Substrate Geometry
Computer-assisted interval computation / private preview
AConvex range of a spherical-harmonic perturbationHAND PROOFBConvexity thresholds for 27 harmonic bodiesCOMPUTER-ASSISTEDCEquilibrium counts for the m = 1 harmonic bodiesCOMPUTER-ASSISTEDD1Sloan shape 2: upper bound on the convex rangeHAND PROOFD2Sloan shape 2 is strictly convex for beta up to 0.03550477COMPUTER-ASSISTEDD3Sloan shape 2 has the origin as centroid and exactly two equilibriaHAND PROOFD4Sloan shape 1: upper bound on the convex rangeHAND PROOFD5Sloan shape 1 is strictly convex and mono-monostatic for beta up to 0.03229670385COMPUTER-ASSISTEDE1Phase-1 body: strictly convex2 METHODSE2Phase-1 body: exactly one stable and one unstable equilibrium2 METHODSF1Phase-1 gradient floorCOMPUTER-ASSISTEDF2Phase-1 Hessian at the equilibria: flat in one direction, steep in the otherCOMPUTER-ASSISTEDF3How much shape error Phase-1 toleratesCOMPUTER-ASSISTEDF4Is Phase-1 close to the best this family can do?EXPLORATORYG1Phase-1 equilibrium count as a replayable recordCOMPUTER-ASSISTEDG2Single-harmonic m=1 counts from the same checkerCOMPUTER-ASSISTEDG3Convexity of radial bodies, checked against the published thresholdsCOMPUTER-ASSISTEDG4Mesh trials: how much shape error a printed gomboc can takeEXPLORATORYG5A nearest-neighbour scan miscounts a flat bodyEXPLORATORYAConvex range of a spherical-harmonic perturbationHAND PROOFBConvexity thresholds for 27 harmonic bodiesCOMPUTER-ASSISTEDCEquilibrium counts for the m = 1 harmonic bodiesCOMPUTER-ASSISTEDD1Sloan shape 2: upper bound on the convex rangeHAND PROOFD2Sloan shape 2 is strictly convex for beta up to 0.03550477COMPUTER-ASSISTEDD3Sloan shape 2 has the origin as centroid and exactly two equilibriaHAND PROOFD4Sloan shape 1: upper bound on the convex rangeHAND PROOFD5Sloan shape 1 is strictly convex and mono-monostatic for beta up to 0.03229670385COMPUTER-ASSISTEDE1Phase-1 body: strictly convex2 METHODSE2Phase-1 body: exactly one stable and one unstable equilibrium2 METHODSF1Phase-1 gradient floorCOMPUTER-ASSISTEDF2Phase-1 Hessian at the equilibria: flat in one direction, steep in the otherCOMPUTER-ASSISTEDF3How much shape error Phase-1 toleratesCOMPUTER-ASSISTEDF4Is Phase-1 close to the best this family can do?EXPLORATORYG1Phase-1 equilibrium count as a replayable recordCOMPUTER-ASSISTEDG2Single-harmonic m=1 counts from the same checkerCOMPUTER-ASSISTEDG3Convexity of radial bodies, checked against the published thresholdsCOMPUTER-ASSISTEDG4Mesh trials: how much shape error a printed gomboc can takeEXPLORATORYG5A nearest-neighbour scan miscounts a flat bodyEXPLORATORY
UPDATES

New from the program

A running list of what was added and when. A status line on each item says whether it is a result with a tier, floating-point evidence, or software and teaching material that has not been released. The same list is in updates.json.

2026-11-08

2026-11-08
Software

Equilibrium counts for the harmonic bodies, from the same checker

A second family now goes through the same cover and replay checker. At one small amplitude each, degrees 2 to 5 give (l, l, 2l-2) stable, unstable and saddle positions, the class of result C.

Software, not yet released Open
2026-11-08
Software

The Phase-1 count as a record anyone can replay

The count of one stable and one unstable position is now stored as a record of 16053 boxes that a separate short program re-evaluates in about 5 seconds.

Software, not yet released Open
2026-11-08
Software

A convexity check for any radial body

The convexity matrix is evaluated on cube-face charts and changes sign at the published thresholds for degrees 2, 3 and 4. Convexity is shown for every amplitude up to 95 percent of the threshold for degree 2.

Software, not yet released Open
2026-11-08
Software

A browser page that replays a record

A prototype page loads the checker into the browser and replays a record from a file. It says VALID for the Phase-1 count in 28.9 seconds and rejects a copy with a changed claim.

Prototype, local only Open
2026-11-08
Teaching

A classroom notebook: when plots lie

A notebook for students on how a picture, a scan and a replayable record can disagree about the same body, with a teacher guide and an answer key.

Draft, not yet released Open
2026-11-08
Trial

How much shape error can a printed gomboc take?

In mesh trials with smooth random error, most Phase-1 meshes keep one stable and one unstable position at a relative error of 1e-4 and most do not at 1e-3. Exploratory: floating point, no physical print.

Exploratory Open
2026-11-08
Trial

A scan reported 9 stable positions on a body that has one

A nearest-neighbour scan of the Phase-1 landscape changes its answer from 9 minima to 1 as the neighbourhood widens. The enclosure count does not move.

Exploratory Open

2026-11-07

2026-11-07
Result

Sloan's first shape: where the stated range stops being convex

The first of Sloan's two shapes is not convex beyond a closed-form limit, well below the range stated for it. Convexity and a single stable position are checked below that limit.

Manuscript, not yet posted Open
2026-11-07
Result

Counts for the m=1 harmonics across the whole convex range

The equilibrium class of each m=1 harmonic body is constant over its whole convex range, for degrees 2 to 7, by interval computation.

Manuscript, not yet posted Open
2026-11-07
Result

Sloan's second shape: a third check of the convex range

A third, independent computation covers the whole range up to 0.0355047718 and narrows the gap to the closed-form limit to 9.2e-11.

Manuscript, not yet posted Open
2026-11-07
Paper

The flagship manuscript, 19 pages

The paper on how close to degenerate a gomboc is now includes the tolerance study, the first shape of Sloan and the extended m=1 counts. It is not yet posted.

Manuscript, not yet posted Open