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Mahler's Volume Conjecture

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· convex geometry / Banach space theory · ~1 min read · difficulty 5/5

convex-geometry

The problem

Mahler volume conjecture: for every centrally symmetric convex body \(K \subset \mathbb{R}^n\), the volume product \(vol(K)\,vol(K^\circ)\) is minimised by the cube (value \(4^n/n!\)); i.e. \(vol(K)vol(K^\circ) \geq 4^n/n!\). Known for \(n \leq 3\); open for \(n \geq 4\).

History & significance

Mahler posed it in 1939 from geometry of numbers: the volume product \(vol(K)vol(K^\circ)\) is affine-invariant, Santaló's inequality caps it above (equality for ellipsoids), and Mahler asked for the floor. The cube (and Hanner polytopes generally) are the conjectured minimisers. Settled for \(n = 2\) (Mahler–Reisner) and \(n = 3\) (Iriyeh–Shibata 2020), plus zonoids and unconditional bodies; Bourgain–Milman gives the bound up to an absolute constant. Dimension 4 and above remain open, with recent symplectic reformulations (Viterbo, Kuperberg) opening new fronts.

Still open.

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