Semidefinite functions on categories
| Authors |
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| Publication date | 2009 |
| Journal | The Electronic Journal of Combinatorics |
| Volume | Issue number | 16 | 2 |
| Pages (from-to) | R14 |
| Number of pages | 16 |
| Organisations |
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| Abstract | Freedman, Lovász and Schrijver characterized graph parameters that can be represented as the (weighted) number of homomorphisms into a fixed graph. Several extensions of this result have been proved. We use the framework of categories to prove a general theorem of this kind. Similarly as previous results, the characterization uses certain infinite matrices, called connection matrices, which are required to be positive semidefinite. |
| Document type | Article |
| Downloads |
Schrijver-Lovasz-EJC.pdf
(Final published version)
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