T-013: Goebel's packing: seven verified first-order flexes, each refused at second order
V3 C3 rigidity confirmed
Goebel's packing is infinitesimally flexible -- seven verified independent first-order flexes turn the sixteen-square tilted block -- and every retained flex is refused at second order by a verified non-negative self-stress, exactly over Q(sqrt 2), so no first-order argument can establish rigidity here.
Significance, composition and next rung
- Significance
- The first separation of infinitesimal from finite rigidity in this literature's cases: the sources assert rigidity without the distinction, and this refines rather than contradicts them.
- Next rung
- Characterise the admissible cone past dimension 45 (the corner-touching branch obstruction, D-391) or establish local rigidity by another route; the rigidity property stays undetermined until then.
- Novelty
- apparently-novel Not found in the recorded search, subject to its stated gaps
The case
Results on the case
12 results in the register on , oldest first, each with what it established and how it stands now.
2005 published T-007
for
V0 C1 lower bound incomplete on this case, superseded by T-145
Nagamochi · Nagamochi 2005 · source · register
2026-08-30 established T-013 this result
Goebel's packing: seven verified first-order flexes, each refused at second order
V3 C3 rigidity confirmed
Levy · register
2026-09-04 published T-085
Nagamochi 2005, Lemma 1 is false for every container with and
V3 C3 correction confirmed
Karakuş; chelokot · Karakuş 2026 · chelokot Nagamochi counterexample 2026 · packet · register
2026-09-22 published T-044
Weighted point lower bounds for ten counts in , plus seven from the same files
V3 C3 lower bound confirmed superseded by T-145
wand125 after Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 point bounds 2026 · packet · source · review · register
2026-09-27 published T-045
Rectangle-density lower bounds replayed at 15 counts in
V3 C3 lower bound confirmed superseded by T-145
wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026 · packet · packet · source · review · register
2026-09-27 published T-046
Rectangle-density lower bounds reported for 48 counts in
V0 C0 lower bound recorded superseded by T-145
wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026 · wand125 rectangle bounds 2026-09-28 · packet · packet · register
2026-09-29 published T-058
Rectangle-certificate ceiling
α·UB(n)proved for ..100;B·UB(n)on 64 grid rowsV3 C3 method limit confirmed
wand125 after Tokoharu, Daniel · wand125 tools 2026 · packet · register
2026-09-29 published T-083
for every nonsquare
V3 C3 lower bound confirmed on this case, superseded by T-145
Karakuş · Karakuş 2026 · source · register
2026-10-01 published T-068
Rectangle-density lower bounds verified at 34 counts in
V3 C3 lower bound confirmed on this case, superseded by T-145
wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-10-01 · packet · source · review · register
2026-10-01 published T-074
Rectangle-density lower bounds replayed at 31 counts in
V3 C3 lower bound confirmed on this case, superseded by T-145
wand125 after Tokoharu, Levy, Stromquist, Nagamochi, Burns, Massaccesi · wand125 rectangle bounds 2026-10-01 · packet · packet · source · review · register
2026-10-10 published T-133
, by a clipped-corner transfer on a 401-direction net
V3 C3 lower bound confirmed superseded by T-145
Guzhou0806 after wand125, Tokoharu, Levy, Stromquist, Burns, Massaccesi · Guzhou0806 n40 clipped corner 2026-10-10 · packet · packet · source 1 · source 2 · review · register
2026-10-10 published T-145
, by a continuous-pose interval kernel
V3 C3 lower bound confirmed
Guzhou0806 after wand125, Tokoharu, Levy, Stromquist, Burns, Massaccesi · Guzhou0806 n40 continuous pose 2026-10-10 · packet · packet · source 1 · source 2 · review · register
Links
- On this site
- Case record, · Frontier row, · T-013 in the results table
On GitHub, at main
- Register
- T-013 in
results.yaml, line 615 - Evidence
E-n040-first-order-flexibility- Proofs and certificates
- certificate
bc-049-n40-rigidity-bracket.json - Artifacts
devtools/assess_n40_rigidity.py·campaign/series/series-000-smoke-and-calibration/results/bc-049-n40-rigidity-bracket.json·tests/test_minus_w_stress.py·tests/test_minus_w_row_jets.py- Case file
frontier/n-040.md(verified lower, verified upper, reported lower, reported upper)