| Title | Semidefinite functions on categories |
|---|---|
| Published in | The Electronic Journal of Combinatorics, Vol. 16, No. 2, p.R14-. ISSN 10778926. |
| Author | Lovász, L.; Schrijver, A. |
| Date | 2009 |
| Type | article |
| 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. |
| Publication | http://dare.uva.nl/record/328560 |
| Persistent Identifier | urn:nbn:nl:ui:29-328560 |
| Metadata | XML |
| Repository | University of Amsterdam |
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