didericis
409dea565a
- Replace the chord-apex TODO with a full proof by contradiction: assume
merged != spike, define X, Y, Z, W, lift to G' so that the externals
inherit \psi(f) = (X, Y, Z, W, W), and split on W in {X, Z}. Either case
meets the hypothesis of lem:pentagonal-externals, which extends \psi to a
proper 3-edge-colouring of G' --- contradicting non-3-edge-colourability
via Tait.
- Add fig:chord-apex-proof: the assumed reduced-dual colouring on top, and
the two lifted-G' cases (W=Z, W=X) below, rendered on the dodecahedron.
- Add experiments/draw_chord_apex_proof.py.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
21 lines
1.8 KiB
TeX
21 lines
1.8 KiB
TeX
\relax
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\@writefile{toc}{\contentsline {section}{\tocsection {}{1}{The minimal counterexample}}{1}{}\protected@file@percent }
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\newlabel{lem:triangulate}{{1.1}{1}}
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\newlabel{def:minimal}{{1.2}{1}}
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\newlabel{lem:mindeg}{{1.4}{1}}
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\@writefile{toc}{\contentsline {section}{\tocsection {}{2}{The reduced dual}}{2}{}\protected@file@percent }
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\newlabel{def:reduced-dual}{{2.1}{2}}
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\newlabel{def:edge-names}{{2.3}{2}}
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\@writefile{lof}{\contentsline {figure}{\numberline {1}{\ignorespaces The four steps of Definition\nonbreakingspace 2.1\hbox {}, illustrated on $G' = $ the dodecahedron (dual of the icosahedron) with $F_v$ the inner pentagon and $i = 0$. Top left: delete the five boundary vertices of $F_v$, leaving five degree-$2$ vertices on a new face $F$. Top right: order them clockwise as $A_0,\dots ,A_4$. Bottom left: add $v_n$ joined to $A_0, A_1, A_2$. Bottom right: add the chord $A_3 A_4$, giving the cubic plane graph $\setbox \z@ \hbox {\mathsurround \z@ $\textstyle G$}\mathaccent "0362{G}'_{v,0}$.}}{3}{}\protected@file@percent }
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\newlabel{fig:reduced-dual-steps}{{1}{3}}
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\newlabel{lem:pentagonal-externals}{{2.4}{3}}
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\newlabel{lem:chord-apex}{{2.6}{4}}
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\@writefile{lof}{\contentsline {figure}{\numberline {2}{\ignorespaces The proof of Lemma\nonbreakingspace 2.6\hbox {}, illustrated for $i = 0$ on $G' = $ the dodecahedron. Top: under the assumption $W \neq Y$, propriety at $v_n$ forces $W \in \{X, Z\}$. Bottom: in either case the lift to $G'$ has externals satisfying the hypothesis of Lemma\nonbreakingspace 2.4\hbox {}, which colours $\partial F_v$ to extend $\psi $ to a proper $3$-edge-colouring of $G'$.}}{5}{}\protected@file@percent }
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\newlabel{fig:chord-apex-proof}{{2}{5}}
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\newlabel{tocindent-1}{0pt}
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\newlabel{tocindent1}{17.77782pt}
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\newlabel{tocindent2}{0pt}
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\newlabel{tocindent3}{0pt}
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\gdef \@abspage@last{6}
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