Girth
From Wikipedia, the free encyclopedia
Girth is the circumference of a cylindrical object.
Girth is sometimes used by postal services and delivery companies as basis for pricing. For example (for at least one delivery company), if you have a box to ship, it has three sides: length (the longest side) and height and width. The girth in this case is 2 * (height + width).
In graph theory, the girth of a graph pen is the length of the shortest cycle contained in the graph. If the graph doesn't contain any cycles, its girth is defined to be infinity. For example, a 4-cycle (square) has girth 4. A grid has girth 4 as well, and a triangular mesh has girth 3. A cubic graph of girth g that is as small as possible is known as a g-cage. The Petersen graph is the unique 5-cage (it is the smallest cubic graph of girth 5). The Heawood graph is the unique 6-cage, and the Tutte eight cage is the unique 8-cage. A graph with girth ≥ 4 is called triangle-free.
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The Petersen graph, of girth 5 |
The Heawood graph, of girth 6 |
The Tutte eight cage, of girth 8 |