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Vector Balancing


Vector balancing is the problem of assigning signs to a given collection of vectors so that their signed sum has a small prescribed vector norm. A permutation variant also allows the coordinates of each vector to be independently permuted (Niles-Weed et al. 2026).

The Komlós conjecture asks for a bound independent of the number of vectors and the dimension when their Euclidean norms are at most 1 and the signed sum is measured in the infinity norm. Guo et al. (2026) report a bound less than 3sqrt(2pi), and Karingula and Lovett (2026) give an elementary proof with bound 36. These statements concern the final signed sum with signs alone. As of Oct. 26, 2026, journal peer review of the cited 2026 proofs had not been verified.

Niles-Weed et al. (2026) proved that, for any vectors v_1, v_2, ..., v_m in R^n with Euclidean norm at most 1, there are signs epsilon_i in {-1,1} and coordinate permutations sigma_i such that

 max_(1<=k<=m)||sum_(i=1)^kepsilon_isigma_i(v_i)||_infty<=(sqrt(n-1)+1)/(sqrt(n)),

where ||·||_infty is the infinity norm. The choices can be made online, using only the vectors seen so far. The bound tends to 1 as n->infty and is asymptotically optimal, since a single coordinate unit vector forces a bound of at least 1. The result concerns the variant with permutations, not sign choices alone.


See also

Euclidean Norm, Infinity Norm, Komlós Conjecture, Permutation, Vector Norm

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References

Guo, S.; Fang, E. X.; and Lu, J. "Vector Balancing via Directional Total Variation." 10 Sep 2026. https://arxiv.org/abs/2609.11189.Karingula, S. R. and Lovett, S. "An Elementary Proof of the Komlós Conjecture." 17 Sep 2026. https://arxiv.org/abs/2609.20979.Niles-Weed, J.; Sadovsky, S.; and Shkrob, J. "An Optimal Constant for Vector Balancing with Permutations." 1 Oct 2026. https://arxiv.org/abs/2610.02127.

Cite this as:

Weisstein, Eric W. "Vector Balancing." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/VectorBalancing.html

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