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Fire-farve Sætningen

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<strong>Fire</strong>-<strong>farve</strong><br />

<strong>Sætningen</strong><br />

JB<br />

Oversigt<br />

Historie<br />

Kort og Grafer<br />

Bevis ide<br />

Kempekæder<br />

Beviserne<br />

Afladning<br />

Forbedringer<br />

og generaliseringer<br />

m-pires<br />

Jord-M˚ane<br />

problemet<br />

Liste-farvninger<br />

Andre<br />

overflader<br />

Referencer<br />

m-pires<br />

Hvert land har m regioner. Plan graf G = (V , E).<br />

Euler’s formel giver E ≤ 3(V − 2).<br />

Emperiegraf H = (v, e). V = mv, e ≤ E.<br />

<br />

x∈v deg H(x) = 2e ≤ 2E ≤ 6(V − 2)<br />

Gennemsnitsgraden er<br />

2e<br />

v<br />

Induktion.<br />

≤ 6(V − 2)/v = 6m(V − 2)/V < 6m<br />

Heawood fandt eksempel for m = 2 der kræver 12 <strong>farve</strong>r.<br />

Heawood (1890): 2-pire løst.<br />

Jackson and Ringel (1984): m-pire løst.

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