MathsClub Problems, proofs & good company

← All problems

Optimal Sphere Packing in Dimensions 8 and 24

historic

· discrete geometry · resolved March 2016 · ~1 min read · difficulty 5/5

The problem

Determine the maximum packing density of congruent spheres in \(\mathbb{R}\)⁸ (answer: the E₈ lattice, density π⁴/2⁸) and \(\mathbb{R}^{24}\) (the Leech lattice, π^{12}/12!), and prove optimality.

History & significance

Kepler settled the question's three-dimensional ancestor (see our historic shelf); Cohn and Elkies (2003) developed linear-programming bounds that came tantalisingly close in dimensions 8 and 24 — missing optimality by a whisker for thirteen years.