Semidefinite functions on categories (Q1028868)
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scientific article; zbMATH DE number 5576461
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Semidefinite functions on categories |
scientific article; zbMATH DE number 5576461 |
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Semidefinite functions on categories (English)
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8 July 2009
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Summary: 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 resuts, the characterization uses certain infinite matrices, called connection matrices, which are required to be positive semidefinite.
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connection matrices
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