geometry-topology / Convex geometry

Lassak's Area Bound for Reduced Planar Bodies

Lassak conjectured that a reduced planar convex body of thickness $\Delta$ has area at most $(\pi/4)\Delta^2$, the value for the disc. False: an explicit reduced body of thickness $1$ has area $0.786215\ldots > \pi/4 = 0.785398\ldots$, given by a closed-form support function.

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geometry-topologyJun 26, 2026Significance 15/100Registry: site confirmed

Lassak's Area Bound for Reduced Planar Bodies

Prior state unknowndisproved

Lassak conjectured that a reduced planar convex body of thickness $\Delta$ has area at most $(\pi/4)\Delta^2$, the value for the disc. False: an explicit reduced body of thickness $1$ has area $0.786215\ldots > \pi/4 = 0.785398\ldots$, given by a closed-form support function.

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Lassak conjectured that a reduced planar convex body of thickness $\Delta$ has area at most $(\pi/4)\Delta^2$, the value for the disc. False: an explicit reduced body of thickness $1$ has area $0.786215\ldots > \pi/4 = 0.785398\ldots$, given by a closed-form support function.

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