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
RESULTS LEDGER
Every result, with its tier and its limits
Read results.json for the same facts as data. A row without a source file, or without a not-covered line, cannot be added.
HAND PROOF
A proof written out on paper. A computer may have checked the numbers, but the argument does not depend on one.
2 METHODS
An interval-arithmetic computation, repeated by a second method that shares no chart, symmetry reduction or polar cap with the first, over the whole statement.
COMPUTER-ASSISTED
A statement about ball-arithmetic enclosures, backed by a script and log. Where a second method covers part of it, the row says exactly how much.
EXPLORATORY
A float scan. It shows where to look. It is not a certificate and is never cited as one.
showing 19 of 19
ATheorem AHAND PROOFNote, not yet posted
Convex range of a spherical-harmonic perturbation
Let g be a spherical polynomial of degree at most L with max |g| = 1. The body r = 1 + eps g is strictly convex for every eps < 1 / (L^2 + 1), and the constant cannot be improved: a sectoral harmonic reaches it.
Numbers
Sharp threshold
1 / (L^2 + 1)
Key input
Bernstein-Riesz inequality along great circles
Method
Bernstein's inequality along great circles bounds the second derivative of g by L^2 max|g|; inserting that into the convexity matrix M = r^2 sigma + 2 grad r (x) grad r - r Hess r gives positive definiteness.
Second method
None for this row.
What is not covered
A literature check for prior statements of this inequality is still open.
It bounds the convex range from below only; Table B shows the true range is larger for non-sectoral bodies.
Evidence
convex_range_note/main.tex
BTable BCOMPUTER-ASSISTEDNote, not yet posted
Convexity thresholds for 27 harmonic bodies
For each of the 27 bodies Y_l^m with 2 <= l <= 7, an interval bracket of the largest amplitude that keeps the body strictly convex, with relative width at most 0.5 percent.
Numbers
Bodies
27
Non-sectoral, eps0 (l^2+1)
1.077 to 1.472
Sectoral, eps0 (l^2+1)
0.996 to 1.002
Max bracket width
0.5 %
Method
Branch and bound with a centered form from forward-mode automatic differentiation, in ball arithmetic.
Second method
Cartesian cube-face method on three bodies: Y33, Y44, Y31. The other 24 have the primary method only.
CTheorem CCOMPUTER-ASSISTEDManuscript, not yet posted
Equilibrium counts for the m = 1 harmonic bodies
For l = 2, 3, 4, 5, 6, 7 and every amplitude from just above 0 to the stated upper end, the body has exactly S = U = l stable and unstable equilibria and H = 2l - 2 saddles, all nondegenerate, with none in the polar caps.
Numbers
l = 2
eps above 0 to 0.1994, (2, 2, 2)
l = 3
eps above 0 to 0.1062, (3, 3, 4)
l = 4
eps above 0 to 0.0668, (4, 4, 6)
l = 5
eps above 0 to 0.0452, (5, 5, 8)
l = 6
eps above 0 to 0.0327, (6, 6, 10)
l = 7
eps above 0 to 0.02465, (7, 7, 12)
Method
Amplitude intervals are split into tiles. On each tile the centroid and the equilibrium conditions are evaluated with interval amplitude; Krawczyk uniqueness boxes and exclusion boxes cover the sphere. Below about 60 percent of the range the same is done on the rescaled potential (rho - 1) / (2 eps), which stays smooth down to eps = 0.
Second method
Point checks by the cube-face method at one amplitude each for l = 3, 4, 5, 6, 7 (l = 6 and 7 inside the rescaled cover); inconclusive for l = 2. These are not interval covers.
What is not covered
l = 8 and above.
m = 0 and m of 2 or more.
Second method inconclusive for l = 2 (equilibria on chart seams); only point checks, no second-method cover of the rescaled tiles.
Stable and unstable labels in the second method are floats, checked through S - H + U = 2.
At the point of least radius the Gaussian curvature of Sloan's second shape is an explicit function of beta and is negative on (beta*, 0.2474), with beta* = 0.0355047718919948. The convex range stated in the original note (beta up to 0.17) is therefore not convex.
Numbers
beta*
0.0355047718919948
Stated in the note
beta <= 0.17
Method
Direct evaluation of the curvature at (theta, phi) = (pi/2, pi), where R^4 = 1 - 4 beta.
Second method
None for this row.
What is not covered
Independently re-derived with symbolic algebra on 2026-11-07: the root matches the closed form to 33 digits. A human reading of the derivation is still wanted.
D2Theorem DCOMPUTER-ASSISTEDManuscript, not yet posted
Sloan shape 2 is strictly convex for beta up to 0.03550477
K > 0 on the whole surface for every beta in [0, 0.03550477]. The remaining gap to beta* is 1.9e-9.
Numbers
Primary range
0 to 0.03550477
Second method range
0 to 0.0355047
Gap to beta*
1.9e-9
Boxes (primary)
26,535,337 + 2,797
Method
Compact radial-graph chart plus polar caps, centered form from automatic differentiation.
Second method
Cartesian cube-face method over beta from 0 to 0.0355047. A third route (convexity matrix in (t, psi, beta)) covers the whole range up to 0.0355047718 as a replayable record of the box search, re-validated by a separately written checker; the gap to beta* is 9.2e-11.
What is not covered
The last 7e-8 of the range by the cube-face method (the third route covers it).
Sloan shape 2 has the origin as centroid and exactly two equilibria
For every 0 < beta < 1/4 the centroid is the origin (the integral of sin^3 t exp(i eta) vanishes) and the radius function has exactly two nondegenerate critical points, a minimum at (pi/2, pi) and a maximum at (pi/2, 0). With strict convexity these are the stable and unstable equilibria.
Numbers
Equilibria
2, nondegenerate
Valid for beta
0 < beta < 1/4 (centroid, critical points)
Method
Hand derivation of the centroid integral and the gradient of R on the sphere.
Second method
None for this row.
What is not covered
Re-derived with no algebra errors found. A human reading is still wanted.
The original note states these facts without derivation.
At the point of least radius the Gaussian curvature of Sloan's first shape is (125 beta^2 - 35 beta + 1) / (1 - 4 beta)^(5/2), negative between the roots (7 - sqrt 29) / 50 = 0.03229670385730 and 0.24770329. The convex range stated in the original note (beta up to 0.15) is therefore not convex, too large by a factor of about 4.6.
Numbers
beta*
0.03229670385730
Stated in the note
beta <= 0.15
Method
Symbolic curvature of the implicit surface at (theta, phi) = (pi/2, -pi/2), where R^4 = 1 - 4 beta; the sign is checked by ball arithmetic on [0.0324, 0.15] and [0.0001, 0.032].
Second method
None for this row.
What is not covered
One point of the surface: this refutes the stated range. Convexity below the root and the equilibria of this shape are the subject of D5.
A human reading of the derivation is still wanted.
D5TheoremCOMPUTER-ASSISTEDManuscript, not yet posted
Sloan shape 1 is strictly convex and mono-monostatic for beta up to 0.03229670385
The convexity matrix of Sloan's first shape is positive definite on the whole sphere, poles included, for every beta in [0, 0.03229670385]. With the origin as centroid and exactly two nondegenerate critical points of the radius, the body has one stable and one unstable equilibrium. The remaining gap to the closed-form limit is 7.3e-12.
Numbers
Range covered
0 to 0.03229670385
Gap to beta*
7.3e-12
Boxes
11,629,511 nodes, 5,814,756 leaves
Smallest lower bound of det M
1.2e-16
Method
Branch and bound in ball arithmetic on M11 > 0 and det M > 0 over (t, psi, beta), with psi = p - 5t. The matrix is polynomial in sines and cosines, so the poles, where the phase 5t makes the body only C^1, are covered by the same boxes. Centroid and the two equilibria follow by hand.
Second method
The matrix agrees in sign with the curvature of the implicit surface (automatic differentiation) at 6000 of 6000 random points, 667 of them with K < 0. This is a formula check, not a second box computation. A separately written checker replays the box-search record.
What is not covered
The last 7.3e-12 below the closed-form limit.
A negative control: the same program proves det M < 0 on boxes for beta in [0.0324, 0.0326].
A human reading of the derivation of the matrix is still wanted.
The surface is only C^1 at the poles; local convexity there uses the standard fact that a C^1 surface with positive definite M at every neighbouring point is convex.
Phase-1 body: exactly one stable and one unstable equilibrium
With its centroid enclosed by exact integrals (c_x = -0.0026955695464916...), the Phase-1 body has S = U = 1 and H = 0: exactly two equilibria, both nondegenerate.
Numbers
Centroid c_x
-0.00269556954649164614590662...
Centroid width
below 1e-40
Counts (S, U, H)
(1, 1, 0)
Jacobian determinants
0.042 and 0.047
Exclusion boxes (second method)
51,346
Method
Interval counter with Krawczyk uniqueness boxes on the compact chart and the polar caps.
Second method
Cartesian implicit surface on six cube faces, equilibrium condition N x (x - c) = 0, Krawczyk uniqueness in two boxes and an exclusion proof elsewhere.
What is not covered
The parameters come from an earlier optimiser run that does not reproduce from the text of the earlier preprint. The object certified here is the one with these exact parameters.
F2MarginCOMPUTER-ASSISTEDManuscript, not yet posted
Phase-1 Hessian at the equilibria: flat in one direction, steep in the other
At the stable equilibrium the Hessian eigenvalues lie in [0.0066, 1.741]; at the unstable one in [-1.596, -0.0068]. The landscape is flat in one direction and steep in the other, with a condition number near 260.
Numbers
Stable eigenvalues
0.0066 to 1.741
Unstable eigenvalues
-1.596 to -0.0068
Condition number
about 260
Definite on the box for
r0 <= 0.005
Method
Coordinate Hessian enclosed on boxes around each equilibrium.
Second method
None for this row.
What is not covered
Definiteness is not established on the box at r0 = 0.01.
F3PropositionCOMPUTER-ASSISTEDManuscript, not yet posted
How much shape error Phase-1 tolerates
If a radial perturbation of degree at most k has amplitude a below the stated bound, the perturbed body is still strictly convex and still has exactly one nondegenerate minimum and one nondegenerate maximum of the squared centroid distance. The bounds are sufficient conditions, not sharp ones.
Numbers
k = 1
a <= 2.0e-6
k = 5
a <= 1.1e-6
k = 10
a <= 6.7e-7
k = 50
a <= 1.4e-7
Convexity margin of perturbed body
lambda_min(M) >= 0.0766
Method
A perturbation argument on the two boxes, with every constant enclosed in interval arithmetic: gradient bound, Hessian bound, centroid shift, Bernstein-Riesz.
Second method
None for this row.
What is not covered
A human reader of the proposition and its constants is still wanted.
Over a grid of one extra Fourier harmonic added to Sloan's phase, the best gradient robustness among convex (1,1,0) bodies is about 2.9e-3 against 1.6e-3 for Phase-1, and the best Hessian margin about 9.6e-3 against 6.6e-3. Re-optimising inside this family gains less than a factor of two.
Numbers
Best gradient robustness (scan)
2.9e-3
Phase-1 gradient robustness
1.6e-3
Best Hessian margin (scan)
9.6e-3
Phase-1 Hessian margin
6.6e-3
Method
Grid candidates refined by a continuous root solve. A first version that counted grid extrema reported 21 minima and 19 maxima on flat ridges for a body with exactly one of each; it was discarded.
Second method
None for this row.
What is not covered
A coarse float scan of one phase function. It is not a bound on all gombocs.
G1Software resultCOMPUTER-ASSISTEDSoftware, not yet released
Phase-1 equilibrium count as a replayable record
For every centroid in a stated box around the Phase-1 centroid, the squared centroid distance of the Phase-1 body has one minimum, one maximum and no saddle, and a second, independent program re-evaluates the whole record.
Numbers
Result (S, U, H)
1, 1, 0
Euler characteristic
2
Leaves
16053 (16051 Empty, 2 One)
Search and replay
17 s and 5 s
Replay in a browser
28.9 s (VALID, on a busy machine); a copy claiming 2 stable positions is rejected
Centroid box half-width
1e-24
Method
The sphere is covered by boxes on the six faces of a cube. A box is Empty when the gradient of the squared centroid distance is provably nonzero for every centroid in the box, and One when Krawczyk's operator shows a single critical point, typed by the interval Hessian. The search is untrusted; a short separate checker re-evaluates every box in ball arithmetic and recomputes the totals.
Second method
None for this row.
What is not covered
Strict convexity is an input; row E1 covers it.
The centroid box is the paper's printed value widened by 1e-24, not an enclosure computed here.
The checker is a short program, not a formally verified one.
G2Software resultCOMPUTER-ASSISTEDSoftware, not yet released
Single-harmonic m=1 counts from the same checker
At one small amplitude for each degree l = 2 to 5, the body r = 1 + e P_l'(u_z) u_x has (l, l, 2l-2) stable, unstable and saddle positions, the class reported in row C.
Numbers
l = 2, e = 1/50
(2, 2, 2), 2688 leaves
l = 3, e = 1/100
(3, 3, 4), 4509 leaves
l = 4, e = 1/200
(4, 4, 6), 24622 leaves
l = 5, e = 1/400
(5, 5, 8), 140313 leaves
Method
The same cover and checker as row G1, with the radial formula of the body in place of the Sloan form and an exact rotation of the cube so that no critical point lies on a cube edge (the l = 2 body has its extrema exactly on edges).
Second method
None for this row.
What is not covered
One amplitude for each degree; row C covers the whole range.
Degrees 6 and above were not run here.
The centroid box is exact quadrature padded by 1e-12, not an enclosure.
Convexity of these bodies comes from row G3 and Table B, not from this record.
G3Software resultCOMPUTER-ASSISTEDSoftware, not yet released
Convexity of radial bodies, checked against the published thresholds
A convexity matrix for any radial body, evaluated on the cube-face charts, changes sign at the thresholds of Table B (l = 2, 3, 4, m = 1), and strict convexity of those bodies is shown by interval computation for every amplitude up to a stated fraction of the threshold.
Numbers
Sign check l = 2
+0.00042 at 0.99 of the threshold, -0.00113 at 1.01
Sign check l = 3
+0.00213 at 0.99, -0.00254 at 1.01
Sign check l = 4
+0.00301 at 0.99, -0.00624 at 1.01
Convex up to, l = 2
e = 0.106341 (80 percent), 612392 leaves, replay 80 s; e = 0.12628 (95 percent), 2588916 leaves, replay 292 s
Convex up to, l = 3
e = 0.041712 (80 percent), 233540 leaves, replay 34 s
Convex up to, l = 4
e = 0.020245 (80 percent), 138220 leaves, replay 23 s
Method
Convexity of a radial graph is positive definiteness of M = r^2 g + 2 dr (x) dr - r Hess r on the tangent plane. The matrix is built from the second-order jets of the unit vector in each cube-face chart, and the amplitude is an interval, so one record covers a whole range of amplitudes. The matrix is cross-checked against automatic differentiation of the implicit surface (the sign of its determinant agrees with the Gauss curvature at every checked point) and against the thresholds of Table B.
Second method
None for this row.
What is not covered
Up to 95 percent of the lower bracket for l = 2 and 80 percent for l = 3 and 4; the last few percent need a much larger search.
The hand derivation of the matrix is not machine checked; it is cross-checked against automatic differentiation and the published thresholds.
G4Floating-point trialEXPLORATORYSoftware, not yet released
Mesh trials: how much shape error a printed gomboc can take
In 20 random smooth radial perturbations per level of a Phase-1 mesh, most meshes keep one stable and one unstable position at a relative error of 1e-4 and most do not at 1e-3.
Numbers
Phase-1, error 1e-5
20 of 20 keep one of each
Phase-1, error 1e-4
18 of 20 (6-step test), 20 of 20 (10-step test)
Phase-1, error 1e-3
4 of 20 and 5 of 20
Phase-1, error 3e-3 and 1e-2
0 of 20; 9 of 20 meshes still convex at 1e-2
Sloan shape 2 at the edge of its convex range
20 of 20 at 1e-5, 17 of 20 at 1e-4, 0 of 20 from 1e-3
Scale
1e-4 of the radius is about 5 micrometres on a 100 mm body
Method
A smooth random radial error of sup-norm eps is added to the mesh, the mesh centroid is recomputed, and minima and maxima of the distance from the centroid are counted within a neighbourhood of 6 and of 10 grid steps. Convexity of each perturbed mesh is tested by checking that every vertex lies on the convex hull.
Second method
None for this row.
What is not covered
One kind of smooth error; layer steps and surface roughness are not modelled.
A floating-point scan on a coarse grid, not an enclosure.
Shape 2 was run at the edge of its convex range only, the weakest choice.
G5Floating-point trialEXPLORATORYSoftware, not yet released
A nearest-neighbour scan miscounts a flat body
A nearest-neighbour scan of the Phase-1 landscape reports several minima and maxima that vanish when the neighbourhood is widened, while the body has one of each.
Numbers
Neighbours within 1 grid step
9 minima, 7 maxima
Within 2 steps
7 and 5
Within 3 steps
3 and 3
Within 6 and 10 steps
1 and 1
Method
The surface is sampled on a 91 by 180 grid and grid points that are the strict minimum or maximum of the distance from the centroid among grid points within r steps are counted.
Second method
None for this row.
What is not covered
A larger neighbourhood does not make a scan right in general: an extra position closer than the neighbourhood would be missed.
One body and one grid.
The enclosure counts in rows E2 and G1 are the reference, not this scan.