Widom factors for Chebyshev and residual polynomials on semi-regular subsets of $\mathbb{R}$

arXiv:2608.09884 2026 Optimization 1 ideas extracted · analyzed Sep 1, 2026

What the math gives to ML

The paper gives a quantitative way to design and assess minimax polynomials when the admissible spectral set is disconnected or contains isolated, irregular points. The transferable asset is the separation between the dominant capacity term and a finite correction, exp[IR(E,x_*)], which predicts how isolated spectral components inflate worst-case polynomial response. This suggests replacing interval-only Chebyshev acceleration in neural-network optimization with residual polynomials explicitly constrained on estimated spectral clusters and outliers. The first practical test should use low-degree Hessian-polynomial preconditioning and compare ordinary interval Chebyshev polynomials against minimax polynomials on the full empirical spectrum.

Ideas from this paper

Unverified 2026

Irregular-spectrum residual preconditioner

Use a low-degree residual polynomial of the neural-network Hessian rather than an interval-only Chebyshev polynomial, with the polynomial minimized over the bulk Hessian spectrum and isolated outlier eigenvalues simultaneously. The method should reduce oscillation caused by rare sharp directions without shrinking the learning rate for the bulk spectrum.

Useful6/10
Difficulty6/10
Novelty6/10
Paper: Widom factors for Chebyshev and residual polynomials on semi-regular subsets of $\mathbb{R}$ arXiv:2608.09884