{"id":"https://openalex.org/W2100355951","doi":"https://doi.org/10.37236/80","title":"Semidefinite Functions on Categories","display_name":"Semidefinite Functions on Categories","publication_year":2009,"publication_date":"2009-05-31","ids":{"openalex":"https://openalex.org/W2100355951","doi":"https://doi.org/10.37236/80","mag":"2100355951"},"language":"en","primary_location":{"id":"doi:10.37236/80","is_oa":true,"landing_page_url":"https://doi.org/10.37236/80","pdf_url":"https://www.combinatorics.org/ojs/index.php/eljc/article/download/v16i2r14/pdf","source":{"id":"https://openalex.org/S38448739","display_name":"The Electronic Journal of Combinatorics","issn_l":"1077-8926","issn":["1077-8926","1097-1440"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310317970","host_organization_name":"Electronic Journal of Combinatorics","host_organization_lineage":["https://openalex.org/P4310317970"],"host_organization_lineage_names":["Electronic Journal of Combinatorics"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"The Electronic Journal of Combinatorics","raw_type":"journal-article"},"type":"article","indexed_in":["crossref","doaj"],"open_access":{"is_oa":true,"oa_status":"diamond","oa_url":"https://www.combinatorics.org/ojs/index.php/eljc/article/download/v16i2r14/pdf","any_repository_has_fulltext":true},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5067889485","display_name":"L\u00e1szl\u00f3 Lov\u00e1sz","orcid":"https://orcid.org/0000-0002-6242-5894"},"institutions":[{"id":"https://openalex.org/I1341640284","display_name":"Centrum Wiskunde & Informatica","ror":"https://ror.org/00x7ekv49","country_code":"NL","type":"facility","lineage":["https://openalex.org/I1341640284","https://openalex.org/I2800991832"]},{"id":"https://openalex.org/I887064364","display_name":"University of Amsterdam","ror":"https://ror.org/04dkp9463","country_code":"NL","type":"education","lineage":["https://openalex.org/I887064364"]},{"id":"https://openalex.org/I106118109","display_name":"E\u00f6tv\u00f6s Lor\u00e1nd University","ror":"https://ror.org/01jsq2704","country_code":"HU","type":"education","lineage":["https://openalex.org/I106118109"]}],"countries":["HU","NL"],"is_corresponding":true,"raw_author_name":"L\u00e1szl\u00f3 Lov\u00e1sz","raw_affiliation_strings":["CWI and University of Amsterdam, The Netherlands","Institute of Mathematics E\u00f6tv\u00f6s Lor\u00e1nd University, Budapest, Hungary"],"affiliations":[{"raw_affiliation_string":"CWI and University of Amsterdam, The Netherlands","institution_ids":["https://openalex.org/I1341640284","https://openalex.org/I887064364"]},{"raw_affiliation_string":"Institute of Mathematics E\u00f6tv\u00f6s Lor\u00e1nd University, Budapest, Hungary","institution_ids":["https://openalex.org/I106118109"]}]},{"author_position":"last","author":{"id":"https://openalex.org/A5028190074","display_name":"Alexander Schrijver","orcid":null},"institutions":[{"id":"https://openalex.org/I1341640284","display_name":"Centrum Wiskunde & Informatica","ror":"https://ror.org/00x7ekv49","country_code":"NL","type":"facility","lineage":["https://openalex.org/I1341640284","https://openalex.org/I2800991832"]},{"id":"https://openalex.org/I887064364","display_name":"University of Amsterdam","ror":"https://ror.org/04dkp9463","country_code":"NL","type":"education","lineage":["https://openalex.org/I887064364"]},{"id":"https://openalex.org/I106118109","display_name":"E\u00f6tv\u00f6s Lor\u00e1nd University","ror":"https://ror.org/01jsq2704","country_code":"HU","type":"education","lineage":["https://openalex.org/I106118109"]}],"countries":["HU","NL"],"is_corresponding":false,"raw_author_name":"Alexander Schrijver","raw_affiliation_strings":["Institute of Mathematics E\u00f6tv\u00f6s Lor\u00e1nd University, Budapest, Hungary","CWI and University of Amsterdam, The Netherlands"],"affiliations":[{"raw_affiliation_string":"Institute of Mathematics E\u00f6tv\u00f6s Lor\u00e1nd University, Budapest, Hungary","institution_ids":["https://openalex.org/I106118109"]},{"raw_affiliation_string":"CWI and University of Amsterdam, The Netherlands","institution_ids":["https://openalex.org/I1341640284","https://openalex.org/I887064364"]}]}],"institutions":[],"countries_distinct_count":2,"institutions_distinct_count":2,"corresponding_author_ids":["https://openalex.org/A5067889485"],"corresponding_institution_ids":["https://openalex.org/I106118109","https://openalex.org/I1341640284","https://openalex.org/I887064364"],"apc_list":null,"apc_paid":null,"fwci":0.7047,"has_fulltext":true,"cited_by_count":10,"citation_normalized_percentile":{"value":0.72474389,"is_in_top_1_percent":false,"is_in_top_10_percent":false},"cited_by_percentile_year":{"min":90,"max":95},"biblio":{"volume":"16","issue":"2","first_page":null,"last_page":null},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T12536","display_name":"Topological and Geometric Data Analysis","score":0.9987000226974487,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},"topics":[{"id":"https://openalex.org/T12536","display_name":"Topological and Geometric Data Analysis","score":0.9987000226974487,"subfield":{"id":"https://openalex.org/subfields/1703","display_name":"Computational Theory and Mathematics"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11329","display_name":"Limits and Structures in Graph Theory","score":0.9977999925613403,"subfield":{"id":"https://openalex.org/subfields/2607","display_name":"Discrete Mathematics and Combinatorics"},"field":{"id":"https://openalex.org/fields/26","display_name":"Mathematics"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11151","display_name":"Advanced Topology and Set Theory","score":0.9966999888420105,"subfield":{"id":"https://openalex.org/subfields/2608","display_name":"Geometry and Topology"},"field":{"id":"https://openalex.org/fields/26","display_name":"Mathematics"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/mathematics","display_name":"Mathematics","score":0.8759681582450867},{"id":"https://openalex.org/keywords/homomorphism","display_name":"Homomorphism","score":0.6894638538360596},{"id":"https://openalex.org/keywords/combinatorics","display_name":"Combinatorics","score":0.6301678419113159},{"id":"https://openalex.org/keywords/positive-definite-matrix","display_name":"Positive-definite matrix","score":0.5596040487289429},{"id":"https://openalex.org/keywords/graph","display_name":"Graph","score":0.5312970280647278},{"id":"https://openalex.org/keywords/connection","display_name":"Connection (principal bundle)","score":0.5169312357902527},{"id":"https://openalex.org/keywords/characterization","display_name":"Characterization (materials science)","score":0.4771503806114197},{"id":"https://openalex.org/keywords/discrete-mathematics","display_name":"Discrete mathematics","score":0.4116978943347931},{"id":"https://openalex.org/keywords/eigenvalues-and-eigenvectors","display_name":"Eigenvalues and eigenvectors","score":0.07038888335227966}],"concepts":[{"id":"https://openalex.org/C33923547","wikidata":"https://www.wikidata.org/wiki/Q395","display_name":"Mathematics","level":0,"score":0.8759681582450867},{"id":"https://openalex.org/C4042151","wikidata":"https://www.wikidata.org/wiki/Q215111","display_name":"Homomorphism","level":2,"score":0.6894638538360596},{"id":"https://openalex.org/C114614502","wikidata":"https://www.wikidata.org/wiki/Q76592","display_name":"Combinatorics","level":1,"score":0.6301678419113159},{"id":"https://openalex.org/C49712288","wikidata":"https://www.wikidata.org/wiki/Q77601250","display_name":"Positive-definite matrix","level":3,"score":0.5596040487289429},{"id":"https://openalex.org/C132525143","wikidata":"https://www.wikidata.org/wiki/Q141488","display_name":"Graph","level":2,"score":0.5312970280647278},{"id":"https://openalex.org/C13355873","wikidata":"https://www.wikidata.org/wiki/Q2920850","display_name":"Connection (principal bundle)","level":2,"score":0.5169312357902527},{"id":"https://openalex.org/C2780841128","wikidata":"https://www.wikidata.org/wiki/Q5073781","display_name":"Characterization (materials science)","level":2,"score":0.4771503806114197},{"id":"https://openalex.org/C118615104","wikidata":"https://www.wikidata.org/wiki/Q121416","display_name":"Discrete mathematics","level":1,"score":0.4116978943347931},{"id":"https://openalex.org/C158693339","wikidata":"https://www.wikidata.org/wiki/Q190524","display_name":"Eigenvalues and eigenvectors","level":2,"score":0.07038888335227966},{"id":"https://openalex.org/C62520636","wikidata":"https://www.wikidata.org/wiki/Q944","display_name":"Quantum mechanics","level":1,"score":0.0},{"id":"https://openalex.org/C192562407","wikidata":"https://www.wikidata.org/wiki/Q228736","display_name":"Materials science","level":0,"score":0.0},{"id":"https://openalex.org/C121332964","wikidata":"https://www.wikidata.org/wiki/Q413","display_name":"Physics","level":0,"score":0.0},{"id":"https://openalex.org/C171250308","wikidata":"https://www.wikidata.org/wiki/Q11468","display_name":"Nanotechnology","level":1,"score":0.0},{"id":"https://openalex.org/C2524010","wikidata":"https://www.wikidata.org/wiki/Q8087","display_name":"Geometry","level":1,"score":0.0}],"mesh":[],"locations_count":8,"locations":[{"id":"doi:10.37236/80","is_oa":true,"landing_page_url":"https://doi.org/10.37236/80","pdf_url":"https://www.combinatorics.org/ojs/index.php/eljc/article/download/v16i2r14/pdf","source":{"id":"https://openalex.org/S38448739","display_name":"The Electronic Journal of Combinatorics","issn_l":"1077-8926","issn":["1077-8926","1097-1440"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310317970","host_organization_name":"Electronic Journal of Combinatorics","host_organization_lineage":["https://openalex.org/P4310317970"],"host_organization_lineage_names":["Electronic Journal of Combinatorics"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"The Electronic Journal of Combinatorics","raw_type":"journal-article"},{"id":"pmh:oai:dare.uva.nl:openaire_cris_publications/06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27","is_oa":true,"landing_page_url":"https://dare.uva.nl/personal/pure/en/publications/semidefinite-functions-on-categories(06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27).html","pdf_url":null,"source":{"id":"https://openalex.org/S4306400088","display_name":"UvA-DARE (University of Amsterdam)","issn_l":null,"issn":null,"is_oa":false,"is_in_doaj":false,"is_core":false,"host_organization":"https://openalex.org/I887064364","host_organization_name":"University of Amsterdam","host_organization_lineage":["https://openalex.org/I887064364"],"host_organization_lineage_names":[],"type":"repository"},"license":"other-oa","license_id":"https://openalex.org/licenses/other-oa","version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Lov\u00e1sz, L & Schrijver, A 2009, 'Semidefinite functions on categories', The Electronic Journal of Combinatorics, vol. 16, no. 2, pp. R14.","raw_type":"info:eu-repo/semantics/publishedVersion"},{"id":"pmh:oai:dare.uva.nl:publications/06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27","is_oa":true,"landing_page_url":"https://handle.uba.uva.nl/personal/pure/en/publications/semidefinite-functions-on-categories(06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27).html","pdf_url":"https://pure.uva.nl/ws/files/931932/72883_Schrijver_Lovasz_EJC.pdf","source":{"id":"https://openalex.org/S4306400088","display_name":"UvA-DARE (University of Amsterdam)","issn_l":null,"issn":null,"is_oa":false,"is_in_doaj":false,"is_core":false,"host_organization":"https://openalex.org/I887064364","host_organization_name":"University of Amsterdam","host_organization_lineage":["https://openalex.org/I887064364"],"host_organization_lineage_names":[],"type":"repository"},"license":"other-oa","license_id":"https://openalex.org/licenses/other-oa","version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"Lov\u00e1sz, L & Schrijver, A 2009, 'Semidefinite functions on categories', The Electronic Journal of Combinatorics, vol. 16, no. 2, pp. R14.","raw_type":"info:eu-repo/semantics/publishedVersion"},{"id":"pmh:cwi:oai:cwi.nl:14788","is_oa":false,"landing_page_url":"https://ir.cwi.nl/pub/14788","pdf_url":null,"source":{"id":"https://openalex.org/S4306401843","display_name":"Data Archiving and Networked Services (DANS)","issn_l":null,"issn":null,"is_oa":false,"is_in_doaj":false,"is_core":false,"host_organization":"https://openalex.org/I1322597698","host_organization_name":"Royal Netherlands Academy of Arts and Sciences","host_organization_lineage":["https://openalex.org/I1322597698"],"host_organization_lineage_names":[],"type":"repository"},"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"Electronic Journal of Combinatorics, 16, 0 - 14","raw_type":"info:eu-repo/semantics/article"},{"id":"pmh:oai:CiteSeerX.psu:10.1.1.216.5094","is_oa":false,"landing_page_url":"http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.216.5094","pdf_url":null,"source":null,"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"http://homepages.cwi.nl/~lex/files/category-semidef-1eljc.pdf","raw_type":"text"},{"id":"pmh:oai:CiteSeerX.psu:10.1.1.216.6862","is_oa":false,"landing_page_url":"http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.216.6862","pdf_url":null,"source":null,"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"http://www.combinatorics.org/Volume_16/PDF/v16i2r14.pdf","raw_type":"text"},{"id":"pmh:oai:CiteSeerX.psu:10.1.1.421.7664","is_oa":false,"landing_page_url":"http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.421.7664","pdf_url":null,"source":null,"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"http://homepages.cwi.nl/~lex/files/category-semidef.pdf","raw_type":"text"},{"id":"pmh:oai:dare.uva.nl:publications/06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27","is_oa":false,"landing_page_url":"http://dare.uva.nl/personal/pure/en/publications/semidefinite-functions-on-categories(06bb7cbc-9a6c-4411-b5b1-e4b39c59fc27).html","pdf_url":null,"source":{"id":"https://openalex.org/S4306400088","display_name":"UvA-DARE (University of Amsterdam)","issn_l":null,"issn":null,"is_oa":false,"is_in_doaj":false,"is_core":false,"host_organization":"https://openalex.org/I887064364","host_organization_name":"University of Amsterdam","host_organization_lineage":["https://openalex.org/I887064364"],"host_organization_lineage_names":[],"type":"repository"},"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"","raw_type":""}],"best_oa_location":{"id":"doi:10.37236/80","is_oa":true,"landing_page_url":"https://doi.org/10.37236/80","pdf_url":"https://www.combinatorics.org/ojs/index.php/eljc/article/download/v16i2r14/pdf","source":{"id":"https://openalex.org/S38448739","display_name":"The Electronic Journal of Combinatorics","issn_l":"1077-8926","issn":["1077-8926","1097-1440"],"is_oa":true,"is_in_doaj":true,"is_core":true,"host_organization":"https://openalex.org/P4310317970","host_organization_name":"Electronic Journal of Combinatorics","host_organization_lineage":["https://openalex.org/P4310317970"],"host_organization_lineage_names":["Electronic Journal of Combinatorics"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"The Electronic Journal of Combinatorics","raw_type":"journal-article"},"sustainable_development_goals":[],"awards":[{"id":"https://openalex.org/G6843146680","display_name":null,"funder_award_id":"67867","funder_id":"https://openalex.org/F4320321994","funder_display_name":"Hungarian Scientific Research Fund"}],"funders":[{"id":"https://openalex.org/F4320321994","display_name":"Hungarian Scientific Research Fund","ror":"https://ror.org/00v349e63"}],"has_content":{"pdf":true,"grobid_xml":true},"content_urls":{"pdf":"https://content.openalex.org/works/W2100355951.pdf","grobid_xml":"https://content.openalex.org/works/W2100355951.grobid-xml"},"referenced_works_count":14,"referenced_works":["https://openalex.org/W655258421","https://openalex.org/W1485574018","https://openalex.org/W1534787852","https://openalex.org/W1904915884","https://openalex.org/W1968334723","https://openalex.org/W2001411993","https://openalex.org/W2003078549","https://openalex.org/W2033026830","https://openalex.org/W2082734581","https://openalex.org/W2104417474","https://openalex.org/W2111754130","https://openalex.org/W2141382791","https://openalex.org/W2572078071","https://openalex.org/W4300181465"],"related_works":["https://openalex.org/W4308159138","https://openalex.org/W1979798674","https://openalex.org/W4327811209","https://openalex.org/W3169947911","https://openalex.org/W3037616202","https://openalex.org/W390508480","https://openalex.org/W2375240985","https://openalex.org/W2069134788","https://openalex.org/W3036423744","https://openalex.org/W2001056849"],"abstract_inverted_index":{"Freedman,":[0],"Lov\u00e1sz":[1],"and":[2],"Schrijver":[3],"characterized":[4],"graph":[5],"parameters":[6],"that":[7],"can":[8],"be":[9,60],"represented":[10],"as":[11,44],"the":[12,31,47],"(weighted)":[13],"number":[14],"of":[15,23,33,40],"homomorphisms":[16],"into":[17],"a":[18,37],"fixed":[19],"graph.":[20],"Several":[21],"extensions":[22],"this":[24,41],"result":[25],"have":[26],"been":[27],"proved.":[28],"We":[29],"use":[30],"framework":[32],"categories":[34],"to":[35,59],"prove":[36],"general":[38],"theorem":[39],"kind.":[42],"Similarly":[43],"previous":[45],"resuts,":[46],"characterization":[48],"uses":[49],"certain":[50],"infinite":[51],"matrices,":[52,55],"called":[53],"connection":[54],"which":[56],"are":[57],"required":[58],"positive":[61],"semidefinite.":[62]},"counts_by_year":[{"year":2025,"cited_by_count":1},{"year":2024,"cited_by_count":1},{"year":2023,"cited_by_count":1},{"year":2019,"cited_by_count":1},{"year":2015,"cited_by_count":1},{"year":2014,"cited_by_count":1}],"updated_date":"2026-04-04T16:13:02.066488","created_date":"2025-10-10T00:00:00"}
