Move Section 5 of "Medial Tire Decompositions of Plane Triangulations"
into a new standalone paper, "The Medial Pigeonhole Programme", which
cites the medial tire paper for its terminology and notation. Convert
the three cross-references that pointed into earlier sections (annular
teeth, bite-face-count, boundary medial vertices) into citations.
Remove Section 5 from the medial tire paper and update its abstract to
drop the moved chain-pigeonhole claim, pointing to the follow-up paper.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Bites arise when the inner outerplanar graph O has a bridge: the bridge
edge is traversed twice by the outer-face walk, so its medial vertex is
adjacent to four annular vertices.
- check_remark58_bite.py: a minimal bite tread (outer 4-cycle + interior
bridge u-w) restricts to Kempe-balanced on all colourings (outer face).
- check_remark58_bite_rich.py: O = triangle abc + pendant bridge a-d gives
one bite plus three singleton down teeth in the bite's inner-gap face;
every restriction is Kempe-balanced (the three gap singletons are a
rainbow in every global colouring).
Update Remark 5.8's verification note: the bite case, including singletons
in the bite-gap face, is now confirmed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Computational checks of the necessity of Kempe-balance (Remark 5.8):
- check_medial_face_parity.py shows the naive "even P-coloured vertices
per medial face" claim is false (odd vertex-faces on the octahedron and
stacked triangulations), so the original face-parity justification was
wrong.
- check_remark58_bitefree.py builds genuine bite-free tire pieces (capped
triangulated annuli) and confirms every proper 3-colouring of M(G)
restricts to a Kempe-balanced colouring (|A(T)|=6,8,10,12, all
colourings, zero failures).
Rewrite Remark 5.8 to cite the correct mechanism: the up/down apexes lie
on level cycles, and a P-Kempe cycle meets each level cycle in an even
number of P-coloured incidences (Lemma 5.6). Note the bite case is not
yet checked end to end.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Define Kempe-balanced colourings of a full medial tire graph (Def 5.7):
for each valid face (outer face or interior non-tooth face of B(T)) and
each colour pair {a,b}, the number of tooth apexes incident to the face
coloured a or b must be even. Add Remark 5.8 (necessity: a colouring of
M(T) extends to M(G) only if it is Kempe-balanced) and rename Lemma 5.5
to "Kempe chains are cycles".
Add kempe_valid_colorings.py: enumerate all proper 3-colourings of a full
medial tire graph, label each Kempe-balanced/valid or invalid, and plot
them with the offending face's Kempe chains and odd apex set highlighted
on invalid panels.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Name A(T) the "annular cycle" (Thm 3.3, Def 3.4); clarify the bite-face
condition in Remark 3.8 to count down-tooth apexes interior to each face;
add the non-incidence stipulation for bite edges to Def 3.7.
Add an exhaustive generator over |A(T)| enforcing the 3.1-3.9 properties
(tooth word, non-crossing non-incident bites, >=3 up teeth, bite-face
condition), plus a plotting script and the n=9 atlas (81 dihedral classes).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Adds two TikZ figures (boundary-state worst cases and annular cycle
counterexample), a new subsection on Kempe-cycle conservation across
medial tires, and the experiment scripts/findings for the medial tire
restriction search and annular cycle condition check.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
didericis