rVert_p^p\right)^{q/p}\leq\left\lVert\sum_{j=0}^{n-1}A_j\right\rVert_p^q+\sum_{0\leq j<k\leq n-1}\lVert A_j-A_k\rVert_p^q,

whereas for 0<p≤20<p\leq2,

∥∑j=0n−1Aj∥pq+∑0≤j<k≤n−1∥Aj−Ak∥pq≤n(∑j=0n−1∥Aj∥pp)q/p.\left\lVert\sum_{j=0}^{n-1}A_j\right\rVert_p^q+\sum_{0\leq j<k\leq n-1}\lVert A_j-A_k\rVert_p^q\leq n\left(\sum_{j=0}^{n-1}\lVert A_j\rVert_p^p\right)^{q/p}.

The conjecture is presented as a natural extension of known operator inequalities and would generalize Hanner-type inequalities; the source gives no resolution.

References

Primary source

K. M. R. Audenaert and F. Kittaneh, “Problems and Conjectures in Matrix and Operator Inequalities”, arXiv:1201.5232 (2012).

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