Petersen's graph
This graph gained graph-theorists recognition
for it seems to fail many general properties.
It is often advised that one should always check any new conjecture
about graphs first against Petersen's graph before an attempt
to prove it.
- Petersen graph is a snark: typically 3-regular graph
has edge chromatic number 3. The Petersen graph needs
4 colors.
- Petersen is the unique 5-cage.
Click on the figure to see
two forms of the graph.
Julius Petersen (1839--1910, Denmark)
wrote in 1891 a paper on regular graphs and coloring
from which the Petersen's graph comes from.
He also did research in algebra, number theory,
analysis and mechanic.
Remembered in Denmark as a great teacher.
The harmonic evolution
digraph consists of 16 pretty "bushy" trees:
| Loops | = |
16 L1
|
| Tree | = |
T14 * T2
|
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