didericis
c987259c14
- Add section 3 with Algorithm 3.1 (iterated reduction with protected edges) and remarks on invariants and chord-apex applicability. - Add fig:iterated-reduction-trace illustrating the algorithm on G' = dodecahedron (G' -> H_1 -> H_2 -> terminate). - experiments/iterated_reduction.py: Sage implementation of the algorithm. - experiments/draw_iterated_reduction.py: produces the 3 trace figures. - experiments/check_dodecahedron_kempe.py: enumerate proper 3-edge-colorings of the dodecahedron's reduced dual and check the chord-apex + Kempe-cycle conditions (0 of 36 colorings satisfy all three). - experiments/search_kempe_property.py: search across min-deg-5 triangulations; the n = 14 first plantri triangulation is the smallest hit (reduced dual has 20 v, 30 e). Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
28 lines
3.0 KiB
TeX
28 lines
3.0 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{lem:kempe-spike}{{2.7}{6}}
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\@writefile{toc}{\contentsline {section}{\tocsection {}{3}{An iterated reduction}}{7}{}\protected@file@percent }
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\newlabel{alg:iterated-reduction}{{3.1}{7}}
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\newlabel{rem:alg-invariants}{{3.2}{7}}
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\newlabel{rem:alg-chord-apex}{{3.3}{7}}
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\newlabel{tocindent1}{17.77782pt}
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\@writefile{lof}{\contentsline {figure}{\numberline {3}{\ignorespaces Algorithm\nonbreakingspace 3.1\hbox {} on $G' = $ dodecahedron (dual of the icosahedron). \emph {Left:} $G'$ (20 vertices, 30 edges), with $F_v$ (the inner pentagon) shaded as the face chosen for the first reduction. \emph {Centre:} $H_1$ (16 vertices, 24 edges) after step\nonbreakingspace (1) with $i_1 = 0$, $3$-edge-coloured by Sage; the four edges around $v_n^{(1)}$ in $E$ are drawn thicker. \emph {Right:} $H_2$ (12 vertices, 18 edges) after step\nonbreakingspace (3) with $i_t = 0$; the only safe pentagonal face in $H_1$ was the outer pentagon, whose deletion produces $v_n^{(2)}$ and a second chord, giving eight protected edges. No safe pentagonal face remains, so the algorithm terminates. The generating script is \texttt {experiments/draw\_iterated\_reduction.py}.}}{8}{}\protected@file@percent }
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\newlabel{fig:iterated-reduction-trace}{{3}{8}}
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\gdef \@abspage@last{8}
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