Variance-sensitive Matrix Spencer conjecture

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Let A1,…,An∈Rn×nA_1,\ldots,A_n\in\mathbb R^{n\times n} be symmetric matrices satisfying ∥Ai∥op≤1\|A_i\|_{\mathrm{op}}\le 1. A coloring is a vector x∈{±1}nx\in\{\pm1\}^n. Variance-sensitive Matrix Spencer conjecture. There exists a universal constant CC such that every such family admits a coloring satisfying

∥∑i=1nxiAi∥op≤C∥∑i=1nAi2∥op1/2.\Bigl\|\sum_{i=1}^n x_iA_i\Bigr\|_{\mathrm{op}}\le C\Bigl\|\sum_{i=1}^n A_i^2\Bigr\|_{\mathrm{op}}^{1/2}.

This conjecture is motivated by variance-sensitive noncommutative Khintchine inequalities and would refine the dimension-dependent Matrix Spencer bound. The supplied text presents it as a conjecture and gives no resolution; its general status is therefore open.

References

Primary source

Emrullah Akbas and Suvrit Sra, “An Algebraic Matrix Spencer Theorem”, arXiv:2606.16005 (2026).

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