Two more diagnostics on chord-apex+Kempe colourings (n <= 18,
13,800 colourings) probing how thin the non-constancy obstacle on
V(K_b) is:
1. check_min_flip_structure.py
- Flip count on K_b drops as low as 2 (at n = 18, 12 colourings):
these have a single minority Heawood vertex on K_b. So the
structural obstacle has NO slack: proving "at least 1 minority
vertex on V(K_b)" is the bar.
- All n=14 colourings (216) have flip count = 8 exactly. At
larger n the distribution spreads.
2. check_minority_location.py
- For colourings with K_b flip count <= 4, identify the minority
Heawood vertices and tally where they sit:
v_n : 12.86%
A_{i+1} : 10.82%
A_{i+2} : 8.98%
A_i : 7.76%
A_{i+4} : 5.31%
A_{i+3} : 5.10%
"other" : 49.18%
- About half the minority vertices live on non-named vertices in
the rest of G'. No single named vertex is *always* the
minority. The obstruction is genuinely diffuse / global, not
anchored to a specific structural location.
These together imply that the structural proof of "h_phi non-constant
on V(K_b)" must be global (no local "this vertex must flip"
argument suffices) and handle the edge case where only one minority
vertex exists. Likely requires a topological / homological / global
counting argument.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
didericis
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