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Bollobás–Riordan polynomial

From Wikipedia, the free encyclopedia

The Bollobás–Riordan polynomial can mean a 3-variable invariant polynomial of graphs on orientable surfaces, or a more general 4-variable invariant of ribbon graphs, generalizing the Tutte polynomial.

History

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These polynomials were discovered by Béla Bollobás and Oliver Riordan (2001, 2002).

Formal definition

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The 3-variable Bollobás–Riordan polynomial of a graph is given by

,

where the sum runs over all the spanning subgraphs and

  • is the number of vertices of ;
  • is the number of its edges of ;
  • is the number of components of ;
  • is the rank of , such that ;
  • is the nullity of , such that ;
  • is the number of connected components of the boundary of .

See also

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References

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  • Bollobás, Béla; Riordan, Oliver (2001), "A polynomial invariant of graphs on orientable surfaces", Proceedings of the London Mathematical Society, Third Series, 83 (3): 513–531, doi:10.1112/plms/83.3.513, ISSN 0024-6115, MR 1851080
  • Bollobás, Béla; Riordan, Oliver (2002), "A polynomial of graphs on surfaces", Mathematische Annalen, 323 (1): 81–96, doi:10.1007/s002080100297, ISSN 0025-5831, MR 1906909