English

On maximal hyperplane sections of the unit ball of $l_p$ for $p>2$

Functional Analysis 2025-01-28 v2

Abstract

The maximal hyperplane section of the lnl_\infty^n-ball, i.e. of the nn-cube, is the one perpendicular to 1/sqrt 2 (1,1,0, ... ,0), as shown by Ball. Eskenazis, Nayar and Tkocz extended this result to the lpnl_p^n-balls for very large p1015p \ge 10^{15}. By Oleszkiewicz, Ball's result does not transfer to lpnl_p^n for 2<p<p026.2652 < p < p_0 \simeq 26.265. Then the hyperplane section perpendicular to the main diagonal yields a counterexample for large dimensions nn. We show that the analogue of Ball's result holds in lpnl_p^n-balls for all hyperplanes with normal unit vectors aa, if all coordinates of aa have modulus 12\le \frac 1 {\sqrt 2} and pp has distance 2p\ge 2^{-p} to the even integers. Under similar assumptions, we give a Gaussian upper bound for 20<p<p020 < p < p_0.

Keywords

Cite

@article{arxiv.2409.06432,
  title  = {On maximal hyperplane sections of the unit ball of $l_p$ for $p>2$},
  author = {Hermann König},
  journal= {arXiv preprint arXiv:2409.06432},
  year   = {2025}
}